This tutorial on writing a notepad application gives you a "hands-on" introduction -to the Android framework and the tools you use to build applications on it. -Starting from a preconfigured project file, it guides you through the process of -developing a simple notepad application and provides concrete examples of how to -set up the project, develop the application logic and user interface, and then -compile and run the application.
- -The tutorial presents the application development as a set of -exercises (see below), each consisting of several steps. You should follow -the steps in each exercise to gradually build and refine your -application. The exercises explain each step in detail and provide all the -sample code you need to complete the application.
- -When you are finished with the tutorial, you will have created a functioning -Android application and will have learned many of the most important -concepts in Android development.
- - -This tutorial is designed for experienced developers, especially those with -knowledge of the Java programming language. If you haven't written Java -applications before, you can still use the tutorial, but you might need to work -at a slower pace.
- -Also note that this tutorial uses -the Eclipse development environment, with the Android plugin installed. If you -are not using Eclipse, you can follow the exercises and build the application, -but you will need to determine how to accomplish the Eclipse-specific -steps in your environment.
- - -The tutorial assumes that you have some familiarity with basic Android -application concepts and terminology. If you are not, you -should read Application -Fundamentals before continuing.
- -This tutorial also builds on the introductory information provided in the -Building Your First App -tutorial, which explains how to set up your Eclipse environment -for building Android applications. We recommend you complete the Hello World -tutorial before starting this one.
- -To prepare for this lesson:
- -NotepadCodeLab folder.Inside the NotepadCodeLab folder, you should see six project
-files: Notepadv1,
- Notepadv2, Notepadv3,
- Notepadv1Solution, Notepadv2Solution
- and Notepadv3Solution. The Notepadv# projects are
-the starting points for each of the exercises, while the
-Notepadv#Solution projects are the exercise
- solutions. If you are having trouble with a particular exercise, you
- can compare your current work against the exercise solution.
The table below lists the tutorial exercises and describes the development -areas that each covers. Each exercise assumes that you have completed any -previous exercises.
- -| Exercise -1 | -Start here. Construct a simple notes list that lets the user add new notes but not
-edit them. Demonstrates the basics of ListActivity and creating
-and handling
- menu options. Uses a SQLite database to store the notes. |
-
|---|---|
| Exercise 2 | -Add a second Activity to the
-application. Demonstrates constructing a
-new Activity, adding it to the Android manifest, passing data between the
-activities, and using more advanced screen layout. Also shows how to
-invoke another Activity to return a result, using
-startActivityForResult(). |
-
| Exercise 3 | -Add handling of life-cycle events to -the application, to let it -maintain application state across the life cycle. | -
| Extra -Credit | -Demonstrates how to use the Eclipse -debugger and how you can use it to -view life-cycle events as they are generated. This section is optional but -highly recommended. | -
samples/legacy/NotePad directory of the SDK, though it does not
-match it exactly. When you are done with the tutorial, it is highly recommended
-that you take a closer look at this version of the Notepad application, as it
-demonstrates a variety of interesting additions for your application, such
-as:draw()
- method to make it look like a lined notepad.ContentProvider for notes.In this exercise, you will construct a simple notes list that lets the -user add new notes but not edit them. The exercise demonstrates:
-ListActivities and creating and handling menu
-options. Open up the Notepadv1 project in Eclipse.
Notepadv1 is a project that is provided as a starting point. It
- takes care of some of the boilerplate work that you have already seen if you
- followed the Hello,
- World tutorial.
NotepadCodeLab
- (downloaded during setup)
- and select Notepadv1.Notepadv1 project should open and be
- visible in your Eclipse package explorer.If you see an error about AndroidManifest.xml, or some
- problems related to an Android zip file, right click on the project and
- select Android Tools > Fix Project Properties.
- (The project is looking in the wrong location for the library file,
- this will fix it for you.)
For this - exercise, we are using a SQLite database to store our data. This is useful - if only your application will need to access or modify the data. If you wish for - other activities to access or modify the data, you have to expose the data using a - {@link android.content.ContentProvider ContentProvider}.
-If you are interested, you can find out more about
- content providers or the
-whole
- subject of Data Storage.
- The NotePad sample in the samples/ folder of the SDK also has an example of how
- to create a ContentProvider.
Take a look at the NotesDbAdapter class — this class is provided to
- encapsulate data access to a SQLite database that will hold our notes data
- and allow us to update it.
At the top of the class are some constant definitions that will be used in the application - to look up data from the proper field names in the database. There is also a database creation - string defined, which is used to create a new database schema if one doesn't exist already.
-Our database will have the name data, and have a single table called
- notes, which in turn has three fields: _id, title and
- body. The _id is named with an underscore convention used in a number of
- places inside the Android SDK and helps keep a track of state. The _id
- usually has to be specified when querying or updating the database (in the column projections
- and so on). The other two fields are simple text fields that will store data.
-
The constructor for NotesDbAdapter takes a Context, which allows it to communicate with aspects
- of the Android operating system. This is quite common for classes that need to touch the
- Android system in some way. The Activity class implements the Context class, so usually you will just pass
- this from your Activity, when needing a Context.
The open() method calls up an instance of DatabaseHelper, which is our local
- implementation of the SQLiteOpenHelper class. It calls getWritableDatabase(),
- which handles creating/opening a database for us.
close() just closes the database, releasing resources related to the
- connection.
createNote() takes strings for the title and body of a new note,
- then creates that note in the database. Assuming the new note is created successfully, the
- method also returns the row _id value for the newly created note.
deleteNote() takes a rowId for a particular note, and deletes that note from
- the database.
fetchAllNotes() issues a query to return a {@link android.database.Cursor} over all notes in the
- database. The query() call is worth examination and understanding. The first field is the
- name of the database table to query (in this case DATABASE_TABLE is "notes").
- The next is the list of columns we want returned, in this case we want the _id,
- title and body columns so these are specified in the String array.
- The remaining fields are, in order: selection,
- selectionArgs, groupBy, having and orderBy.
- Having these all null means we want all data, need no grouping, and will take the default
- order. See {@link android.database.sqlite.SQLiteDatabase SQLiteDatabase} for more details.
Note: A Cursor is returned rather than a collection of rows. This allows - Android to use resources efficiently -- instead of putting lots of data straight into memory - the cursor will retrieve and release data as it is needed, which is much more efficient for - tables with lots of rows.
- -fetchNote() is similar to fetchAllNotes() but just gets one note
- with the rowId we specify. It uses a slightly different version of the
- {@link android.database.sqlite.SQLiteDatabase} query() method.
- The first parameter (set true) indicates that we are interested
- in one distinct result. The selection parameter (the fourth parameter) has been specified to search
- only for the row "where _id =" the rowId we passed in. So we are returned a Cursor on
- the one row.
And finally, updateNote() takes a rowId, title and body, and uses a
- {@link android.content.ContentValues ContentValues} instance to update the note of the given
- rowId.
Most Activity classes will have a layout associated with them. The layout - will be the "face" of the Activity to the user. In this case our layout will - take over the whole screen and provide a list of notes.
-Full screen layouts are not the only option for an Activity however. You - might also want to use a floating - layout (for example, a dialog - or alert), - or perhaps you don't need a layout at all (the Activity will be invisible - to the user unless you specify some kind of layout for it to use).
-Open the notepad_list.xml file in res/layout
-and
- take a look at it. (You may have to
- hit the xml tab, at the bottom, in order to view the XML markup.)
This is a mostly-empty layout definition file. Here are some - things you should know about a layout file:
- - -<?xml version="1.0" encoding="utf-8"?>. LinearLayout. android: tags can
- be used through the rest of the file:
- xmlns:android="http://schemas.android.com/apk/res/android"
We need to create the layout to hold our list. Add code inside
- of the LinearLayout element so the whole file looks like this:
-<?xml version="1.0" encoding="utf-8"?> -<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" - android:layout_width="wrap_content" - android:layout_height="wrap_content"> - - <ListView android:id="@android:id/list" - android:layout_width="wrap_content" - android:layout_height="wrap_content"/> - <TextView android:id="@android:id/empty" - android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@string/no_notes"/> - -</LinearLayout> --
ListView and
- TextView tags means
- that the XML parser should parse and expand the rest of
- the id string and use an ID resource.ListView and TextView can be
- thought as two alternative views, only one of which will be displayed at once.
- ListView will be used when there are notes to be shown, while the TextView
- (which has a default value of "No Notes Yet!" defined as a string
- resource in res/values/strings.xml) will be displayed if there
- aren't any notes to display.list and empty IDs are
- provided for us by the Android platform, so, we must
- prefix the id with android: (e.g., @android:id/list).empty id is used
- automatically when the {@link android.widget.ListAdapter} has no data for the ListView. The
- ListAdapter knows to look for this name by default. Alternatively, you could change the
- default empty view by using {@link android.widget.AdapterView#setEmptyView(View)}
- on the ListView.
-
- More broadly, the android.R class is a set of predefined
- resources provided for you by the platform, while your project's
- R class is the set of resources your project has defined.
- Resources found in the android.R resource class can be
- used in the XML files by using the android: name space prefix
- (as we see here).
The folders under res/ in the Eclipse project are for resources. - There is a specific structure -to the - folders and files under res/.
-Resources defined in these folders and files will have - corresponding entries in the R class allowing them to be easily accessed - and used from your application. The R class is automatically generated using the contents - of the res/ folder by the eclipse plugin (or by aapt if you use the command line tools). - Furthermore, they will be bundled and deployed for you as part of the application.
- -To make the list of notes in the ListView, we also need to define a View for each row:
-res/layout called
- notes_row.xml. -<?xml version="1.0" encoding="utf-8"?> -<TextView android:id="@+id/text1" - xmlns:android="http://schemas.android.com/apk/res/android" - android:layout_width="wrap_content" - android:layout_height="wrap_content"/>-
- This is the View that will be used for each notes title row — it has only - one text field in it.
-In this case we create a new id called text1. The
- + after the @ in the id string indicates that the id should
- be automatically created as a resource if it does not already exist, so we are defining
- text1 on the fly and then using it.
Open the R.java class in the
- project and look at it, you should see new definitions for
- notes_row and text1 (our new definitions)
- meaning we can now gain access to these from the our code.
Next, open the Notepadv1 class in the source. In the following steps, we are going to
- alter this class to become a list adapter and display our notes, and also
- allow us to add new notes.
Notepadv1 will inherit from a subclass
- of Activity called a ListActivity,
- which has extra functionality to accommodate the kinds of
- things you might want to do with a list, for
- example: displaying an arbitrary number of list items in rows on the screen,
- moving through the list items, and allowing them to be selected.
Take a look through the existing code in Notepadv1 class.
- There is a currently an unused private field called mNoteNumber that
- we will use to create numbered note titles.
There are also three override methods defined:
- onCreate, onCreateOptionsMenu and
- onOptionsItemSelected; we need to fill these
- out:
onCreate() is called when the activity is
- started — it is a little like the "main" method for an Activity. We use
- this to set up resources and state for the activity when it is
- running.onCreateOptionsMenu() is used to populate the
- menu for the Activity. This is shown when the user hits the menu button,
-and
- has a list of options they can select (like "Create
- Note"). onOptionsItemSelected() is the other half of the
- menu equation, it is used to handle events generated from the menu (e.g.,
- when the user selects the "Create Note" item).
- Change the inheritance of Notepadv1 from
-Activity
- to ListActivity:
public class Notepadv1 extends ListActivity-
Note: you will have to import ListActivity into the
-Notepadv1
- class using Eclipse, ctrl-shift-O on Windows or Linux, or
- cmd-shift-O on the Mac (organize imports) will do this for you
- after you've written the above change.
Fill out the body of the onCreate() method.
Here we will set the title for the Activity (shown at the top of the
- screen), use the notepad_list layout we created in XML,
- set up the NotesDbAdapter instance that will
- access notes data, and populate the list with the available note
- titles:
onCreate method, call super.onCreate() with the
- savedInstanceState parameter that's passed in.setContentView() and pass R.layout.notepad_list.mDbHelper of class
- NotesDbAdapter.
- onCreate method, construct a new
-NotesDbAdapter
- instance and assign it to the mDbHelper field (pass
- this into the constructor for DBHelper)
- open() method on mDbHelper to open (or create) the
- database.
- fillData(), which will get the data and
- populate the ListView using the helper — we haven't defined this method yet.
- onCreate() should now look like this:
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.notepad_list);
- mDbHelper = new NotesDbAdapter(this);
- mDbHelper.open();
- fillData();
- }
- And be sure you have the mDbHelper field definition (right
- under the mNoteNumber definition):
private NotesDbAdapter mDbHelper;- -
The notepad application we are constructing only scratches the - surface with menus.
-You can also add -shortcut keys for menu items, create -submenus and even add -menu items to other applications!.
-Fill out the body of the onCreateOptionsMenu() method.
We will now create the "Add Item" button that can be accessed by pressing the menu -button on the device. We'll specify that it occupy the first position in the menu.
- -strings.xml resource (under res/values), add
- a new string named "menu_insert" with its value set to Add Item:
- <string name="menu_insert">Add Item</string>-
Then save the file and return to Notepadv1.
public static final int INSERT_ID = Menu.FIRST;-
onCreateOptionsMenu() method, change the
- super call so we capture the boolean return as result. We'll return this value at the end.menu.add().The whole method should now look like this: -
- @Override
- public boolean onCreateOptionsMenu(Menu menu) {
- boolean result = super.onCreateOptionsMenu(menu);
- menu.add(0, INSERT_ID, 0, R.string.menu_insert);
- return result;
- }
- The arguments passed to add() indicate: a group identifier for this menu (none,
- in this case), a unique ID (defined above), the order of the item (zero indicates no preference),
- and the resource of the string to use for the item.
Fill out the body of the onOptionsItemSelected() method:
This is going
- to handle our new "Add Note" menu item. When this is selected, the
- onOptionsItemSelected() method will be called with the
- item.getId() set to INSERT_ID (the constant we
- used to identify the menu item). We can detect this, and take the
- appropriate actions:
super.onOptionsItemSelected(item) method call goes at the
- end of this method — we want to catch our events first! item.getItemId().
- In the case of INSERT_ID, call a new method, createNote(),
- and return true, because we have handled this event and do not want to
- propagate it through the system.
onOptionsItemSelected()
- method at the end.
- The whole onOptionsItemSelect() method should now look like
- this:
- @Override
- public boolean onOptionsItemSelected(MenuItem item) {
- switch (item.getItemId()) {
- case INSERT_ID:
- createNote();
- return true;
- }
-
- return super.onOptionsItemSelected(item);
- }
-
-Add a new createNote() method:
In this first version of
- our application, createNote() is not going to be very useful.
-We will simply
- create a new note with a title assigned to it based on a counter ("Note 1",
- "Note 2"...) and with an empty body. At present we have no way of editing
- the contents of a note, so for now we will have to be content making one
- with some default values:
- String noteName = "Note " + mNoteNumber++mDbHelper.createNote() using noteName as the
- title and "" for the body
- fillData() to populate the list of notes (inefficient but
- simple) — we'll create this method next.
- The whole createNote() method should look like this:
- private void createNote() {
- String noteName = "Note " + mNoteNumber++;
- mDbHelper.createNote(noteName, "");
- fillData();
- }
-
-
-Our example uses a {@link android.widget.SimpleCursorAdapter - SimpleCursorAdapter} to bind a database {@link android.database.Cursor Cursor} - into a ListView, and this is a common way to use a {@link android.widget.ListAdapter - ListAdapter}. Other options exist like {@link android.widget.ArrayAdapter ArrayAdapter} which - can be used to take a List or Array of in-memory data and bind it in to - a list as well.
-Define the fillData() method:
This
- method uses SimpleCursorAdapter, which takes a database Cursor
- and binds it to fields provided in the layout. These fields define the row elements of our list
- (in this case we use the text1 field in our
- notes_row.xml layout), so this allows us to easily populate the list with
- entries from our database.
To do this we have to provide a mapping from the title field in the returned Cursor, to
- our text1 TextView, which is done by defining two arrays: the first a string array
- with the list of columns to map from (just "title" in this case, from the constant
- NotesDbAdapter.KEY_TITLE) and, the second, an int array
- containing references to the views that we'll bind the data into
- (the R.id.text1 TextView).
This is a bigger chunk of code, so let's first take a look at it:
- -
- private void fillData() {
- // Get all of the notes from the database and create the item list
- Cursor c = mDbHelper.fetchAllNotes();
- startManagingCursor(c);
-
- String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
- int[] to = new int[] { R.id.text1 };
-
- // Now create an array adapter and set it to display using our row
- SimpleCursorAdapter notes =
- new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to);
- setListAdapter(notes);
- }
-
- Here's what we've done:
-mDbHelper.fetchAllNotes(), we
- use an Activity method called
- startManagingCursor() that allows Android to take care of the
- Cursor lifecycle instead of us needing to worry about it. (We will cover the implications
- of the lifecycle in exercise 3, but for now just know that this allows Android to do some
- of our resource management work for us.)this for the context (since subclasses of Activity
- implement Context). We pass the notes_row View we created as the receptacle
- for the data, the Cursor we just created, and then our arrays.
- In the future, remember that the mapping between the from columns and to resources
- is done using the respective ordering of the two arrays. If we had more columns we wanted
- to bind, and more Views to bind them in to, we would specify them in order, for example we
- might use { NotesDbAdapter.KEY_TITLE, NotesDbAdapter.KEY_BODY } and
- { R.id.text1, R.id.text2 } to bind two fields into the row (and we would also need
- to define text2 in the notes_row.xml, for the body text). This is how you can bind multiple fields
- into a single row (and get a custom row layout as well).
- If you get compiler errors about classes not being found, ctrl-shift-O or - (cmd-shift-O on the mac) to organize imports. -
- -Run it! -
Notepadv1 project.You can see the solution to this class in Notepadv1Solution
-from
-the zip file to compare with your own.
Once you are ready, move on to Tutorial -Exercise 2 to add the ability to create, edit and delete notes.
- diff --git a/docs/html/training/notepad/notepad-ex2.jd b/docs/html/training/notepad/notepad-ex2.jd deleted file mode 100644 index 5ebd1aa966df4..0000000000000 --- a/docs/html/training/notepad/notepad-ex2.jd +++ /dev/null @@ -1,645 +0,0 @@ -excludeFromSuggestions=true -page.title=Notepad Exercise 2 -parent.title=Notepad Tutorial -parent.link=index.html -@jd:body - - -In this exercise, you will add a second Activity to your notepad application, to let the user -create and edit notes. You will also allow the user to delete existing notes through a context menu. -The new Activity assumes responsibility for creating new notes by -collecting user input and packing it into a return Bundle provided by the intent. This exercise -demonstrates:
-startActivityForResult()Create a new Android project using the sources from Notepadv2 under the
-NotepadCodeLab folder, just like you did for the first exercise. If you see an error about
-AndroidManifest.xml, or some problems related to an
-android.zip file, right click on the project and select Android
-Tools > Fix Project Properties.
Open the Notepadv2 project and take a look around:
strings.xml file under
- res/values — there are several new strings which we will use
- for our new functionality
- Notepadv2 class,
- you will notice several new constants have been defined along with a new mNotesCursor
- field used to hold the cursor we are using.
- fillData() method has a few more comments and now uses
- the new field to store the notes Cursor. The onCreate() method is
- unchanged from the first exercise. Also notice that the member field used to store the
- notes Cursor is now called mNotesCursor. The m denotes a member
- field and is part of the Android coding style standards.
- onCreateContextMenu(), onContextItemSelected(),
- onListItemClick() and onActivityResult())
- which we will be filling in below.
- Context menus should always be used when performing actions upon specific elements in the UI. -When you register a View to a context menu, the context menu is revealed by performing a "long-click" -on the UI component (press and hold the touchscreen or highlight and hold down the selection key for about two seconds).
-First, let's create the context menu that will allow users to delete individual notes. -Open the Notepadv2 class.
- -registerForContextMenu() and pass it our ListView. So, at the very end of
- the onCreate() method add this line:
- registerForContextMenu(getListView());-
Because our Activity extends the ListActivity class, getListView() will return us
- the local ListView object for the Activity. Now, each list item in this ListView will activate the
- context menu.
-
onCreateContextMenu() method. This callback is similar to the other
- menu callback used for the options menu. Here, we add just one line, which will add a menu item
- to delete a note. Call menu.add() like so:
-
-public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
- super.onCreateContextMenu(menu, v, menuInfo);
- menu.add(0, DELETE_ID, 0, R.string.menu_delete);
-}
- The onCreateContextMenu() callback passes some other information in addition to the Menu object,
- such as the View that has been triggered for the menu and
- an extra object that may contain additional information about the object selected. However, we don't care about
- these here, because we only have one kind of object in the Activity that uses context menus. In the next
- step, we'll handle the menu item selection.
Now that we've registered our ListView for a context menu and defined our context menu item, we need
- to handle the callback when it is selected. For this, we need to identify the list ID of the
- selected item, then delete it. So fill in the
- onContextItemSelected() method like this:
-public boolean onContextItemSelected(MenuItem item) {
- switch(item.getItemId()) {
- case DELETE_ID:
- AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
- mDbHelper.deleteNote(info.id);
- fillData();
- return true;
- }
- return super.onContextItemSelected(item);
-}
-Here, we retrieve the {@link android.widget.AdapterView.AdapterContextMenuInfo AdapterContextMenuInfo}
-with {@link android.view.MenuItem#getMenuInfo()}. The id field of this object tells us
-the position of the item in the ListView. We then pass this to the deleteNote()
-method of our NotesDbAdapter and the note is deleted. That's it for the context menu — notes
-can now be deleted.
In this example our Intent uses a class name specifically. - As well as - starting intents in - classes we already know about, be they in our own application or another - application, we can also create Intents without knowing exactly which - application will handle it.
-For example, we might want to open a page in a - browser, and for this we still use - an Intent. But instead of specifying a class to handle it, we use - a predefined Intent constant, and a content URI that describes what we - want to do. See {@link android.content.Intent - android.content.Intent} for more information.
-Fill in the body of the createNote() method:
-
Create a new Intent to create a note
- (ACTIVITY_CREATE) using the NoteEdit class.
- Then fire the Intent using the startActivityForResult() method
- call:
-Intent i = new Intent(this, NoteEdit.class); -startActivityForResult(i, ACTIVITY_CREATE);-
This form of the Intent call targets a specific class in our Activity, in this case
- NoteEdit. Since the Intent class will need to communicate with the Android
- operating system to route requests, we also have to provide a Context (this).
The startActivityForResult() method fires the Intent in a way that causes a method
- in our Activity to be called when the new Activity is completed. The method in our Activity
- that receives the callback is called
- onActivityResult() and we will implement it in a later step. The other way
- to call an Activity is using startActivity() but this is a "fire-and-forget" way
- of calling it — in this manner, our Activity is not informed when the Activity is completed, and there is
- no way to return result information from the called Activity with startActivity().
-
Don't worry about the fact that NoteEdit doesn't exist yet,
- we will fix that soon.
Fill in the body of the onListItemClick() override.
onListItemClick() is a callback method that we'll override. It is called when
- the user selects an item from the list. It is passed four parameters: the
- ListView object it was invoked from, the View
- inside the ListView that was clicked on, the
- position in the list that was clicked, and the
- mRowId of the item that was clicked. In this instance we can
- ignore the first two parameters (we only have one ListView it
- could be), and we ignore the mRowId as well. All we are
- interested in is the position that the user selected. We use
- this to get the data from the correct row, and bundle it up to send to
- the NoteEdit Activity.
In our implementation of the callback, the method creates an
- Intent to edit the note using
- the NoteEdit class. It then adds data into the extras Bundle of
- the Intent, which will be passed to the called Activity. We use it
- to pass in the title and body text, and the mRowId for the note we are
- editing. Finally, it will fire the Intent using the
- startActivityForResult() method call. Here's the code that
- belongs in onListItemClick():
-super.onListItemClick(l, v, position, id); -Cursor c = mNotesCursor; -c.moveToPosition(position); -Intent i = new Intent(this, NoteEdit.class); -i.putExtra(NotesDbAdapter.KEY_ROWID, id); -i.putExtra(NotesDbAdapter.KEY_TITLE, c.getString( - c.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE))); -i.putExtra(NotesDbAdapter.KEY_BODY, c.getString( - c.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY))); -startActivityForResult(i, ACTIVITY_EDIT);-
putExtra() is the method to add items into the extras Bundle
- to pass in to intent invocations. Here, we are
- using the Bundle to pass in the title, body and mRowId of the note we want to edit.
- moveToPosition() method.NoteEdit class by passing startActivityForResult()
- the Intent and the request code. (The request code will be
- returned to onActivityResult as the requestCode parameter.)Note: We assign the mNotesCursor field to a local variable at the - start of the method. This is done as an optimization of the Android code. Accessing a local - variable is much more efficient than accessing a field in the Dalvik VM, so by doing this - we make only one access to the field, and five accesses to the local variable, making the - routine much more efficient. It is recommended that you use this optimization when possible.
- - -The above createNote() and onListItemClick()
- methods use an asynchronous Intent invocation. We need a handler for the callback, so here we fill
- in the body of the onActivityResult().
onActivityResult() is the overridden method
- which will be called when an Activity returns with a result. (Remember, an Activity
- will only return a result if launched with startActivityForResult.) The parameters provided
- to the callback are:
requestCode — the original request code
- specified in the Intent invocation (either ACTIVITY_CREATE or
- ACTIVITY_EDIT for us).
- resultCode — the result (or error code) of the call, this
- should be zero if everything was OK, but may have a non-zero code indicating
- that something failed. There are standard result codes available, and you
- can also create your own constants to indicate specific problems.
- intent — this is an Intent created by the Activity returning
- results. It can be used to return data in the Intent "extras."
- The combination of startActivityForResult() and
- onActivityResult() can be thought of as an asynchronous RPC
- (remote procedure call) and forms the recommended way for an Activity to invoke
- another and share services.
Here's the code that belongs in your onActivityResult():
-super.onActivityResult(requestCode, resultCode, intent);
-Bundle extras = intent.getExtras();
-
-switch(requestCode) {
-case ACTIVITY_CREATE:
- String title = extras.getString(NotesDbAdapter.KEY_TITLE);
- String body = extras.getString(NotesDbAdapter.KEY_BODY);
- mDbHelper.createNote(title, body);
- fillData();
- break;
-case ACTIVITY_EDIT:
- Long mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
- if (mRowId != null) {
- String editTitle = extras.getString(NotesDbAdapter.KEY_TITLE);
- String editBody = extras.getString(NotesDbAdapter.KEY_BODY);
- mDbHelper.updateNote(mRowId, editTitle, editBody);
- }
- fillData();
- break;
-}
-
- ACTIVITY_CREATE and
- ACTIVITY_EDIT activity results in this method.
- fillData() at the end ensures everything is up to date .
- The provided - note_edit.xml layout file is the most sophisticated one in the application we will be building, - but that doesn't mean it is even close to the kind of sophistication you will be likely to want - in real Android applications.
-Creating a - good UI is part art and part science, and the rest is work. Mastery of XML Layouts is an essential part of -creating - a good looking Android application.
-The ApiDemos sample project is a good resource for - learning how to create different layouts.
-Open the file note_edit.xml that has been provided and take a
- look at it. This is the UI code for the Note Editor.
This is the most - sophisticated UI we have dealt with yet. The file is given to you to avoid - problems that may sneak in when typing the code. (The XML is very strict - about case sensitivity and structure, mistakes in these are the usual cause - of problems with layout.)
-There is a new parameter used
- here that we haven't seen before: android:layout_weight (in
- this case set to use the value 1 in each case).
layout_weight is used in LinearLayouts
- to assign "importance" to Views within the layout. All Views have a default
- layout_weight of zero, meaning they take up only as much room
- on the screen as they need to be displayed. Assigning a value higher than
- zero will split up the rest of the available space in the parent View, according
- to the value of each View's layout_weight and its ratio to the
- overall layout_weight specified in the current layout for this
- and other View elements.
To give an example: let's say we have a text label
- and two text edit elements in a horizontal row. The label has no
- layout_weight specified, so it takes up the minimum space
- required to render. If the layout_weight of each of the two
- text edit elements is set to 1, the remaining width in the parent layout will
- be split equally between them (because we claim they are equally important).
- If the first one has a layout_weight of 1
- and the second has a layout_weight of 2, then one third of the
- remaining space will be given to the first, and two thirds to the
- second (because we claim the second one is more important).
This layout also demonstrates how to nest multiple layouts - inside each other to achieve a more complex and pleasant layout. In this - example, a horizontal linear layout is nested inside the vertical one to - allow the title label and text field to be alongside each other, - horizontally.
- - -Create a NoteEdit class that extends
- android.app.Activity.
This is the first time we will have
- created an Activity without the Android Eclipse plugin doing it for us. When
- you do so, the onCreate() method is not automatically
- overridden for you. It is hard to imagine an Activity that doesn't override
- the onCreate() method, so this should be the first thing you do.
com.android.demo.notepad2 package
- in the Package Explorer, and select New > Class from the popup
- menu.NoteEdit for the Name: field in the
- dialog.Superclass: field, enter
- android.app.Activity (you can also just type Activity and hit
- Ctrl-Space on Windows and Linux or Cmd-Space on the Mac, to invoke code
- assist and find the right package and class).NoteEdit class, right click in the editor
- window and select Source > Override/Implement Methods...onCreate(Bundle) — and check the box next to it.The method should now appear in your class.
Fill in the body of the onCreate() method for NoteEdit.
This will set the title of our new Activity to say "Edit Note" (one
- of the strings defined in strings.xml). It will also set the
- content view to use our note_edit.xml layout file. We can then
- grab handles to the title and body text edit views, and the confirm button,
- so that our class can use them to set and get the note title and body,
- and attach an event to the confirm button for when it is pressed by the
- user.
We can then unbundle the values that were passed in to the Activity
- with the extras Bundle attached to the calling Intent. We'll use them to pre-populate
- the title and body text edit views so that the user can edit them.
- Then we will grab and store the mRowId so we can keep
- track of what note the user is editing.
onCreate(), set up the layout:setContentView(R.layout.note_edit);-
setTitle(R.string.edit_note);-
These are found by the
- IDs associated to them in the R class, and need to be cast to the right
- type of View (EditText for the two text views,
- and Button for the confirm button):
-mTitleText = (EditText) findViewById(R.id.title); -mBodyText = (EditText) findViewById(R.id.body); -Button confirmButton = (Button) findViewById(R.id.confirm);-
Note that mTitleText and mBodyText are member
- fields (you need to declare them at the top of the class definition).
Long mRowId private field to store
- the current mRowId being edited (if any).
- onCreate(),
- add code to initialize the title, body and
- mRowId from the extras Bundle in
- the Intent (if it is present):
-mRowId = null;
-Bundle extras = getIntent().getExtras();
-if (extras != null) {
- String title = extras.getString(NotesDbAdapter.KEY_TITLE);
- String body = extras.getString(NotesDbAdapter.KEY_BODY);
- mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
-
- if (title != null) {
- mTitleText.setText(title);
- }
- if (body != null) {
- mBodyText.setText(body);
- }
-}
- title and
- body out of the
- extras Bundle that was set from the
- Intent invocation.
- onClickListener() for the button:
- Listeners can be one of the more confusing aspects of UI
- implementation, but
- what we are trying to achieve in this case is simple. We want an
- onClick() method to be called when the user presses the
- confirm button, and use that to do some work and return the values
- of the edited note to the Intent caller. We do this using something called
- an anonymous inner class. This is a bit confusing to look at unless you
- have seen them before, but all you really need to take away from this is
- that you can refer to this code in the future to see how to create a
- listener and attach it to a button. (Listeners are a common idiom
- in Java development, particularly for user interfaces.) Here's the empty listener:
-
-confirmButton.setOnClickListener(new View.OnClickListener() {
-
- public void onClick(View view) {
-
- }
-
-});
- Fill in the body of the onClick() method of the OnClickListener created in the last step.
This is the code that will be run when the user clicks on the
- confirm button. We want this to grab the title and body text from the edit
- text fields, and put them into the return Bundle so that they can be passed
- back to the Activity that invoked this NoteEdit Activity. If the
- operation is an edit rather than a create, we also want to put the
- mRowId into the Bundle so that the
- Notepadv2 class can save the changes back to the correct
- note.
Bundle and put the title and body text into it using the
- constants defined in Notepadv2 as keys:
-Bundle bundle = new Bundle();
-
-bundle.putString(NotesDbAdapter.KEY_TITLE, mTitleText.getText().toString());
-bundle.putString(NotesDbAdapter.KEY_BODY, mBodyText.getText().toString());
-if (mRowId != null) {
- bundle.putLong(NotesDbAdapter.KEY_ROWID, mRowId);
-}
- -Intent mIntent = new Intent(); -mIntent.putExtras(bundle); -setResult(RESULT_OK, mIntent); -finish();-
setResult() method is used to set the result
- code and return Intent to be passed back to the
- Intent caller. In this case everything worked, so we return RESULT_OK for the
- result code.finish() call is used to signal that the Activity
- is done (like a return call). Anything set in the Result will then be
- returned to the caller, along with execution control.The full onCreate() method (plus supporting class fields) should
- now look like this:
-private EditText mTitleText;
-private EditText mBodyText;
-private Long mRowId;
-
-@Override
-protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.note_edit);
-
- mTitleText = (EditText) findViewById(R.id.title);
- mBodyText = (EditText) findViewById(R.id.body);
-
- Button confirmButton = (Button) findViewById(R.id.confirm);
-
- mRowId = null;
- Bundle extras = getIntent().getExtras();
- if (extras != null) {
- String title = extras.getString(NotesDbAdapter.KEY_TITLE);
- String body = extras.getString(NotesDbAdapter.KEY_BODY);
- mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
-
- if (title != null) {
- mTitleText.setText(title);
- }
- if (body != null) {
- mBodyText.setText(body);
- }
- }
-
- confirmButton.setOnClickListener(new View.OnClickListener() {
-
- public void onClick(View view) {
- Bundle bundle = new Bundle();
-
- bundle.putString(NotesDbAdapter.KEY_TITLE, mTitleText.getText().toString());
- bundle.putString(NotesDbAdapter.KEY_BODY, mBodyText.getText().toString());
- if (mRowId != null) {
- bundle.putLong(NotesDbAdapter.KEY_ROWID, mRowId);
- }
-
- Intent mIntent = new Intent();
- mIntent.putExtras(bundle);
- setResult(RESULT_OK, mIntent);
- finish();
- }
- });
-}
-
-
-
-The AndroidManifest.xml file is the way in which Android sees your - application. This file defines the category of the application, where - it shows up (or even if it shows up) in the launcher or settings, what - activities, services, and content providers it defines, what intents it can - receive, and more.
-For more information, see the reference document - The AndroidManifest.xml -File
-Finally, the new Activity has to be defined in the manifest file:
-Before the new Activity can be seen by Android, it needs its own
- Activity entry in the AndroidManifest.xml file. This is to let
- the system know that it is there and can be called. We could also specify
- which IntentFilters the activity implements here, but we are going to skip
- this for now and just let Android know that the Activity is
- defined.
There is a Manifest editor included in the Eclipse plugin that makes it much easier - to edit the AndroidManifest file, and we will use this. If you prefer to edit the file directly - or are not using the Eclipse plugin, see the box at the end for information on how to do this - without using the new Manifest editor.
-
AndroidManifest.xml file in the package explorer to open it.
- If you see a dialog with radiobuttons at the top, select the top radio button: - "Create a new element at the top level, in Application".
.NoteEdit into the Name*
- field to the right. Press Return/Enter.The Android Manifest editor helps you add more complex entries into the AndroidManifest.xml - file, have a look around at some of the other options available (but be careful not to select - them otherwise they will be added to your Manifest). This editor should help you understand - and alter the AndroidManifest.xml file as you move on to more advanced Android applications.
- -If you prefer to edit this file directly, simply open the
- AndroidManifest.xml file and look at the source (use the
- AndroidManifest.xml tab in the eclipse editor to see the source code directly).
- Then edit the file as follows:
- <activity android:name=".NoteEdit" />
- This should be placed just below the line that reads:
- </activity> for the .Notepadv2 activity.
Now Run it!
-You should now be able to add real notes from -the menu, as well as delete an existing one. Notice that in order to delete, you must -first use the directional controls on the device to highlight the note. -Furthermore, selecting a note title from the list should bring up the note -editor to let you edit it. Press confirm when finished to save the changes -back to the database. - -
You can see the solution to this exercise in Notepadv2Solution
-from the zip file to compare with your own.
Now try editing a note, and then hitting the back button on the emulator -instead of the confirm button (the back button is below the menu button). You -will see an error come up. Clearly our application still has some problems. -Worse still, if you did make some changes and hit the back button, when you go -back into the notepad to look at the note you changed, you will find that all -your changes have been lost. In the next exercise we will fix these -problems.
- --Once you are ready, move on to Tutorial -Exercise 3 where you will fix the problems with the back button and lost -edits by introducing a proper life cycle into the NoteEdit Activity.
- - diff --git a/docs/html/training/notepad/notepad-ex3.jd b/docs/html/training/notepad/notepad-ex3.jd deleted file mode 100644 index 648f9f2d9bb74..0000000000000 --- a/docs/html/training/notepad/notepad-ex3.jd +++ /dev/null @@ -1,367 +0,0 @@ -excludeFromSuggestions=true -page.title=Notepad Exercise 3 -parent.title=Notepad Tutorial -parent.link=index.html -@jd:body - - -In this exercise, you will use life-cycle event callbacks to store and -retrieve application state data. This exercise demonstrates:
-Import Notepadv3 into Eclipse. If you see an error about
-AndroidManifest.xml, or some problems related to an Android zip
-file, right click on the project and select Android Tools >
-Fix Project Properties from the popup menu. The starting point for this exercise is
-exactly where we left off at the end of the Notepadv2.
The current application has some problems — hitting the back button when editing -causes a crash, and anything else that happens during editing will cause the -edits to be lost.
-To fix this, we will move most of the functionality for creating and editing -the note into the NoteEdit class, and introduce a full life cycle for editing -notes.
- -NoteEdit that parses the title and body
- from the extras Bundle.
- Instead, we are going to use the DBHelper class
- to access the notes from the database directly. All we need passed into the
- NoteEdit Activity is a mRowId (but only if we are editing, if creating we pass
- nothing). Remove these lines:
-String title = extras.getString(NotesDbAdapter.KEY_TITLE); -String body = extras.getString(NotesDbAdapter.KEY_BODY);-
extras Bundle, which we were using to set the title
- and body text edit values in the UI. So delete:
-
-if (title != null) {
- mTitleText.setText(title);
-}
-if (body != null) {
- mBodyText.setText(body);
-}
- Create a class field for a NotesDbAdapter at the top of the NoteEdit class:
private NotesDbAdapter mDbHelper;-
Also add an instance of NotesDbAdapter in the
- onCreate() method (right below the super.onCreate() call):
- mDbHelper = new NotesDbAdapter(this);- -
- mDbHelper.open();
In NoteEdit, we need to check the savedInstanceState for the
-mRowId, in case the note
- editing contains a saved state in the Bundle, which we should recover (this would happen
- if our Activity lost focus and then restarted).
mRowId:
- mRowId = null;
-
- Bundle extras = getIntent().getExtras();
- if (extras != null) {
- mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
- }
-
- with this:
-
- mRowId = (savedInstanceState == null) ? null :
- (Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
- if (mRowId == null) {
- Bundle extras = getIntent().getExtras();
- mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
- : null;
- }
-
- savedInstanceState, and we still need to load up
- mRowId from the extras Bundle if it is not
- provided by the savedInstanceState. This is a ternary operator shorthand
- to safely either use the value or null if it is not present.
- Bundle.getSerializable() instead of
- Bundle.getLong(). The latter encoding returns a long primitive and
- so can not be used to represent the case when mRowId is null.
- Next, we need to populate the fields based on the mRowId if we
- have it:
populateFields();-
This goes before the confirmButton.setOnClickListener() line.
- We'll define this method in a moment.
Get rid of the Bundle creation and Bundle value settings from the
- onClick() handler method. The Activity no longer needs to
- return any extra information to the caller. And because we no longer have
- an Intent to return, we'll use the shorter version
- of setResult():
-public void onClick(View view) {
- setResult(RESULT_OK);
- finish();
-}
- We will take care of storing the updates or new notes in the database - ourselves, using the life-cycle methods.
- -The whole onCreate() method should now look like this:
-super.onCreate(savedInstanceState);
-
-mDbHelper = new NotesDbAdapter(this);
-mDbHelper.open();
-
-setContentView(R.layout.note_edit);
-
-mTitleText = (EditText) findViewById(R.id.title);
-mBodyText = (EditText) findViewById(R.id.body);
-
-Button confirmButton = (Button) findViewById(R.id.confirm);
-
-mRowId = (savedInstanceState == null) ? null :
- (Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
-if (mRowId == null) {
- Bundle extras = getIntent().getExtras();
- mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
- : null;
-}
-
-populateFields();
-
-confirmButton.setOnClickListener(new View.OnClickListener() {
-
- public void onClick(View view) {
- setResult(RESULT_OK);
- finish();
- }
-
-});
-
-Define the populateFields() method.
-private void populateFields() {
- if (mRowId != null) {
- Cursor note = mDbHelper.fetchNote(mRowId);
- startManagingCursor(note);
- mTitleText.setText(note.getString(
- note.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE)));
- mBodyText.setText(note.getString(
- note.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY)));
- }
-}
-This method uses the NotesDbAdapter.fetchNote() method to find the right note to
-edit, then it calls startManagingCursor() from the Activity class, which
-is an Android convenience method provided to take care of the Cursor life-cycle. This will release
-and re-create resources as dictated by the Activity life-cycle, so we don't need to worry about
-doing that ourselves. After that, we just look up the title and body values from the Cursor
-and populate the View elements with them.
If you are used to always having control in your applications, you - might not understand why all this life-cycle work is necessary. The reason - is that in Android, you are not in control of your Activity, the - operating system is!
-As we have already seen, the Android model is based around activities - calling each other. When one Activity calls another, the current Activity - is paused at the very least, and may be killed altogether if the - system starts to run low on resources. If this happens, your Activity will - have to store enough state to come back up later, preferably in the same - state it was in when it was killed.
-- Activities have a well-defined life -cycle. - Lifecycle events can happen even if you are not handing off control to - another Activity explicitly. For example, perhaps a call comes in to the - handset. If this happens, and your Activity is running, it will be swapped - out while the call Activity takes over.
-Still in the NoteEdit class, we now override the methods
- onSaveInstanceState(), onPause() and
- onResume(). These are our life-cycle methods
- (along with onCreate() which we already have).
onSaveInstanceState() is called by Android if the
- Activity is being stopped and may be killed before it is
- resumed! This means it should store any state necessary to
- re-initialize to the same condition when the Activity is restarted. It is
- the counterpart to the onCreate() method, and in fact the
- savedInstanceState Bundle passed in to onCreate() is the same
- Bundle that you construct as outState in the
- onSaveInstanceState() method.
onPause() and onResume() are also
- complimentary methods. onPause() is always called when the
- Activity ends, even if we instigated that (with a finish() call for example).
- We will use this to save the current note back to the database. Good
- practice is to release any resources that can be released during an
- onPause() as well, to take up less resources when in the
- passive state. onResume() will call our populateFields() method
- to read the note out of the database again and populate the fields.
So, add some space after the populateFields() method
- and add the following life-cycle methods:
- onSaveInstanceState():
-
- @Override
- protected void onSaveInstanceState(Bundle outState) {
- super.onSaveInstanceState(outState);
- saveState();
- outState.putSerializable(NotesDbAdapter.KEY_ROWID, mRowId);
- }
- We'll define saveState() next.
- onPause():
-
- @Override
- protected void onPause() {
- super.onPause();
- saveState();
- }
-
- onResume():
-
- @Override
- protected void onResume() {
- super.onResume();
- populateFields();
- }
- Note that saveState() must be called in both onSaveInstanceState()
-and onPause() to ensure that the data is saved. This is because there is no
-guarantee that onSaveInstanceState() will be called and because when it is
-called, it is called before onPause().
Define the saveState() method to put the data out to the
-database.
- private void saveState() {
- String title = mTitleText.getText().toString();
- String body = mBodyText.getText().toString();
-
- if (mRowId == null) {
- long id = mDbHelper.createNote(title, body);
- if (id > 0) {
- mRowId = id;
- }
- } else {
- mDbHelper.updateNote(mRowId, title, body);
- }
- }
- Note that we capture the return value from createNote() and if a valid row ID is
- returned, we store it in the mRowId field so that we can update the note in future
- rather than create a new one (which otherwise might happen if the life-cycle events are
- triggered).
Now pull out the previous handling code from the
- onActivityResult() method in the Notepadv3
- class.
All of the note retrieval and updating now happens within the
- NoteEdit life cycle, so all the onActivityResult()
- method needs to do is update its view of the data, no other work is
- necessary. The resulting method should look like this:
-@Override
-protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
- super.onActivityResult(requestCode, resultCode, intent);
- fillData();
-}
-
-Because the other class now does the work, all this has to do is refresh - the data.
- -Also remove the lines which set the title and body from the
- onListItemClick() method (again they are no longer needed,
- only the mRowId is):
- Cursor c = mNotesCursor; - c.moveToPosition(position);-
- i.putExtra(NotesDbAdapter.KEY_TITLE, c.getString( - c.getColumnIndex(NotesDbAdapter.KEY_TITLE))); - i.putExtra(NotesDbAdapter.KEY_BODY, c.getString( - c.getColumnIndex(NotesDbAdapter.KEY_BODY)));-
- super.onListItemClick(l, v, position, id); - Intent i = new Intent(this, NoteEdit.class); - i.putExtra(NotesDbAdapter.KEY_ROWID, id); - startActivityForResult(i, ACTIVITY_EDIT);- -
You can also now remove the mNotesCursor field from the class, and set it back to using
- a local variable in the fillData() method:
-
- Cursor notesCursor = mDbHelper.fetchAllNotes();-
Note that the m in mNotesCursor denotes a member field, so when we
- make notesCursor a local variable, we drop the m. Remember to rename the
- other occurrences of mNotesCursor in your fillData() method.
-
-
-Run it! (use Run As -> Android Application on the project right -click menu again)
- -You can see the solution to this exercise in Notepadv3Solution
-from
-the zip file to compare with your own.
-When you are ready, move on to the Tutorial -Extra Credit exercise, where you can use the Eclipse debugger to -examine the life-cycle events as they happen.
diff --git a/docs/html/training/notepad/notepad-extra-credit.jd b/docs/html/training/notepad/notepad-extra-credit.jd deleted file mode 100644 index 8ab20218788c5..0000000000000 --- a/docs/html/training/notepad/notepad-extra-credit.jd +++ /dev/null @@ -1,71 +0,0 @@ -excludeFromSuggestions=true -page.title=Notepad Extra Credit -parent.title=Notepad Tutorial -parent.link=index.html -@jd:body - - -In this exercise, you will use the debugger to look at the work you did -in Exercise 3. This exercise demonstrates:
-Using the working Notepadv3, put breakpoints in the code at the
- beginning of the onCreate(), onPause(),
- onSaveInstanceState() and onResume() methods in the
- NoteEdit class (if you are not familiar with Eclipse, just
- right click in the narrow grey border on the left of the edit window at the
- line you want a breakpoint, and select Toggle Breakpoint, you
-should see a blue dot appear).
Now start the notepad demo in debug mode:
- -Notepadv3 project and from the Debug menu
- select Debug As -> Android Application.adb kill-server, and then restart
-Eclipse and try again.When you edit or create a new note you should see the breakpoints getting - hit and the execution stopping.
- -Hit the Resume button to let execution continue (yellow rectangle with a -green triangle to its right in the Eclipse toolbars near the top).
- -Experiment a bit with the confirm and back buttons, and try pressing Home and - making other mode changes. Watch what life-cycle events are generated and -when.
- -The Android Eclipse plugin not only offers excellent debugging support for -your application development, but also superb profiling support. You can also -try using Traceview to profile your application. If your application is running too slow, this can help you -find the bottlenecks and fix them.
- diff --git a/docs/html/training/notepad/notepad-index.jd b/docs/html/training/notepad/notepad-index.jd deleted file mode 100644 index fde43fa7db268..0000000000000 --- a/docs/html/training/notepad/notepad-index.jd +++ /dev/null @@ -1,144 +0,0 @@ -excludeFromSuggestions=true -page.title=Notepad Tutorial -@jd:body - - -The tutorial in this section gives you a "hands-on" introduction -to the Android framework and the tools you use to build applications on it. -Starting from a preconfigured project file, it guides you through the process of -developing a simple notepad application and provides concrete examples of how to -set up the project, develop the application logic and user interface, and then -compile and run the application.
- -The tutorial presents the notepad application development as a set of -exercises (see below), each consisting of several steps. You can follow along -with the steps in each exercise and gradually build up and refine your -application. The exercises explain each step in detail and provide all the -sample code you need to complete the application.
- -When you are finished with the tutorial, you will have created a functioning -Android application and learned in depth about many of the most important -concepts in Android development. If you want to add more complex features to -your application, you can examine the code in an alternative implementation -of a notepad application, in the -Sample Code documentation.
- - - -This tutorial is designed for experienced developers, especially those with -knowledge of the Java programming language. If you haven't written Java -applications before, you can still use the tutorial, but you might need to work -at a slower pace.
- -The tutorial assumes that you have some familiarity with the basic Android -application concepts and terminology. If you aren't yet familiar with those, you -should read Overview of an Android -Application before continuing.
- -Also note that this tutorial uses -the Eclipse development environment, with the Android plugin installed. If you -are not using Eclipse, you can follow the exercises and build the application, -but you will need to determine how to accomplish the Eclipse-specific -steps in your environment.
- - -This tutorial builds on the information provided in the Installing the SDK and Hello Android -documents, which explain in detail how to set up your development environment -for building Android applications. Before you start this tutorial, you should -read both these documents, have the SDK installed, and your work environment set up.
- -To prepare for this lesson:
- -NotepadCodeLab folderInside the NotepadCodeLab folder, you should see six project
-files: Notepadv1,
- Notepadv2, Notepadv3,
- Notepadv1Solution, Notepadv2Solution
- and Notepadv3Solution. The Notepadv# projects are
-the starting points for each of the exercises, while the
-Notepadv#Solution projects are the exercise
- solutions. If you are having trouble with a particular exercise, you
- can compare your current work against the exercise solution.
The table below lists the tutorial exercises and describes the development -areas that each covers. Each exercise assumes that you have completed any -previous exercises.
- -| Exercise -1 | -Start here. Construct a simple notes list that lets the user add new notes but not
-edit them. Demonstrates the basics of ListActivity and creating
-and handling
- menu options. Uses a SQLite database to store the notes. |
-
|---|---|
| Exercise 2 | -Add a second Activity to the
-application. Demonstrates constructing a
-new Activity, adding it to the Android manifest, passing data between the
-activities, and using more advanced screen layout. Also shows how to
-invoke another Activity to return a result, using
-startActivityForResult(). |
-
| Exercise 3 | -Add handling of life-cycle events to -the application, to let it -maintain application state across the life cycle. | -
| Extra -Credit | -Demonstrates how to use the Eclipse -debugger and how you can use it to -view life-cycle events as they are generated. This section is optional but -highly recommended. | -
samples/ directory of your downloaded SDK.samples/ directory of the SDK, though it does not match it exactly.
-When you are done with the tutorial,
-it is highly recommended that you take a closer look at this version of the Notepad
-application,
-as it demonstrates a variety of interesting additions for your application,
-such as:draw()
-method to
- make it look like a lined notepad.ContentProvider for notes.