From 2e1c7b7495f2317ba30ae809b4964fdafcf504ce Mon Sep 17 00:00:00 2001 From: Joe Malin Date: Fri, 30 Aug 2013 15:30:54 -0700 Subject: [PATCH] DOC CHANGE: Android Beam training class Change-Id: I4960d2b0ef8fdd32cf985f2104b0819e1311337b --- docs/html/training/beam-files/index.jd | 61 ++++ .../html/training/beam-files/receive-files.jd | 313 ++++++++++++++++++ docs/html/training/beam-files/send-files.jd | 294 ++++++++++++++++ docs/html/training/training_toc.cs | 20 +- 4 files changed, 685 insertions(+), 3 deletions(-) create mode 100644 docs/html/training/beam-files/index.jd create mode 100644 docs/html/training/beam-files/receive-files.jd create mode 100644 docs/html/training/beam-files/send-files.jd diff --git a/docs/html/training/beam-files/index.jd b/docs/html/training/beam-files/index.jd new file mode 100644 index 0000000000000..71550924a8f8d --- /dev/null +++ b/docs/html/training/beam-files/index.jd @@ -0,0 +1,61 @@ +page.title=Sharing Files with NFC + +trainingnavtop=true +startpage=true + + +@jd:body + +
+
+ +

Dependencies and prerequisites

+
    +
  • Android 4.1 (API Level 16) or higher
    • +
  • At least two NFC-enabled Android devices (NFC is not supported in the emulator)
    • +
+ +

You should also read

+ + +
+
+ +

+ Android allows you to transfer large files between devices using the Android Beam file transfer + feature. This feature has a simple API and allows users to start the transfer process by simply + touching devices. In response, Android Beam file transfer automatically copies files from one + device to the other and notifies the user when it's finished. +

+

+ While the Android Beam file transfer API handles large amounts of data, the Android Beam NDEF + transfer API introduced in Android 4.0 (API level 14) handles small amounts of data such as + URIs or other small messages. In addition, Android Beam is only one of the features available + in the Android NFC framework, which allows you to read NDEF messages from NFC tags. To learn + more about Android Beam, see the topic + Beaming NDEF Messages to Other Devices. To learn more about the NFC framework, see the + Near Field Communication API guide. +

+

Lessons

+
+
+ Sending Files to Another Device +
+
Learn how to set up your app to send files to another device.
+ +
+ Receiving Files from Another Device +
+
+ Learn how to set up your app to receive files sent by another device. +
+
+ + diff --git a/docs/html/training/beam-files/receive-files.jd b/docs/html/training/beam-files/receive-files.jd new file mode 100644 index 0000000000000..06136125e8a61 --- /dev/null +++ b/docs/html/training/beam-files/receive-files.jd @@ -0,0 +1,313 @@ +page.title=Receiving Files from Another Device + +trainingnavtop=true +@jd:body + +
+ +
+ +

+ Android Beam file transfer copies files to a special directory on the receiving device. It also + scans the copied files using the Android Media Scanner and adds entries for media files to + the {@link android.provider.MediaStore} provider. This lesson shows you how to respond when the + file copy is complete, and how to locate the copied files on the receiving device. +

+

Respond to a Request to Display Data

+

+ When Android Beam file transfer finishes copying files to the receiving device, it posts a + notification containing an {@link android.content.Intent} with the action + {@link android.content.Intent#ACTION_VIEW ACTION_VIEW}, the MIME type of the first file that + was transferred, and a URI that points to the first file. When the user clicks the notification, + this intent is sent out to the system. To have your app respond to this intent, add an + <intent-filter> element for the + <activity> element of the {@link android.app.Activity} that should respond. + In the <intent-filter> element, add the following child elements: +

+
+
+ <action android:name="android.intent.action.VIEW" /> +
+
+ Matches the {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent sent from the + notification. +
+
+ <category android:name="android.intent.category.CATEGORY_DEFAULT" /> +
+
+ Matches an {@link android.content.Intent} that doesn't have an explicit category. +
+
+ <data android:mimeType="mime-type" /> +
+
+ Matches a MIME type. Specify only those MIME types that your app can handle. +
+
+

+ For example, the following snippet shows you how to add an intent filter that + triggers the activity com.example.android.nfctransfer.ViewActivity: +

+
+    <activity
+        android:name="com.example.android.nfctransfer.ViewActivity"
+        android:label="Android Beam Viewer" >
+        ...
+        <intent-filter>
+            <action android:name="android.intent.action.VIEW"/>
+            <category android:name="android.intent.category.DEFAULT"/>
+            ...
+        </intent-filter>
+    </activity>
+
+

+ Note: Android Beam file transfer is not the only source of an + {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent. Other apps on the receiving + device can also send an {@link android.content.Intent} with this action. + Handling this situation is discussed in the section Get the directory from a content URI. +

+

Request File Permissions

+

+ To read files that Android Beam file transfer copies to the device, request the permission + {@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE}. For example: +

+
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
+

+ If you want to copy transferred files to your app's own storage area, request the permission + {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE WRITE_EXTERNAL_STORAGE} instead. + {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE WRITE_EXTERNAL_STORAGE} includes + {@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE}. +

+

+ Note: As of Android 4.2.2 (API level 17), the permission + {@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE} is + only enforced if the user chooses to do so. Future versions of the platform may require this + permission in all cases. To ensure forward compatibility, request the permission now, before it + becomes required. +

+

+ Since your app has control over its internal storage area, you don't need to request + write permission to copy a transferred file to your internal storage area. +

+

Get the Directory for Copied Files

+

+ Android Beam file transfer copies all the files in a single transfer to one directory + on the receiving device. The URI in the content {@link android.content.Intent} sent by the + Android Beam file transfer notification points to the first transferred file. However, your + app may also receive an {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent from a + source other than Android Beam file transfer. To determine how you should handle the incoming + {@link android.content.Intent}, you need to examine its scheme and authority. +

+

+ To get the scheme for the URI, call {@link android.net.Uri#getScheme() Uri.getScheme()}. The + following code snippet shows you how to determine the scheme and handle the URI accordingly: +

+
+public class MainActivity extends Activity {
+    ...
+    // A File object containing the path to the transferred files
+    private File mParentPath;
+    // Incoming Intent
+    private Intent mIntent;
+    ...
+    /*
+     * Called from onNewIntent() for a SINGLE_TOP Activity
+     * or onCreate() for a new Activity. For onNewIntent(),
+     * remember to call setIntent() to store the most
+     * current Intent
+     *
+     */
+    private void handleViewIntent() {
+        ...
+        // Get the Intent action
+        mIntent = getIntent();
+        String action = mIntent.getAction();
+        /*
+         * For ACTION_VIEW, the Activity is being asked to display data.
+         * Get the URI.
+         */
+        if (TextUtils.equals(action, Intent.ACTION_VIEW)) {
+            // Get the URI from the Intent
+            Uri beamUri = mIntent.getData();
+            /*
+             * Test for the type of URI, by getting its scheme value
+             */
+            if (TextUtils.equals(beamUri.getScheme(), "file")) {
+                mParentPath = handleFileUri(beamUri);
+            } else if (TextUtils.equals(
+                    beamUri.getScheme(), "content")) {
+                mParentPath = handleContentUri(beamUri);
+            }
+        }
+        ...
+    }
+    ...
+}
+
+

Get the directory from a file URI

+

+ If the incoming {@link android.content.Intent} contains a file URI, the URI contains the + absolute file name of a file, including the full directory path and file name. For Android Beam + file transfer, the directory path points to the location of the other transferred files, if + any. To get the directory path, get the path part of the URI, which contains all of the URI + except the file: prefix. Create a {@link java.io.File} from the path part, then + get the parent path of the {@link java.io.File}: +

+
+    ...
+    public String handleFileUri(Uri beamUri) {
+        // Get the path part of the URI
+        String fileName = beamUri.getPath();
+        // Create a File object for this filename
+        File copiedFile = new File(fileName);
+        // Get a string containing the file's parent directory
+        return copiedFile.getParent();
+    }
+    ...
+
+ +

Get the directory from a content URI

+

+ If the incoming {@link android.content.Intent} contains a content URI, the URI may point to a + directory and file name stored in the {@link android.provider.MediaStore} content provider. You + can detect a content URI for {@link android.provider.MediaStore} by testing the URI's + authority value. A content URI for {@link android.provider.MediaStore} may come from + Android Beam file transfer or from another app, but in both cases you can retrieve a directory + and file name for the content URI. +

+

+ You can also receive an incoming {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} + intent containing a content URI for a content provider other than + {@link android.provider.MediaStore}. In this case, the content URI doesn't contain the + {@link android.provider.MediaStore} authority value, and the content URI usually doesn't point + to a directory. +

+

+ Note: For Android Beam file transfer, you receive a content URI in the + {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent if the first incoming file + has a MIME type of "audio/*", "image/*", or "video/*", indicating that the file is media- + related. Android Beam file transfer indexes the media files it transfers by running Media + Scanner on the directory where it stores transferred files. Media Scanner writes its results + to the {@link android.provider.MediaStore} content provider, then it passes a content URI + for the first file back to Android Beam file transfer. This content URI is the one you + receive in the notification {@link android.content.Intent}. To get the directory + of the first file, you retrieve it from {@link android.provider.MediaStore} using the content + URI. +

+

Determine the content provider

+

+ To determine if you can retrieve a file directory from the content URI, determine the + the content provider associated with the URI by calling + {@link android.net.Uri#getAuthority Uri.getAuthority()} to get the URI's authority. The + result has two possible values: +

+
+
+ {@link android.provider.MediaStore#AUTHORITY MediaStore.AUTHORITY} +
+
+ The URI is for a file or files tracked by {@link android.provider.MediaStore}. Retrieve the + full file name from {@link android.provider.MediaStore}, and get directory from the file + name. +
+
+ Any other authority value +
+
+ A content URI from another content provider. Display the data associated with the content + URI, but don't get the file directory. +
+
+

+ To get the directory for a {@link android.provider.MediaStore} content URI, + run a query that specifies the incoming content URI for the {@link android.net.Uri} argument and + the column {@link android.provider.MediaStore.MediaColumns#DATA MediaColumns.DATA} for the + projection. The returned {@link android.database.Cursor} contains the full path and name for + the file represented by the URI. This path also contains all the other files that Android Beam + file transfer just copied to the device. +

+

+ The following snippet shows you how to test the authority of the content URI and retrieve the + the path and file name for the transferred file: +

+
+    ...
+    public String handleContentUri(Uri beamUri) {
+        // Position of the filename in the query Cursor
+        int filenameIndex;
+        // File object for the filename
+        File copiedFile;
+        // The filename stored in MediaStore
+        String fileName;
+        // Test the authority of the URI
+        if (!TextUtils.equals(beamUri.getAuthority(), MediaStore.AUTHORITY)) {
+            /*
+             * Handle content URIs for other content providers
+             */
+        // For a MediaStore content URI
+        } else {
+            // Get the column that contains the file name
+            String[] projection = { MediaStore.MediaColumns.DATA };
+            Cursor pathCursor =
+                    getContentResolver().query(beamUri, projection,
+                    null, null, null);
+            // Check for a valid cursor
+            if (pathCursor != null &&
+                    pathCursor.moveToFirst()) {
+                // Get the column index in the Cursor
+                filenameIndex = pathCursor.getColumnIndex(
+                        MediaStore.MediaColumns.DATA);
+                // Get the full file name including path
+                fileName = pathCursor.getString(filenameIndex);
+                // Create a File object for the filename
+                copiedFile = new File(fileName);
+                // Return the parent directory of the file
+                return new File(copiedFile.getParent());
+             } else {
+                // The query didn't work; return null
+                return null;
+             }
+        }
+    }
+    ...
+
+

+ To learn more about retrieving data from a content provider, see the section + Retrieving Data from the Provider. +

diff --git a/docs/html/training/beam-files/send-files.jd b/docs/html/training/beam-files/send-files.jd new file mode 100644 index 0000000000000..917b87f11594f --- /dev/null +++ b/docs/html/training/beam-files/send-files.jd @@ -0,0 +1,294 @@ +page.title=Sending Files to Another Device + +trainingnavtop=true +@jd:body + + +
+ +
+

+ This lesson shows you how to design your app to send large files to another device using + Android Beam file transfer. To send files, you request permission to use NFC and external + storage, test to ensure your device supports NFC, and provide URIs to Android Beam file + transfer. +

+

+ The Android Beam file transfer feature has the following requirements: +

+
    +
  1. + Android Beam file transfer for large files is only available in Android 4.1 (API level 16) + and higher. +
    2. +
  2. + Files you want to transfer must reside in external storage. To learn more about using + external storage, read Using the External Storage. +
    3. +
  3. + Each file you want to transfer must be world-readable. You can set this permission by + calling the method {@link java.io.File#setReadable File.setReadable(true,false)}. +
    4. +
  4. + You must provide a file URI for the files you want to transfer. Android Beam file transfer + is unable to handle content URIs generated by + {@link android.support.v4.content.FileProvider#getUriForFile FileProvider.getUriForFile}. +
    5. +
+ +

Declare Features in the Manifest

+

+ First, edit your app manifest to declare the permissions and features your app needs. +

+

Request Permissions

+

+ To allow your app to use Android Beam file transfer to send files from external storage using + NFC, you must request the following permissions in your app manifest: +

+
+
+ {@link android.Manifest.permission#NFC NFC} +
+
+ Allows your app to send data over NFC. To specify this permission, add the following element + as a child of the <manifest> element: +
+    <uses-permission android:name="android.permission.NFC" />
+
+
+
+ {@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE} +
+
+ Allows your app to read from external storage. To specify this permission, add the following + element as a child of the + <manifest> element: +
+    <uses-permission
+            android:name="android.permission.READ_EXTERNAL_STORAGE" />
+
+

+ Note: As of Android 4.2.2 (API level 17), this permission is not + enforced. Future versions of the platform may require it for apps that want to read from + external storage. To ensure forward compatibility, request the permission now, before it + becomes required. +

+
+
+

Specify the NFC feature

+

+ Specify that your app uses NFC, by adding a + <uses-feature> element as a child + of the <manifest> element. Set the android:required attribute to + true to indicate that your app won't function unless NFC is present. +

+

+ The following snippet shows you how to specify the + <uses-feature> element: +

+
+<uses-feature
+    android:name="android.hardware.nfc"
+    android:required="true" />
+

+ Note that if your app only uses NFC as an option, but still functions if NFC isn't present, you + should set android:required to false, and test for NFC in code. +

+

Specify Android Beam file transfer

+

+ Since Android Beam file transfer is only available in Android 4.1 (API level 16) and later, + if your app depends on Android Beam file transfer for a key part of its functionality you must + specify the <uses-sdk> element with the + android:minSdkVersion="16" attribute. Otherwise, you can set + android:minSdkVersion to another value as necessary, and test for the platform + version in code, as described in the following section. +

+

Test for Android Beam File Transfer Support

+

+ To specify in your app manifest that NFC is optional, you use the following element: +

+
+<uses-feature android:name="android.hardware.nfc" android:required="false" />
+

+ If you set the attribute + android:required="false", you must test for NFC support and Android Beam file + transfer support in code. +

+

+ To test for Android Beam file transfer support in code, start by testing that the device + supports NFC by calling {@link android.content.pm.PackageManager#hasSystemFeature + PackageManager.hasSystemFeature()} with the argument + {@link android.content.pm.PackageManager#FEATURE_NFC FEATURE_NFC}. Next, check that the Android + version supports Android Beam file transfer by testing the value of + {@link android.os.Build.VERSION#SDK_INT}. If Android Beam file transfer is supported, get an + instance of the NFC controller, which allows you to communicate with the NFC hardware. + For example: +

+
+public class MainActivity extends Activity {
+    ...
+    NfcAdapter mNfcAdapter;
+    // Flag to indicate that Android Beam is available
+    boolean mAndroidBeamAvailable  = false;
+    ...
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        ...
+        // NFC isn't available on the device
+        if (!PackageManager.hasSystemFeature(PackageManager.FEATURE_NFC)) {
+            /*
+             * Disable NFC features here.
+             * For example, disable menu items or buttons that activate
+             * NFC-related features
+             */
+            ...
+        // Android Beam file transfer isn't supported
+        } else if (Build.VERSION.SDK_INT <
+                Build.VERSION_CODES.JELLY_BEAN_MR1) {
+            // If Android Beam isn't available, don't continue.
+            mAndroidBeamAvailable = false;
+            /*
+             * Disable Android Beam file transfer features here.
+             */
+            ...
+        // Android Beam file transfer is available, continue
+        } else {
+        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
+        ...
+        }
+    }
+    ...
+}
+ +

+ Create a Callback Method that Provides Files +

+

+ Once you've verified that the device supports Android Beam file transfer, add a callback + method that the system invokes when Android Beam file transfer detects that the user wants + to send files to another NFC-enabled device. In this callback method, return an array of + {@link android.net.Uri} objects. Android Beam file transfer copies the files represented by + these URIs to the receiving device. +

+

+ To add the callback method, implement the + {@link android.nfc.NfcAdapter.CreateBeamUrisCallback} interface and its method + {@link android.nfc.NfcAdapter.CreateBeamUrisCallback#createBeamUris createBeamUris()}. The + following snippet shows you how to do this: +

+
+public class MainActivity extends Activity {
+    ...
+    // List of URIs to provide to Android Beam
+    private Uri[] mFileUris = new Uri[10];
+    ...
+    /**
+     * Callback that Android Beam file transfer calls to get
+     * files to share
+     */
+    private class FileUriCallback implements
+            NfcAdapter.CreateBeamUrisCallback {
+        public FileUriCallback() {
+        }
+        /**
+         * Create content URIs as needed to share with another device
+         */
+        @Override
+        public Uri[] createBeamUris(NfcEvent event) {
+            return mFileUris;
+        }
+    }
+    ...
+}
+
+

+ Once you've implemented the interface, provide the callback to Android Beam file transfer by + calling {@link android.nfc.NfcAdapter#setBeamPushUrisCallback setBeamPushUrisCallback()}. The + following snippet shows you how to do this: +

+
+public class MainActivity extends Activity {
+    ...
+    // Instance that returns available files from this app
+    private FileUriCallback mFileUriCallback;
+    ...
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        ...
+        // Android Beam file transfer is available, continue
+        ...
+        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
+        /*
+         * Instantiate a new FileUriCallback to handle requests for
+         * URIs
+         */
+        mFileUriCallback = new FileUriCallback();
+        // Set the dynamic callback for URI requests.
+        mNfcAdapter.setBeamPushUrisCallback(mFileUriCallback,this);
+        ...
+    }
+    ...
+}
+
+

+ Note: You can also provide the array of {@link android.net.Uri} objects + directly to the NFC framework through your app's {@link android.nfc.NfcAdapter} instance. Choose + this approach if you can define the URIs to transfer before the NFC touch event occurs. + To learn more about this approach, see {@link android.nfc.NfcAdapter#setBeamPushUris + NfcAdapter.setBeamPushUris()}. +

+

Specify the Files to Send

+

+ To transfer one or more files to another NFC-enabled device, get a file URI (a URI with a + file scheme) for each file and then add the URI to an array of + {@link android.net.Uri} objects. To transfer a file, you must also have permanent read access + for the file. For example, the following snippet shows you how to get a file URI from a file + name and then add the URI to the array: +

+
+        /*
+         * Create a list of URIs, get a File,
+         * and set its permissions
+         */
+        private Uri[] mFileUris = new Uri[10];
+        String transferFile = "transferimage.jpg";
+        File extDir = getExternalFilesDir(null);
+        File requestFile = new File(extDir, transferFile);
+        requestFile.setReadable(true, false);
+        // Get a URI for the File and add it to the list of URIs
+        fileUri = Uri.fromFile(requestFile);
+        if (fileUri != null) {
+            mFileUris[0] = fileUri;
+        } else {
+            Log.e("My Activity", "No File URI available for file.");
+        }
+
diff --git a/docs/html/training/training_toc.cs b/docs/html/training/training_toc.cs index 77ac235e88601..27e7004cadba7 100644 --- a/docs/html/training/training_toc.cs +++ b/docs/html/training/training_toc.cs @@ -423,7 +423,22 @@ include the action bar on devices running Android 2.1 or higher." - +
  • +
    + Sharing Files with NFC +
    + +
  • Resolving Cloud Save Conflicts -
    • +
  • @@ -1181,7 +1196,6 @@ include the action bar on devices running Android 2.1 or higher."