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Merge "Docs: Added contents for Vector Drawables" into nyc-docs

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Hemal Patel
2016-09-26 20:44:15 +00:00
committed by Android (Google) Code Review
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@@ -21,6 +21,7 @@ parent.link=index.html
</li> </li>
<li><a href="#shape-drawable">Shape Drawable</a></li> <li><a href="#shape-drawable">Shape Drawable</a></li>
<li><a href="#nine-patch">Nine-patch</a></li> <li><a href="#nine-patch">Nine-patch</a></li>
<li><a href="#vector-drawable">Vector Drawables</a></li>
</ol> </ol>
<h2>See also</h2> <h2>See also</h2>
@@ -428,58 +429,66 @@ state
of the object it's attached to. of the object it's attached to.
--> -->
<h2 id="nine-patch">Nine-patch</h2> <h2 id="nine-patch">Nine-patch</h2>
<p>A {@link android.graphics.drawable.NinePatchDrawable} graphic is a stretchable bitmap <p>
image, which Android A {@link android.graphics.drawable.NinePatchDrawable} graphic is a
will automatically resize to accommodate the contents of the View in which you have stretchable bitmap image, which Android will automatically resize to
placed it as the background. accommodate the contents of the View in which you have placed it as the
An example use of a NinePatch is the backgrounds used by standard Android buttons &mdash; background. An example use of a NinePatch is the backgrounds used by
buttons must stretch to accommodate strings of various lengths. A NinePatch drawable is a standard Android buttons — buttons must stretch to accommodate strings of
standard PNG various lengths. A NinePatch drawable is a standard PNG image that includes
image that includes an extra 1-pixel-wide border. It must be saved with the extension an extra 1-pixel-wide border. It must be saved with the extension
<code>.9.png</code>, <code>.9.png</code>, and saved into the <code>res/drawable/</code> directory
and saved into the <code>res/drawable/</code> directory of your project. of your project.
</p>
<p>
The border is used to define the stretchable and static areas of
the image. You indicate a stretchable section by drawing one (or more) 1-pixel-wide
black line(s) in the left and top part of the border (the other border pixels should
be fully transparent or white). You can have as many stretchable sections as you want:
their relative size stays the same, so the largest sections always remain the largest.
</p>
<p>
You can also define an optional drawable section of the image (effectively,
the padding lines) by drawing a line on the right and bottom lines.
If a View object sets the NinePatch as its background and then specifies the
View's text, it will stretch itself so that all the text fits inside only
the area designated by the right and bottom lines (if included). If the
padding lines are not included, Android uses the left and top lines to
define this drawable area.
</p>
<p>To clarify the difference between the different lines, the left and top lines define
which pixels of the image are allowed to be replicated in order to stretch the image.
The bottom and right lines define the relative area within the image that the contents
of the View are allowed to lie within.</p>
<p>
Here is a sample NinePatch file used to define a button:
</p>
<img src="{@docRoot}images/ninepatch_raw.png" alt="" />
<p>This NinePatch defines one stretchable area with the left and top lines
and the drawable area with the bottom and right lines. In the top image, the dotted grey
lines identify the regions of the image that will be replicated in order to stretch the
image. The pink
rectangle in the bottom image identifies the region in which the contents of the View are
allowed.
If the contents don't fit in this region, then the image will be stretched so that they
do.
</p> </p>
<p>The <a href="{@docRoot}tools/help/draw9patch.html">Draw 9-patch</a> tool offers <p>
an extremely handy way to create your NinePatch images, using a WYSIWYG graphics editor. It The border is used to define the stretchable and static areas of the image.
even raises warnings if the region you've defined for the stretchable area is at risk of You indicate a stretchable section by drawing one (or more) 1-pixel-wide
producing drawing artifacts as a result of the pixel replication. black line(s) in the left and top part of the border (the other border
pixels should be fully transparent or white). You can have as many
stretchable sections as you want: their relative size stays the same, so the
largest sections always remain the largest.
</p>
<p>
You can also define an optional drawable section of the image (effectively,
the padding lines) by drawing a line on the right and bottom lines. If a
View object sets the NinePatch as its background and then specifies the
View's text, it will stretch itself so that all the text fits inside only
the area designated by the right and bottom lines (if included). If the
padding lines are not included, Android uses the left and top lines to
define this drawable area.
</p>
<p>
To clarify the difference between the different lines, the left and top
lines define which pixels of the image are allowed to be replicated in order
to stretch the image. The bottom and right lines define the relative area
within the image that the contents of the View are allowed to lie within.
</p>
<p>
Here is a sample NinePatch file used to define a button:
</p>
<img src="{@docRoot}images/ninepatch_raw.png" alt="">
<p>
This NinePatch defines one stretchable area with the left and top lines and
the drawable area with the bottom and right lines. In the top image, the
dotted grey lines identify the regions of the image that will be replicated
in order to stretch the image. The pink rectangle in the bottom image
identifies the region in which the contents of the View are allowed. If the
contents don't fit in this region, then the image will be stretched so that
they do.
</p>
<p>
The <a href="{@docRoot}tools/help/draw9patch.html">Draw 9-patch</a> tool
offers an extremely handy way to create your NinePatch images, using a
WYSIWYG graphics editor. It even raises warnings if the region you've
defined for the stretchable area is at risk of producing drawing artifacts
as a result of the pixel replication.
</p> </p>
<h3>Example XML</h3> <h3>Example XML</h3>
@@ -516,3 +525,265 @@ stretches to accommodate it.
</p> </p>
<img src="{@docRoot}images/ninepatch_examples.png" alt=""/> <img src="{@docRoot}images/ninepatch_examples.png" alt=""/>
<h2 id="vector-drawable">
Vector Drawables
</h2>
<p>
A {@link android.graphics.drawable.VectorDrawable} graphic replaces multiple
PNG assets with a single vector graphic. The vector graphic is defined in an
XML file as a set of points, lines, and curves along with its associated
color information.
</p>
<p>
The major advantage of using a vector graphic is image scalability. Using
vector graphics resizes the same file for different screen densities without
loss of image quality. This results in smaller APK files and less developer
maintenance. You can also use vector images for animation by using multiple
XML files instead of multiple images for each display resolution.
</p>
<p>
Let's go through an example to understand the benefits. An image of size 100
x 100 dp may render good quality on a smaller display resolution. On larger
devices, the app might want to use a 400 x 400 dp version of the image.
Normally, developers create multiple versions of an asset to cater to
different screen densities. This approach consumes more development efforts,
and results in a larger APK, which takes more space on the device.
</p>
<p>
As of Android 5.0 (API level 21), there are two classes that support vector
graphics as a drawable resource: {@link
android.graphics.drawable.VectorDrawable} and {@link
android.graphics.drawable.AnimatedVectorDrawable}. For more information
about using the VectorDrawable and the AnimatedVectorDrawable classes, read
the <a href="#vector-drawable-class">About VectorDrawable class</a> and
<a href="#animated-vector-drawable-class">About AnimatedVectorDrawable
class</a> sections.
</p>
<h3 id="vector-drawable-class">About VectorDrawable class</h3>
<p>
{@link android.graphics.drawable.VectorDrawable} defines a static drawable
object. Similar to the SVG format, each vector graphic is defined as a tree
hierachy, which is made up of <code>path</code> and <code>group</code> objects.
Each <code>path</code> contains the geometry of the object's outline and
<code>group</code> contains details for transformation. All paths are drawn
in the same order as they appear in the XML file.
</p>
<img src="{@docRoot}images/guide/topics/graphics/vectorpath.png" alt=""/>
<p class="img-caption">
<strong>Figure 1.</strong> Sample hierarchy of a vector drawable asset
</p>
<p>
The <a href="{@docRoot}studio/write/vector-asset-studio.html">Vector Asset
Studio</a> tool offers a simple way to add a vector graphic to the project
as an XML file.
</p>
<h4>
Example XML
</h4>
<p>
Here is a sample <code>VectorDrawable</code> XML file that renders an image
of a battery in the charging mode.
</p>
<pre>
&lt;!-- res/drawable/battery_charging.xml --&gt;
&lt;vector xmlns:android="http://schemas.android.com/apk/res/android"
&lt;!-- intrinsic size of the drawable --&gt;
android:height="24dp"
android:width="24dp"
&lt;!-- size of the virtual canvas --&gt;
android:viewportWidth="24.0"
android:viewportHeight="24.0"&gt;
&lt;group
android:name="rotationGroup"
android:pivotX="10.0"
android:pivotY="10.0"
android:rotation="15.0" &gt;
&lt;path
android:name="vect"
android:fillColor="#FF000000"
android:pathData="M15.67,4H14V2h-4v2H8.33C7.6,4 7,4.6 7,5.33V9h4.93L13,7v2h4V5.33C17,4.6 16.4,4 15.67,4z"
android:fillAlpha=".3"/&gt;
&lt;path
android:name="draw"
android:fillColor="#FF000000"
android:pathData="M13,12.5h2L11,20v-5.5H9L11.93,9H7v11.67C7,21.4 7.6,22 8.33,22h7.33c0.74,0 1.34,-0.6 1.34,-1.33V9h-4v3.5z"/&gt;
&lt;/group&gt;
&lt;/vector&gt;
</pre>
<p>This XML renders the following image:
</p>
<img src=
"{@docRoot}images/guide/topics/graphics/ic_battery_charging_80_black_24dp.png"
alt=""/>
<h3 id="animated-vector-drawable-class">
About AnimatedVectorDrawable class
</h3>
<p>
{@link android.graphics.drawable.AnimatedVectorDrawable
AnimatedVectorDrawable} adds animation to the properties of a vector
graphic. You can define an animated vector graphic as three separate
resource files or as a single XML file defining the entire drawable. Let's
look at both the approaches for better understanding: <a href=
"#multiple-files">Multiple XML files</a> and <a href="#single-file">Single
XML file</a>.
</p>
<h4 id="multiple-files">
Multiple XML files
</h4>
<p>
By using this approach, you can define three separate XML files:
<ul>
<li>A {@link android.graphics.drawable.VectorDrawable} XML file.
</li>
<li>
An {@link android.graphics.drawable.AnimatedVectorDrawable} XML file that
defines the target {@link android.graphics.drawable.VectorDrawable}, the
target paths and groups to animate, the properties, and the animations defined
as {@link android.animation.ObjectAnimator ObjectAnimator} objects or {@link
android.animation.AnimatorSet AnimatorSet} objects.
</li>
<li>An animator XML file.
</li>
</ul>
</p>
<h5>
Example of multiple XML files
</h5>
<p>
The following XML files demonstrate the animation of a vector graphic.
<ul>
<li>VectorDrawable's XML file: <code>vd.xml</code>
</li>
<li style="list-style: none; display: inline">
<pre>
&lt;vector xmlns:android="http://schemas.android.com/apk/res/android"
android:height="64dp"
android:width="64dp"
android:viewportHeight="600"
android:viewportWidth="600" &gt;
&lt;group
android:name="rotationGroup"
android:pivotX="300.0"
android:pivotY="300.0"
android:rotation="45.0" &gt;
&lt;path
android:name="vectorPath"
android:fillColor="#000000"
android:pathData="M300,70 l 0,-70 70,70 0,0 -70,70z" /&gt;
&lt;/group&gt;
&lt;/vector&gt;
</pre>
</li>
<li>AnimatedVectorDrawable's XML file: <code>avd.xml</code>
</li>
<li style="list-style: none; display: inline">
<pre>
&lt;animated-vector xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/vd" &gt;
&lt;target
android:name="rotationGroup"
android:animation="@anim/rotation" /&gt;
&lt;target
android:name="vectorPath"
android:animation="@anim/path_morph" /&gt;
&lt;/animated-vector&gt;
</pre>
</li>
<li>Animator XML files that are used in the AnimatedVectorDrawable's XML
file: <code>rotation.xml</code> and <code>path_morph.xml</code>
</li>
<li style="list-style: none; display: inline">
<pre>
&lt;objectAnimator
android:duration="6000"
android:propertyName="rotation"
android:valueFrom="0"
android:valueTo="360" /&gt;
</pre>
<pre>
&lt;set xmlns:android="http://schemas.android.com/apk/res/android"&gt;
&lt;objectAnimator
android:duration="3000"
android:propertyName="pathData"
android:valueFrom="M300,70 l 0,-70 70,70 0,0 -70,70z"
android:valueTo="M300,70 l 0,-70 70,0 0,140 -70,0 z"
android:valueType="pathType"/&gt;
&lt;/set&gt;
</pre>
</li>
</ul>
</p>
<h4 id="single-file">
Single XML file
</h4>
<p>
By using this approach, you can merge the related XML files into a single
XML file through the XML Bundle Format. At the time of building the app, the
<code>aapt</code> tag creates separate resources and references them in the
animated vector. This approach requires Build Tools 24 or higher, and the
output is backward compatible.
</p>
<h5>
Example of a single XML file
</h5>
<pre>
&lt;animated-vector
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:aapt="http://schemas.android.com/aapt"&gt;
&lt;aapt:attr name="android:drawable"&gt;
&lt;vector
android:width="24dp"
android:height="24dp"
android:viewportWidth="24"
android:viewportHeight="24"&gt;
&lt;path
android:name="root"
android:strokeWidth="2"
android:strokeLineCap="square"
android:strokeColor="?android:colorControlNormal"
android:pathData="M4.8,13.4 L9,17.6 M10.4,16.2 L19.6,7" /&gt;
&lt;/vector&gt;
&lt;/aapt:attr&gt;
&lt;target android:name="root"&gt;
&lt;aapt:attr name="android:animation"&gt;
&lt;objectAnimator
android:propertyName="pathData"
android:valueFrom="M4.8,13.4 L9,17.6 M10.4,16.2 L19.6,7"
android:valueTo="M6.4,6.4 L17.6,17.6 M6.4,17.6 L17.6,6.4"
android:duration="300"
android:interpolator="@android:interpolator/fast_out_slow_in"
android:valueType="pathType" /&gt;
&lt;/aapt:attr&gt;
&lt;/target&gt;
&lt;/animated-vector&gt;
</pre>

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