1page.title=View Animation
2parent.title=Animation
3parent.link=animation.html
4@jd:body
5
6
7
8  <p>You can use the view animation system to perform tweened animation on Views. Tween animation
9  calculates the animation with information such as the start point, end point, size, rotation, and
10  other common aspects of an animation.
11  </p>
12
13  <p>A tween animation can perform a series of simple transformations (position, size, rotation,
14  and transparency) on the contents of a View object. So, if you have a {@link
15  android.widget.TextView} object, you can move, rotate, grow, or shrink the text. If it has a
16  background image, the background image will be transformed along with the text. The {@link
17  android.view.animation animation package} provides all the classes used in a tween animation.</p>
18
19  <p>A sequence of animation instructions defines the tween animation, defined by either XML or
20  Android code. As with defining a layout, an XML file is recommended because it's more readable,
21  reusable, and swappable than hard-coding the animation. In the example below, we use XML. (To
22  learn more about defining an animation in your application code, instead of XML, refer to the
23  {@link android.view.animation.AnimationSet} class and other {@link
24  android.view.animation.Animation} subclasses.)</p>
25
26  <p>The animation instructions define the transformations that you want to occur, when they will
27  occur, and how long they should take to apply. Transformations can be sequential or simultaneous
28  - for example, you can have the contents of a TextView move from left to right, and then rotate
29  180 degrees, or you can have the text move and rotate simultaneously. Each transformation takes a
30  set of parameters specific for that transformation (starting size and ending size for size
31  change, starting angle and ending angle for rotation, and so on), and also a set of common
32  parameters (for instance, start time and duration). To make several transformations happen
33  simultaneously, give them the same start time; to make them sequential, calculate the start time
34  plus the duration of the preceding transformation.</p>
35
36  <p>The animation XML file belongs in the <code>res/anim/</code> directory of your Android
37  project. The file must have a single root element: this will be either a single
38  <code>&lt;alpha&gt;</code>, <code>&lt;scale&gt;</code>, <code>&lt;translate&gt;</code>,
39  <code>&lt;rotate&gt;</code>, interpolator element, or <code>&lt;set&gt;</code> element that holds
40  groups of these elements (which may include another <code>&lt;set&gt;</code>). By default, all
41  animation instructions are applied simultaneously. To make them occur sequentially, you must
42  specify the <code>startOffset</code> attribute, as shown in the example below.</p>
43
44  <p>The following XML from one of the ApiDemos is used to stretch, then simultaneously spin and
45  rotate a View object.</p>
46  <pre>
47&lt;set android:shareInterpolator="false"&gt;
48    &lt;scale
49        android:interpolator="@android:anim/accelerate_decelerate_interpolator"
50        android:fromXScale="1.0"
51        android:toXScale="1.4"
52        android:fromYScale="1.0"
53        android:toYScale="0.6"
54        android:pivotX="50%"
55        android:pivotY="50%"
56        android:fillAfter="false"
57        android:duration="700" /&gt;
58    &lt;set android:interpolator="@android:anim/decelerate_interpolator"&gt;
59        &lt;scale
60           android:fromXScale="1.4"
61           android:toXScale="0.0"
62           android:fromYScale="0.6"
63           android:toYScale="0.0"
64           android:pivotX="50%"
65           android:pivotY="50%"
66           android:startOffset="700"
67           android:duration="400"
68           android:fillBefore="false" /&gt;
69        &lt;rotate
70           android:fromDegrees="0"
71           android:toDegrees="-45"
72           android:toYScale="0.0"
73           android:pivotX="50%"
74           android:pivotY="50%"
75           android:startOffset="700"
76           android:duration="400" /&gt;
77    &lt;/set&gt;
78&lt;/set&gt;
79</pre>
80
81  <p>Screen coordinates (not used in this example) are (0,0) at the upper left hand corner, and
82  increase as you go down and to the right.</p>
83
84  <p>Some values, such as pivotX, can be specified relative to the object itself or relative to the
85  parent. Be sure to use the proper format for what you want ("50" for 50% relative to the parent,
86  or "50%" for 50% relative to itself).</p>
87
88  <p>You can determine how a transformation is applied over time by assigning an {@link
89  android.view.animation.Interpolator}. Android includes several Interpolator subclasses that
90  specify various speed curves: for instance, {@link android.view.animation.AccelerateInterpolator}
91  tells a transformation to start slow and speed up. Each one has an attribute value that can be
92  applied in the XML.</p>
93
94  <p>With this XML saved as <code>hyperspace_jump.xml</code> in the <code>res/anim/</code>
95  directory of the project, the following code will reference it and apply it to an {@link
96  android.widget.ImageView} object from the layout.</p>
97  <pre>
98ImageView spaceshipImage = (ImageView) findViewById(R.id.spaceshipImage);
99Animation hyperspaceJumpAnimation = AnimationUtils.loadAnimation(this, R.anim.hyperspace_jump);
100spaceshipImage.startAnimation(hyperspaceJumpAnimation);
101</pre>
102
103  <p>As an alternative to <code>startAnimation()</code>, you can define a starting time for the
104  animation with <code>{@link android.view.animation.Animation#setStartTime(long)
105  Animation.setStartTime()}</code>, then assign the animation to the View with <code>{@link
106  android.view.View#setAnimation(android.view.animation.Animation) View.setAnimation()}</code>.</p>
107
108  <p>For more information on the XML syntax, available tags and attributes, see <a href=
109  "{@docRoot}guide/topics/resources/animation-resource.html">Animation Resources</a>.</p>
110
111  <p class="note"><strong>Note:</strong> Regardless of how your animation may move or resize, the
112  bounds of the View that holds your animation will not automatically adjust to accommodate it.
113  Even so, the animation will still be drawn beyond the bounds of its View and will not be clipped.
114  However, clipping <em>will occur</em> if the animation exceeds the bounds of the parent View.</p>
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