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Android ApiDemos示例解析(3): App->Activity->Animation

App->Activity->Animation 示例用于演示不同Activity切换时动态效果。例子中定义了两种动画效果,渐变Fade In, 新出现的Activity由浅入深逐渐显示,放大效果Zoom ,新出现的Activity由小及大逐渐显示。

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Android 中 Animation 资源可以分为两种:

Tween Animation 对单个图像进行各种变换(缩放,平移,旋转等)来实现动画。
Frame Animation 由一组图像顺序显示显示动画。
Animation 中使用的是Tween Animation, 使用的资源为R.anim.fade, R.anim.hold,R.anim.zoom_enter, R.anim.zoom_exit。

其中R.anim.fade, R.anim.zoom_enter分别为Fade In 和 Zoom动画资源。其定义为

fade.xml

[html] 
<alpha xmlns:android=”http://schemas.android.com/apk/res/android” 
 android:interpolator=”@android:anim/accelerate_interpolator” 
 android:fromAlpha=”0.0″ android:toAlpha=”1.0″ 
 android:duration=”@android:integer/config_longAnimTime” /> 
<alpha xmlns:android=”http://schemas.android.com/apk/res/android”
 android:interpolator=”@android:anim/accelerate_interpolator”
 android:fromAlpha=”0.0″ android:toAlpha=”1.0″
 android:duration=”@android:integer/config_longAnimTime” />

 

zoom_center.xml

[html]
<set xmlns:android=”http://schemas.android.com/apk/res/android” 
 android:interpolator=”@android:anim/decelerate_interpolator”> 
 <scale android:fromXScale=”2.0″ android:toXScale=”1.0″ 
 android:fromYScale=”2.0″ android:toYScale=”1.0″ 
 android:pivotX=”50%p” android:pivotY=”50%p” 
 android:duration=”@android:integer/config_mediumAnimTime” /> 
 </set> 
<set xmlns:android=”http://schemas.android.com/apk/res/android”
 android:interpolator=”@android:anim/decelerate_interpolator”>
 <scale android:fromXScale=”2.0″ android:toXScale=”1.0″
 android:fromYScale=”2.0″ android:toYScale=”1.0″
 android:pivotX=”50%p” android:pivotY=”50%p”
 android:duration=”@android:integer/config_mediumAnimTime” />
 </set>

 

tween animation 资源定义的格式如下:

[html]
<?xml version=”1.0″ encoding=”utf-8″?> 
 <set xmlns:android=”http://schemas.android.com/apk/res/android” 
 android:interpolator=”@[package:]anim/interpolator_resource” 
 android:shareInterpolator=[ ” true ” false “> 
 <alpha 
 android:fromAlpha=”float” 
 android:toAlpha=”float” /> 
 <scale 
 android:fromXScale=”float” 
 android:toXScale=”float” 
 android:fromYScale=”float” 
 android:toYScale=”float” 
 android:pivotX=”float” 
 android:pivotY=”float” /> 
 <translate 
 android:fromXDelta=”float” 
 android:toXDelta=”float” 
 android:fromYDelta=”float” 
 android:toYDelta=”float” /> 
 <rotate 
 android:fromDegrees=”float” 
 android:toDegrees=”float” 
 android:pivotX=”float” 
 android:pivotY=”float” /> 
 <set> … 
 </set> 
 </set> 
<?xml version=”1.0″ encoding=”utf-8″?>
 <set xmlns:android=”http://schemas.android.com/apk/res/android”
 android:interpolator=”@[package:]anim/interpolator_resource”
 android:shareInterpolator=[ ” true ” false “>
 <alpha
 android:fromAlpha=”float”
 android:toAlpha=”float” />
 <scale
 android:fromXScale=”float”
 android:toXScale=”float”
 android:fromYScale=”float”
 android:toYScale=”float”
 android:pivotX=”float”
 android:pivotY=”float” />
 <translate
 android:fromXDelta=”float”
 android:toXDelta=”float”
 android:fromYDelta=”float”
 android:toYDelta=”float” />
 <rotate
 android:fromDegrees=”float”
 android:toDegrees=”float”
 android:pivotX=”float”
 android:pivotY=”float” />
 <set> …
 </set>
 </set>

 

<set> 为其它animation类型<alpha>,<scale>,<translate>和<rotate>或其它<set>的容器。

android:interpolator 为Interpolator资源ID,Interpolator定义了动画的变化速率,动画的各帧的显示可以加速,减速,重复显示。

android:shareInterpolator 如果想为<set>中的各个子动画定义共享interpolator,shareInterpolator 则设为true.

<alpha> 定义Fade in ,Fade out 动画,其对应的Android类AlphaAnimation,参数由fromAlpha,toAlpha定义。

<scale>定义缩放动画,其对应的Android类为ScaleAnimation,参数由fromXScale,toXScale,fromYScale,toYScale,pivotX,pivotY定义,pivotX,pivotY定义了缩放时的中心。

<translate>定义平移动画,其对应的Android类为TranslateAnimation,参数由fromXDelta,toXDelta,fromYDelta,toYDelta定义。

<rotate>定义选择动画,其对应的Android类RotateAnimation,参数由fromDegrees,toDegrees,pivotX,pivotY, pivotX,pivotY定义选择中心。

Animation中的Fade In和Zoom In按钮的事件处理代码:

[java] 
private OnClickListener mFadeListener = new OnClickListener() { 
 public void onClick(View v) { 
 // Request the next activity transition (here starting a new one).  
 startActivity(new Intent(Animation.this, Controls1.class)); 
 // Supply a custom animation.  This one will just fade the new  
 // activity on top.  Note that we need to also supply an animation  
 // (here just doing nothing for the same amount of time) for the  
 // old activity to prevent it from going away too soon.  
 overridePendingTransition(R.anim.fade, R.anim.hold); 
 } 
};</p> 
<p>private OnClickListener mZoomListener = new OnClickListener() { 
 public void onClick(View v) { 
 // Request the next activity transition (here starting a new one).  
 startActivity(new Intent(Animation.this, Controls1.class)); 
 // This is a more complicated animation, involving transformations  
 // on both this (exit) and the new (enter) activity.  Note how for  
 // the duration of the animation we force the exiting activity  
 // to be Z-ordered on top (even though it really isn't) to achieve  
 // the effect we want.  
&nb

补充:移动开发 , Android ,
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