实现两个 Activity 切换时的动画。在Activity中使用
有两个参数：进入动画和出去的动画。

注意
1、必须在 StartActivity()  或 finish() 之后立即调用。
2、而且在 2.1 以上版本有效
3、手机设置-显示-动画，要开启状态

//实现淡入浅出的效果
startActivity(new Intent(MainActivity.this,SecondActivity.class));
overridePendingTransition(android.R.anim.fade_in,android.R.anim.fade_out);

// 由左向右滑入的效果
startActivity(new Intent(MainActivity.this,SecondActivity.class));
overridePendingTransition(android.R.anim.slide_in_left,android.R.anim.slide_out_right);

// 实现zoommin 和 zoomout (自定义的动画)
startActivity(new Intent(OverridePendingTransitionActivity.this,SecondActivity.class));
overridePendingTransition(R.anim.zoomin, R.anim.zoomout);

anim/zoomin.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android :anim/decelerate_interpolator" >
  <scale
        android:duration="@android :integer/config_mediumAnimTime"
        android:fromXScale="0.1"
        android:fromYScale="0.1"
        android:pivotX="50%p"
        android:pivotY="50%p"
        android:toXScale="1.0"
        android:toYScale="1.0" />
  <alpha
        android:duration="@android :integer/config_mediumAnimTime"
        android:fromAlpha="0"
        android:toAlpha="1.0" />
</set>

anim/zoomout.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android :anim/decelerate_interpolator"
    android:zAdjustment="top" >
    <scale
        android:duration="@android :integer/config_mediumAnimTime"
        android:fromXScale="1.0"
        android:fromYScale="1.0"
        android:pivotX="50%p"
        android:pivotY="50%p"
        android:toXScale="0.1"
        android:toYScale="0.1" />
    <alpha
        android:duration="@android:integer/config_mediumAnimTime"
        android:fromAlpha="1.0"
        android:toAlpha="0" />
</set>

关于 overridePendingTransition()使用