PopupWindow添加动画效果

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate 
        android:fromYDelta="100%p"
        android:toYDelta="0"
        android:duration="1000"/>
    <alpha 
        android:fromAlpha="0.0"
        android:toAlpha="1.0"
        android:duration="1000"/>
</set>

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromYDelta="0"
        android:toYDelta="100%p"
        android:duration="1000"/>
    <alpha 
        android:fromAlpha="1.0"
        android:toAlpha="0.0"
        android:duration="1000"/>
</set>

<resources>
    <style name="popupAnimation">
        <item name="android:windowEnterAnimation">@anim/popup_enter</item>
        <item name="android:windowExitAnimation">@anim/popup_exit</item>
    </style>
</resources>

inflater = getLayoutInflater();
layout = inflater.inflate(R.layout.menu, null);
menu = new PopupWindow(layout, WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.WRAP_CONTENT);
menu.setAnimationStyle(R.style.popupAnimation);//添加动画