是想显示在某个控件的底部?

popupWindow.showAsDropDown(view_main, 0, 0);

用这个方法就可以让popupWindow显示在view_main的下面.

后面的那两个参数是水平和竖直方向的偏移量.

在styles.xml文件中添加如下代码：

  <style name="AnimationFade">
        <!-- PopupWindow弹出的效果 -->
        <item name="android:windowEnterAnimation">@anim/poupshow</item>
        <item name="android:windowExitAnimation">@anim/pouphide</item>
    </style>

res/anim/pouphide.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <scale  
        android:duration="100"  
        android:fillAfter="false"  
        android:fromXScale="1.0"  
        android:fromYScale="0.0"  
        android:interpolator="@android:anim/accelerate_interpolator"  
        android:pivotY="100%"  
        android:toXScale="1.0"  
        android:toYScale="1.0" />  

</set>

res/anim/poupshow.xml
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
     <scale  
        android:duration="200"  
        android:fillAfter="false"  
        android:fromXScale="1.0"  
        android:fromYScale="1.0"  
        android:interpolator="@android:anim/accelerate_interpolator"  
        android:pivotY="100%"  
        android:toXScale="1.0"  
        android:toYScale="0.0" />  
</set>

popupWindow.setAnimationStyle(R.style.popup_animation);

设置动画

<style name="popup_animation " parent="android:Animation">

    <item name="android:windowEnterAnimation">@anim/in</item>

    <item name="android:windowExitAnimation">@anim/out</item>

 </style>

动画还得自己写