PopupWindow的onScrollChanged系统bug

malong26

最近遇到一个问题，在项目中使用actionbar做标题栏，action按钮点击弹出popupwindow，内容部分使用ScrollView。发现在弹出popupwindow后将其dismiss掉，再滑动ScrollView的时候报错：
11-29 09:11:13.217: E/AndroidRuntime(2380): FATAL EXCEPTION: main
11-29 09:11:13.217: E/AndroidRuntime(2380): java.lang.NullPointerException
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.widget.PopupWindow$1.onScrollChanged(PopupWindow.java:127)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.view.ViewTreeObserver.dispatchOnScrollChanged(ViewTreeObserver.java:607)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.view.ViewRoot.draw(ViewRoot.java:1393)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.view.ViewRoot.performTraversals(ViewRoot.java:1263)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.view.ViewRoot.handleMessage(ViewRoot.java:1892)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.os.Handler.dispatchMessage(Handler.java:99)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.os.Looper.loop(Looper.java:130)
11-29 09:11:13.217: E/AndroidRuntime(2380): at android.app.ActivityThread.main(ActivityThread.java:3835)
11-29 09:11:13.217: E/AndroidRuntime(2380): at java.lang.reflect.Method.invokeNative(Native Method)
11-29 09:11:13.217: E/AndroidRuntime(2380): at java.lang.reflect.Method.invoke(Method.java:507)
11-29 09:11:13.217: E/AndroidRuntime(2380): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:864)
11-29 09:11:13.217: E/AndroidRuntime(2380): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622)
11-29 09:11:13.217: E/AndroidRuntime(2380): at dalvik.system.NativeStart.main(Native Method)

经查阅，发现这是android的一个系统bug，在蜂巢版本修复了，就是3.0之前的版本还存在这个bug，见链接
https://groups.google.com/forum/?fromgroups=#!msg/osmeditor4android/RsHYoY6XqlU/-WGSKWm5OMAJ