popwindow的bug

java.lang.NullPointerException
	at android.widget.PopupWindow$1.onScrollChanged(PopupWindow.java:127)
	at android.view.ViewTreeObserver.dispatchOnScrollChanged(ViewTreeObserver.java:607)
	at android.view.ViewRoot.draw(ViewRoot.java:1367)
	at android.view.ViewRoot.performTraversals(ViewRoot.java:1264)
	at android.view.ViewRoot.handleMessage(ViewRoot.java:1866)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loop(Looper.java:130)
	at android.app.ActivityThread.main(ActivityThread.java:3687)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at java.lang.reflect.Method.invoke(Method.java:507)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
	at dalvik.system.NativeStart.main(Native Method)

上网搜了下，这就是android 3.0以前报的bug，可参见

https://groups.google.com/forum/?fromgroups=#!msg/osmeditor4android/RsHYoY6XqlU/-WGSKWm5OMAJ