弹出窗口中的自动完成下拉框会导致 Android 应用程序强制关闭。为什么？

Question

我有一个自动完成框，我试图在我的 Android 应用程序的弹出窗口中实现它。将此弹出框放入我的主要活动布局中效果很好。当我将其移动到弹出布局时，它将成功显示在屏幕上。但是，当我输入超出自动完成阈值并找到匹配项（从而触发与我的部分文本匹配的项目的下拉列表）时，应用程序崩溃并出现以下错误：

08-08 11:12:53.803 E/AndroidRuntime(22221): android.view.WindowManager$BadTokenException: Unable to add window -- token android.view.ViewRoot$W@4057f5c0 is not valid; is your activity running?
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.view.ViewRoot.setView(ViewRoot.java:544)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:177)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.view.Window$LocalWindowManager.addView(Window.java:430)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.PopupWindow.invokePopup(PopupWindow.java:916)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:828)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.AutoCompleteTextView.showDropDown(AutoCompleteTextView.java:1277)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.AutoCompleteTextView.updateDropDownForFilter(AutoCompleteTextView.java:1081)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.AutoCompleteTextView.onFilterComplete(AutoCompleteTextView.java:1064)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:285)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.os.Handler.dispatchMessage(Handler.java:99)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.os.Looper.loop(Looper.java:143)
08-08 11:12:53.803 E/AndroidRuntime(22221): at android.app.ActivityThread.main(ActivityThread.java:4196)
08-08 11:12:53.803 E/AndroidRuntime(22221): at java.lang.reflect.Method.invokeNative(Native Method)
08-08 11:12:53.803 E/AndroidRuntime(22221): at java.lang.reflect.Method.invoke(Method.java:507)
08-08 11:12:53.803 E/AndroidRuntime(22221): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-08 11:12:53.803 E/AndroidRuntime(22221): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-08 11:12:53.803 E/AndroidRuntime(22221): at dalvik.system.NativeStart.main(Native Method)

这是我使用的代码（弹出窗口在单击按钮，该按钮位于活动的主布局中）：

public void onClick(View v) {
   LayoutInflater inflater = 
             (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
   PopupWindow pw = new PopupWindow(
             inflater.inflate(R.layout.auto_complete_location, null, false), 
             400, 600, true);
   AutoCompleteTextView autoCompleteLocationsView =(AutoCompleteTextView)
             pw.getContentView().findViewById(R.id.autoCompleteLocations);
   ArrayAdapter<String> adapter = new ArrayAdapter<String>
             (autoCompleteLocationsView.getContext(),
              android.R.layout.simple_dropdown_item_1line, locationNames);
   autoCompleteLocationsView.setAdapter(adapter);
   pw.showAtLocation(findViewById(R.id.mainActivityContainer), Gravity.CENTER, 0, 0);
}

提前感谢您的任何帮助。