相关疑难解决方法(0)

显示PopupWindow时出现以下错误.错误由行触发:

checkInPopup.showAtLocation((ViewGroup) mapView.getParent(), Gravity.CENTER_HORIZONTAL, 0, 0);

mapView是一个MapView,没有任何东西是空的.堆栈跟踪:

01-08 18:00:09.402: E/AndroidRuntime(27768): Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.view.ViewRootImpl.setView(ViewRootImpl.java:513)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:301)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:215)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.view.Window$LocalWindowManager.addView(Window.java:537)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.widget.PopupWindow.invokePopup(PopupWindow.java:988)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.widget.PopupWindow.showAtLocation(PopupWindow.java:845)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.widget.PopupWindow.showAtLocation(PopupWindow.java:809)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at com.geoloc.ActivityCheckIn.onCreate(ActivityCheckIn.java:50)
01-08 18:00:09.402: E/AndroidRuntime(27768):    at android.app.Activity.performCreate(Activity.java:4465)
01-08 18:00:09.402: E/AndroidRuntime(27768): …