相关疑难解决方法(0)

我正在编写一个显示MapView的应用程序,显示谷歌地图.我使用了http://developer.android.com/resources/tutorials/views/hello-mapview.html中的"hello map view"教程,这项工作到目前为止:地图显示,居中和缩放正确,甚至是OverlayItems我添加正确显示.

但是当我点击我添加的其中一个叠加项时,应用程序崩溃并出现空指针异常:

07-23 16:24:48.167: ERROR/AndroidRuntime(2530): java.lang.NullPointerException
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at     com.android.internal.app.AlertController$AlertParams.<init>(AlertController.java:753)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.app.AlertDialog$Builder.<init>(AlertDialog.java:273)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at net.xenonite.wifiloc.act_map$MapItemizedOverlay.onTap(act_map.java:182)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at com.google.android.maps.ItemizedOverlay.onTap(ItemizedOverlay.java:453)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at com.google.android.maps.OverlayBundle.onTap(OverlayBundle.java:83)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at com.google.android.maps.MapView$1.onSingleTapUp(MapView.java:347)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at com.google.android.maps.GestureDetector.onTouchEvent(GestureDetector.java:533)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at com.google.android.maps.MapView.onTouchEvent(MapView.java:647)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.View.dispatchTouchEvent(View.java:3709)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:874)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924) …