無法啓動新MapActivity

Question

我一直在試圖創造什麼我想象會是一個相當簡單的應用程序 - 在開始活動，有一個按鈕按下，然後將推出一個MapActivity顯示您當前的位置。

但是，每當我按下按鈕，我立即收到一條錯誤和我被迫退出應用程序。

這裏的日誌：

10-23 19:15:10.826: D/PhoneWindow(3227): DebugMonitor class=com.android.find.my.friends.MainActivity focus=true 
10-23 19:15:19.496: D/AndroidRuntime(3227): Shutting down VM 
10-23 19:15:19.496: W/dalvikvm(3227): threadid=3: thread exiting with uncaught exception (group=0x4001db88) 
10-23 19:15:19.496: E/AndroidRuntime(3227): Uncaught handler: thread main exiting due to uncaught exception 
10-23 19:15:19.506: E/AndroidRuntime(3227): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.find.my.friends/com.android.find.my.friends.ShowMap}: java.lang.NullPointerException 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2464) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2486) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread.access$2100(ActivityThread.java:123) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1843) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.os.Handler.dispatchMessage(Handler.java:99) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.os.Looper.loop(Looper.java:123) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread.main(ActivityThread.java:4321) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at java.lang.reflect.Method.invokeNative(Native Method) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at java.lang.reflect.Method.invoke(Method.java:521) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at dalvik.system.NativeStart.main(Native Method) 
10-23 19:15:19.506: E/AndroidRuntime(3227): Caused by: java.lang.NullPointerException 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at com.android.find.my.friends.ShowMap.onCreate(ShowMap.java:30) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2418) 
10-23 19:15:19.506: E/AndroidRuntime(3227):  ... 11 more 
10-23 19:15:19.516: I/dalvikvm(3227): threadid=7: reacting to signal 3 
10-23 19:15:19.546: I/dalvikvm(3227): Wrote stack trace to '/data/anr/traces.txt' 

我上的HTC紋身測試這個運行Android 1.6。我以前也能夠創建一個只顯示MapActivity的應用程序。

任何幫助傢伙？

[編輯]

這裏是我的onCreate方法：

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); // bind the layout to the activity 

    mapView = (MapView) findViewById(R.id.mapview); 
    mapView.setBuiltInZoomControls(true); 
    mapView.setStreetView(true); 
    mapController = mapView.getController(); 
    mapController.setZoom(14); // Zoom 1 is world view 
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 
      0, new GeoUpdateHandler()); 

} 

Answer 1

看來，你在你的ShowMap類有NullPointerException在第30行。如果你可以發佈你的onCreate方法和第30行，我可以幫你找出原因。

難道你還粘貼異常本身發生就行了？ findViewById可能返回null，在這種情況下，您的mapView將爲空。確保您的MapView的佈局佈局與您傳入setContentView的佈局相同。