谷歌地圖說： 「不幸的是，<app name>已停止」

Question

每次我嘗試運行我的應用程序我得到這個錯誤：

unfortunately, has stopped

來源：

package com.example.mapsapp; 

import com.google.android.maps.GeoPoint; 
import com.google.android.maps.MapActivity; 
import com.google.android.maps.MapController; 
import com.google.android.maps.MapView; 

import android.os.Bundle; 
import android.view.Menu; 


public class HichRideActivity extends MapActivity 
{ 


    MapController mControl; 
    GeoPoint geop; 
    MapView mapV; 

    @Override 
    public void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_hich_ride); 

     mapV= (MapView) findViewById(R.id.menu_settings); 
     mapV.displayZoomControls(true); 
     mapV.setBuiltInZoomControls(true); 


     double lat= 40.8; 
     double longi=-96.666; 

     geop = new GeoPoint ((int)(lat * 1E6), (int)(longi * 1E6)); 
     mControl.animateTo(geop); 
     mControl.setZoom(13); 

    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) 
    { 
     getMenuInflater().inflate(R.menu.activity_hich_ride, menu); 
     return true; 
    } 

    @Override 
    protected boolean isRouteDisplayed() 
    { 
     // TODO Auto-generated method stub 
     return false; 
    } 


} 

，這裏是logcat的，它說我有NullPointerException的，但我不知道哪個參數是null。

logcat的：

07-31 13:40:46.344: E/Trace(1043): error opening trace file: No such file or directory (2) 
07-31 13:40:47.134: D/AndroidRuntime(1043): Shutting down VM 
07-31 13:40:47.134: W/dalvikvm(1043): threadid=1: thread exiting with uncaught exception (group=0x40a13300) 
07-31 13:40:47.194: D/dalvikvm(1043): GC_CONCURRENT freed 195K, 3% free 8273K/8519K, paused 80ms+5ms, total 166ms 
07-31 13:40:47.194: D/dalvikvm(1043): WAIT_FOR_CONCURRENT_GC blocked 26ms 
07-31 13:40:47.194: E/AndroidRuntime(1043): FATAL EXCEPTION: main 
07-31 13:40:47.194: E/AndroidRuntime(1043): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mapsapp/com.example.mapsapp.HichRideActivity}: java.lang.NullPointerException 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread.access$600(ActivityThread.java:130) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.os.Looper.loop(Looper.java:137) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread.main(ActivityThread.java:4745) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at dalvik.system.NativeStart.main(Native Method) 
07-31 13:40:47.194: E/AndroidRuntime(1043): Caused by: java.lang.NullPointerException 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at com.example.mapsapp.HichRideActivity.onCreate(HichRideActivity.java:27) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.Activity.performCreate(Activity.java:5008) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
07-31 13:40:47.194: E/AndroidRuntime(1043):  ... 11 more 
07-31 13:40:47.214: W/CursorWrapperInner(1043): Cursor finalized without prior close() 
07-31 13:40:47.214: W/CursorWrapperInner(1043): Cursor finalized without prior close()

Answer 1

mapV= (MapView) findViewById(R.id.menu_settings); 
            ^^^^^^^^^^^^^ 

這應該是ID的MapView，它應該在activity_hich_ride.xml

Answer 2

這些行聲明：mControl.animateTo(geop); mControl.setZoom(13); 是你的問題。您正在使用尚未創建的MapController，您將其聲明在課程頂部，但您從未實例化過 - 因此，在聲明MapView後，請添加以下行：mControl = mapV.getController();。嘗試一下，讓我知道它是否有效！