无法通过Mapsforge获取位置

Question

我试图通过Mapsforge 0.6.1获取经纬度，但出现错误。我正在使用Android Studio。

的logcat：

E/AndroidRuntime: FATAL EXCEPTION: main 
    Process: com.example.luis.safe, PID: 27378 
    java.lang.RuntimeException: Unable to create service com.example.luis.safe.Tracker: java.lang.NullPointerException: Attempt to invoke virtual method 'double org.mapsforge.core.model.LatLong.getLatitude()' on a null object reference 
     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2905) 
     at android.app.ActivityThread.access$1900(ActivityThread.java:157) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1439) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5530) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622) 
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double org.mapsforge.core.model.LatLong.getLatitude()' on a null object reference 
     at com.example.luis.safe.Tracker.onCreate(Tracker.java:57) 
     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2895) 
     at android.app.ActivityThread.access$1900(ActivityThread.java:157) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1439) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5530) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622) 

这是我的代码。在onCreate方法中，我调用getLatitude，并出现错误。

import android.Manifest; 
import android.app.Service; 
import android.content.Intent; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.location.LocationProvider; 
import android.os.Bundle; 
import android.os.IBinder; 
import android.support.v4.app.ActivityCompat; 
import android.util.Log; 

import com.google.android.gms.common.api.GoogleApiClient; 

import org.mapsforge.core.model.LatLong; 
import org.mapsforge.map.model.MapViewPosition; 
import org.mapsforge.core.model.Point; 
import org.mapsforge.core.model.BoundingBox; 

public class Tracker extends Service implements LocationListener{ 
    public Tracker() { 
    } 

    // flag for GPS status 
    boolean isGPSEnabled = false; 

    // flag for network status 
    boolean isNetworkEnabled = false; 

    boolean canGetLocation = false; 

    private static final String TAG = Tracker.class.getSimpleName(); 

    Location location; 
    double latitude = 0.0; 
    double longitude = 0.0; 

    private LatLong latLong; 

    // The minimum distance to change Updates in meters 
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 5; // 5  meters 

    // The minimum time between updates in milliseconds 
    private static final long MIN_TIME_BW_UPDATES = 1000 * 5 * 1; // 5  segundos, 1000 * 60 * 1 ---> 1 minuto 

    // Declaring a Location Manager 
    protected LocationManager locationManager; 

    @Override 
    public void onCreate() { 
     super.onCreate(); 

     latitude = latLong.getLatitude(); 
     longitude = latLong.getLongitude(); 
    } 

    @Override 
    public IBinder onBind(Intent intent) { 
     // TODO: Return the communication channel to the service. 
     throw new UnsupportedOperationException("Not yet implemented"); 
    } 

    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) { 
     //myTask.execute(); 
     return super.onStartCommand(intent, flags, startId); 
    } 

    @Override 
    public void onStatusChanged(String arg0, int arg1, Bundle arg2) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public void onProviderEnabled(String arg0) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public void onProviderDisabled(String arg0) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public void onLocationChanged(Location arg0) { 
     System.out.println(latitude + "" + longitude); 

    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 

    } 
} 

Answer 1

由于日志说：latLong是null。在初始化latLong之前，您不能使用getLatitude()或getLongitude()。在onLocationChanged(Location arg0)中初始化latLong。并检查出这code为了了解你应该做什么。