如何执行一个在活动中启动的服务上定义的方法并返回结果？

Question

如果我有这项服务，我需要创建一个方法getCoordinates（），因为我想从服务中进行广播，但是我希望这些坐标可用于需要时从活动中消费。比方说，我有一个方法getCoordinates（），这是创建一个可访问的方法来调用它的活动的最佳方式？那个电话会在想要消费它的活动中如何呢？如果服务没有启动不会导致应用程序崩溃，那么是否需要进行任何检查？我目前的代码在下面提供。非常感谢你。

@SuppressWarnings("MissingPermission") 
public class GPSService extends Service { 

    private LocationListener listener; 
    private LocationManager locationManager; 


    @Nullable 
    @Override 
    public IBinder onBind(Intent intent) { 
     return null; 
    } 

    @Override 
    public void onCreate() { 
     super.onCreate(); 
     listener= new LocationListener() { 
      @Override 
      public void onLocationChanged(Location location) { 
       //To transfer the data to the main activity I use broadcast receiver in the main activity, using an intent filter location_update 
       Intent intentSendLocationMainActivity = new Intent("location_update"); 
       Log.d("Location-update",location.getLongitude()+" "+location.getLongitude()); 
       intentSendLocationMainActivity.putExtra("coordinates",location.getLongitude()+" "+location.getLongitude()); 
       //I need to differentiate here if the app is killed or not to send the location to main activity or to a server 
       sendBroadcast(intentSendLocationMainActivity); 
      } 

      @Override 
      public void onStatusChanged(String s, int i, Bundle bundle) { 

      } 

      @Override 
      public void onProviderEnabled(String s) { 

      } 

      @Override 
      public void onProviderDisabled(String s) { 
       Intent activateGPSIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
       activateGPSIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
       startActivity(activateGPSIntent); 

      } 
     }; 
     locationManager = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE); 
     //noinspection MissingPermission, listen for updates every 3 seconds 
     locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,3000,0,listener); 
    } 

    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) { 
     Log.d("ClearFromRecentService", "Service Started"); 
     return START_STICKY; 
    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     Log.d("ClearFromRecentService", "Service Destroyed, Removing update location listener"); 
     //unregistering the listener 
     /*if(locationManager != null){ 
      locationManager.removeUpdates(listener); 
     }*/ 

    } 

    public void onTaskRemoved(Intent rootIntent) { 
     Log.e("ClearFromRecentService", "END"); 
     //here you can call a background network request to post you location to server when app is killed 
     Toast.makeText(getApplicationContext(), "Warning: App killed", Toast.LENGTH_LONG).show(); 
     //stopSelf(); //call this method to stop the service 
    } 

    public void getCoordinate(){ 
     //return coordinates to the user 
    } 
} 

Answer 1

您可以定义getCoordinates（）方法是如何静态方法：你

public static void getCoordinate(){ 
    //return coordinates to the user 
} 

有了这个soluction随处调用它，总是。

注意：你已经定义了getCoordinates（）如何void，它不能返回任何东西。

Answer 2

在您的服务中创建一个扩展Binder的类，并在此类中创建一个返回指向该服务本身的指针的函数。还可以创建你的活页夹类的同TIPE的成员变量，并在onBind()返回此对象......这一切都为您服务

private final IBinder mBinder = new GPSBinder(); 

public class GPSBinder extends Binder { 
    public GPSService getService() { 
     return GPSService.this; 
    } 
} 

@Override 
public IBinder onBind(Intent intent) { 
    return mBinder; 
} 

里面在您的活动，您需要添加一种GPSServie的变量，和绑定到服务，可能在你onResume()，并添加绑定完成后，将被通知的ServiceConnection对象，你会得到活页夹，你可以用它来获得你的服务实例的实例

GPSService mService; 

bindService(intent, mConnection, Context.BIND_AUTO_CREATE); // Put this in onResume() 

private ServiceConnection mConnection = new ServiceConnection() { 
    @Override 
    public void onServiceConnected(ComponentName className, IBinder service) { 
     // We've bound to LocalService, cast the IBinder and get LocalService instance 
     GPSService.GPSBinder binder = (GPSService.GPSBinder)service; 
     myService = binder.getService(); 
    } 

    @Override 
    public void onServiceDisconnected(ComponentName arg0) { 
     mService = null; 
    } 
}; 

最后，无论何时您需要调用getCoordinate（），您只需使用服务变量竹叶提取

if (myService!=null) 
    myService.getCoordinate(); // YEAH!!!!! 

不要忘记从服务解除绑定上onPause()