Android locationManager Null Pointer Exception? (how to pass the context?)

问题

I have a problem here and I cant get it to work... I want to get the latest gps positions but all i get is an null pointer exception. It works with the first class GPSActivity but not with the 2nd SmsReceiver.

I read that this is maybe because I have to pass the Context to the 2nd class but I dont know how... please help!

Here comes the code:

GPSActivity.class:

import android.app.Activity;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class GPSActivity extends Activity {
  long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 1; // in Meters
  long MINIMUM_TIME_BETWEEN_UPDATES = 10000; // in Milliseconds

  LocationManager locationManager;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);  
    locationManager = 
      (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    locationManager.getAllProviders();
    locationManager.requestLocationUpdates(
            LocationManager.GPS_PROVIDER, 
            MINIMUM_TIME_BETWEEN_UPDATES, 
            MINIMUM_DISTANCE_CHANGE_FOR_UPDATES,
            new MyLocationListener());

  }    

  public void showCurrentLocation() {
    Location location = 
      locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

    if (location != null) {
      String message = String.format(
              "Current Location \n Longitude: %1$s \n Latitude: %2$s",
              location.getLongitude(), location.getLatitude());
      Toast.makeText(GPSActivity.this, message,
              Toast.LENGTH_LONG).show();
    }
  }
}

(I stripped the code a bit)

Now, I can call showCurrentLocation and it showes me the long and lat values.

How can I do this here:

SmsReceive.class (when a sms is received, send the gps coordinates)

import ...
public class SmsReceiver extends BroadcastReceiver
{   


  @Override
  public void onReceive(Context context, Intent intent) 
  {
    GPSActivity myGPS;
    myGPS = new GPSActivity();

    //---get the SMS message passed in---
    Bundle bundle = intent.getExtras();        
    SmsMessage[] msgs = null;
    if (bundle != null) {
      //HERE I GET THE NULL POINTER EXCEPTION
      Location loc =
        myGPS.locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 
      double varLong = loc.getLongitude();
      double varLat = loc.getLatitude();
      String locationData = "LONG: " + varLong+ " LAT: " + varLat;
      Toast.makeText(context, locationData, Toast.LENGTH_SHORT).show();
    }
  }
}

thanks!

回答1:

declare a new locationManager in the smsReceiver class and use the following lines

mLocationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
 Location loc = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

回答2:

Create the One class which extends the Service and into this implement the GPS task because in Activity which will stop/pause/destroy and you can't get every time. Service will run into background so you can get the GPS co-ordinate at any time any and define the location object as public static so you can use anywhere into your application.

来源：https://stackoverflow.com/questions/7724685/android-locationmanager-null-pointer-exception-how-to-pass-the-context

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java

android

gps

locationmanager