Getting current location in Android Studio app

问题:

I am developing my first Android app which should get the latitude and longitude of an android device and send it via a web service to a template document.

I followed the guide of getting the location from http://developer.android.com/training/location/retrieve-current.html.

This is the code from my .java class:

import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.provider.Settings;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.EditText;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationServices;

public class GetLocation extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
    private GoogleApiClient mGoogleApiClient;
    EditText textLat;
    EditText textLong;
    EditText lat;
    EditText lon;

    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.get_location);

        textLat = (EditText) findViewById(R.id.latitude);
        textLong = (EditText) findViewById(R.id.longitude);

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    private boolean isGPSEnabled() {
        LocationManager cm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        return cm.isProviderEnabled(LocationManager.GPS_PROVIDER);
    }

    @Override
    public void onConnected(Bundle bundle) {
        Location mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if (mLastLocation != null) {
            lat.setText(String.valueOf(mLastLocation.getLatitude()));
            lon.setText(String.valueOf(mLastLocation.getLongitude()));
        }
    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {

    }

    public void onButtonClick(View v){
        if(v.getId() == R.id.getGpsLocation){
            if(!isGPSEnabled()){
                new AlertDialog.Builder(this)
                        .setMessage("Please activate your GPS Location!")
                        .setCancelable(false)
                        .setPositiveButton("Settings", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                                startActivity(i);
                            }
                        })
                        .setNegativeButton("Cancel", null)
                        .show();
            } else {
                textLat.setText(String.valueOf(lat));
                textLong.setText(String.valueOf(lon));
            }

        }
    }


}

I don't get any errors but when I am tapping the button which should get the coordinates, I get 'null' text in both views.

I also have included permissions for internet, access fine and coarse location.

Thanks in advance!

回答1:

I have written detailed tutorial covering this topic here on demonuts.com.You can find more description here and also you can download whole demo source code for better understanding.

First of all, put this in gradle file

 compile 'com.google.android.gms:play-services:9.0.2'

then implement necessary interfaces

public class MainActivity  extends BaseActivitiy implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener

declare instances

  private GoogleApiClient mGoogleApiClient;
  private Location mLocation;
  private LocationManager locationManager;
  private LocationRequest mLocationRequest;

put this in onCreate()

 mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

At last, override necessary methods

 @Override
    public void onConnected(Bundle bundle) {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        } startLocationUpdates();
        mLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if(mLocation == null){
            startLocationUpdates();
        }
        if (mLocation != null) {
            double latitude = mLocation.getLatitude();
            double longitude = mLocation.getLongitude();
        } else {
            // Toast.makeText(this, "Location not Detected", Toast.LENGTH_SHORT).show();
        }
    }

    protected void startLocationUpdates() {
        // Create the location request
        mLocationRequest = LocationRequest.create()
                .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
                .setInterval(UPDATE_INTERVAL)
                .setFastestInterval(FASTEST_INTERVAL);
        // Request location updates
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient,
                mLocationRequest, this);
        Log.d("reque", "--->>>>");
    }

    @Override
    public void onConnectionSuspended(int i) {
        Log.i(TAG, "Connection Suspended");
        mGoogleApiClient.connect();
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Log.i(TAG, "Connection failed. Error: " + connectionResult.getErrorCode());
    }

    @Override
    public void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mGoogleApiClient.isConnected()) {
            mGoogleApiClient.disconnect();
        }
    }
    @Override
    public void onLocationChanged(Location location) {

    }

Don't forget to start GPS in your device before running app.

回答2:

You need to define LocationListener .

public class MainActivity extends Activity implements LocationListener{
    protected LocationManager locationManager;
    protected LocationListener locationListener;
    protected Context context;
    TextView txtLat;
    String lat;
    String provider;
    protected String latitude,longitude; 
    protected boolean gps_enabled,network_enabled;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txtLat = (TextView) findViewById(R.id.textview1);

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
    }
    @Override
    public void onLocationChanged(Location location) {
        txtLat = (TextView) findViewById(R.id.textview1);
        txtLat.setText("Latitude:" + location.getLatitude() + ", Longitude:" + location.getLongitude());
    }

    @Override
    public void onProviderDisabled(String provider) {
        Log.d("Latitude","disable");
    }

    @Override
    public void onProviderEnabled(String provider) {
        Log.d("Latitude","enable");
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        Log.d("Latitude","status");
    }
}

And need to give below permission :

ACCESS_COARSE_LOCATION : It is used when we use network location provider for our Android app.

ACCESS_FINE_LOCATION : It is providing permission for both providers.

INTERNET : permission is must for the use of network provider.

回答3:

Here is a working example of user location:

https://github.com/keithweaver/Android-Samples/tree/master/Location