android - 从应用程序提示启用 gps 后如何刷新并获取当前位置？

Question

我目前正在开发一个 Android 应用程序，如果它没有打开，它会提示用户启用 GPS，为此我使用了 Alert Dialog。在我从设置中启用 GPS 并通过按返回按钮返回到我的应用程序后， toast 消息显示 0.00,0.00。虽然如果我在运行该应用程序之前打开了 GPS，该应用程序会正确显示我的位置。我想知道启用 GPS 后使用哪种方法刷新用户位置。任何相关文章都会很有帮助。

这是我的GPS类(class)

          public class GpsTracker extends Service implements LocationListener {

private final Context mContext;

// flag for GPS status
boolean isGPSEnabled = false;

// flag for network status
boolean isNetworkEnabled = false;

// flag for GPS status
boolean canGetLocation = false;

Location location; // location
double latitude; // latitude
double longitude; // longitude

// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

// Declaring a Location Manager
protected LocationManager locationManager;

public GpsTracker(Context context) {
    this.mContext = context;
    getLocation();
}

public Location getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            if (ActivityCompat.checkSelfPermission(mContext, 
             Manifest.permission.ACCESS_FINE_LOCATION) != 
                PackageManager.PERMISSION_GRANTED
                    && ActivityCompat.checkSelfPermission(mContext, 
                       Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

                return null;
            }
            this.canGetLocation = true;
            // First get location from Network Provider
            if (isNetworkEnabled) {

              /*  locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);*/
                Log.d("Network", "Network");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    if (ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                            && ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

                        return null;
                    }
                  /*  locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);*/
                    Log.d("GPS Enabled", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

    return location;
}

/**
 * Stop using GPS listener
 * Calling this function will stop using GPS in your app
 * */
public void stopUsingGPS(){

    if(locationManager != null){
        if (ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return ;
        }
        locationManager.removeUpdates(GpsTracker.this);
    }
}

/**
 * Function to get latitude
 * */
public double getLatitude(){
    if(location != null){
        latitude = location.getLatitude();
    }

    // return latitude
    return latitude;
}

/**
 * Function to get longitude
 * */
public double getLongitude(){
    if(location != null){
        longitude = location.getLongitude();
    }

    // return longitude
    return longitude;
}

/**
 * Function to check GPS/wifi enabled
 * @return boolean
 * */
public boolean canGetLocation() {
    return this.canGetLocation;
}

/**
 * Function to show settings alert dialog
 * On pressing Settings button will lauch Settings Options
 * */
public void showSettingsAlert(){
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

    // Setting Dialog Title
    alertDialog.setTitle("GPS is settings");

    // Setting Dialog Message
    alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

    // On pressing Settings button
    alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            mContext.startActivity(intent);

        }
    });

    // on pressing cancel button
    alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    // Showing Alert Message
    alertDialog.show();
}

@Override
public void onLocationChanged(Location location) {
}

@Override
public void onProviderDisabled(String provider) {
}

@Override
public void onProviderEnabled(String provider) {
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}

@Override
public IBinder onBind(Intent arg0) {
    return null;
}

}

Answer 1

启用GPS后使用以下代码获取当前位置；

public class MainActivity extends AppCompatActivity implements LocationListener,
    GoogleApiClient.ConnectionCallbacks,
    GoogleApiClient.OnConnectionFailedListener, OnMapReadyCallback {

final String TAG = "GPS";
GoogleMap googleMap;
Marker mCurrLocationMarker;
private long UPDATE_INTERVAL = 2 * 1000;  /* 10 secs */
private long FASTEST_INTERVAL = 2000; /* 2 sec */
static final int MY_PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 1;
private static final int GPS_CHECK = 112;
GoogleApiClient gac;
LocationRequest locationRequest;
TextView tvLatitude, tvLongitude, tvTime;
LocationManager locationManager;
Button capture;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tvLatitude = (TextView) findViewById(R.id.tvLatitude);
    tvLongitude = (TextView) findViewById(R.id.tvLongitude);
    tvTime = (TextView) findViewById(R.id.tvTime);
    capture = (Button) findViewById(R.id.capture);

    isGooglePlayServicesAvailable();

    //        if (!isLocationEnabled())
    //            showAlert();

    locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
        showAlert();
    }

    locationRequest = new LocationRequest();
    locationRequest.setInterval(UPDATE_INTERVAL);
    locationRequest.setFastestInterval(FASTEST_INTERVAL);
    locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    gac = new GoogleApiClient.Builder(this)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .addApi(LocationServices.API)
            .build();

    SupportMapFragment mapFragment = (SupportMapFragment)
            getSupportFragmentManager()
                    .findFragmentById(R.id.map);

    mapFragment.getMapAsync(this);
}

@Override
protected void onStart() {
    gac.connect();
    super.onStart();
}

@Override
protected void onStop() {
    gac.disconnect();
    super.onStop();
}

@Override
public void onLocationChanged(Location location) {
    if (location != null) {
        updateUI(location);
    }
}

@Override
public void onConnected(@Nullable 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) {
        ActivityCompat.requestPermissions(MainActivity.this,
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                MY_PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION);

        return;
    }
    Log.d(TAG, "onConnected");

    Location ll = LocationServices.FusedLocationApi.getLastLocation(gac);
    Log.d(TAG, "LastLocation: " + (ll == null ? "NO LastLocation" : ll.toString()));

    updateUI(ll);

    LocationServices.FusedLocationApi.requestLocationUpdates(gac, locationRequest, this);
}

@Override
public void onRequestPermissionsResult(
        int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(MainActivity.this, "Permission was granted!", Toast.LENGTH_LONG).show();

                try {
                    LocationServices.FusedLocationApi.requestLocationUpdates(
                            gac, locationRequest, this);
                } catch (SecurityException e) {
                    Toast.makeText(MainActivity.this, "SecurityException:\n" + e.toString(), Toast.LENGTH_LONG).show();
                }
            } else {
                Toast.makeText(MainActivity.this, "Permission denied!", Toast.LENGTH_LONG).show();
            }
            return;
        }
    }
}

@Override
public void onConnectionSuspended(int i) {
}

@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
    Toast.makeText(MainActivity.this, "onConnectionFailed: \n" + connectionResult.toString(),
            Toast.LENGTH_LONG).show();
    Log.d("DDD", connectionResult.toString());
}

private void updateUI(Location loc) {
    Log.d(TAG, "updateUI");
    try {
        tvLatitude.setText(Double.toString(loc.getLatitude()));
        tvLongitude.setText(Double.toString(loc.getLongitude()));
        tvTime.setText(DateFormat.getTimeInstance().format(loc.getTime()));

        double lattitude = loc.getLatitude();
        double longitude = loc.getLongitude();

        //Place current location marker
        LatLng latLng = new LatLng(lattitude, longitude);


        if(mCurrLocationMarker!=null){
            mCurrLocationMarker.setPosition(latLng);
        }else{
            mCurrLocationMarker = googleMap.addMarker(new MarkerOptions()
                    .position(latLng)
                    .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED))
                    .title("I am here"));
        }

        googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 18));
        googleMap.getUiSettings().setZoomControlsEnabled(true);
    }
    catch (Exception e)
    {

    }
}

private boolean isLocationEnabled() {
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
            locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}

private boolean isGooglePlayServicesAvailable() {
    final int PLAY_SERVICES_RESOLUTION_REQUEST = 9000;
    GoogleApiAvailability apiAvailability = GoogleApiAvailability.getInstance();
    int resultCode = apiAvailability.isGooglePlayServicesAvailable(this);
    if (resultCode != ConnectionResult.SUCCESS) {
        if (apiAvailability.isUserResolvableError(resultCode)) {
            apiAvailability.getErrorDialog(this, resultCode, PLAY_SERVICES_RESOLUTION_REQUEST)
                    .show();
        } else {
            Log.d(TAG, "This device is not supported.");
            finish();
        }
        return false;
    }
    Log.d(TAG, "This device is supported.");
    return true;
}

private void showAlert() {
    final AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    dialog.setTitle("Enable Location")
            .setMessage("Your Locations Settings is set to 'Off'.\nPlease Enable Location to " +
                    "use this app")
            .setPositiveButton("Location Settings", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface paramDialogInterface, int paramInt) {
                    startActivityForResult(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS), GPS_CHECK);
                }
            })
            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface paramDialogInterface, int paramInt) {

                }
            });
    dialog.show();
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == GPS_CHECK) {
        if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
            capture.setVisibility(View.GONE);
            Toast.makeText(getApplicationContext(), "Please turn on gps...", Toast.LENGTH_SHORT).show();
            Log.e("BBBBBBBBBBBBBBB", "");
        }
        else
        {
            gac.connect();
            googleMap.setOnMyLocationButtonClickListener(new GoogleMap.OnMyLocationButtonClickListener() {

                @Override
                public boolean onMyLocationButtonClick()
                {
                    try
                    {
                        Location myLocation = googleMap.getMyLocation();
                        onLocationChanged(myLocation);
                    }
                    catch (Exception e)
                    {
                        Log.getStackTraceString(e);
                    }
                    return false;
                }
            });
        }
    }

}

@Override
public void onMapReady(GoogleMap map) {
    googleMap = map;
    map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
    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;
    }
    map.setMyLocationEnabled(true);
    map.setTrafficEnabled(true);
    map.setIndoorEnabled(true);
    map.setBuildingsEnabled(true);
    map.getUiSettings().setZoomControlsEnabled(true);
}
}