第一次在棉花糖中启动应用程序时如何获取位置信息

Question

我正在创建一个应用。 安装应用程序然后打开它并允许位置访问权限时，我没有得到当前位置，但仅显示地图。重新打开应用程序后，将显示当前位置。 使用以下代码-

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

    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;

    LatLng latLng;
    GoogleMap mMap;
    SupportMapFragment mFragment;
    Marker CurrentMarker;

    private static final int PERMISSION_REQUEST_CODE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);




        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        mFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        mFragment.getMapAsync(this);

       // Button request_permission = (Button)findViewById(R.id.request_permission);

        //request_permission.setOnClickListener(this);

        if (!checkPermission()) {

            requestPermission();

        } else {

            Toast.makeText(this,"Permission already granted.",Toast.LENGTH_SHORT).show();

        }


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        //final int LOCATION_PERMISSION_REQUEST_CODE = 100;
       // ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION, android.Manifest.permission.ACCESS_COARSE_LOCATION},
              //  LOCATION_PERMISSION_REQUEST_CODE);
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

           return;
        }
        mMap.setMyLocationEnabled(true);
        buildGoogleApiClient();
        mGoogleApiClient.connect();

    }

    private void buildGoogleApiClient() {

        // TODO Auto-generated method stub
        Toast.makeText(this, "buildGoogleApiClient", Toast.LENGTH_SHORT).show();
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    @Override
    public void onConnected(Bundle bundle) {


        Toast.makeText(this, "Onconnection", Toast.LENGTH_SHORT).show();
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return;
        }
        Location mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if(mLastLocation != null){
            latLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());
            MarkerOptions markerOptions = new MarkerOptions();
            markerOptions.position(latLng);
            markerOptions.title("Current Location");
            markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
            CurrentMarker = mMap.addMarker(markerOptions);
        }
        mLocationRequest = new LocationRequest();
        //mLocationRequest.setInterval(5000);
       // mLocationRequest.setFastestInterval(3000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);

    }

    @Override
    public void onConnectionSuspended(int i) {
        Toast.makeText(this,"onConnectionSuspended",Toast.LENGTH_SHORT).show();

    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        Toast.makeText(this,"onConnectionFailed",Toast.LENGTH_SHORT).show();

    }

    @Override
    public void onLocationChanged(Location location) {

        if (CurrentMarker != null){
            CurrentMarker.remove();
        }
        latLng = new LatLng(location.getLatitude(), location.getLongitude());
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latLng);
        markerOptions.title("Current Position");
        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
        CurrentMarker = mMap.addMarker(markerOptions);
        Toast.makeText(this,"Location changed",Toast.LENGTH_SHORT).show();

        CameraPosition cameraPosition = new CameraPosition.Builder().target(latLng).zoom(14).build();

        mMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

    }


    private boolean checkPermission(){
        int result = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION);
        if (result == PackageManager.PERMISSION_GRANTED){

            return true;

        } else {

            return false;

        }
    }

    private void requestPermission(){

        if (ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.ACCESS_FINE_LOCATION)){

            Toast.makeText(this,"GPS permission allows us to access location data. Please allow in App Settings for additional functionality.",Toast.LENGTH_LONG).show();

        } else {

            ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.ACCESS_FINE_LOCATION},PERMISSION_REQUEST_CODE);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_REQUEST_CODE:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {



                } else {



                }
                break;
        }
    }
}

请告诉我安装后如何获取位置，然后首次打开它。使用我的源代码。

谢谢

Answer 1

在棉花糖中，除非用户在运行时允许对应用程序的位置访问，否则无法获取位置。 当用户允许位置权限重新启动活动时

  Intent intent= new Intent(MainActivity.this,MainActivity.class);
    startActivity(intent);
    finish();

Answer 2

为什么没有第一次显示：因为您在授予后没有处理。

您为何第二次显示：因为您之前已授予许可。

 @Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    switch (requestCode) {
        case PERMISSION_REQUEST_CODE:
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

            // TRY GETTING THE LOCATION HERE ON FIRST TIME (AFTER GRANTING)
             Location mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
            } else {}
            break;
    }
}