相机不跟随用户在谷歌地图中的当前位置答案

【问题标题】：Camera does not follow user current location in Google Maps相机不跟随用户在谷歌地图中的当前位置
【发布时间】：2018-08-25 14:25:08
【问题描述】：

我有以下代码，我可以在启动应用程序时显示我的当前位置。

public class MainActivity extends AppCompatActivity implements LocationListener {
   //private fields

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (isGooglePlayServicesOk()) {
            getLocationPermissions();
        }
    }

    @Override
    public void onLocationChanged(Location location) {
        this.location = location;
    //NO TOAST MESSAGE - NOTHING HAPPENS <=============
    Toast.makeText(context, location.getLatitude() + " / " + location.getLongitude(), Toast.LENGTH_SHORT).show();
    }

    //Other three empty methods onStatusChanged, onProviderEnabled and onProviderDisabled

    private void getDeviceLocation() {
        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);

        try {
            if (locationPermissionsGranted) {
                Task task = fusedLocationProviderClient.getLastLocation();
                task.addOnCompleteListener(new OnCompleteListener() {
                    @Override
                    public void onComplete(@NonNull Task task) {
                        if (task.isSuccessful()) {
                            location = (Location) task.getResult();
                            LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
                            mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, 18f));
                        }
                    }
                });
            }
        } catch (SecurityException se) {
            Log.d(TAG, se.getMessage());
        }
    }

    public boolean isGooglePlayServicesOk() {
        //Method that check Google Play Services
    }

    private void initializeMap() {
        SupportMapFragment supportMapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        supportMapFragment.getMapAsync(new OnMapReadyCallback() {
            @Override
            public void onMapReady(GoogleMap googleMap) {
                mMap = googleMap;

                if (locationPermissionsGranted) {
                    getDeviceLocation();
                    if (/* Manifest Conditions */) {return;}
                    mMap.setMyLocationEnabled(true);
                }
            }
        });
    }

    private void getLocationPermissions() {
        String[] permissions = {COARSE_LOCATION, FINE_LOCATION};
        if (ContextCompat.checkSelfPermission(this.getApplicationContext(), COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            if (ContextCompat.checkSelfPermission(this.getApplicationContext(), FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                locationPermissionsGranted = true;
                initializeMap();
            } else {
                ActivityCompat.requestPermissions(this, permissions, LOCATION_PERMISSION_REQUEST_CODE);
            }
        } else {
            ActivityCompat.requestPermissions(this, permissions, LOCATION_PERMISSION_REQUEST_CODE);
        }
    }

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

        switch (requestCode) {
            case LOCATION_PERMISSION_REQUEST_CODE: {
                if (grantResults.length > 0) {
                    for (int grantResult : grantResults) {
                        if (grantResult != PackageManager.PERMISSION_GRANTED) {
                            locationPermissionsGranted = false;
                            return;
                        }
                    }
                    locationPermissionsGranted = true;
                    initializeMap();
                }
            }
        }
    }
}

所以每次我移动时，我都不会在地图中保持居中。要将我再次置于地图中心，我需要按下位置按钮。我已经从LocationListener 接口实现了onLocationChanged() 方法，但没有任何反应。甚至没有显示 Toast 消息。我该如何解决这个问题，让我无论走到哪里，都始终保持在地图的中心？

提前致谢！

【问题讨论】：

你在哪里设置你的 LocationListener？
@Eselfar 我正在实施它。 class MainActivity extends AppCompatActivity implements LocationListener
是的，你有一个监听器，它是你的 Activity 本身，因为它实现了接口。但是现在你需要将它设置在某个地方（可能在地图上）才能使用
类似map.setLocationListener(MainActivity.this);
@Eselfar 如我所见，我的mMap 上没有可以调用的setLocationListener。

标签： android google-maps google-maps-api-3 google-maps-markers locationlistener

【解决方案1】：

由于您正在关注this tutorial 来实施该位置，如其末尾所述，您需要关注this one 以使用新位置进行更新。

创建回调：

mLocationCallback = new LocationCallback() {
  @Override
  public void onLocationResult(LocationResult locationResult) {
      if (locationResult == null) {
          return;
      }
      for (Location location : locationResult.getLocations()) {
          // Update UI with location data
          // ...
      }
  };
};

设置监听器/回调：

mFusedLocationClient.requestLocationUpdates(mLocationRequest,
  mLocationCallback,
  null /* Looper */);

【讨论】：