Question

这是我的代码：

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    FusedLocationProviderClient mFusedLocationClient;
    LocationRequest mLocationRequest;
    LocationCallback mLocationCallback;

    private void startLocationUpdates() {

        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(MapsActivity.this,new String[]{Manifest.permission.ACCESS_COARSE_LOCATION,Manifest.permission.ACCESS_FINE_LOCATION},99);

            return;
        }

        mFusedLocationClient.requestLocationUpdates(mLocationRequest,
                mLocationCallback,
                null );
    }

    public void getLastLocationFun() {


        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(this, "Not permitted", Toast.LENGTH_SHORT).show();
        }
        mFusedLocationClient.getLastLocation().addOnCompleteListener(new OnCompleteListener<Location>() {
            @Override
            public void onComplete(@NonNull Task<Location> task) {
                if (task.isSuccessful()) {
                    Location location = task.getResult();
                    mMap.clear();
                    LatLng currentLocation = new LatLng(location.getLatitude(), location.getLongitude());
                    mMap.addMarker(new MarkerOptions().position(currentLocation).title("Current Location"));
                    mMap.moveCamera(CameraUpdateFactory.newLatLng(currentLocation));
                    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(currentLocation,18.0f));
                }
            }
        });

    }

    public void reqP(){
        ActivityCompat.requestPermissions(MapsActivity.this,
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION},
                99);
    }

    public boolean checkP(){
        return (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED);
    }

    private void stopLocationUpdates() {
        mFusedLocationClient.removeLocationUpdates(mLocationCallback);
    }

    protected void createLocationRequest() {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(2000);
        mLocationRequest.setFastestInterval(2000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

        if(!checkP()){
            reqP();
        }

        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);

        createLocationRequest();

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

                    // Add a marker on current location and move the camera

                    mMap.clear();
                    LatLng currentLocation = new LatLng(location.getLatitude(), location.getLongitude());
                    mMap.addMarker(new MarkerOptions().position(currentLocation).title("Current Location"));
                    mMap.moveCamera(CameraUpdateFactory.newLatLng(currentLocation));
                    mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(currentLocation,18.0f));
                }
            }
        };
        getLastLocationFun();
        startLocationUpdates();
        ProcessLifecycleOwner.get().getLifecycle().addObserver(new AppLifecycleListener());

    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        stopLocationUpdates();
    }

    public class AppLifecycleListener implements LifecycleObserver {

        @OnLifecycleEvent(Lifecycle.Event.ON_START)
        public void onMoveToForeground() {
            // app moved to foreground
        }

        @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
        public void onMoveToBackground() {
            Toast.makeText(MapsActivity.this, "LifeCycleEvent", Toast.LENGTH_SHORT).show();
            startService(new Intent(MapsActivity.this, MyService.class));
        }
    }
}

在这里，我尝试使用FusedLocationListener获取位置并在该位置显示标记。
但是，谷歌地图仅在首次启动应用程序时显示默认的世界地图。
随后，当我从最近的应用程序中删除该应用程序并再次启动该应用程序时，它运行正常。
我第一次启动时无法获得位置吗？

Answer 1

您需要在班级中添加它。这样您就可以在用户授予位置权限时获取位置。

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
List<Fragment> fragments = getSupportFragmentManager().getFragments();
if (requestCode != 0) {
    mFusedLocationClient.requestLocationUpdates(mLocationRequest,
            mLocationCallback,
            null );
}

}

首次启动应用程序时无法获取位置

1 个答案: