使用FusedLocationProviderClient-Android

Question

我已经实现了来自developers.android.com的代码，用于获取设备的位置纬度和经度并在UI上显示。我成功地动态授予了权限。但是，所需的字符串未在UI中显示。显示的日志中没有错误。请多谢并提出建议。

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.content.IntentSender;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Bundle;
import android.os.Looper;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.common.api.ResolvableApiException;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.location.LocationSettingsRequest;
import com.google.android.gms.location.LocationSettingsResponse;
import com.google.android.gms.location.SettingsClient;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;


public class MainActivity extends AppCompatActivity {

private FusedLocationProviderClient fusedLocationClient;
public static final int MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION =1;
LocationRequest locationRequest;
protected static final int REQUEST_CHECK_SETTINGS = 0x1;
LocationCallback locationCallback;
//public static final int PERMISSION_DENIED = -1;
//int flag = -1;
// String packageName, permissionName;

Location  mCurrentLocation;
TextView textView, textView2;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    getLocationPermission();
    textView = findViewById(R.id.locationlat);
    textView2 = findViewById(R.id.locationlong);
    fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);

    fusedLocationClient.getLastLocation()
            .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                @Override
                public void onSuccess(Location location) {
                    // Got last known location. In some rare situations this can be null.
                    if (location != null) {
                        // Logic to handle location object

                        mCurrentLocation = location;
                    }
                }
            });

    createLocationRequest();

    LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
            .addLocationRequest(locationRequest);

    SettingsClient client = LocationServices.getSettingsClient(this);
    Task<LocationSettingsResponse> task = client.checkLocationSettings(builder.build());

    task.addOnSuccessListener(this, new OnSuccessListener<LocationSettingsResponse>() {
        @Override
        public void onSuccess(LocationSettingsResponse locationSettingsResponse) {
            // All location settings are satisfied. The client can initialize
            // location requests here.
            // ...
        }
    });

    task.addOnFailureListener(this, new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            if (e instanceof ResolvableApiException) {
                // Location settings are not satisfied, but this can be fixed
                // by showing the user a dialog.
                try {
                    // Show the dialog by calling startResolutionForResult(),
                    // and check the result in onActivityResult().
                    ResolvableApiException resolvable = (ResolvableApiException) e;
                    resolvable.startResolutionForResult(MainActivity.this,
                            REQUEST_CHECK_SETTINGS);
                } catch (IntentSender.SendIntentException sendEx) {
                    // Ignore the error.
                }
            }
        }
    });

    locationCallback = new LocationCallback() {
        @Override
        public void onLocationResult(LocationResult locationResult) {
            if (locationResult == null) {
                return;
            }
            for (Location location : locationResult.getLocations()) {
                // Update UI with location data
                // ...
                String latitudeStr=String.valueOf(location.getLatitude());
                String longitudeStr=String.valueOf(location.getLongitude());

                textView.setText(latitudeStr);
                textView2.setText(longitudeStr);
            }
        };
    };

}

private void getLocationPermission(){

    // Here, 'this' is the current activity
    if (ContextCompat.checkSelfPermission(this,
            Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {
        Toast.makeText(this, "Please Grant Location Permission", Toast.LENGTH_SHORT).show();
        // Permission is not granted
        // Should we show an explanation?
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.ACCESS_COARSE_LOCATION)) {
            // Show an explanation to the user *asynchronously* -- don't block
            // this thread waiting for the user's response! After the user
            // sees the explanation, try again to request the permission.
        } else {
            // No explanation needed; request the permission
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
                    MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION);

            // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
            // app-defined int constant. The callback method gets the
            // result of the request.
        }
    } else {
        Toast.makeText(this, "Location Permission Granted", Toast.LENGTH_SHORT).show();
        // Permission has already been granted
    }
}


@Override
public void onRequestPermissionsResult(int requestCode,
                                       String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_ACCESS_COARSE_LOCATION: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // permission was granted, yay! Do the
                // contacts-related task you need to do.
            } else {
                Toast.makeText(this, "Location Permission not Granted", Toast.LENGTH_SHORT).show();
                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

        // other 'case' lines to check for other
        // permissions this app might request.
    }
}

protected void createLocationRequest() {
    locationRequest = LocationRequest.create();
    locationRequest.setInterval(10000);
    locationRequest.setFastestInterval(5000);
    locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}

@Override
protected void onResume() {
    super.onResume();
    boolean requestingLocationUpdates = true;
    if (requestingLocationUpdates) {
        startLocationUpdates();
    }
}

private void startLocationUpdates() {
    fusedLocationClient.requestLocationUpdates(locationRequest,
            locationCallback,
            Looper.getMainLooper());
}
}

非常感谢您的宝贵时间。