FusedLocationProvider 始终返回 null Location 对象
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【中文标题】FusedLocationProvider 始终返回 null Location 对象【英文标题】：FusedLocationProvider always returns null Location object 【发布时间】：2022-01-21 16:12:15 【问题描述】：我已经尝试了无数的 FusedLocationProviderClient 实现，我在互联网上找到并使用文档，但每次我都无法获得位置和空对象。这是我在主要活动中使用 FusedLocationProviderClient 获取位置的最终代码。然后我在另一个片段中使用 Location 对象来显示用户的坐标。
这是活动代码
ActivityMainBinding activityMainBinding;
NavHostFragment navHostFragment;
NavController navController;
LocationRequest mLocationRequest;
Location mLocation;
FusedLocationProviderClient mFusedLocationClient;
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
startLocation();
activityMainBinding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(activityMainBinding.getRoot());
navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerMain);
navController = navHostFragment.getNavController();
activityMainBinding.bottomNavigation.setOnItemSelectedListener(new NavigationBarView.OnItemSelectedListener()
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item)
switch(item.getItemId())
case R.id.menuItemHome:
navController.navigate(R.id.homeFragment);
break;
case R.id.menuItemSearch:
navController.navigate(R.id.searchFragment);
break;
case R.id.menuItemProfile:
navController.navigate(R.id.profileFragment);
break;
case R.id.menuItemSettings:
navController.navigate(R.id.settingsFragment);
break;
return true;
);
@Override
public void onBackPressed()
navController.navigate(R.id.homeFragment);
activityMainBinding.bottomNavigation.setSelectedItemId(R.id.menuItemHome);
public void startLocation()
mLocationRequest = LocationRequest.create();
mLocationRequest.setInterval(10000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
if ( (ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED )
|| ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) )
//Location Permission granted
mFusedLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
LocationServices.getFusedLocationProviderClient(this).getLastLocation().addOnSuccessListener(new OnSuccessListener<Location>()
@Override
public void onSuccess(@NonNull Location location)
mLocation = location;
);
else
//Request Location Permission
checkLocationPermission();
public void stopLocationUpdates()
if( mFusedLocationClient != null )
mFusedLocationClient.removeLocationUpdates(mLocationCallback);
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
private void checkLocationPermission()
if ( (ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED )
|| ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) )
if ( ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)
|| ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_COARSE_LOCATION) )
//Request location message for user
new AlertDialog.Builder(this)
.setTitle("Location Permission Needed")
.setMessage("This app needs the Location permission, please accept to use location functionality")
.setPositiveButton("OK", new DialogInterface.OnClickListener()
@Override
public void onClick(DialogInterface dialogInterface, int i)
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(MainActivity.this,
new String[]Manifest.permission.ACCESS_COARSE_LOCATION,
MY_PERMISSIONS_REQUEST_LOCATION );
)
.create()
.show();
else
//request the permission.
ActivityCompat.requestPermissions(this,
new String[]Manifest.permission.ACCESS_COARSE_LOCATION,
MY_PERMISSIONS_REQUEST_LOCATION );
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults)
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == MY_PERMISSIONS_REQUEST_LOCATION)
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED)
// permission was granted
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_COARSE_LOCATION)
== PackageManager.PERMISSION_GRANTED)
mFusedLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
LocationCallback mLocationCallback = new LocationCallback()
@Override
public void onLocationResult(LocationResult locationResult)
if (locationResult == null)
return;
for (Location location : locationResult.getLocations())
if (location != null)
mLocation = location;
return;
;
这是片段类中我要显示坐标的代码
public class HomeFragment extends Fragment
private HomeFragmentBinding homeFragmentBinding;
private NavController navController;
private MainViewModel mainViewModel;
private Location userLocation;
private MainActivity mainActivity;
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
mainViewModel = new ViewModelProvider(getActivity()).get(MainViewModel.class);
mainActivity = (MainActivity) getActivity();
userLocation = mainActivity.mLocation;
homeFragmentBinding.textDist1.setText("Lat: " + userLocation.getLatitude() + " Long: " + userLocation.getLongitude());
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
homeFragmentBinding = HomeFragmentBinding.inflate(inflater, container, false);
return homeFragmentBinding.getRoot();
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState)
super.onViewCreated(view, savedInstanceState);
navController = Navigation.findNavController(view);
homeFragmentBinding.textDist1.setText("Lat: " + userLocation.getLatitude() + " Long: " + userLocation.getLongitude());
我还在清单中添加了 ACCESS_FINE_LOCATION 和 ACCESS_COARSE_LOCATION 的权限，并且
implementation 'com.google.android.gms:play-services-location:19.0.0'
在 gradle 构建中。
每次运行应用程序时，我都会收到空 Location 对象的空指针异常。用户也没有获得提供位置访问权限的弹出窗口。 我从我的 android 虚拟设备的设置中手动打开了位置访问，但没有任何改变。在 android 文档和旧的 *** 页面上经过无数小时后，我找不到问题。 感谢您的帮助。
【问题讨论】：
在获得该位置之前，您需要避免尝试使用该位置。现在，onViewCreated() 中的片段尝试使用该位置，而不考虑您何时实际获得该位置。将所有位置逻辑移动到片段（或 Jetpack ViewModel）中，并在 onLocationResult() 获取位置时更新您的 UI。
我按照你说的做了，把我所有的位置逻辑都移到了片段类中，并在 onSuccessListener 的 onSuccess 方法中为 textView 调用了 setText。我还添加了一条 toast 消息以确认实际调用了 onSuccess 方法。然后我在 onCreate 和 onViewCreated 上调用了我的 startLocation 方法（只是为了确定），但我看到 textFields 没有变化，也没有收到 toast 消息。有什么问题？
【参考方案1】：
首先，创建一个 Fused Location Provider Client 的实例。
mFusedLocationClient= LocationServices.getFusedLocationProviderClient(this)
然后执行位置请求。
mFusedLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
我想官方文档很清楚。参考-https://developer.android.com/training/location/
【讨论】：
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