从 Settings Api 对话框打开位置后，getLastLocation() 返回 null
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【中文标题】从 Settings Api 对话框打开位置后，getLastLocation() 返回 null【英文标题】：getLastLocation() returns null after turning on location from Settings Api Dialog 【发布时间】：2016-05-21 04:06:49 【问题描述】：我正在使用以下函数打开一个设置 API 对话框，使用户能够打开位置服务，然后访问用户的当前位置：
public void onConnected(Bundle bundle)
if(ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION)== PackageManager.PERMISSION_GRANTED)
googleMapGlobal.setMyLocationEnabled(true);
Location mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
if (mCurrentLocation == null)
// Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
//getApplicationContext().startActivity(intent);
LocationRequest locationRequest = LocationRequest.create();
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
locationRequest.setInterval(30 * 1000);
locationRequest.setFastestInterval(5 * 1000);
LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder().addLocationRequest(locationRequest);
builder.setAlwaysShow(true);
PendingResult<LocationSettingsResult> result =
LocationServices.SettingsApi.checkLocationSettings(googleApiClient, builder.build());
result.setResultCallback(new ResultCallback<LocationSettingsResult>()
@Override
public void onResult(LocationSettingsResult result)
final Status status = result.getStatus();
final LocationSettingsStates state = result.getLocationSettingsStates();
switch (status.getStatusCode())
case LocationSettingsStatusCodes.SUCCESS:
// All location settings are satisfied. The client can initialize location
// requests here.
break;
case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
// Location settings are not satisfied. But could be fixed by showing the user
// a dialog.
try
// Show the dialog by calling startResolutionForResult(),
// and check the result in onActivityResult().
status.startResolutionForResult(VendorsOnMap.this, 1000);
catch (IntentSender.SendIntentException e)
// Ignore the error.
break;
case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
// Location settings are not satisfied. However, we have no way to fix the
// settings so we won't show the dialog.
break;
);
else
CameraPosition position = CameraPosition.builder()
.target(new LatLng(mCurrentLocation.getLatitude(),
mCurrentLocation.getLongitude()))
.zoom(15f)
.bearing(0.0f)
.tilt(0.0f)
.build();
googleMapGlobal.animateCamera(CameraUpdateFactory
.newCameraPosition(position), null);
LatLng latLng = new LatLng(31.220, 75.750);
Toast.makeText(getApplicationContext(), mCurrentLocation.getLatitude() + ", " + mCurrentLocation.getLongitude(), Toast.LENGTH_LONG).show();
googleMapGlobal.addMarker(new MarkerOptions().position(latLng).title("Marker here"));
else
ActivityCompat.requestPermissions(getParent(),
new String[]android.Manifest.permission.ACCESS_FINE_LOCATION, MY_PERMISSION_ACCESS_FINE_LOCATION);
protected void onActivityResult(int requestCode, int resultCode, Intent intent)
final LocationSettingsStates states = LocationSettingsStates.fromIntent(intent);
if (ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
Toast.makeText(getApplicationContext(), resultCode + " " + Activity.RESULT_OK, Toast.LENGTH_SHORT).show();
switch (requestCode)
case 1000:
switch (resultCode)
case Activity.RESULT_OK:
googleMapGlobal.setMyLocationEnabled(true);
Location mCurrentLocation;
mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
CameraPosition position = CameraPosition.builder()
.target(new LatLng(mCurrentLocation.getLatitude(), mCurrentLocation.getLongitude()))
.zoom(15f)
.bearing(0.0f)
.tilt(0.0f)
.build();
googleMapGlobal.animateCamera(CameraUpdateFactory.newCameraPosition(position), null);
LatLng latLng = new LatLng(31.220, 75.750);
Toast.makeText(getApplicationContext(), mCurrentLocation.getLatitude() + ", " + mCurrentLocation.getLongitude(), Toast.LENGTH_LONG).show();
googleMapGlobal.addMarker(new MarkerOptions().position(latLng).title("Marker here"));
break;
case Activity.RESULT_CANCELED:
break;
default:
break;
break;
问题是当我通过打开位置来使用应用程序时，它运行得非常好，但是如果我从应用程序内的设置 API 对话框中打开位置，返回的位置为空。请帮忙。
【问题讨论】：
***.com/questions/31521849/… @DanielNugent 您提供的链接显示每次都返回 null 的位置，但在我的情况下，只有在应用程序内打开位置服务时才会发生这种情况（设置 API 对话框）。 您看到的是此用例的预期行为。在您启用服务和您尝试获取位置之间，没有足够的时间让其他应用请求位置。您永远不应该依赖 getLastLocation()，因为它可以而且会经常返回 null。 请务必在此处阅读答案/cmets：***.com/questions/16830047/… 【参考方案1】：开始工作了。我在理解getLastLocation() 的工作原理时犯了一个基本错误。它实际上是在寻找系统而不是应用程序接收到的位置。这是我修改后的代码。我现在使用设置 API 对话框让用户能够打开位置服务，但是
在此之前，我拨打了requestLocationUpdates() 的电话，以允许我的应用请求位置更新。
然后我在无限循环中调用getLastLocation()，直到它返回的值不为空。这样我就得到了设备的当前位置。
public void onConnected(Bundle bundle)
if(ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION)== PackageManager.PERMISSION_GRANTED)
googleMapGlobal.setMyLocationEnabled(true);
locationRequest = LocationRequest.create();
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
locationRequest.setInterval(0);
locationRequest.setFastestInterval(5 * 1000);
locationRequest.setNumUpdates(5);
LocationServices.FusedLocationApi.requestLocationUpdates(googleApiClient, locationRequest, this);
// Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
//getApplicationContext().startActivity(intent);
LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder().addLocationRequest(locationRequest);
builder.setAlwaysShow(true);
PendingResult<LocationSettingsResult> result =
LocationServices.SettingsApi.checkLocationSettings(googleApiClient, builder.build());
result.setResultCallback(new ResultCallback<LocationSettingsResult>()
@Override
public void onResult(LocationSettingsResult result)
final Status status = result.getStatus();
final LocationSettingsStates state = result.getLocationSettingsStates();
switch (status.getStatusCode())
case LocationSettingsStatusCodes.SUCCESS:
// All location settings are satisfied. The client can initialize location
// requests here.
while(mCurrentLocation==null)
if(ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION)== PackageManager.PERMISSION_GRANTED)
mCurrentLocation=LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
CameraPosition position = CameraPosition.builder()
.target(new LatLng(mCurrentLocation.getLatitude(),
mCurrentLocation.getLongitude()))
.zoom(15f)
.bearing(0.0f)
.tilt(0.0f)
.build();
googleMapGlobal.animateCamera(CameraUpdateFactory
.newCameraPosition(position), null);
LatLng latLng = new LatLng(31.220, 75.750);
Toast.makeText(getApplicationContext(), mCurrentLocation.getLatitude() + ", " + mCurrentLocation.getLongitude(), Toast.LENGTH_LONG).show();
googleMapGlobal.addMarker(new MarkerOptions().position(latLng).title("Marker here"));
break;
case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
// Location settings are not satisfied. But could be fixed by showing the user
// a dialog.
try
// Show the dialog by calling startResolutionForResult(),
// and check the result in onActivityResult().
status.startResolutionForResult(VendorsOnMap.this, 1000);
catch (IntentSender.SendIntentException e)
// Ignore the error.
break;
case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
// Location settings are not satisfied. However, we have no way to fix the
// settings so we won't show the dialog.
break;
);
else
ActivityCompat.requestPermissions(getParent(),
new String[]android.Manifest.permission.ACCESS_FINE_LOCATION, MY_PERMISSION_ACCESS_FINE_LOCATION);
protected void onActivityResult(int requestCode, int resultCode, Intent intent)
final LocationSettingsStates states = LocationSettingsStates.fromIntent(intent);
if (ContextCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
Toast.makeText(getApplicationContext(), resultCode + " " + Activity.RESULT_OK, Toast.LENGTH_SHORT).show();
switch (requestCode)
case 1000:
switch (resultCode)
case Activity.RESULT_OK:
while (mCurrentLocation==null)
mCurrentLocation=LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
CameraPosition position = CameraPosition.builder()
.target(new LatLng(mCurrentLocation.getLatitude(), mCurrentLocation.getLongitude()))
.zoom(15f)
.bearing(0.0f)
.tilt(0.0f)
.build();
googleMapGlobal.animateCamera(CameraUpdateFactory.newCameraPosition(position), null);
LatLng latLng = new LatLng(31.220, 75.750);
Toast.makeText(getApplicationContext(), mCurrentLocation.getLatitude() + ", " + mCurrentLocation.getLongitude(), Toast.LENGTH_LONG).show();
googleMapGlobal.addMarker(new MarkerOptions().position(latLng).title("Marker here"));
break;
case Activity.RESULT_CANCELED:
break;
default:
break;
break;
这里的mCurrentLocation是一个Location类型的全局变量。
【讨论】：
主线程无限循环？不好。您现在的代码将冻结您的整个应用程序，如果您没有立即获得位置（这可能由于多种原因而发生），则抛出 ANR 正确的方法是在onResult() 中调用 requestLocationUpdates()，然后获取来自onLocationChanged() 的位置。可以调用getLastLocation()一次，如果位置不为空，则使用它。否则，请致电requestLocationUpdates()，并在'onLocationChanged（）'中获得一个位置后处理该位置
是的！对不起！我不喜欢在 UI 线程中放置 while 循环。我通过在 AsyncTask 中放置无限循环来完成相同的任务，它不会冻结 UI 并且也可以完成我的工作。以上是关于从 Settings Api 对话框打开位置后，getLastLocation() 返回 null的主要内容，如果未能解决你的问题，请参考以下文章