我遇到这个问题，我的Android位置始终为空，但似乎只有在我的应用从后台转到前台时才会发生。这是我的代码：
Public.java：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
String userId = AccessToken.getCurrentAccessToken().getUserId();
//Open DB and get freinds from db & posts.
datasource = new FriendsDataSource(getContext());
datasource.open();
postsDataSource = new PostsDataSource(getContext());
postsDataSource.open();
fragmentView = inflater.inflate(R.layout.public_tab, container, false);
populateNewsFeedList(fragmentView);
return fragmentView;
}
public void populateNewsFeedList(View fragmentView) {
RecyclerView rv = (RecyclerView)
fragmentView.findViewById(R.id.rv_public_feed);
LinearLayoutManager llm = new LinearLayoutManager(getContext());
rv.setLayoutManager(llm);
Location location = checkLocation();
//Set a 24140.2 meter, or a 15 mile radius.
adapter = new PostRecyclerViewAdapter(postsDataSource.getAllPublicPosts(location.getLatitude(), location.getLongitude(), 24140.2), getContext(), true);
rv.setAdapter(adapter);
}
private Location checkLocation() {
Location location = LocationService.getLastLocation();
if(location == null){
System.out.println("Null location");
LocationService.getLocationManager(getContext());
//Connect to google play services to get last location
LocationService.getGoogleApiClient().connect();
location = LocationService.getLastLocation();
return location;
}
else {
return location;
}
}
LocationService.java：
public class LocationService implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
//Google Location Services API
private static LocationService instance = null;
public static GoogleApiClient googleApiClient;
private static Location lastLocation;
LocationManager locationManager;
Context context;
private static final int PERMISSION_REQUEST_COARSE_LOCATION = 1;
/**
* Singleton implementation
* @return
*/
public static LocationService getLocationManager(Context context) {
if (instance == null) {
instance = new LocationService(context);
}
return instance;
}
/**
* Local constructor
*/
private LocationService( Context context ) {
this.context = context;
initLocationService(context);
}
/**
* Sets up location service after permissions is granted
*/
private void initLocationService(Context context) {
if (googleApiClient == null) {
googleApiClient = new GoogleApiClient.Builder(context)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(com.google.android.gms.location.LocationServices.API)
.build();
}
}
@Override
public void onConnected(Bundle bundle) {
try {
lastLocation = LocationServices.FusedLocationApi.getLastLocation(
googleApiClient);
} catch (SecurityException e){
System.out.println("Security Exception: " + e);
}
}
public static Location getLastLocation(){
return lastLocation;
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
protected static void onStart() {
googleApiClient.connect();
}
protected void onStop() {
googleApiClient.disconnect();
}
public static GoogleApiClient getGoogleApiClient() {
return googleApiClient;
}
}
问题是，即使我在checkLocation()中输入Public.java函数（我实现了尝试初始化我的位置服务以防止我的位置为空），我看到了LocationService 1}}被正确初始化了所有内容，每当我调用Location.getLastLocation()时，我总是返回一个空值。我真的不确定为什么会发生这种情况，这似乎只有在我的应用程序从后台转到前台时才会发生。任何帮助将不胜感激，谢谢！
答案 0 :(得分：0)
试试这个，
private LocationManager locationManager;
private String provider;
private Location location;
private boolean isGPSEnabled;
private static boolean isNetworkEnabled;
public static double lat=0.0;
public static double lng=0.0;
public void checkLocation(Activity activity) {
locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
Criteria c = new Criteria();
provider = locationManager.getBestProvider(c, false);
location = getLocation(activity);
locationManager.requestLocationUpdates(provider, 400, 1, this);
locationManager.removeUpdates(this);
if (location != null) {
// get latitude and longitude of the location
onLocationChanged(location);
} else {
Log.d("TAG","Unable to find Location");
}
}
public Location getLocation(Activity activity) {
try {
locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 400, 0, this);
Log.d("Network", "Network Enabled");
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
lat = location.getLatitude();
lng = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 400, 0, this);
Log.d("GPS", "GPS Enabled");
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
lat = location.getLatitude();
lng = location.getLongitude();
}
}
}
}
}
} catch (SecurityException e) {
Log.e("PERMISSION_EXCEPTION","PERMISSION_NOT_GRANTED");
}catch (Exception e) {
e.printStackTrace();
}
return location;
}
@Override
public void onLocationChanged(Location location) {
lat = location.getLatitude();
lng = location.getLongitude();
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}