当 onSuccess() 方法终止时，myLocation 值变为 null。我是 Android 应用程序开发新手。我想将当前位置的值永久存储在 myLocation 中。
我正在按照谷歌的开发人员指南获取我的当前位置，并且我想将其存储到 myLocation(全局变量)。我已成功获取当前位置，但它并未永久存储在 myLocation 中。在 onSuccess() 方法之后，myLocation 变为 null。
公共(public)类 MapsActivity 扩展 FragmentActivity 实现 OnMapReadyCallback {
private GoogleMap mMap;
private FusedLocationProviderClient mFusedLocationClient;
SupportMapFragment mapFragment;
Location myLocation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
myLocation = new Location(LocationManager.NETWORK_PROVIDER);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED ) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
}
else{
mapFragment.getMapAsync(this);
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED ) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
}
mFusedLocationClient.getLastLocation()
.addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location currentlocation) {
myLocation=currentlocation;
// Got last known location. In some rare situations this can be null.
if (currentlocation != null) {
LatLng sydney = new LatLng(myLocation.getLatitude(), myLocation.getLongitude());
mMap.addMarker(new MarkerOptions().position(sydney).title("My Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}
}
});
Log.i("myLocation",myLocation.toString());
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == 1) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mapFragment.getMapAsync(this);
} else {
Toast.makeText(getApplicationContext(), "Please provide permission", Toast.LENGTH_SHORT).show();
}
}
}
}
myLocation 应该等于 currentlocation，但在日志中发现它为空。 日志 - I/myLocation:位置[网络 0.000000,0.000000 acc=??? t=？!？等=？!？] 请帮助我并提前致谢。
最佳答案
日志在 onSuccess() 之前被调用，因为它是一个Listener。你应该做的是调用
Log.i("myLocation",myLocation.toString());
在你的onSuccess()中，之后你就得到了正确的值。
关于java - 为什么即使 myLocation 是全局变量，当 onSuccess() 终止时 myLocation 也会变为 null？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/54597878/