Android 试图在谷歌地图上的我的当前位置上设置标记会导致Nullpointer异常
我已经在我的Android项目中集成了Android 试图在谷歌地图上的我的当前位置上设置标记会导致Nullpointer异常,android,google-maps,nullpointerexception,locationmanager,Android,Google Maps,Nullpointerexception,Locationmanager,我已经在我的Android项目中集成了谷歌地图。我正在设备上查看地图。我想将标记设置为我的当前位置。我已经完成了以下编码,但它在第43行(即下一行)上给了我一个空指针异常 mMap.addMarker(新标记选项() .position(新车床(location.getLatitude(),location.getLongitude()) .title(“Hello world”) 我的代码如下。请一步一步地告诉我出了什么问题 public class location extends
谷歌地图
。我正在设备上查看地图。我想将标记设置为我的当前位置。我已经完成了以下编码,但它在第43行(即下一行)上给了我一个空指针异常
mMap.addMarker(新标记选项()
.position(新车床(location.getLatitude(),location.getLongitude())
.title(“Hello world”)代码>
我的代码如下。请一步一步地告诉我出了什么问题
public class location extends Activity implements LocationListener {
private GoogleMap mMap;
LocationManager locationManager;
private static final long MIN_TIME = 400;
private static final float MIN_DISTANCE = 1000;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.map_location);
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.the_map)).getMap();
mMap.setMyLocationEnabled(true);
//mMap.addMarker(new MarkerOptions());
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME, MIN_DISTANCE, this);
Location location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
mMap.addMarker(new MarkerOptions()
.position(new LatLng(location.getLatitude(), location.getLongitude()))
.title("Hello world"));
}
@Override
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(latLng, 10);
mMap.animateCamera(cameraUpdate);
// locationManager.removeUpdates(this);
}
你的代码似乎是正确的。只需检查您的位置对象,它可能为空。请尝试下面的代码,它对我有用
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.map_location);
// Getting Google Play availability status
int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());
// Showing status
if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available
int requestCode = 10;
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
dialog.show();
}else { // Google Play Services are available
// Getting reference to the SupportMapFragment of activity_main.xml
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Getting GoogleMap object from the fragment
googleMap = fm.getMap();
// Enabling MyLocation Layer of Google Map
googleMap.setMyLocationEnabled(true);
// Getting LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location
Location location = locationManager.getLastKnownLocation(provider);
LocationListener locationListener = new LocationListener() {
void onLocationChanged(Location location) {
// redraw the marker when get location update.
drawMarker(location);
}
if(location!=null){
//PLACE THE INITIAL MARKER
drawMarker(location);
}
locationManager.requestLocationUpdates(provider, 20000, 0, locationListener);
}
}
private void drawMarker(Location location){
googleMap.clear();
LatLng currentPosition = new LatLng(location.getLatitude(),location.getLongitude());
googleMap.addMarker(new MarkerOptions()
.position(currentPosition)
.snippet("Lat:" + location.getLatitude() + "Lng:"+ location.getLongitude()));
.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE))
.title("ME"));
}
@Override
public void onLocationChanged(Location location) {
// Add a marker in Sydney and move the camera
mLocation = location;
LatLng myLocation = new LatLng(mLocation.getLatitude(), mLocation.getLongitude());
mMap.addMarker(new MarkerOptions()
.position(myLocation)
.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED))
.title("My Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(myLocation));
Log.d("location", "Latitude:" + mLocation.getLatitude() + "\n" + "Longitude:" + mLocation.getLongitude());
}