所以在我测试我的应用程序时，我正在关闭并在我的GPS上试图找出检查GPS是否已启用的最佳方法。不幸的是，我无法找到最好的方法。但是，启用GPS时代码工作正常，但现在不能正常工作。这就是说location.getLatitude（）是一个空对象引用。
以下是我要说的代码：
public class ThirdFragment extends Fragment implements OnMapReadyCallback {
View myView;
private GoogleMap mMap;
MapFragment mapFrag;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
myView = inflater.inflate(R.layout.third_layout, container, false);
return myView;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
mapFrag = (MapFragment) getChildFragmentManager().findFragmentById(R.id.map);
mapFrag.getMapAsync(this);
//mapFrag.onResume();
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
mMap.setMyLocationEnabled(true);
Criteria criteria = new Criteria();
LocationManager locationManager = (LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);
String provider = locationManager.getBestProvider(criteria, false);
Location location = locationManager.getLastKnownLocation(provider);
double lat = location.getLatitude();
double lng = location.getLongitude();
LatLng coordinate = new LatLng(lat, lng);
CameraUpdate yourLocation = CameraUpdateFactory.newLatLngZoom(coordinate, 13);
mMap.animateCamera(yourLocation);
} else {
final AlertDialog alertDialogGPS = new AlertDialog.Builder(getActivity()).create();
alertDialogGPS.setTitle("Info");
alertDialogGPS.setMessage("Looks like you have not given GPS permissions. Please give GPS permissions and return back to the app.");
alertDialogGPS.setIcon(android.R.drawable.ic_dialog_alert);
alertDialogGPS.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intentSettings = new Intent(Settings.ACTION_APPLICATION_SETTINGS);
startActivity(intentSettings);
alertDialogGPS.dismiss();
}
});
alertDialogGPS.show();
}
}
@Override
public void onResume() {
super.onResume();
if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
mapFrag.getMapAsync(this);
}
else {
}
}
}
不确定为什么它在以前工作时返回null，任何想法如何在片段中处理它？</ p>
更新：
我甚至试过这个，但仍然得到它：
if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
mMap.setMyLocationEnabled(true);
Criteria criteria = new Criteria();
LocationManager locationManager = (LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);
String provider = locationManager.getBestProvider(criteria, false);
if(locationManager != null) {
Location location = locationManager.getLastKnownLocation(provider);
double lat = location.getLatitude();
double lng = location.getLongitude();
LatLng coordinate = new LatLng(lat, lng);
CameraUpdate yourLocation = CameraUpdateFactory.newLatLngZoom(coordinate, 13);
mMap.animateCamera(yourLocation);
} else
{
locationManager.requestLocationUpdates(provider, 1000, 0, (LocationListener) this);
}
}
我收到的错误消息：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jamessingleton.chffrapi, PID: 18112
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at com.example.jamessingleton.chffrapi.ThirdFragment.onMapReady(ThirdFragment.java:84)
at com.google.android.gms.maps.MapFragment$zza$1.zza(Unknown Source)
at com.google.android.gms.maps.internal.zzt$zza.onTransact(Unknown Source)
at android.os.Binder.transact(Binder.java:387)
at xz.a(:com.google.android.gms.DynamiteModulesB:82)
at maps.ad.u$5.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
W/DynamiteModule: Local module descriptor class for com.google.android.gms.googlecertificates not found.
W/ResourcesManager: getTopLevelResources: /data/app/com.google.android.gms-2/base.apk / 1.0 running in com.example.jamessingleton.chffrapi rsrc of package com.google.android.gms
I/DynamiteModule: Considering local module com.google.android.gms.googlecertificates:0 and remote module com.google.android.gms.googlecertificates:1
I/DynamiteModule: Selected remote version of com.google.android.gms.googlecertificates, version >= 1
D/ChimeraFileApk: Primary ABI of requesting process is arm64-v8a
D/ChimeraFileApk: Classloading successful. Optimized code found.
D/GoogleCertificates: com.google.android.gms.googlecertificates module is loaded
D/GoogleCertificatesImpl: Fetched 163 Google release certificates
D/GoogleCertificatesImpl: Fetched 318 Google certificates
I/Process: Sending signal. PID: 18112 SIG: 9
Application terminated.
答案 0 :(得分：0)
当你不应该将新的和旧的位置API混合在一起时。
要获取最后一个已知位置，您只需致电
mLocationClient.getLastLocation();
连接位置服务后。
阅读如何使用新的位置API