我是Android的新手，并使用FusedLocationProviderClient获取MyLocation并放大它。
当我的位置关闭并打开并调用getDeviceLocation（）函数时，它会在我的logcat上抛出此错误并强行关闭应用程序：
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at myProjectPackageName.MainActivity$2.onComplete(MainActivity.java:108)
at com.google.android.gms.tasks.zzj.run(Unknown Source:23)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
我的整个代码：
public class MainActivity extends AppCompatActivity
implements
OnMapReadyCallback,
GoogleMap.OnMapClickListener {
private GoogleMap mMap;
private FusedLocationProviderClient mFusedLocationProviderClient;
// The geographical location where the device is currently located. That is, the last-known
// location retrieved by the Fused Location Provider.
private Location mLastKnownLocation;
// A default location and zoom to use when location permission is not granted.
private final LatLng defaultLocation = new LatLng(36.2896307,59.6011211);
private static final int DEFAULT_ZOOM_GRANTED = 17;
private static final int DEFAULT_ZOOM_DENIED = 10;
// Permission Check
private static final int ACCESS_FINE_LOCATION_REQUEST_CODE = 1;
private boolean locationPermissionGranted = false;
// Location Service Status
private LocationManager locationManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
mFusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
ImageView myLocationImageView = findViewById(R.id.iv_main_myLocation);
myLocationImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(locationPermissionGranted) {
if (checkGpsStatus()) {
getDeviceLocation();
} else {
//TODO : Alert Dialog For Enabling Location Service
Toast.makeText(MainActivity.this, "Please Enable GPS", Toast.LENGTH_SHORT).show();
}
}else{
getLocationPermission();
}
}
});
}
private boolean checkGpsStatus() {
return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
mMap.setOnMapClickListener(this);
//mMap.getUiSettings().setZoomControlsEnabled(true);
getLocationPermission();
getDeviceLocation();
}
private void getDeviceLocation() {
try {
if (locationPermissionGranted) {
if (checkGpsStatus()) {
Task<Location> locationResult = mFusedLocationProviderClient.getLastLocation();
locationResult.addOnCompleteListener(this, new OnCompleteListener<Location>() {
@Override
public void onComplete(@NonNull Task<Location> task) {
if (task.isSuccessful()) {
// Set the map's camera position to the current location of the device.
mLastKnownLocation = task.getResult();
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(
new LatLng(mLastKnownLocation.getLatitude(),
mLastKnownLocation.getLongitude()), DEFAULT_ZOOM_GRANTED);
mMap.animateCamera(cameraUpdate);
}
}
});
}else{
//TODO : Alert Dialog For Enabling Location Service
Toast.makeText(MainActivity.this, "Please Enable GPS", Toast.LENGTH_SHORT).show();
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(defaultLocation, DEFAULT_ZOOM_DENIED);
mMap.animateCamera(cameraUpdate);
}
}else{
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(defaultLocation, DEFAULT_ZOOM_DENIED);
mMap.animateCamera(cameraUpdate);
}
} catch (SecurityException e) {
Log.e("Exception: %s", e.getMessage());
}
}
private void getLocationPermission() {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
setMyLocationEnabled();
} else {
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
//TODO : Add Alert Dialog For Getting Request Again & Remove Below Codes
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
ACCESS_FINE_LOCATION_REQUEST_CODE); } else {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
ACCESS_FINE_LOCATION_REQUEST_CODE);
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
switch (requestCode) {
case ACCESS_FINE_LOCATION_REQUEST_CODE: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
setMyLocationEnabled();
} else {
Toast.makeText(this,"Denied",Toast.LENGTH_SHORT).show();
}
}
}
}
private void setMyLocationEnabled() {
locationPermissionGranted = true;
try{
mMap.setMyLocationEnabled(true);
mMap.getUiSettings().setMyLocationButtonEnabled(false);
}catch (SecurityException e){
Log.e("setMyLocationEnabled : ",e.toString());
}
getDeviceLocation();
}
@Override
public void onMapClick(LatLng latLng) {
Toast.makeText(this, "Lat :" + latLng.latitude + "Lng : " + latLng.longitude, Toast.LENGTH_LONG).show();
}
}
我不想使用谷歌地图MyLocationButton，如何在我的应用程序中实现该功能？