我想在打开MapActivity时使地图聚焦在当前位置。我对特定行有问题：
mMap.setMyLocationEnabled(true);
调用需要权限，可能会被用户拒绝：代码应该显式检查权限是否可用（"checkPermission"）或显式处理潜在的"SecurityException"。
如何解决此问题？当我搜索这个问题时，我已经阅读了一些东西，但我找不到有用的东西。
这是完整的代码：
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private static final String FIREBASE_URL="https://haerev.firebaseio.com/";
private Firebase firebaseRef;
private GoogleMap mMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps2);
Firebase.setAndroidContext(this);
firebaseRef = new Firebase(FIREBASE_URL);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
mMap.setMyLocationEnabled(true);
// Check if we were successful in obtaining the map.
if (mMap != null) {
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
@Override
public void onMyLocationChange(Location arg0) {
// TODO Auto-generated method stub
mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("It's Me!"));
}
});
}
}
}
看完一些评论，再看完这个问题：http：//developer.android.com/training/permissions/requesting.html
我添加了这些行：
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
if (ContextCompat.checkSelfPermission(MapsActivity.this,
Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
if (ActivityCompat.shouldShowRequestPermissionRationale(MapsActivity.this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
checkSelfPermission("You have to accept to enjoy the most hings in this app");
} else {
ActivityCompat.requestPermissions(MapsActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION);
}
}
mMap.setMyLocationEnabled(true);
// Check if we were successful in obtaining the map.
if (mMap != null) {
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
@Override
public void onMyLocationChange(Location arg0) {
// TODO Auto-generated method stub
mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("It's Me!"));
}
});
}
}
}
但现在我有一个新的问题。它不识别行
"MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION"。
我想我以错误的方式使用它。我应该如何使用它？
在网络上进行了大量研究之后，这就是对我有用的：
private void setUpMapIfNeeded() {
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
mMap.setMyLocationEnabled(true);
} else {
Toast.makeText(MapsActivity.this, "You have to accept to enjoy all app's services!", Toast.LENGTH_LONG).show();
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
mMap.setMyLocationEnabled(true);
}
}
if (mMap != null) {
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
@Override
public void onMyLocationChange(Location arg0) {
// TODO Auto-generated method stub
CameraUpdate center= CameraUpdateFactory.newLatLng(new LatLng(arg0.getLatitude(), arg0.getLongitude()));
CameraUpdate zoom=CameraUpdateFactory.zoomTo(12);
mMap.moveCamera(center);
mMap.animateCamera(zoom);
}
});
}
}
}
更清晰的实现：
@Override
public void onMapReady(GoogleMap googleMap) {
MapsInitializer.initialize(getContext());
mGoogleMap = googleMap;
if(checkPermission())
mGoogleMap.setMyLocationEnabled(true);
else askPermission();
}
// Check for permission to access Location
private boolean checkPermission() {
Log.d(TAG, "checkPermission()");
// Ask for permission if it wasn't granted yet
return (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED );
}
// Asks for permission
private void askPermission() {
Log.d(TAG, "askPermission()");
ActivityCompat.requestPermissions(
getActivity(),
new String[] { Manifest.permission.ACCESS_FINE_LOCATION },
REQ_PERMISSION
);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
Log.d(TAG, "onRequestPermissionsResult()");
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch ( requestCode ) {
case REQ_PERMISSION: {
if ( grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED ){
// Permission granted
if(checkPermission())
mGoogleMap.setMyLocationEnabled(true);
} else {
// Permission denied
}
break;
}
}
}
实际上，这段代码是在我观看解决方案后由Android Studio自动生成的。我正在处理片段，所以我不得不将"this"更改为"getContext"
try {
MapsInitializer.initialize(getActivity().getApplicationContext());
} catch (Exception e) {
e.printStackTrace();
}
mMapView.getMapAsync(new OnMapReadyCallback() {
@Override
public void onMapReady(GoogleMap mMap) {
googleMap = mMap;
if (ActivityCompat.checkSelfPermission(getContext(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getContext(),
Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return;
}
试试这个
任一组
targetSdkVersion 22
或请求运行时权限，请参阅此处：-http://coderzpassion.com/android-new-runtime-permissions/希望有帮助，谢谢