java - Android Studio "error: incompatible types: Fragment cannot be converted to SupportMapFragment"

Question

您好，我正在尝试在 fragment 中创建 map ，我按照在线教程进行操作，该教程旨在将其放入 Activity 中，但我遇到了问题。我到处都找过了，但找不到解决方案。

当我尝试在 android studio 中编译时，它在我的 map 中出现错误“初始化行错误:

 incompatible types: Fragment cannot be converted to SupportMapFragment"

错误发生在initMap()上:

行:

SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map);

在我将导入从 import android.support.v4.app.Fragment; 更改为 import android.app.Fragment; (我必须由于其他应用程序错误而保留)

这是我的 fragment 代码:

public class MapFragment extends Fragment implements OnMapReadyCallback
{

    private static final String TAG = "MapFragment";

    private Boolean LocationPermissionsGranted = false;  //boolean for location method
    private GoogleMap Map;
    private static final int ERROR_REQUEST = 69; //error code relates to isservicesOK method
    private static final String FINE_LOCATION = Manifest.permission.ACCESS_FINE_LOCATION;
    private static final String COURSE_LOCATION = Manifest.permission.ACCESS_COARSE_LOCATION;
    private static final int LOCATION_PERMISSION_CODE = 1234;

    public MapFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate( savedInstanceState );
        //TODO: Instead of hardcoding the title perhaps take the user name from somewhere?
        // Note the use of getActivity() to reference the Activity holding this fragment
        getActivity().setTitle( "YOUR CLINICS" );
        isServicesOK();
        getLocationPermission();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        ButterKnife.bind( getActivity() );

        return inflater.inflate( R.layout.fragment_map, container, false );


    }
    @Override
    public void onMapReady(GoogleMap googleMap) {
        Toast.makeText(getActivity(), "Maps is ready", Toast.LENGTH_SHORT).show();
        Log.d(TAG, "Map is ready");
        Map = googleMap;
    }
    private void initMap() {
        Log.d(TAG, "initializing map...");
        SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map); //ignore warning

        mapFragment.getMapAsync(MapFragment.this);
    }

    private void getLocationPermission()
    {
        Log.d(TAG, "Retrieving location permissions");
        String[] permissions = {android.Manifest.permission.ACCESS_FINE_LOCATION,
                android.Manifest.permission.ACCESS_COARSE_LOCATION};

        if (ContextCompat.checkSelfPermission(this.getActivity().getApplicationContext(), //ignore
                FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            if (ContextCompat.checkSelfPermission(this.getActivity().getApplicationContext(),
                    COURSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                LocationPermissionsGranted = true;
            } else {
               requestPermissions(permissions,
                        LOCATION_PERMISSION_CODE);
            }
        } else {
            requestPermissions(permissions,
                    LOCATION_PERMISSION_CODE);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults)
    {
        Log.d(TAG, "onRequestPermissionsResult: called.");
        LocationPermissionsGranted = false;

        switch (requestCode)
        {
            case LOCATION_PERMISSION_CODE:
            {
                if (grantResults.length > 0)
                {
                    for (int i = 0; i < grantResults.length; i++) //ignore
                    {
                        if (grantResults[i] != PackageManager.PERMISSION_GRANTED)
                        {
                            LocationPermissionsGranted = false;
                            Log.d(TAG, "onRequestPermissionsResult: permission failed");
                            return;
                        }
                    }
                    Log.d(TAG, "onRequestPermissionsResult: permission granted");
                    LocationPermissionsGranted = true;
                    //if permissions are granted we initialize the map
                    initMap();
                }
            }
        }
    }


    // integrate this method with the start of the application eg after a button has been clicked
    // Debugging method- checks if google services is available/functional
    public boolean isServicesOK ()
    {
        Log.d(TAG, "isServicesOK: checking if your Google Services is up to date"); //debugging

        int available = GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable(getActivity()); /*//log d = debug*/

        if (available == ConnectionResult.SUCCESS)
        {
            /*//checks if everything is fine*/
            Log.d(TAG, "isServicesOK: Google Play Services is functional");
            return true;
        }
        else if (GoogleApiAvailability.getInstance().isUserResolvableError(available))
        {
            /* //If an error occurs, and it is resolvable*/
            Log.d(TAG, "isServicesOK: A fixable error has occured!");
            Dialog dialog = GoogleApiAvailability.getInstance().getErrorDialog(getActivity(), available, ERROR_REQUEST);
            dialog.show();  /*//This prompts google to provide a error message and solution when a fixable error has occurred*/
        }

        else
        {
            Toast.makeText(getActivity(), "Google Play Services is dysfunctional, sorry!", Toast.LENGTH_SHORT).show(); /*//if it cant be fixed for whatever reason lmao*/
        }
        return false;
    }

}

Answer 1

This problem occured after i changed my import from import android.support.v4.app.Fragment; to import android.app.Fragment; (which i have to keep due to other application errors)

如果不使用支持库 Fragment API，您无法使用SupportMapFragment。 SupportMapFragment 是一个支持库Fragment，虽然框架Fragment和支持库Fragment具有相同的名称和非常相似的方法，但它们不是相同且不能混合。

SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map); //ignore warning

使用框架 Fragment API(而不是支持库 API)时，getChildFragmentManager() 只能管理框架 Fragment。因此，此 FragmentManager 不可能返回 SupportMapFragment。

如果您想使用SupportMapFragment，则必须更改应用程序的其余部分以允许您使用支持库Fragments。