无法加载地图成的FrameLayout

Question

MapFragment.java

public class MapFragment extends SupportMapFragment implements OnMapReadyCallback{ 
    private GoogleMap googleMap; 
    private Context context; 

    public MapFragment(){ 

    } 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
    { 
     super.onCreateView(inflater, container, savedInstanceState); 
     View root = inflater.inflate(R.layout.item_individual_warehouse, null, false); 
     onMapReady(googleMap); 
     return root; 
    } 

    private void initializeMap(){ 
     if(googleMap == null) { 
      SupportMapFragment fm =(SupportMapFragment)getChildFragmentManager().findFragmentById(R.id.map); 
      fm.getMapAsync(this); 
      if(googleMap == null){ 
       Toast.makeText(context,"Sorry! We are unable to load maps", Toast.LENGTH_SHORT).show(); 
      } 
     } 
    } 

    @Override 
    public void onMapReady(GoogleMap gm) { 
     googleMap = gm; 
     initializeMap(); 
    } 
} 

以我onCreate方法在RetrieveIndividualWarehouseSales.java

public void onCreate(Bundle savedInstanceState){ 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.item_individual_warehouse); 
     new RetrieveItem().execute(); 
     MapFragment mf = new MapFragment(); 
     mf.onMapReady(googleMap); 

    } 

item_individual_warehouse.xml

<FrameLayout 
    android:id="@+id/map" 
    android:name="com.google.android.gms.maps.SupportMapFragment" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_below="@+id/sales_location"/> 

错误是：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference 

我试图实例化RetrieveIndividualWarehouseSales.java的MapFragment对象，以便我可以显示item_individual_warehouse.xml地图包含了一堆textviews和一个FrameLayout里这是为地图。

Answer 1

使用此。

public class MapLocationActivity extends AppCompatActivity 
     implements OnMapReadyCallback, 
     GoogleApiClient.ConnectionCallbacks, 
     GoogleApiClient.OnConnectionFailedListener, 
     LocationListener { 

    GoogleMap mGoogleMap; 
    SupportMapFragment mapFrag; 
    LocationRequest mLocationRequest; 
    GoogleApiClient mGoogleApiClient; 
    Location mLastLocation; 
    Marker mCurrLocationMarker; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
      checkLocationPermission(); 
     } 

     mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map); 
     mapFrag.getMapAsync(this); 
    } 

    @Override 
    public void onPause() { 
     super.onPause(); 

     //stop location updates when Activity is no longer active 
     if (mGoogleApiClient != null) { 
      LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); 
     } 
    } 

    @Override 
    public void onMapReady(GoogleMap googleMap) 
    { 
     mGoogleMap=googleMap; 
     mGoogleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID); 

     //Initialize Google Play Services 
     if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
       if (ContextCompat.checkSelfPermission(this, 
         Manifest.permission.ACCESS_FINE_LOCATION) 
         == PackageManager.PERMISSION_GRANTED) { 
        buildGoogleApiClient(); 
        mGoogleMap.setMyLocationEnabled(true); 
       } 
     } 
     else { 
      buildGoogleApiClient(); 
      mGoogleMap.setMyLocationEnabled(true); 
     } 
    } 

    protected synchronized void buildGoogleApiClient() { 
     mGoogleApiClient = new GoogleApiClient.Builder(this) 
       .addConnectionCallbacks(this) 
       .addOnConnectionFailedListener(this) 
       .addApi(LocationServices.API) 
       .build(); 
     mGoogleApiClient.connect(); 
    } 

    @Override 
    public void onConnected(Bundle bundle) { 
     mLocationRequest = new LocationRequest(); 
     mLocationRequest.setInterval(1000); 
     mLocationRequest.setFastestInterval(1000); 
     mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY); 
     if (ContextCompat.checkSelfPermission(this, 
       Manifest.permission.ACCESS_FINE_LOCATION) 
       == PackageManager.PERMISSION_GRANTED) { 
      LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this); 
     } 
    } 

    @Override 
    public void onConnectionSuspended(int i) {} 

    @Override 
    public void onConnectionFailed(ConnectionResult connectionResult) {} 

    @Override 
    public void onLocationChanged(Location location) 
    { 
     mLastLocation = location; 
     if (mCurrLocationMarker != null) { 
      mCurrLocationMarker.remove(); 
     } 

     //Place current location marker 
     LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude()); 
     MarkerOptions markerOptions = new MarkerOptions(); 
     markerOptions.position(latLng); 
     markerOptions.title("Current Position"); 
     markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA)); 
     mCurrLocationMarker = mGoogleMap.addMarker(markerOptions); 

     //move map camera 
     mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng)); 
     mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(11)); 

     //stop location updates 
     if (mGoogleApiClient != null) { 
      LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); 
     } 
    } 

    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99; 
    public boolean checkLocationPermission(){ 
     if (ContextCompat.checkSelfPermission(this, 
       Manifest.permission.ACCESS_FINE_LOCATION) 
       != PackageManager.PERMISSION_GRANTED) { 

      // Should we show an explanation? 
      if (ActivityCompat.shouldShowRequestPermissionRationale(this, 
        Manifest.permission.ACCESS_FINE_LOCATION)) { 

       //TODO: 
       // Show an expanation to the user *asynchronously* -- don't block 
       // this thread waiting for the user's response! After the user 
       // sees the explanation, try again to request the permission. 

       //Prompt the user once explanation has been shown 
       //(just doing it here for now, note that with this code, no explanation is shown) 
       ActivityCompat.requestPermissions(this, 
         new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 
         MY_PERMISSIONS_REQUEST_LOCATION); 


      } else { 
       // No explanation needed, we can request the permission. 
       ActivityCompat.requestPermissions(this, 
         new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 
         MY_PERMISSIONS_REQUEST_LOCATION); 
      } 
      return false; 
     } else { 
      return true; 
     } 
    } 

    @Override 
    public void onRequestPermissionsResult(int requestCode, 
              String permissions[], int[] grantResults) { 
     switch (requestCode) { 
      case MY_PERMISSIONS_REQUEST_LOCATION: { 
       // If request is cancelled, the result arrays are empty. 
       if (grantResults.length > 0 
         && grantResults[0] == PackageManager.PERMISSION_GRANTED) { 

        // permission was granted, yay! Do the 
        // location-related task you need to do. 
        if (ContextCompat.checkSelfPermission(this, 
          Manifest.permission.ACCESS_FINE_LOCATION) 
          == PackageManager.PERMISSION_GRANTED) { 

         if (mGoogleApiClient == null) { 
          buildGoogleApiClient(); 
         } 
         mGoogleMap.setMyLocationEnabled(true); 
        } 

       } else { 

        // permission denied, boo! Disable the 
        // functionality that depends on this permission. 
        Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show(); 
       } 
       return; 
      } 

      // other 'case' lines to check for other 
      // permissions this app might request 
     } 
    } 
}