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问题:
mMapFragment = (SupportMapFragment) getSupportFragmentManager() .findFragmentByTag(MAP_FRAGMENT_TAG); // We only create a fragment if it doesn't already exist. if (mMapFragment == null) { mMapFragment = SupportMapFragment.newInstance(); // Then we add it using a FragmentTransaction. FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction(); fragmentTransaction.add(MapLay.getId(), mMapFragment, MAP_FRAGMENT_TAG); fragmentTransaction.commit(); mMap=mMapFragment.getMap();
By this code map is visible but unable to access the map
mMap=mMapFragment.getMap(); show null value error how to fix this
回答1:
Update 1: getMap() is deprecated
It is better to use getMapAsync() method of MapFragment/SupportMapFragment. The example how to use the method shown below (copied from their documentation).
import com.google.android.gms.maps.*; import com.google.android.gms.maps.model.*; import android.app.Activity; import android.os.Bundle; public class MapPane extends Activity implements OnMapReadyCallback { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.map_activity); MapFragment mapFragment = (MapFragment) getFragmentManager() .findFragmentById(R.id.map); mapFragment.getMapAsync(this); } @Override public void onMapReady(GoogleMap map) { LatLng sydney = new LatLng(-33.867, 151.206); map.setMyLocationEnabled(true); map.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney, 13)); map.addMarker(new MarkerOptions() .title("Sydney") .snippet("The most populous city in Australia.") .position(sydney)); } }
Quoting Google's MapFragment/SupportMapFragment
A GoogleMap can only be acquired using getMap() when the underlying maps system is loaded and the underlying view in the fragment exists. This class automatically initializes the maps system and the view; however you cannot be guaranteed when it will be ready because this depends on the availability of the Google Play services APK. If a GoogleMap is not available, getMap() will return null.
On your code, you immediately retrieve GoogleMap AFTER Committing MapFragment. Wait until the MapFragment is fully loaded on activity so you can get the GoogleMap.
Perhaps, you can deliver the GoogleMap from MapFragment to Activity using interface, like this.
public class MyMapFragment extends SupportMapFragment { private MapCallback callback; public void setMapCallback(MapCallback callback) { this.callback = callback; } public static interface MapCallback { public void onMapReady(GoogleMap map); } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); if(callback != null) callback.onMapReady(getMap()); } } public class MyActivity extends Activity implements MyMapFragment.MapCallback { // ......... @Override public void onCreate(Bundle onsavedInstanceState) { mMapFragment = (MyMapFragment) getSupportFragmentManager() .findFragmentByTag(MAP_FRAGMENT_TAG); // We only create a fragment if it doesn't already exist. if (mMapFragment == null) { mMapFragment = MyMapFragment.newInstance(); mMapFragment.setMapCallback(this); // This activity will receive the Map object once the map fragment is fully loaded // Then we add it using a FragmentTransaction. FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction(); fragmentTransaction.add(MapLay.getId(), mMapFragment, MAP_FRAGMENT_TAG); fragmentTransaction.commit(); } else { mMapFragment.setMapCallback(this); // This activity will receive the Map object once the map fragment is fully loaded } @Override public void onMapReady(GoogleMap map) { // Do what you want to map } }
回答2:
import part
import com.google.android.gms.maps.GoogleMap; import com.google.android.gms.maps.SupportMapFragment;
inside the oncreate
SupportMapFragment mapFragment = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map); mMap = mapFragment.getMap();
And Xml Part
Make sure you have put in
inside your
and give these permission in manifet file
回答3:
Your xml should have SupportMapFragment
回答4:
I solved this problem when I put this code:
@Override public void onPause() { Fragment fragment = (getFragmentManager().findFragmentById(R.id.map_tab)); FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction(); ft.remove(fragment); ft.commit(); super.onPause(); }
or I put this code in onCreate
if (mView != null) { ViewGroup parent = (ViewGroup) mView.getParent(); if (parent != null) { parent.removeView(mView); } } try { mView = inflater.inflate(R.layout.tab_map_layout, container, false); } catch (InflateException e) { }
回答5:
Following the @Glenn-- comment from Oct 1 '13 at 6:05 to create this piece of source code.
My Implementation is replacing the SupportMapFragment with MapFragment and support Google Maps Version 2
I want to remember again:
A GoogleMap can only be acquired using getMap() when the underlying maps system is loaded and the underlying view in the fragment exists. This class automatically initializes the maps system and the view; however you cannot be guaranteed when it will be ready because this depends on the availability of the Google Play services APK. If a GoogleMap is not available, getMap() will return null.
My Implementation:
AndroidManifest.xml
activity_main.xml
ApplicationMapFragment.java
public class ApplicationMapFragment extends MapFragment { private MapCallback callback; public void setMapCallback(MapCallback callback) { this.callback = callback; } public static interface MapCallback { public void onMapReady(GoogleMap map); } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); if(callback != null) callback.onMapReady(getMap()); } /** * Initialize default Google Maps Options for our Application * @return GoogleMapOptions */ public GoogleMapOptions initializeGoogleMapsOptions() { GoogleMapOptions googleMapOptions = new GoogleMapOptions() .mapType(GoogleMap.MAP_TYPE_HYBRID); return googleMapOptions; } }
MainActivity.java
public class MainActivity extends Activity implements ApplicationMapFragment.MapCallback { // Get Class Name private static String TAG = MainActivity.class.getName(); // Create a new Map fragment private ApplicationMapFragment mapFragment; // Google Map Fragment Name private static String MAP_FRAGMENT_TAG = "google_maps_fragment"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); try { initilizeMapFragment(); } catch (Exception e) { e.printStackTrace(); Log.e(TAG, "Google Maps can't be loaded", e); } } /** * Initialize a new Map Fragment */ private void initilizeMapFragment() { // Try to get Map Fragment mapFragment = (ApplicationMapFragment) getFragmentManager() .findFragmentByTag(MAP_FRAGMENT_TAG); // We only create a fragment if it doesn't already exist. if (mapFragment == null) { mapFragment = new ApplicationMapFragment(); mapFragment.initializeGoogleMapsOptions(); // This activity will receive the Map object once the map fragment is fully loaded mapFragment.setMapCallback(this); // Then we add it using a FragmentTransaction. FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction(); fragmentTransaction.add(R.id.google_map_container, mapFragment, MAP_FRAGMENT_TAG); fragmentTransaction.commit(); } else { // This activity will receive the Map object once the map fragment is fully loaded mapFragment.setMapCallback(this); } } @Override public void onMapReady(GoogleMap map) { Log.d(TAG, "Google Map is loaded"); MarkerOptions marker = new MarkerOptions() .position(new LatLng(10, 10)) .title("Hello World"); map.addMarker(marker); } }
回答6:
Really hackish solution but, because given the poor fragment API...
Note that I'm doing this from a custom View and accessing the Activity using (Activity)getContext()
addOnLayoutChangeListener(new OnLayoutChangeListener(){ @Override public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) { GoogleMap map = mapFragment.getMap(); if (map != null) { //Do stuff }else{ removeOnLayoutChangeListener(this); } } });
翻译