Null pointer exception at mapFragment.getMapAsync(

问题:

When I use v6.5.87 of Google Play Services, I get a null pointer exception when I call getMapAsync(). I'm using a SupportMapFragment in my Fragment's xml layout.

My code:

SupportMapFragment mapFragment = (SupportMapFragment) getActivity()
        .getSupportFragmentManager().findFragmentById(R.id.mapFragment);

mapFragment.getMapAsync(this);

Note: There's no problem when calling getMap() on older Google Play Services versions, but getMap() is now deprecated (docs).

Here's the stack trace for the NPE:

java.lang.NullPointerException
            at com.decos.fixi.fragments.FragmentLocationMap.initializeMap(FragmentLocationMap.java:132)
            at com.decos.fixi.fragments.FragmentLocationMap.onCreateView(FragmentLocationMap.java:95)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
            at dalvik.system.NativeStart.main(Native Method)

回答1:

Finally I got the answer!

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

instead of

SupportMapFragment mapFragment = (SupportMapFragment) this.getSupportFragmentManager()
                .findFragmentById(R.id.mapFragment);

getChildFragmentManager() did the trick.

回答2:

In addition, If you are using SupportMapFragment mapFragment = (SupportMapFragment).....

Then be sure you have set this class attribute in XML

class="com.google.android.gms.maps.SupportMapFragment"

Not

class ="com.google.android.gms.maps.MapFragment"

回答3:

In AppCompatActivity extend

FragmentManager mFragmentManager = getSupportFragmentManager();
SupportMapFragment mVTMapFragment =(SupportMapFragment)mFragmentManager.findFragmentById(R.id.mapRideview);
mVTMapFragment.getMapAsync(this);

and implement onMapReady callback method

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    setUpMap();
}

回答4:

Have you implement the callback function for your getMapAsync()?

If not, You need to implement the onMapReady() method in your code, and then you can do adding markers or moving camera stuff in your onMapReady() method.

You can see this example about onMapReady().

回答5:

Heading

run your program by adding this

 SupportMapFragment supportMapFragment

ADD THIS in ON CREATE METHOD()

supportMapFragment = SupportMapFragment.newInstance(); 

FragmentManager fm = getFragmentManager();
fm.beginTransaction().replace(R.id.maplayout, new MapFragmentClass()).commit();
supportMapFragment.getMapAsync(this);

android.support.v4.app.FragmentManager sfm = getSupportFragmentManager();
sfm.beginTransaction().add(R.id.map,supportMapFragment).commit();

this will work check it