初始化谷歌地图时，mapFragment.getMapAsync(this)处出现空指针异常

当我使用 Google Play Services v6.5.87 时，调用时出现空指针异常getMapAsync()。我正在使用一个SupportMapFragment in my Fragment的 xml 布局。

My code:

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

mapFragment.getMapAsync(this);

注：调用时没有问题getMap()在较旧的 Google Play 服务版本上，但是getMap()现已弃用（docs).

这是 NPE 的堆栈跟踪：

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)

终于我得到了答案！

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

代替

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

getChildFragmentManager() 成功了。