在嵌套的mapfragment中调用getMap（）会给出nullpointerexception

Question

我在自定义片段中有一个mapfragment，通过调用它来提供here

不幸的是，如果我调用了getMap（） - Method（参见附件代码），那么会出现NullPointerException。有谁知道为什么？谢谢你的帮助！

private void initializeMap() {
    initializeMapFragment();

    try {
        // show current location
        map.setMyLocationEnabled(true);
        map.getUiSettings().setRotateGesturesEnabled(true);
        map.getUiSettings().setZoomGesturesEnabled(true);

        // adding marker
        addDestinationMarker();

        // zoom to current location
        Location myLocation = map.getMyLocation();
        if (myLocation != null) {
            LatLng currentPosition = new LatLng(myLocation.getLatitude(), myLocation.getLongitude());
            CameraPosition cameraPosition = new CameraPosition.Builder().target(currentPosition).zoom(12).build();
            map.moveCamera(CameraUpdateFactory.newLatLng(currentPosition));
            map.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private void initializeMapFragment() {
    MapFragment mapFragment = MapFragment.newInstance();
    FragmentManager fm = getFragmentManager();
    if (fm.findFragmentByTag("my_map_fragment") == null) {
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.map_container, mapFragment, "my_map_fragment").commit();
    }
    map = mapFragment.getMap();
}

编辑//

HomeFragment的xml如下所示：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent" android:weightSum="1">

<FrameLayout
        android:id="@+id/map_container"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1">
</FrameLayout>

<LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top|bottom|left|right|center"
        android:background="@drawable/bg_lines"
        android:orientation="horizontal">

    <Button
            android:id="@+id/alarmButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            style="@style/BlueButtonStyle"
            android:text="@string/btn_alarm"/>
</LinearLayout>