getSupportFragmentManager().findFragmentById对于Android片段中的Google地图返回null? [英] getSupportFragmentManager().findFragmentById returns null for google maps in fragment in android?

问题描述

我在使用Google Maps时遇到问题，即getSupportFragmentManager().findFragmentById始终返回null.您有解决方法的想法吗?

I have a problem with Google Maps, i.e. getSupportFragmentManager().findFragmentById returns always null. Do you have an idea how to solve this?

这是代码:

fragment_map.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.myapp.something.MapFragment">
<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />                  
</FrameLayout>

MapsFragment.java:

MapsFragment.java:

public class MapFragment extends Fragment implements OnMapReadyCallback, android.location.LocationListener

public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    SupportMapFragment mapFragment = (SupportMapFragment) this.getActivity().getSupportFragmentManager().findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);
...

我在活动"中使用了Google地图，并且可以使用以下代码:

I have Google Maps in Activity and it works with code:

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

我正试图在片段中重用它，因为我需要在片段中而不是活动中使用地图，但这是行不通的.

I am trying to reuse this in fragment, becouse I need maps in fragment, not in activity, but it doesn't work.

我尝试过:

• 在"onCreateView"函数中调用此代码
• SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);
• GoogleMap mGoogleMap = ((SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map)).getMap();已过时，应用程序崩溃
• SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map); 和类似的变体，但在所有情况下，mapFragment都为空.

• calling this code in "onCreateView" function
• SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);
• GoogleMap mGoogleMap = ((SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map)).getMap(); is deprecated, and application crashes
• SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map); and similar variations, but in all cases I get null for mapFragment.

您知道我该如何解决这个问题?

Do you know how could I solve this problem?

推荐答案

问题是您正在尝试使用Activity的FragmentManager，而您应该使用Fragment的子FragmentManager.

The problem is that you're trying to use the Activity's FragmentManager, and you should be using the Fragment's child FragmentManager.

删除片段中的onCreate()替代，并在填充布局并调用getMapAsync()的位置添加onCreateView()替代:

Remove the onCreate() override in the Fragment, and add an onCreateView() Override where you inflate the layout and call getMapAsync():

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_map, container, false);

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

    mapFragment.getMapAsync(this);

    return rootView;
}

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