SupportMapFragment' s的getMap()返回null [英] SupportMapFragment's getMap() returns null

问题描述

我正在尝试动态创建 SupportMapFragment 并将其放入 FrameLayout 容器中.

I'm trying to create a SupportMapFragment dynamically and to put it in a FrameLayout container.

我的问题是 mMapFragment.getMap()返回 null ...

My issue is that mMapFragment.getMap() returns null...

有人可以帮忙吗?

CenterMapFragment.java

public class CenterMapFragment extends Fragment {

    private SupportMapFragment mMapFragment;

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

        return inflater.inflate(R.layout.center_map_fragment, container, false);
    }

    @Override
    public void onActivityCreated (Bundle savedInstanceState){
        super.onActivityCreated(savedInstanceState);

        if (GooglePlayServicesUtil.isGooglePlayServicesAvailable(getActivity()) == ConnectionResult.SUCCESS) {
            setUpMapIfNeeded();
        }
    }


    private void setUpMapIfNeeded() {

        if (mMapFragment == null) {

            mMapFragment = SupportMapFragment.newInstance();
            FragmentTransaction fragmentTransaction =
                            getChildFragmentManager().beginTransaction();
            fragmentTransaction.replace(R.id.map, mMapFragment);
            fragmentTransaction.commit(); 

            setUpMap();
        }
    }

    private void setUpMap() {       

        GoogleMap map = mMapFragment.getMap();  

        // map is null!

    }

    @Override
    public void onResume()
    {
        super.onResume();
        setUpMapIfNeeded();     
    }
}

center_map_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <FrameLayout
        android:id="@+id/map"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </FrameLayout>

    <Button
        android:id="@+id/btn_loc"
        android:layout_width="60dp"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:background="@drawable/locbtn" />

</RelativeLayout>

在 FragmentTransaction 上的

推荐答案

commit()不会立即执行其操作.到您调用 setUpMap()时，将不会在 SupportMapFragment 上调用 onCreateView()，因此不会是地图.

commit() on a FragmentTransaction does not perform its operations immediately. By the time you call setUpMap(), onCreateView() will not have been called on the SupportMapFragment, and hence there will not yet be a map.

一种方法是不使用嵌套片段，而是选择扩展 CenterMapFragment 扩展 SupportMapFragment ，在这种情况下， getMap()应该可以工作 onCreateView()之后的时间(例如， onActivityCreated()).

One approach is to not use nested fragments, electing instead to have CenterMapFragment extend SupportMapFragment, in which case getMap() should work any time after onCreateView() (e.g., onActivityCreated()).

这篇关于SupportMapFragment' s的getMap()返回null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！