HERE Map/MapView 不使用 MapFragment popupBackstack 问题

Question

我有一个 Activity 并将两个片段（MapScreenFragment 和 OtherFragment）加载到后台堆栈。我遇到的问题是，当我开始从后台弹出一些片段时，MapScreenFragment 显示黑屏。

我应该为 MapView 设置新的地图吗？

map = new Map();
mapView.setMap(map);

XML 布局

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<com.here.android.mpa.mapping.MapView
    android:id="@+id/map_view"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"/>

</FrameLayout>

片段类

public class MapScreenFragment extends Fragment {
@Override
public void onResume() {
    super.onResume();
    Log.d(TAG, "onResume");

    if(isMapEngineInitialized && mapEngine != null) {
        mapEngine.onResume();
        mapView.onResume();
        Log.d(TAG, " onResume Map engine reference " + mapEngine.getResourceReferenceCount());
    }
}

@Override
public void onPause() {
    super.onPause();

    Log.d(TAG, "onPause");

    if(isMapEngineInitialized && mapEngine != null) {
        mapEngine.onPause();
        mapView.onPause();
        Log.d(TAG, " onPause Map engine reference " + mapEngine.getResourceReferenceCount());
    }
}
}

/***** added ******/
OnEngineInitListener onEngineInitListener = new OnEngineInitListener() {
    @Override
    public void onEngineInitializationCompleted(Error error) {
        if(error == Error.NONE) {
            isMapEngineInitialized = true;

            if(map == null) {
                Log.d(TAG, " Map is null");
                map = new Map();
            }

            mapView.setMap(map);
            mapView.setMapMarkerDragListener(MapScreenFragment.this);

            map = mapView.getMap();
            map.addTransformListener(MapScreenFragment.this);

            mapGesture = mapView.getMapGesture();
            mapGesture.setAllGesturesEnabled(true);
            mapGesture.addOnGestureListener(MapScreenFragment.this);

            setUpMap();

            Log.d(TAG, "MapEngine initialized! " + mapEngine.getResourceReferenceCount());

        }

    }
};

MainActivity Backpressed 并添加 Fragments

mapFragment = new MapScreenFragment ();
mFragmentTransaction =  getSupportFragmentManager().beginTransaction();
mFragmentTransaction.add(R.id.main_frame_layout, mapFragment , mdmFragmentID);
mFragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
mFragmentTransaction.addToBackStack(null);
mFragmentTransaction.commit();



otherFragment = new OtherFragment ();
mFragmentTransaction =  getSupportFragmentManager().beginTransaction();
mFragmentTransaction.replace(R.id.main_frame_layout, otherFragment , mdmFragmentID);
mFragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
mFragmentTransaction.addToBackStack(null);mFragmentTransaction.commit();


@Override
public void onBackPressed() {
    Log.d(TAG, "Back stack count " + getSupportFragmentManager().getBackStackEntryCount());
    if( getSupportFragmentManager().getBackStackEntryCount() == 1) {
        finish();
    } else {
        getSupportFragmentManager().popBackStack();
    }
}

Answer 1

确保在 isMapEngineInitialized == false 的情况下调用 MapView#onResume()，尤其是在回调 MapEngine#onEngineInit 侦听器时。

通常，应用程序生命周期调用 onResume() 远早于引擎初始化。如果未调用 MapView#onResume()，则不会启动底层渲染构造。有关示例，请参阅我们的示例应用程序。

另外，为什么不使用嵌套片段？您始终可以将 MapFragment 嵌入到另一个片段中，以便自动处理生命周期。