android - 旋转时回收Android Maps V2 SupportMapFragment

Question

我希望在设备旋转时提高 SupportMapFragment 的性能。似乎必须重新创建 fragment 。我不确定这一点，但是当设备旋转时，必须重新加载 map 图 block 。从性能的角度来看，保留和重用整个 mapfragment 而不必重新实例化 fragment 是有意义的。对此有任何见解将不胜感激。

我在 xml 中声明 SupportMapFragment 并使用 SetupMapIfNeeded()，如 api 文档中所述。

private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the
    // map.
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        mMap = ((SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map)).getMap();
        // Check if we were successful in obtaining the map.
        if (mMap != null) {
            setUpMap();
        }
    }
}

Answer 1

检查示例中的 RetainMapActivity 类。奇迹般有效。这是:

public class RetainMapActivity extends FragmentActivity {

private GoogleMap mMap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.basic_demo);

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

    if (savedInstanceState == null) {
        // First incarnation of this activity.
        mapFragment.setRetainInstance(true);
    } else {
        // Reincarnated activity. The obtained map is the same map instance in the previous
        // activity life cycle. There is no need to reinitialize it.
        mMap = mapFragment.getMap();
    }
    setUpMapIfNeeded();
}

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

private void setUpMapIfNeeded() {
    if (mMap == null) {
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                .getMap();
        if (mMap != null) {
            setUpMap();
        }
    }
}

private void setUpMap() {
    mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
}