谷歌地图v2在从堆栈弹出碎片后出现延迟

Question

我有一个Activity和一个MapFragment，我使用FragmentTransaction以编程方式添加到Activity:

private static final String MAP_FRAGMENT_TAG = "map";
private MapFragment mapFragment = null;
...
protected void onCreate(Bundle savedInstanceState) {
    ...
    mapFragment = (MapFragment) getFragmentManager().findFragmentByTag(MAP_FRAGMENT_TAG);
    if (mapFragment == null) {
        mapFragment = MapFragment.newInstance();
        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragmentTransaction.add(R.id.fragment_wrapper, mapFragment, MAP_FRAGMENT_TAG);
        fragmentTransaction.commit();
    }
    ...
}

标准方法。然后我从mapFragment中获得GoogleMap实例并设置它的设置，设置侦听器，用它做一些事情。一切正常

当用户完成映射时，AsyncTask被触发以显示ProgressDialog，执行一些操作，将不同的片段放入fragment_wrapper并再次解散ProgressDialog:

private class GetFlightsTask extends AsyncTask<Double, Void, String> {
@Override
protected void onPreExecute() {
    super.onPreExecute();
    // the activity context has been passed to the AsyncTask through its constructor
    loadingFlightsSpinner = new ProgressDialog(context);
    // setting the dialog up
    loadingFlightsSpinner.show();
}
@Override
protected String doInBackground(Double... params) {
    // some pretty long remote API call
    // (loading a JSON file from http://some.website.com/...)
}
@Override
protected void onPostExecute(String flightsJSON) {
    super.onPostExecute(flightsJSON);
    // here I do stuff with the JSON and then I swtich the fragments like this
    FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
    FlightsFragment fragment = new FlightsFragment();
    fragmentTransaction.replace(R.id.fragment_wrapper, fragment);
    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();
    loadingFlightsSpinner.dismiss();
}

一切都很好。用户在FlightsFragment中做了一些事情，然后可能决定返回地图。按返回按钮，地图再次弹出。这就是地图延迟的时候。上面的国家/城市名称加载非常慢，在移动地图时严重滞后…我不知道为什么，我不做任何弹出MapFragment回来。

有趣的是，它得到修复，例如按home按钮，然后再次返回到应用程序…

我做错了什么?

谢谢你的建议

Answer 1

我运行了一个简单的测试:

public class MapFragmentOnBackStackExample extends FragmentActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.map_fragment_on_back_stack_example);
        FragmentManager fm = getSupportFragmentManager();
        Fragment f = fm.findFragmentById(R.id.fragment_container);
        if (f == null) {
            f = SupportMapFragment.newInstance();
            FragmentTransaction transaction = fm.beginTransaction();
            transaction.add(R.id.fragment_container, f);
            transaction.commit();
        }
    }
    public void onAddFragmentClick(View view) {
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction transaction = fm.beginTransaction();
        transaction.replace(R.id.fragment_container, new MyFragment());
        transaction.addToBackStack(null);
        transaction.commit();
    }
    public static class MyFragment extends Fragment {
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            TextView textView = new TextView(getActivity());
            textView.setText("MyFragment: " + hashCode());
            return textView;
        }
    }
}

看不出有什么问题。

我可以看到的问题，当评论if (f == null) {离开它总是创建新的片段旋转，这显然是错误的，但这带来了一些怀疑。

你能同时在内存中看到1个以上的MapFragment吗?尝试使用Eclipse内存分析器(MAT)。

Answer 2

只有按下后退键才会延迟?

如果这是问题，尝试阻止后退按钮或使其退出应用程序试试下面的代码:

    @Override
public void onBackPressed(){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("You wanna leave the aplication?").setPositiveButton("Yes", dialogClickListener)
            .setNegativeButton("No", dialogClickListener).show();
}

或尝试这个代码，它的一种方式，把一个地图片段内的另一个片段(嵌套地图片段)，它为我工作了一个星期前:

Java类:

public class Yourfragment extends Fragment {
    private MapView mMapView;
    private GoogleMap mMap;
    private Bundle mBundle;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View inflatedView = inflater.inflate(R.layout.map_fragment, container, false);
        try {
            MapsInitializer.initialize(getActivity());
        } catch (GooglePlayServicesNotAvailableException e) {
            // TODO handle this situation
        }
        mMapView = (MapView) inflatedView.findViewById(R.id.map);
        mMapView.onCreate(mBundle);
        setUpMapIfNeeded(inflatedView);
        return inflatedView;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mBundle = savedInstanceState;
    }
    private void setUpMapIfNeeded(View inflatedView) {
        if (mMap == null) {
            mMap = ((MapView) inflatedView.findViewById(R.id.map)).getMap();
            if (mMap != null) {
                setUpMap();
            }
        }
    }
    private void setUpMap() {
        mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
    }
    @Override
    public void onResume() {
        super.onResume();
        mMapView.onResume();
    }
    @Override
    public void onPause() {
        super.onPause();
        mMapView.onPause();
    }
    @Override
    public void onDestroy() {
        mMapView.onDestroy();
        super.onDestroy();
    }
}

XML:

<com.google.android.gms.maps.MapView
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent" />

把这段代码放在post execute上:

View inflatedView = inflater.inflate(R.layout.map_fragment, container, false);
try {
    MapsInitializer.initialize(getActivity());
} catch (GooglePlayServicesNotAvailableException e) {
    // TODO handle this situation
}
mMapView = (MapView) inflatedView.findViewById(R.id.map);
mMapView.onCreate(mBundle);
setUpMapIfNeeded(inflatedView);
return inflatedView;

并在oncreateview 上调用asynctask

试试这个:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    //Call assyncTask
}
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mBundle = savedInstanceState;
}
private void setUpMapIfNeeded(View inflatedView) {
    if (mMap == null) {
        mMap = ((MapView) inflatedView.findViewById(R.id.map)).getMap();
        if (mMap != null) {
            setUpMap();
        }
    }
}
private void setUpMap() {
    mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
}
@Override
public void onResume() {
    super.onResume();
    mMapView.onResume();
}
@Override
public void onPause() {
    super.onPause();
    mMapView.onPause();
}
@Override
public void onDestroy() {
    mMapView.onDestroy();
    super.onDestroy();
}
private class GetFlightsTask extends AsyncTask<Double, Void, String> {
@Override
protected void onPreExecute() {
    super.onPreExecute();
    // if I remove the next line, everything gets fixed
    loadingFlightsSpinner.show();
}
@Override
protected String doInBackground(Double... params) {
    // some pretty long remote API call
    // (loading a JSON file from http://some.website.com/flights?...)
    // works fine
    String flightsJSON = loadJSON("flights?flyFrom=CZ&to=...");
}
@Override
protected void onPostExecute(String flightsJSON) {
    super.onPostExecute(flightsJSON);
    loadingFlightsSpinner.dismiss();
    // here I do stuff with the JSON and then replace the fragment
    dohardwork()
}
public view dohardwork(){
    View inflatedView = inflater.inflate(R.layout.map_fragment, container, false);
    try {
        MapsInitializer.initialize(getActivity());
    } catch (GooglePlayServicesNotAvailableException e) {
        // TODO handle this situation
    }
    mMapView = (MapView) inflatedView.findViewById(R.id.map);
    mMapView.onCreate(mBundle);
    setUpMapIfNeeded(inflatedView);
    return inflatedView;
}

Answer 3

我已经通过在AsyncTask的doInBackground()方法的末尾而不是在onPostExecute()方法的开始驳回ProgressDialog来修复它。

这有点奇怪，因为我实际上认为我不应该在doInBackground()方法中触摸UI中的东西…如果有人想详细说明一下，我很乐意知道为什么它是这样工作的。