Question

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

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();
    }

    ...

}

标准方式。然后我从GoogleMap获取mapFragment实例并设置其设置，设置监听器，用它做事。一切正常。

然后当用户完成地图后，会触发AsyncTask以显示ProgressDialog，执行某些操作，将不同的片段放入fragment_wrapper并关闭{{ 1}}再次：

ProgressDialog

一切仍然正常。用户在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(); }中执行某些操作，然后可能决定返回到地图。按后退按钮，地图再次弹出。这就是地图变得迟钝的时候。它上面的国家/城市名称加载速度非常慢，它在移动地图方面严重滞后......而且我不知道为什么，我在弹出FlightsFragment时没有做任何事情。

有趣的是，例如在按下 home 按钮然后再次返回应用程序时，它会得到修复...

我做错了什么？

感谢您的任何想法。

Answer 1

只有按下后退按钮才会延迟？

如果那个问题试图阻止后退按钮或让它退出应用程序尝试此代码：

    @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();

}

或尝试使用此代码将一个地图片段放入另一个片段（嵌套的Map Fragment）中，这个片段在几个星期前就适用于我：

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" />

将此代码放在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assynctask

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 2

我做了一个简单的测试：

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;
        }
    }
}

并且看不到任何问题。

我在评论if (f == null) {时可以看到问题，让它始终在旋转时创建新的片段，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多个MapFragment吗？尝试使用Eclipse Memory Analyzer（MAT）。

Answer 3

我已经通过在ProgressDialog的{{1}}方法的末尾而不是在AsyncTask方法的开头解雇doInBackground()来修复它。

这有点奇怪，因为我实际上认为我不应该在onPostExecute()方法中触摸UI中的内容......如果有人想详细说明一下，我会很高兴知道为什么它就像这样。

谷歌地图v2从堆栈弹出片段后滞后

3 个答案: