方向更改后 Recyclerview 未填充数据

Question

我有一个 recyclerview，它具有不同的纵向和横向布局。当 activity 启动时，无论方向如何，recyclerview 都会填充数据。但如果方向改变，则不会显示任何数据。并且没有显示有关随之发生的方向变化的数据。

 public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    Log.d("CCC", "OnCreate View called");
    View view = inflater.inflate(R.layout.fragment_coach_list, container, false);
    new NetworkConnector(getActivity(), coachListURL, method, null, new OnRequestComplete());
    Log.d("CCC", "Network connector called");
    return view;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    Log.d("CCC", "On View created called");
    //if rv is declared in oncreateview then NPE during setadapter
    coachRecyclerView = (RecyclerView) getActivity().findViewById(R.id.fcoachlist_rv);
    final LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    Log.d("CCC", "orientation " + layoutManager.getOrientation());
    coachRecyclerView.setLayoutManager(layoutManager);
}

private class OnRequestComplete implements RequestCompleteListener<String> {

    public OnRequestComplete() {
    }

    @Override
    public void onRequestExecuted(String responseType, String result) {
        if (!responseType.equals("error")) {
            try {
                JSONObject jsonResponse = new JSONObject(result);
                Log.d("CCC", "Result: " + result);
                String coachResult = jsonResponse.getString("success");
                switch (coachResult) {
                    case "1":
                        ArrayList<CoachList> coachListData = parseJSONResponse(jsonResponse);
                        coachListAdapter = new CoachListAdapter(getActivity());
                        coachListAdapter.setCoachList(coachListData);
                        coachRecyclerView.setAdapter(coachListAdapter);
                        if(coachRecyclerView.getAdapter()== null){
                            Log.d("CCC", "Adapter is null");
                        } else if (coachRecyclerView.getAdapter()== coachListAdapter){
                            Log.d("CCC", "Adapter is coachlistAdapter");
                        } else {
                            Log.d("CCC", "This is odd!!");
                        }
                        Log.d("CCC", "Size " + coachListAdapter.getItemCount());
                        break;
                    case "0":
                        Toast.makeText(getActivity(), "No trainers available currently", Toast.LENGTH_LONG).show();
                        break;
                    case "-1":
                        Toast.makeText(getActivity(), "Please try again later", Toast.LENGTH_LONG).show();
                        break;
                }
            } catch (JSONException e) {
                Log.d("CCC", "CoachList JSONException");
            }
        }
    }
}

NetworkConnector 是一个 class 执行 volley stringrequest。

这里是 logcat 启动 activity 且方向不变的情况。

03-18 07:06:57.702 30392-30392/in.jiyofit.the_app D/CCC: OnCreate View called
03-18 07:06:57.722 30392-30392/in.jiyofit.the_app D/CCC: Network connector called
03-18 07:06:57.722 30392-30392/in.jiyofit.the_app D/CCC: On View created called
03-18 07:06:57.722 30392-30392/in.jiyofit.the_app D/CCC: orientation 1
03-18 07:06:57.774 30392-30392/in.jiyofit.the_app W/EGL_genymotion: eglSurfaceAttrib not implemented
03-18 07:06:57.774 30392-30392/in.jiyofit.the_app E/RecyclerView: No adapter attached; skipping layout
03-18 07:06:57.778 30392-30392/in.jiyofit.the_app D/CCC: Result:    {"success":"1","Coaches":[{"CoachID":"1","Coach_Name":"Tyler //lots of json
03-18 07:06:57.778 30392-30392/in.jiyofit.the_app D/CCC: Adapter is coachlistAdapter
03-18 07:06:57.778 30392-30392/in.jiyofit.the_app D/CCC: Size 4
03-18 07:06:57.946 30392-30488/in.jiyofit.the_app D/dalvikvm: GC_FOR_ALLOC freed 414K, 6% free 8585K/9076K, paused 8ms, total 8ms
03-18 07:06:59.426 30392-30392/in.jiyofit.the_app D/CCC: Result:    {"success":"1","Coaches":[{"CoachID":"1","Coach_Name":"Tyler ...//lots of json  
03-18 07:06:59.426 30392-30392/in.jiyofit.the_app D/CCC: Adapter is coachlistAdapter
03-18 07:06:59.426 30392-30392/in.jiyofit.the_app D/CCC: Size 4

这是方向改变后的logcat。

03-18 07:13:53.792 30392-30392/in.jiyofit.the_app D/CCC: OnCreate View called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: Network connector called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: On View created called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: orientation 1
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: OnCreate View called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: Network connector called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: On View created called
03-18 07:13:53.796 30392-30392/in.jiyofit.the_app D/CCC: orientation 1
03-18 07:13:53.856 30392-30392/in.jiyofit.the_app W/EGL_genymotion: eglSurfaceAttrib not implemented
03-18 07:13:53.856 30392-30392/in.jiyofit.the_app E/RecyclerView: No adapter attached; skipping layout
03-18 07:13:53.856 30392-30392/in.jiyofit.the_app E/RecyclerView: No adapter attached; skipping layout
03-18 07:13:53.872 30392-30392/in.jiyofit.the_app D/dalvikvm: GC_FOR_ALLOC freed 554K, 7% free 9823K/10452K, paused 4ms, total 4ms
03-18 07:13:53.888 30392-30392/in.jiyofit.the_app D/CCC: Result:    {"success":"1","Coaches":[{"CoachID":"1","Coach_Name":"Tyler //lots of json
03-18 07:13:53.888 30392-30392/in.jiyofit.the_app D/CCC: Adapter is coachlistAdapter
03-18 07:13:53.888 30392-30392/in.jiyofit.the_app D/CCC: Size 4
03-18 07:13:53.996 30392-30392/in.jiyofit.the_app E/RecyclerView: No adapter attached; skipping layout
03-18 07:13:54.676 30392-30392/in.jiyofit.the_app D/CCC: Result:    {"success":"1","Coaches":[{"CoachID":"1","Coach_Name":"Tyler //lots of json  
03-18 07:13:54.680 30392-30392/in.jiyofit.the_app D/CCC: Adapter is coachlistAdapter
03-18 07:13:54.680 30392-30392/in.jiyofit.the_app D/CCC: Size 4
03-18 07:13:54.736 30392-30392/in.jiyofit.the_app D/CCC: Result:    {"success":"1","Coaches":[{"CoachID":"1","Coach_Name":"Tyler //lots of json  
03-18 07:13:54.736 30392-30392/in.jiyofit.the_app D/CCC: Adapter is coachlistAdapter
03-18 07:13:54.736 30392-30392/in.jiyofit.the_app D/CCC: Size 4

可以看出，代码的某些部分被重复调用。我不知道为什么。在方向更改后调用 onViewCreated 后，将再次调用 OnCreateView。可能这是导致问题的原因。任何帮助，将不胜感激。谢谢

Answer 1

protected void onSaveInstanceState(Bundle state) {
super.onSaveInstanceState(state);
// Save list state
mListState = mLayoutManager.onSaveInstanceState();
state.putParcelable(LIST_STATE_KEY, mListState);
}
Restore state in the onRestoreInstanceState():

protected void onRestoreInstanceState(Bundle state) {
super.onRestoreInstanceState(state);

// Retrieve list state and list/item positions
if(state != null)
mListState = state.getParcelable("myState");
}
Then update the LayoutManager (I do in onResume()):

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

if (mListState != null) {
mLayoutManager.onRestoreInstanceState(mListState);
}
}

Answer 2

通过在 activity 中保存片段实例解决了这个问题。在片段中保存布局管理器的状态并在旋转时恢复它并没有解决这个问题。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //this activity extends baseactivity
    //inflating activity layout in a framelayout inside baseactivity 
    getLayoutInflater().inflate(R.layout.activity_hire_coach, contentFrameLayout);
    if (savedInstanceState != null) {
        //Restore the fragment's instance
        coachListFragment = (CoachListFragment) getFragmentManager().getFragment(savedInstanceState, "coachListFrag");
    } else {
        coachListFragment = new CoachListFragment();
        getFragmentManager().beginTransaction().add(R.id.ahirecoach_layout, coachListFragment, "coachListFragment").commit();
    }
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    //Save the fragment's instance
    getFragmentManager().putFragment(outState, "coachListFrag", coachListFragment);
}

参考：

Answer 3

在片段中，在旋转时保留数据的一种简单方法是创建适配器 onCreate()，同时设置片段以保留其状态 setRetainInstance(true)。 onResume() 将适配器应用于您的 recyclerview，同时调用 adapter.notifyDataSetChanged() 来填充您的 recyclerView。这就是它对我有用的方式。

方向更改后 Recyclerview 未填充数据

Recyclerview not populating with data after orientation change

android

android-recyclerview

screen-orientation

orientation-changes