方向更改后 Recyclerview 未填充数据

Question

我有一个 recyclerview 具有不同的纵向和横向布局。当活动开始时，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而来的方向变化的数据。

 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 是一个执行 volley stringrequest 的类。

这是活动开始且方向未更改时的 logcat。

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

这是更改方向时的 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

这是通过在活动中保存片段的实例来解决的。将 layoutmanager 的状态保存在片段中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：https : //stackoverflow.com/a/17135346/5512020

Answer 2

在片段中，在旋转时保留数据的一种简单方法是创建您的适配器 onCreate() 并设置片段以保留其 state setRetainInstance(true)。onResume()将适配器应用到您的 recyclerview，同时调用 adapter.notifyDataSetChanged() 来填充您的 recyclerView。这就是它对我的工作方式。