方向更改后 Recyclerview 未填充数据答案

【问题标题】：Recyclerview not populating with data after orientation change方向更改后 Recyclerview 未填充数据
【发布时间】：2016-07-05 03:05:32
【问题描述】：

我有一个纵向和横向布局不同的回收站视图。当活动开始时，recyclerview 会填充数据，而与方向无关。但如果方向改变，则不会显示任何数据。并且没有显示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 Activity 启动且方向未更改时的 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

这是改变方向时的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。

【问题讨论】：

您确定您的代码没有添加该片段的多个实例吗？
只调用片段的单个实例
如果您只想允许屏幕旋转但没有具体取决于布局，那么我相信您必须覆盖活动中的 onConfigurationChanged 方法。也将其添加到清单文件中。更多解释请看这里：stackoverflow.com/a/2418763/1750013
我得到了解决它的答案。它在下面提到，但我还不能将其标记为正确答案。但你的回答不会奏效，因为无论如何我都需要再次调用 oncreate。

标签： android android-recyclerview screen-orientation orientation-changes

【解决方案1】：

通过在活动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不能解决这个问题。

@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

【讨论】：

【解决方案2】：

在片段中，在旋转时保留数据的简单方法是在其中创建适配器 onCreate() 并将片段设置为保留其状态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。这就是它对我的工作方式。

【讨论】：

【解决方案3】：

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);
}
}

【讨论】：

我试过这个。它没有用。问题不在于丢失数据。即使再次检索数据，也不会显示。回收站视图仍然是空的。适配器也设置好了。