Android:带有RecyclerView方向改变错误的fragments

Question

我在我的应用程序中使用滑动选项卡，我有一个视图页2片段。在fragment内部也有一个recycle视图。

<<p> 类别片段/strong>

public class Categories extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    if (cat == null) {
        cat = inflater.inflate(R.layout.categories, container, false);
    } else {
        ((ViewGroup) cat.getParent()).removeAllViews();
    }
     catData = new ArrayList<>();
    if(mRecyclerView == null) {
        mRecyclerView = (RecyclerView) cat.findViewById(R.id.recyclerView);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    }else{
        ((ViewGroup) mRecyclerView.getParent()).removeAllViews();
    }
    return mRecyclerView;
}
 Handler handler = new Handler();
Runnable mStatusChecker = new Runnable() {
    @Override
    public void run() {
        GetCategoriesTask access = new GetCategoriesTask();
        access.execute();
        //this function can change value of mInterval.
        handler.postDelayed(mStatusChecker, 10000);
    }
};

private class GetCategoriesTask extends AsyncTask<Void, Void, ArrayList<CategoryData>> {
    @Override
    protected void onPreExecute() {
    }
    //task is running in background
    @Override
    protected ArrayList<CategoryData> doInBackground(Void... arg0) {
        ServiceHandler sh = new ServiceHandler();
        String baseAddress = "url";
        String jsonStr = sh.makeServiceCall(ServiceHandler.GET,baseAddress);
        if(jsonStr != null){
            try{
                JSONObject jsonObj = new JSONObject(jsonStr);
                JSONArray data = jsonObj.getJSONArray("data");
                catData.clear();
                for(int i = 0;i < data.length();i++){
                    JSONObject c = data.getJSONObject(i);
                    String categoryName = c.getString("category");
                    catData.add(new CategoryData(categoryName));
                }
                return catData;
            }catch (JSONException ex){
                ex.printStackTrace();
            }
        }
        Log.d("Response: ", "> " + jsonStr);
        return null;
    }
    //after executing background task, this method will execute.
    @Override
    protected void onPostExecute(ArrayList<CategoryData> data) {
        if(!notifier) {
            adapter = new CategoryRecyclerViewAdapter(getContext(), data);
            mRecyclerView.setAdapter(adapter);
            notifier = true;
        }
        else{                
                adapter.notifyDataSetChanged();
                Toast.makeText(getContext(), "changed", Toast.LENGTH_SHORT).show();
        }
    }
}
@Override
public void onResume() {
    super.onResume();     
    mStatusChecker.run();
}
@Override
public void onSaveInstanceState(final Bundle outState) {
    // super.onSaveInstanceState(outState);
}
@Override
public void onPause() {
    super.onPause();
    handler.removeCallbacks(mStatusChecker);
}
@Override
public void onDestroy() {
    super.onDestroy();
    handler.removeCallbacks(mStatusChecker);
}
@Override
public void onStop() {
    super.onStop();        
    handler.removeCallbacks(mStatusChecker);
}}

<<p> 发现片段/strong>

我只有oncreate方法。

public class Discover extends Fragment{
public View v;
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    if (v == null) {
        v = inflater.inflate(R.layout.categories, container, false);
    } else {
        ((ViewGroup) v.getParent()).removeAllViews();
    }
    return v;
}

问题是，当我改变应用程序的方向，它给出了一个异常，并显示消息"不幸的ezycity已停止"。当我点击ok按钮时，应用程序重新启动并正常工作。

logcat

08-26 10:17:25.954    4452-4452/com.ezycity.seneru.ezycity E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.ezycity.seneru.ezycity, PID: 4452
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ezycity.seneru.ezycity/com.ezycity.seneru.ezycity.MainActivity}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
        at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3950)
        at android.app.ActivityThread.access$900(ActivityThread.java:151)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1309)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5257)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
 Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.view.ViewGroup.addViewInner(ViewGroup.java:3936)
        at android.view.ViewGroup.addView(ViewGroup.java:3786)
        at android.support.v4.view.ViewPager.addView(ViewPager.java:1342)
        at android.view.ViewGroup.addView(ViewGroup.java:3727)
        at android.view.ViewGroup.addView(ViewGroup.java:3700)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1032)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1197)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1179)
        at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1991)
        at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:165)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:507)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1236)
        at android.app.Activity.performStart(Activity.java:6006)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2288)

那么我如何解决这个问题呢?

Answer 1

让我们来看看这段代码:

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup    container, @Nullable Bundle savedInstanceState) {
    if (cat == null) {
        cat = inflater.inflate(R.layout.categories, container, false);
    } else {
        (   (ViewGroup) cat.getParent()).removeAllViews();
    }
     catData = new ArrayList<>();
    if(mRecyclerView == null) {
        mRecyclerView = (RecyclerView) cat.findViewById(R.id.recyclerView);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    }else{
        ((ViewGroup) mRecyclerView.getParent()).removeAllViews();
    }
    return mRecyclerView;
}

首先，由于最后一个参数，您正在膨胀未附加到根的cat。

则在cat中搜索mRecyclerView。这也意味着mRecyclerView的父节点是cat。

之后返回mRecyclerView。因此，寻呼机试图将mRecyclerView添加到页面中，但mRecyclerView已经有父(cat)。

---

所以这个片段的解决方案可能是:

代替:

 return mRecyclerView;

使用:

return cat;