Как сохранить элементы списка/адаптер в фрагменте и восстановить из заднего стека

Question

Я пытался найти эту проблему, но я не смог найти решение. У меня проблема с сохранением элементов ListView в фрагменте. Дело в том, у меня есть несколько фрагментов

Пусть говорят ФРАГМЕНТ A, ФРАГМЕНТ B и ФРАГМЕНТ C, и ФРАГМЕНТ А имеет ListView, элемент в ListView может быть изменен при прокрутке (так же, как сроки в социальной медиа-приложения). Когда я меняю фрагмент A, я использовал метод addToBackStack (null).

Проблема в том, как сохранить список и восстановить его, если нажата кнопка «Назад»?

onSaveInstanceState() никогда не вызывается, потому что хост активность никогда не убивают, только изменить фрагмент с помощью этого:

public void changeFragment(Fragment fragment, ColorDrawable colorDrawable){ 
    Fragment newFrag = fragment; 
    ColorDrawable newColor = colorDrawable; 

    String backStateName = fragment.getClass().getName(); 
    FragmentManager manager = getSupportFragmentManager(); 
    boolean fragmentPopped = manager.popBackStackImmediate (backStateName, 0); 
    if (!fragmentPopped){ //fragment not in back stack, create it. 
     FragmentTransaction ft = manager.beginTransaction(); 
     ft.replace(R.id.content_fragment, fragment); 
     ft.addToBackStack(backStateName); 
     ft.commit(); 
    } 

    //to change the actionbar color 
    getSupportActionBar().setBackgroundDrawable(newColor); 
} 

вот мой код пытается сохранить и восстановить ListView:

@Override 
    public void onDestroyView() { 
     super.onDestroyView(); 
     //try to save listview scroll 
     index = myList.getFirstVisiblePosition(); 
     View v = myList.getChildAt(0); 
     top = (v == null) ? 0 : (v.getTop() - myList.getPaddingTop()); 
     index = 1; 
     //try to save listview items 
     savedAdapter = adapter; 
     fromBackStack = true; 
    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 

     myList.setSelectionFromTop(index, top); 
     myList.setAdapter(savedAdapter); 
    } 

здесь код, который я сделал до сих пор:

package com.ngapainya.ngapainya.fragment; 


import android.app.Activity; 
import android.graphics.drawable.ColorDrawable; 
import android.net.ParseException; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.widget.SwipeRefreshLayout; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AbsListView; 
import android.widget.AdapterView; 
import android.widget.ListView; 

import com.ngapainya.ngapainya.R; 
import com.ngapainya.ngapainya.activity.volunteer.ContainerActivity; 
import com.ngapainya.ngapainya.adapter.HomeAdapter; 
import com.ngapainya.ngapainya.fragment.child.DetailPostFragment; 
import com.ngapainya.ngapainya.model.Home; 

import java.util.ArrayList; 

/** 
* A simple {@link Fragment} subclass. 
*/ 
public class HomeFragment extends Fragment implements AdapterView.OnItemClickListener, SwipeRefreshLayout.OnRefreshListener{ 
    private FragmentActivity myContext; 
    private View myFragmentView; 
    private ArrayList<Home> filelist; 
    private ListView myList; 
    private HomeAdapter adapter; 
    private SwipeRefreshLayout swipeRefreshLayout; 

    //try save instance listview 
    boolean fromBackStack = false; 
    int index; 
    int top; 
    HomeAdapter savedAdapter; 

    @Override 
    public void onDestroyView() { 
     super.onDestroyView(); 
     //try to save listview scroll 
     index = myList.getFirstVisiblePosition(); 
     View v = myList.getChildAt(0); 
     top = (v == null) ? 0 : (v.getTop() - myList.getPaddingTop()); 
     index = 1; 
     //try to save listview items 
     savedAdapter = adapter; 
     fromBackStack = true; 
    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 

     myList.setSelectionFromTop(index, top); 
     myList.setAdapter(savedAdapter); 
    } 

    @Override 
    public void onAttach(Activity activity) { 
     myContext = (FragmentActivity) activity; 
     super.onAttach(activity); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     myFragmentView = inflater.inflate(R.layout.fragment_home, container, false); 

     filelist = new ArrayList<Home>(); 

     //dummy data 
     filelist.add(new Home("post", 1)); //post image 
     filelist.add(new Home("post", 2)); //post location 
     filelist.add(new Home("post", 3)); //post url 
     filelist.add(new Home("post", 4)); //become friend with 
     filelist.add(new Home("post", 0)); //post status 

     swipeRefreshLayout = (SwipeRefreshLayout) myFragmentView.findViewById(R.id.swipe_refresh_layout); 
     swipeRefreshLayout.setOnRefreshListener(this); 
     /** 
     * Showing Swipe Refresh animation on activity create 
     * As animation won't start on onCreate, post runnable is used 
     */ 
     swipeRefreshLayout.post(new Runnable() { 
            @Override 
            public void run() { 
             swipeRefreshLayout.setRefreshing(true); 
             //do something 
             swipeRefreshLayout.setRefreshing(false); 
            } 
           } 
     ); 

     myList = (ListView) myFragmentView.findViewById(R.id.list_home); 
     //myList.setAdapter(new HomeAdapter(myContext, filelist)); 
     adapter = new HomeAdapter(myContext, filelist); 
     myList.setOnItemClickListener(this); 

     if(!fromBackStack) { 
      new RemoteDataTask().execute(); 
     } 

     return myFragmentView; 
    } 

    /** 
    * This method is called when swipe refresh is pulled down 
    */ 
    @Override 
    public void onRefresh() { 
     //do something 
     myList.setAdapter(adapter); 
     ArrayList<Home> new_filelist = new ArrayList<>(); 
     new_filelist.add(new Home("Post", 4)); 

     filelist.addAll(0, new_filelist); 
     adapter.notifyDataSetChanged(); 
     swipeRefreshLayout.setRefreshing(false); 
    } 

    @Override 
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
     Home tmp = (Home) parent.getItemAtPosition(position); 
     DetailPostFragment detailPostFragment = new DetailPostFragment(); 
     Bundle args = new Bundle(); 
     switch (tmp.type) { 
      case 0: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 1: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 2: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 3: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 4: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
     } 
    } 

    private class RemoteDataTask extends AsyncTask<String, Void, ArrayList<Home>> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
     } 

     @Override 
     protected ArrayList<Home> doInBackground(String... urls) { 
      try { 
       ArrayList<Home> new_filelist = new ArrayList<Home>(); 
       new_filelist.add(new Home("post", 3)); //post url 
       new_filelist.add(new Home("post", 4)); //become friend with 
       new_filelist.add(new Home("post", 0)); //post status 
       filelist.addAll(new_filelist); 
      } catch (ParseException e) { 
       Log.e("Error", e.getMessage()); 
       e.printStackTrace(); 
      } 
      return filelist; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<Home> organization) { 
      myList.setAdapter(new HomeAdapter(myContext, filelist)); 
      // Create an OnScrollListener 
      myList.setOnScrollListener(new AbsListView.OnScrollListener() { 

       @Override 
       public void onScrollStateChanged(AbsListView view, 
               int scrollState) { // TODO Auto-generated method stub 
        int threshold = 1; 
        int count = myList.getCount(); 

        if (scrollState == SCROLL_STATE_IDLE) { 
         if (myList.getLastVisiblePosition() >= count 
           - threshold) { 
          // Execute LoadMoreDataTask AsyncTask 
          new LoadMoreDataTask().execute(); 
         } 
        } 
       } 

       @Override 
       public void onScroll(AbsListView view, int firstVisibleItem, 
            int visibleItemCount, int totalItemCount) { 
        // TODO Auto-generated method stub 

       } 

      }); 
     } 
    } 

    public class LoadMoreDataTask extends AsyncTask<String, Void, ArrayList<Home>> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
     } 

     @Override 
     protected ArrayList<Home> doInBackground(String... urls) { 
      try { 
       // web service request 
       ArrayList<Home> new_filelist = new ArrayList<Home>(); 
       new_filelist.add(new Home("post", 0)); //post status 
       if(new_filelist != null && new_filelist.size() > 0){ 
        filelist.addAll(new_filelist); 
       } 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
      return filelist; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<Home> organization) { 
      int position = myList.getLastVisiblePosition(); 
      adapter = new HomeAdapter(myContext, filelist); 
      myList.setAdapter(adapter); 
      adapter.notifyDataSetChanged(); 
      myList.setSelectionFromTop(position, 0); 
     } 
    } 

} 

Я надеюсь, что кто-то может помочь мне, спасибо.

Обновленный код Это мой код до сих пор, она работает, когда я пытаюсь спасенных пунктов ListView и его адаптер, возможно, это немного сложнее. Если у кого-то есть какая-то идея, это будет оценено по достоинству.

package com.ngapainya.ngapainya.fragment; 
import android.app.Activity; 
import android.graphics.drawable.ColorDrawable; 
import android.net.ParseException; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.widget.SwipeRefreshLayout; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AbsListView; 
import android.widget.AdapterView; 
import android.widget.ListView; 

import com.ngapainya.ngapainya.R; 
import com.ngapainya.ngapainya.activity.volunteer.ContainerActivity; 
import com.ngapainya.ngapainya.adapter.HomeAdapter; 
import com.ngapainya.ngapainya.fragment.child.DetailPostFragment; 
import com.ngapainya.ngapainya.model.Home; 

import java.util.ArrayList; 

/** 
* A simple {@link Fragment} subclass. 
*/ 
public class HomeFragment extends Fragment implements AdapterView.OnItemClickListener, SwipeRefreshLayout.OnRefreshListener{ 
    private FragmentActivity myContext; 
    private View myFragmentView; 
    private ArrayList<Home> filelist; 
    private ListView myList; 
    private HomeAdapter adapter; 
    private SwipeRefreshLayout swipeRefreshLayout; 

    /* 
    * these variables used to restore the listview 
    * when calling the fragment from backstack 
    * */ 
    private boolean fromBackStack = false; 
    private HomeAdapter savedAdapter; 
    private ArrayList<Home> savedFilelist; 

    @Override 
    public void onDestroyView() { 
     super.onDestroyView(); 
     savedAdapter = adapter; 
     savedFilelist = filelist; 
     fromBackStack = true; 
     Log.e("onDestroyView", "onDestroyView"); 
    } 

    @Override 
    public void onAttach(Activity activity) { 
     myContext = (FragmentActivity) activity; 
     super.onAttach(activity); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     myFragmentView = inflater.inflate(R.layout.fragment_home, container, false); 

     Log.e("onCreateView", "onCreateView"); 

     swipeRefreshLayout = (SwipeRefreshLayout) myFragmentView.findViewById(R.id.swipe_refresh_layout); 
     swipeRefreshLayout.setOnRefreshListener(this); 
     /** 
     * Showing Swipe Refresh animation on activity create 
     * As animation won't start on onCreate, post runnable is used 
     */ 
     /*swipeRefreshLayout.post(new Runnable() { 
            @Override 
            public void run() { 
             swipeRefreshLayout.setRefreshing(true); 
             //do something 
             swipeRefreshLayout.setRefreshing(false); 
            } 
           } 
     );*/ 

     myList = (ListView) myFragmentView.findViewById(R.id.list_home); 
     //myList.setAdapter(new HomeAdapter(myContext, filelist)); 

     myList.setOnItemClickListener(this); 

     filelist = new ArrayList<Home>(); 
     adapter = new HomeAdapter(myContext, filelist); 

     if(fromBackStack) { 
      filelist = savedFilelist; 
      adapter = savedAdapter; 
     } 

     new RemoteDataTask().execute(); 
     return myFragmentView; 
    } 

    /** 
    * This method is called when swipe refresh is pulled down 
    */ 
    @Override 
    public void onRefresh() { 
     ArrayList<Home> new_filelist = new ArrayList<>(); 
     new_filelist.add(new Home("Post", 4)); 

     filelist.addAll(0, new_filelist); 
     adapter.notifyDataSetChanged(); 
     swipeRefreshLayout.setRefreshing(false); 

     Log.e("onRefresh", "onRefresh"); 
    } 

    /* 
    * This method is called whenever the listview item is clicked 
    * */ 

    @Override 
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
     Home tmp = (Home) parent.getItemAtPosition(position); 
     DetailPostFragment detailPostFragment = new DetailPostFragment(); 
     Bundle args = new Bundle(); 
     switch (tmp.type) { 
      case 0: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 1: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 2: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 3: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
      case 4: 
       args.putInt("postType", tmp.type); 
       detailPostFragment.setArguments(args); 
       ((ContainerActivity) getActivity()).changeFragment(detailPostFragment, new ColorDrawable(getResources().getColor(R.color.ColorPrimary))); 
       break; 
     } 
    } 

    /* 
    * This method is called in onCreateView method 
    * Used to load data from server and populate them into 
    * the listview 
    * */ 

    private class RemoteDataTask extends AsyncTask<String, Void, ArrayList<Home>> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
     } 

     @Override 
     protected ArrayList<Home> doInBackground(String... urls) { 
      try { 
       ArrayList<Home> new_filelist = new ArrayList<Home>(); 
       //dummy data 
       new_filelist.add(new Home("post", 1)); //post image 
       new_filelist.add(new Home("post", 2)); //post location 
       new_filelist.add(new Home("post", 3)); //post url 
       new_filelist.add(new Home("post", 4)); //become friend with 
       new_filelist.add(new Home("post", 0)); //post status 
       new_filelist.add(new Home("post", 3)); //post url 
       new_filelist.add(new Home("post", 4)); //become friend with 
       new_filelist.add(new Home("post", 0)); //post status 
       filelist.addAll(new_filelist); 
      } catch (ParseException e) { 
       Log.e("Error", e.getMessage()); 
       e.printStackTrace(); 
      } 
      return filelist; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<Home> organization) { 
      myList.setAdapter(adapter); 
      // Create an OnScrollListener 
      myList.setOnScrollListener(new AbsListView.OnScrollListener() { 

       @Override 
       public void onScrollStateChanged(AbsListView view, 
               int scrollState) { // TODO Auto-generated method stub 
        int threshold = 1; 
        int count = myList.getCount(); 

        if (scrollState == SCROLL_STATE_IDLE) { 
         if (myList.getLastVisiblePosition() >= count 
           - threshold) { 
          // Execute LoadMoreDataTask AsyncTask 
          new LoadMoreDataTask().execute(); 
         } 
        } 
       } 

       @Override 
       public void onScroll(AbsListView view, int firstVisibleItem, 
            int visibleItemCount, int totalItemCount) { 
        // TODO Auto-generated method stub 

       } 

      }); 
     } 
    } 

    /* 
    * This method is called when the listview pulled down 
    * it will trigger this method to load more items from server 
    * */ 

    public class LoadMoreDataTask extends AsyncTask<String, Void, ArrayList<Home>> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
     } 

     @Override 
     protected ArrayList<Home> doInBackground(String... urls) { 
      try { 
       // web service request 
       ArrayList<Home> new_filelist = new ArrayList<Home>(); 
       new_filelist.add(new Home("post", 0)); //post status 
       new_filelist.add(new Home("post", 1)); 
       if(new_filelist != null && new_filelist.size() > 0){ 
        filelist.addAll(new_filelist); 
       } 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
      return filelist; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<Home> organization) { 
      int position = myList.getLastVisiblePosition(); 
      //adapter = new HomeAdapter(myContext, filelist); 
      myList.setAdapter(adapter); 
      adapter.notifyDataSetChanged(); 
      myList.setSelectionFromTop(position, 0); 
     } 
    } 

} 

Answer 1

Наконец я понял это ... я не знаю, это ли лучшее решение или нет, но он работает до сих пор для меня. Мне нужен только один метод и несколько переменных, например.

@Override 
public void onDestroyView() { 
    super.onDestroyView(); 
    savedAdapter = adapter; 
    savedFilelist = filelist; 
    fromBackStack = true; 
    Log.e("onDestroyView", "onDestroyView"); 
} 

Спасибо.