改變ArrayAdapter的內容沒有更新

Question

清除或添加數據並不在我的自定義一個ArrayAdapter類的方法addData得到更新。到底是怎麼回事？我也嘗試更新饋送到ArrayAdapter的列表，但該列表不會被更改，兩次適配器中的項目數量都保持不變。請幫忙！

類別：

package sukh.app.ireddit; 

import java.util.ArrayList; 
import java.util.Collection; 
import java.util.List; 

import android.app.Activity; 
import android.os.Bundle; 
import android.os.Handler; 
import android.support.v4.app.Fragment; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AbsListView; 
import android.widget.AbsListView.OnScrollListener; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 
import android.widget.TextView; 

/** 
* While this looks like a lot of code, all this class 
* actually does is load the posts in to the listview. 
* 
* @author Hathy 
*/ 
public class PostsFragment extends Fragment{ 

    ListView postsList; 
    PostAdapter adapter; 
    Handler handler; 
    Activity activity; 

    String subreddit; 
    List<Post> posts; 
    PostsHolder postsHolder; 

    public PostsFragment(){ 
     handler=new Handler(); 
     posts=new ArrayList<Post>(); 
     activity=getActivity(); 
    }  

    public static Fragment newInstance(String subreddit){ 
     PostsFragment pf=new PostsFragment(); 
     pf.subreddit=subreddit; 
     pf.postsHolder=new PostsHolder(pf.subreddit);   
     return pf; 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, 
          ViewGroup container, 
          Bundle savedInstanceState) { 
     View v=inflater.inflate(R.layout.posts 
           , container 
           , false); 
     postsList=(ListView)v.findViewById(R.id.posts_list); 
     return v; 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setRetainInstance(true); 
    } 

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

    private void initialize(){ 
     // This should run only once for the fragment as the 
     // setRetainInstance(true) method has been called on 
     // this fragment 

     if(posts.size()==0){ 

      // Must execute network tasks outside the UI 
      // thread. So create a new thread. 

      new Thread(){ 
       public void run(){ 
        posts.addAll(postsHolder.fetchPosts()); 

        // UI elements should be accessed only in 
        // the primary thread, so we must use the 
        // handler here. 

        handler.post(new Runnable(){ 
         public void run(){ 
          createAdapter(); 
         } 
        }); 
       } 
      }.start(); 
     }else{ 
      createAdapter(); 
     } 
    } 
    /** 
    * This method creates the adapter from the list of posts 
    * , and assigns it to the list. 
    */ 
    private void createAdapter(){ 

     // Make sure this fragment is still a part of the activity. 
     if(getActivity()==null) return; 

     adapter=new PostAdapter(posts); 
     postsList.setAdapter(adapter); 
     Log.i("sukh", "setting adapter"); 
     postsList.setOnScrollListener(adapter); 
    } 

    protected class PostAdapter extends ArrayAdapter<Post> implements OnScrollListener { 
     private int previousTotal = 0; 
     private boolean loading = true; 
     //PostAdapter _adapter = this; 

     public PostAdapter(List<Post> posts){ 
      super(getActivity(), R.layout.post_item, posts); 
     } 

     @Override 
     public View getView(int position, View convertView, ViewGroup parent) { 
      if(convertView == null){ 
       convertView = getActivity().getLayoutInflater().inflate(R.layout.post_item, null); 
      } 

      Post thePost = getItem(position); 

      TextView postTitleTextView = (TextView) convertView.findViewById(R.id.post_title); 
      postTitleTextView.setText(thePost.getTitle()); 

      TextView postDetailsTextView = (TextView) convertView.findViewById(R.id.post_details); 
      postDetailsTextView.setText(thePost.getDetails()); 

      TextView postScoreTextView = (TextView) convertView.findViewById(R.id.post_score); 
      postScoreTextView.setText(thePost.getScore()); 

      return convertView; 
     } 

     private void addData() { 
      //final List<Post> newPosts = new ArrayList<Post>(); 
      Log.i("update1", this.adapterToString()); 
      new Thread(){ 
       public void run(){ 
        //neither of these following statements make a difference 
        //neither does posts.clear() or posts.addAll... 
        //adapter.addAll(postsHolder.fetchMorePosts()); 
        adapter.clear(); 
       } 
      }; 
      Log.i("sukh", "executed scroll");  
     adapter.notifyDataSetChanged(); 
     Log.i("update2", this.adapterToString()); 
     } 

     private String adapterToString() { 
      StringBuilder sb = new StringBuilder(); 
      int total = this.getCount(); 
      sb.append("contents: "); 
      /*for (int i = 0; i < this.getCount(); i ++) { 
       sb.append(this.getItem(i).title + "/n"); 
      }*/ 
      //return sb.toString(); 
      return sb.append(total).toString(); 
     } 

     @Override 
     public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { 

      if (loading) { 
       if (totalItemCount > previousTotal) { 
        loading = false; 
        previousTotal = totalItemCount;  
       } 
      } 

      if (!loading && 
        (firstVisibleItem + visibleItemCount + 1 >= totalItemCount) 
        ) { 
       addData(); 
       loading = true; 
      } 

     } 

     @Override 
     public void onScrollStateChanged(AbsListView view, int scrollState) { 
     } 
    } 


} 

編輯：固定。增加了新的類，它擴展了ASyncTask並在更新適配器之前擁有了fetchMorePosts。

類顯示：

private class AddPostsTask extends AsyncTask<Void, Void, Void> { 
     @Override 
     protected Void doInBackground(Void... params) { 
      Log.i("update2", "start fetchMorePosts"); 
      posts.addAll(postsHolder.fetchMorePosts()); 
      Log.i("update2", "end fetchMorePosts"); 
      return null; 
     } 

     @Override 
     protected void onPostExecute(Void result) { 
      Log.i("update2", "start adapterChange"); 
      adapter.notifyDataSetChanged(); 
      Log.i("update2", "start adapterChange"); 
      super.onPostExecute(result); 
     } 

    } 

Answer 1

在addData功能

，你在一個線程notifyDataSetChanged '後' 清適配器（）被調用。