删除/刷新新数据的自定义列表适配器

Question

每次下载数据时，我都会使用自定义适配器填充 ListView。问题是每次 onResume 调用下载方法时，视图都是重复的，而不是删除旧视图并替换为新视图。

如何解决停止重复？下面是我的代码，我尝试制作一种删除视图的方法，但我认为它的工作正常或更好但尚未完成。

  public class CommentAdapter extends BaseAdapter{


private ArrayList<ListItem> listData;
private LayoutInflater layoutInflater;
ViewHolder holder;
public CommentAdapter(Context context, ArrayList<ListItem> listData) {
this.listData = listData;
notifyDataSetChanged();
layoutInflater = LayoutInflater.from(context);
}


@Override
public int getCount() {
return listData.size();
}

@Override
public Object getItem(int position) {
return listData.get(position); 
}

@Override
public long getItemId(int position) {
return position;
}

 public View getView(int position, View convertView, ViewGroup parent) {

 if (convertView == null) {
 convertView = layoutInflater.inflate(R.layout.singlecomment, null);
 holder = new ViewHolder();
 holder.username = (TextView) convertView.findViewById(R.id.usernme);
 holder.message = (TextView) convertView.findViewById(R.id.postCommentBox);
 holder.timeStamp = (TextView) convertView.findViewById(R.id.timeAgo);

 convertView.setTag(holder);

} else {
  holder = (ViewHolder) convertView.getTag();
}

 ListItem newsItem = listData.get(position);
 holder.username.setText(newsItem.getUsername());
 holder.message.setText(newsItem.getmComment());
  holder.timeStamp.setText(newsItem.getTimeStamp());

 return convertView;
 }


 //method to delete old views i tried implementing
 //from each adapter
 public void deleteOldViews(){
 listData.clear();
 this.notifyDataSetChanged();
  }

 static class ViewHolder {
 TextView username;
TextView message;
TextView timeStamp;

 }

} //CustomAdapter的实现

 //ListAdapter
  private void updateList() {
// Locate the listview in listview_main.xml
ArrayList<ListItem> listData = getListData();
   final ListView listView = getListView();
     listView.deferNotifyDataSetChanged();
    listView.setAdapter(new CommentAdapter(PostComments.this, listData));
    AsyncTask

类 LoadAuto 扩展 AsyncTask {

@Override
protected String doInBackground(String... params) {
    int success;


    try {


        // Building Parameters
        List<NameValuePair> param = new ArrayList<NameValuePair>();
        param.add(new BasicNameValuePair("postID", postID));

        //Posting user data to script
        JSONObject json = jsonParser.makeHttpRequest(
                LOAD_COMMENT_URL, "POST", param);

        // full json response
        Log.d("Post Comment attempt", json.toString());

        // json success element
        success = json.getInt(TAG_SUCCESS);

        if (success == 1) {
            Log.d("Comment Added!", json.toString());

            //Updating Json
            mCommentList = new ArrayList<HashMap<String, String>>();


            try {

                //check connection before search for posts
                mComments = json.getJSONArray(TAG_POSTS);

                // looping through all posts according to the json object       returned
                for (int i = 0; i < mComments.length(); i++) {
                    JSONObject c = mComments.getJSONObject(i);

                    // gets the content of each tag;
                    // gets the content of each tag;
                    String time = c.getString(TAG_TIMESTAMP);
                    content = c.getString(TAG_COMMENT);
                    username = c.getString(TAG_USERNAME);

                    //getting comments

                    mUsername.add("By " + username);
                    TimeStamp.add(time);
                    Comment.add(content);
                }

            } catch (JSONException e) {
                e.printStackTrace();
            }


            return json.getString(TAG_MESSAGE);
        } else {
            Log.d("Comment Failure!", json.getString(TAG_MESSAGE));
            return json.getString(TAG_MESSAGE);

        }


    } catch (JSONException e) {
        e.printStackTrace();
    } catch (NullPointerException npe) {
        //Handle Exception

        String s = "NullPointerException";
        return s;


    }
    return null;
}


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

}


protected void onPostExecute(String file_url) {


 //Updating List
        updateList();
     ;
    }


}

getlistdata 方法

   private ArrayList<ListItem> getListData() { 
  ArrayList<ListItem> listMockData = new ArrayList<ListItem>();
   String[] username = mUsername.toArray(new String[mUsername.size()]);
  String[] comments = Comment.toArray(new String[Comment.size()]); 
  String[] time = TimeStamp.toArray(new String[TimeStamp.size()]);

  for (int i = 0; i < username.length; i++) {
      ListItem newsData = new ListItem();
      newsData.setUsername(username[i]); 
      newsData.setmComment(comments[i]);
       newsData.setTimeStamp(time[i]);
        listMockData.add(newsData); 
         System.gc();
      } 
      return listMockData;
        }

Answer 1

我认为你必须声明全局适配器变量，而不是每次设置列表视图适配器时都创建一个新变量。

CommentAdapter commentAdapter;

然后在updateList()方法中

commentAdapter = new CommentAdapter(PostComments.this, listData);
listView.setAdapter(commentAdapter );

使用此代码，您不会丢失对适配器的引用，希望对您有所帮助

Answer 2

我不认为它是一个全局变量，那是直接创建一个类的实例，并且由于它是一个listadapter，它被直接分配给listview，你认为应该做的是让适配器成为一个全局变量然后在设置任何数据之前调用 .notifyDataSetChanged()，然后设置适配器并为其提供所需的正确数据。

    adapter.notifyDataSetChanged();

    adapter = new CommentAdapter(this,listData);
    listView.setAdapter(adapter);

Answer 3

尝试简单地使用listView.setAdapter(null); 清空ListView，然后重新设置您的适配器。