ListView中的重复条目

Question

我在ListView中获得重复的项目。往回滚动有时会改变项目顺序。 我搜索了一下，发现很多线程都报告了这个错误，但是他们都没有帮我解决我的问题。

这里是我的代码：

活动：

package com.github.progval.SeenDroid; 

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

import com.github.progval.SeenDroid.lib.Connection; 
import com.github.progval.SeenDroid.lib.Message; 
import com.github.progval.SeenDroid.lib.MessageFetcher; 
import com.github.progval.SeenDroid.lib.Query.ParserException; 

import android.app.Activity; 
import android.app.ListActivity; 
import android.content.SharedPreferences; 
import android.os.Bundle; 

public class ShowUserActivity extends ListActivity { 
    private Connection connection; 

    public ArrayList<Message> listMessages = new ArrayList<Message>(); 
    public MessageAdapter adapter; 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.profile); 
     this.connection = new Connection(); 
     this.setTitle(R.string.homefeed_title); 


     this.listMessages = new MessageFetcher(this.connection).fetchUser(); 
     this.bindUi(); 
    } 

    private void bindUi() { 
     this.adapter = new MessageAdapter(this, this.listMessages); 
     this.setListAdapter(adapter); 

     // TODO Bind buttons 
    } 
} 

MessageAdapter：

package com.github.progval.SeenDroid; 

import java.util.ArrayList; 
import java.util.List; 
import java.util.zip.Inflater; 

import com.github.progval.SeenDroid.lib.Message; 

import android.content.Context; 
import android.text.Layout; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.webkit.WebView; 
import android.widget.ArrayAdapter; 
import android.widget.BaseAdapter; 
import android.widget.LinearLayout; 
import android.widget.TextView; 

public class MessageAdapter extends BaseAdapter { 
    private Context context; 
    private List<Message> items = new ArrayList<Message>(); 
    private int lastPosition = 0; 

    public MessageAdapter(Context context, List<Message> items) { 
     super(); 
     this.context = context; 
     this.items = items; 
    } 

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

     if (null == convertView) { 
      LinearLayout view; 
      view = (LinearLayout) LinearLayout.inflate(this.context, R.layout.message, null); 
      Log.d("SeenDroid", String.format("Get view %d", position)); 
      TextView title = new TextView(view.getContext()); 
      title.setText(this.items.get(position).getTitle()); 
      view.addView(title); 
      return view; 
     } else { 
      return convertView; 
     } 
    } 


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


    @Override 
    public Object getItem(int location) { 
     return this.items.get(location); 
    } 


    @Override 
    public long getItemId(int arg0) { 
     return arg0; 
    } 


} 

顺便说一句，输出为：

D/SeenDroid(30939): Get view 0 
D/SeenDroid(30939): Get view 1 
D/SeenDroid(30939): Get view 2 
D/SeenDroid(30939): Get view 3 
D/SeenDroid(30939): Get view 4 
D/SeenDroid(30939): Get view 5 
D/SeenDroid(30939): Get view 6 
D/SeenDroid(30939): Get view 7 
D/SeenDroid(30939): Get view 8 
D/SeenDroid(30939): Get view 0 
D/SeenDroid(30939): Get view 16 

问候， ProgVal

Answer 1

试试这个：

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

    if (null == convertView) { 
     LinearLayout view = (LinearLayout) LinearLayout.inflate(this.context, 
      R.layout.message, null); 
     Log.d("SeenDroid", String.format("Get view %d", position)); 
     TextView title = new TextView(view.getContext()); 
     title.setText(this.items.get(position).getTitle()); 
     view.addView(title); 
     return view; 
    } else { 
     LinearLayout view = (LinearLayout) convertView; 
     TextView title = (TextView) view.getChildAt(0); 
     title.setText(this.items.get(position).getTitle()); 
     return convertView; 
    } 
} 

说明：你有重复的，因为在Android重用UI对象名单。预计您将重用convertView，而不是创建一个新的如果它不为空。当然，您有责任为正在重用的实例设置适当的值。否则，该值将从最后一个“用法”中留下。

Answer 2

建议 - 在title.setText后面添加一个日志语句并写入从getTitle（）获得的值。你可能会知道为什么你会得到重复的条目。

Answer 3

ListView不保证您添加的项目的唯一性。这是你的责任。您正在使用ArrayList来存储项目，并且可以根据需要存储尽可能多的重复项目。

如果你想删除重复的把你的物品放入集，然后将列表中再次：

listMessages = new ArrayList<Messages>(new LinkedHashSet<Message>(listMessages))

的LinkedHashSet将删除重复保留项目的初始订单，ArrayList将允许按位置访问元素。

Answer 4

您应该使用ViewHolder PARADIGMA在ListAdapter

一个很好的例子可以在这里找到： http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/List14.html

Answer 5

public View getView(int position, View convertView, ViewGroup parent) { 
    LayoutInflater inflater = (LayoutInflater) context 
     .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    View gridView; 
    if (convertView == null) { 
     gridView = new View(context); 
    } else { 
     gridView = (View) convertView; 
    } 
    gridView = inflater.inflate(R.layout.worker_listmain, null); 
    // your source code here!!! Run 100% 
    // I got this problem also, I found out the way to solve it! 
    // Please use my source code :D SIMPLE is PERFECT :D 
    return gridView; 
}