Android UI组件----自定义ListView实现动态刷新

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     tools:context=".MainActivity" >
 6     <ListView
 7         android:id="@+id/listView1"
 8         android:layout_width="match_parent"
 9         android:layout_height="match_parent" >
10     </ListView>
11 </LinearLayout>

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical" >
 6     <TextView
 7     android:id="@+id/textView1_title"
 8     android:layout_width="match_parent"
 9     android:layout_height="wrap_content"
10     android:text="Large Text"
11     android:textAppearance="?android:attr/textAppearanceLarge" />
12     <TextView
13         android:id="@+id/textView2_content"
14         android:layout_width="match_parent"
15         android:layout_height="wrap_content"
16         android:text="TextView" />
17 </LinearLayout>

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="wrap_content"
 5     android:orientation="horizontal"
 6     android:gravity="center" >
 7 
 8     <ProgressBar
 9         android:id="@+id/progressBar1"
10         android:layout_width="25dp"
11         android:layout_height="25dp" />
12 
13     <TextView
14         android:id="@+id/textView1"
15         android:layout_width="wrap_content"
16         android:layout_height="wrap_content"
17         android:text="正在加载···" />
18 
19 </LinearLayout>

  1 package com.smyhvae.smyh005listview5;
  2 
  3 import java.util.Vector;
  4 
  5 import android.app.Activity;
  6 import android.os.Bundle;
  7 import android.os.Handler;
  8 import android.os.Message;
  9 import android.view.Menu;
 10 import android.view.View;
 11 import android.view.ViewGroup;
 12 import android.widget.AbsListView;
 13 import android.widget.AbsListView.OnScrollListener;
 14 import android.widget.BaseAdapter;
 15 import android.widget.ListView;
 16 import android.widget.TextView;
 17 
 18 public class MainActivity extends Activity {
 19 
 20     private ListView listView;
 21     Vector<News> news = new Vector<News>();
 22     //private ArrayList<News> news = new ArrayList<News>();上面一行与这一行，二选一
 23     MyAdapter myAdapter;
 24     
 25     @Override
 26     protected void onCreate(Bundle savedInstanceState) {
 27         super.onCreate(savedInstanceState);
 28         setContentView(R.layout.activity_main);
 29         listView = (ListView)findViewById(R.id.listView1);
 30         
 31         listView.setOnScrollListener(new ListViewListener());  //绑定监听器
 32         
 33         //设置底部视图
 34         View footer = getLayoutInflater().inflate(R.layout.activity_main_load, null);
 35         listView.addFooterView(footer);        
 36         
 37 //        initData();
 38         new LoadDataThread().start();//加载数据的工作线程
 39             
 40         myAdapter = new MyAdapter();
 41         listView.setAdapter(myAdapter);
 42     }
 43 
 44    //定义一个数据的类
 45     class News {
 46         String title;
 47         String content;
 48     }
 49     
 50     int index = 1;//数据的记数器(索引)
 51     //初始化数据
 52     void initData(){        
 53         System.out.println("initData");
 54         for (int i = 0; i < 15; i++) {
 55             News n = new News();  //这句话一定要放在循环的里面，否则每个item显示的内容都是一样的
 56             n.title = "title-"+index;
 57             n.content = "content"+index;
 58             index++;
 59             news.add(n);  //这一步很关键，我就是少了这一步，导致运行时，界面为空
 60         }
 61     }
 62     
 63     
 64     
 65     //自定义适配器
 66     class MyAdapter extends BaseAdapter{
 67 
 68         @Override
 69         public int getCount() {
 70             // TODO Auto-generated method stub
 71             return news.size();
 72         }
 73         public Object getItem(int position) {
 74             return news.get(position);
 75         }
 76 
 77         @Override
 78         public long getItemId(int position) {
 79             return position;
 80         }
 81 
 82         @Override
 83         public View getView(int position, View convertView, ViewGroup parent) {
 84             ViewHolder viewHolder = new ViewHolder();
 85             //通过下面的条件判断语句，来循环利用。如果convertView = null ，表示屏幕上没有可以被重复利用的对象。
 86             if(convertView==null){
 87                 //创建View
 88                 convertView = getLayoutInflater().inflate(R.layout.activity_main_item, null);
 89                 viewHolder.tvTitle = (TextView) convertView.findViewById(R.id.textView1_title);
 90                 viewHolder.tvContent = (TextView) convertView.findViewById(R.id.textView2_content);
 91                 convertView.setTag(viewHolder);
 92             }else{
 93                 viewHolder = (ViewHolder)convertView.getTag();
 94             }
 95             //从Vector中取出数据填充到ListView列表项中
 96             News n = news.get(position);
 97             viewHolder.tvTitle.setText(n.title);
 98             viewHolder.tvContent.setText(n.content);
 99             return convertView;
100         }
101         
102     }
103 
104     static class ViewHolder{
105         TextView tvTitle;
106         TextView tvContent;
107     }    
108 
109     
110 
111     
112     //实现ListView的监听器的接口
113     int visibleLastIndex = 0; //最后一个显示的索引    
114     public class ListViewListener implements OnScrollListener{        
115         @Override
116         public void onScrollStateChanged(AbsListView view, int scrollState) {
117             //如果屏幕滑到最下面了，并且scrollState的状态为：滚动完毕之后ListView处于停止状态（手离开屏幕），
118             if(visibleLastIndex==myAdapter.getCount() && scrollState==OnScrollListener.SCROLL_STATE_IDLE){
119                 new LoadDataThread().start();//如果满足上面的条件，此时，可以加载新数据了
120             }
121         }
122 
123         @Override
124         public void onScroll(AbsListView view, int firstVisibleItem,
125             int visibleItemCount, int totalItemCount) {
126             visibleLastIndex = firstVisibleItem+visibleItemCount-1;
127             
128         }
129         
130     }
131     
132     //额外开启一个线程，模拟加载数据
133     class LoadDataThread extends Thread{
134         @Override
135         public void run() {
136             initData();
137             try {
138                 Thread.sleep(2000);//休眠两秒
139             } catch (InterruptedException e) {
140                 // TODO Auto-generated catch block
141                 e.printStackTrace();
142             }
143             
144             //新数据加载完成后，通过handle通知主线程，将这个新数据显示在UI界面上（因为涉及到线程安全问题）
145             handler.sendEmptyMessage(1);
146         }
147     }      
148     
149     //handler为线程之间通信的桥梁    
150     private Handler handler = new Handler(){
151         public void handleMessage(Message msg) {
152             switch(msg.what){
153             case 1:  //根据上面的提示，当Message为1，表示数据处理完了，可以通知主线程了
154                  myAdapter.notifyDataSetChanged();        //这个方法一旦调用，UI界面就刷新了
155                 break;
156                 
157             default :
158                 break;
159             }
160         }
161         
162     };
163     
164     
165     @Override
166     public boolean onCreateOptionsMenu(Menu menu) {
167         // Inflate the menu; this adds items to the action bar if it is present.
168         getMenuInflater().inflate(R.menu.main, menu);
169         return true;
170     }
171 
172 
173     
174 }