ListView 分页显示

 列表的显示需要三个元素：

1．ListVeiw 用来展示列表的View。

2．适配器 用来把数据映射到ListView上的中介。

3．数据    具体的将被映射的字符串，图片，或者基本组件。

根据列表的适配器类型，列表分为三种，ArrayAdapter，SimpleAdapter和SimpleCursorAdapter

其中以ArrayAdapter最为简单，只能展示一行字。SimpleAdapter有最好的扩充性，可以自定义出各种效果。 SimpleCursorAdapter可以认为是SimpleAdapter对数据库的简单结合，可以方面的把数据库的内容以列表的形式展示出来。

 

当数据罗列过多的时候，我们需要Listview分页显示，此时怎么办呢

下面一个简单的例子介绍一下

package com.ideasandroid.demo;

import android.app.Activity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

public class listMoreTest extends Activity {
    ListView lv;
    Button btnLeft, btnRight;
    
     View.OnClickListener cl;
     
     MoreAdapter ma;
    
     String[] data = {
             "0","1","2","3","4","5","6","7","8","9","10",
             "11","12","13","14","15","16","17","18","19","20",
             "21","22","23","24","25","26","27","28","29","30",
             "31","32","33","34","35","36","37","38","39","40",
             "41","42","43","44","45","46","47","48","49","50",
             "51","52","53","54","55","56","57","58","59","60",
            "61","62","64","64","65","66","67","68","69","70",
             "71","72","73","74","75","76","77","78","79","80",
             "81","82","83","84","85","86","87","88","89","90",
             "91","92","93","94","95","96","97","98","99","100"
     };
     
     //用于显示每列5个Item项。
     int VIEW_COUNT = 5;
     
     //用于显示页号的索引
     int index = 0;     
     /** Called when the activity is first created. */
     
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.listview);
         
         //加载Listview和2个Button
         initView();
         
         //设置ListView的Adapter
         ma = new MoreAdapter(this);
         lv.setAdapter(ma);
         //此处是双向绑定吗？
         
        
         cl = new Button.OnClickListener(){
             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub
                 switch(v.getId()){
                 case R.id.btnLeft:
                     leftView();
                     break;
                     
                 case R.id.btnRight:
                     rightView();
                     break;
                 }
            }

         };         
         //添加2个Button的监听事件。
         btnLeft.setOnClickListener(cl);
         btnRight.setOnClickListener(cl);
         
         //检查2个Button是否是可用的
         checkButton();
         
     }
     
     public void initView(){
         lv = (ListView)findViewById(R.id.list);
         
         btnLeft = (Button)findViewById(R.id.btnLeft);
         btnRight = (Button)findViewById(R.id.btnRight);
         
     }
     
     //点击左边的Button，表示向前翻页，索引值要减1.
     public void leftView(){
         index--;
         
         //刷新ListView里面的数值。         
         ma.notifyDataSetChanged();
         
         //检查Button是否可用。
         checkButton();
     }     
   //点击右边的Button，表示向后翻页，索引值要加1.
     public void rightView(){
         index++;
         
         //刷新ListView里面的数值。
         ma.notifyDataSetChanged();
         
         //检查Button是否可用。
         checkButton();
     }
     
     public void checkButton(){
         //索引值小于等于0，表示不能向前翻页了，以经到了第一页了。         //将向前翻页的按钮设为不可用。
         if(index <=0){
             btnLeft.setEnabled(false);
         }
         //值的长度减去前几页的长度，剩下的就是这一页的长度，如果这一页的长度比View_Count小，表示这是最后的一页了，后面在没有了。
         //将向后翻页的按钮设为不可用。
         else if(data.length - index*VIEW_COUNT <= VIEW_COUNT){
             btnRight.setEnabled(false);
         }
         
         //否则将2个按钮都设为可用的。
         else {
            btnLeft.setEnabled(true);
             btnRight.setEnabled(true);
         }
         
     }
     
     //ListView的Adapter，这个是关键的导致可以分页的根本原因。
     public class MoreAdapter extends BaseAdapter {
         Activity activity;
          public MoreAdapter(Activity a){
             activity = a;
         }
         
         
         //设置每一页的长度，默认的是View_Count的值。
         @Override
         public int getCount() {
             // TODO Auto-generated method stub
             //return data.length            
             //ori表示到目前为止的前几页的总共的个数。
             int ori = VIEW_COUNT * index;
             
             //值的总个数-前几页的个数就是这一页要显示的个数，如果比默认的值小，说明这是最后一页，只需显示这么多就可以了
             if(data.length - ori < VIEW_COUNT ){
                 return data.length - ori;
             }
             //如果比默认的值还要大，说明一页显示不完，还要用换一页显示，这一页用默认的值显示满就可以了。
            else {
                return VIEW_COUNT;
             }
             
         }
 
        @Override
        public Object getItem(int position) {
             // TODO Auto-generated method stub
             return position;
         }
 
         @Override
         public long getItemId(int position) {
             // TODO Auto-generated method stub
             return position;
        } 
         
         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             // TODO Auto-generated method stub
             //return addTestView(position);
             
             TextView tv = new TextView(activity);
             tv.setGravity(Gravity.CENTER);
             //TextView要显示的是当前的位置+前几页已经显示的位置个数的对应的位置上的值。
             tv.setText(data[position+index*VIEW_COUNT]);
             return tv;
             
         }
     }
 }