Android系列之ListView实现分页和类似异步加载效果

在做项目的时候我遇到这样一种业务，就是我需要将联系人已列表的形式展示出来以供选择，当然手机中的联系人肯定不止一条，大多情况很难一屏展示，那么就需要类似分页的效果。这里用ListView去实现。首先上效果图

点击加载后就继续加载后面的12条数据。

这样我们就实现了我们想要的分页效果了。

首先创建一个activity_link.xml作为承载view。代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/kehuan05"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/listview_item"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</LinearLayout>

其中就一个ListView比较简单，然后我们再新建一个ListView(我们可以这样去理解)模板 link_listview_item.xml这个页决定了ListView怎样展示，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <CheckBox
        android:id="@+id/checkBox1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/list_item_text_num"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingRight="15dp"
        android:textColor="@color/wite" />

    <TextView
       
        android:layout_width="wrap_content"
        android:textColor="@color/wite"
        android:layout_height="wrap_content"
        android:id="@+id/list_item_text_name" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/flag" />

</LinearLayout>

从代码中很容易看出，左边一个选择框最右边是图片。请参照上图不难理解。

再添加一个适配器：

package com.egojit.crm;

import java.util.HashMap;
import java.util.List;

import com.egojit.crm.Model.ModelLinkMain;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;


public class AdapterLinkList extends BaseAdapter {

    private List<ModelLinkMain> items;
    private LayoutInflater inflater;
    private static HashMap<Integer,View> m=new HashMap<Integer,View>();
    
    
    public AdapterLinkList( List<ModelLinkMain> items, Context context) {
        super();
        this.items = items;
        this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }
    
    
    
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return items.size();
    }

    @Override
    public Object getItem(int arg0) {
        // TODO Auto-generated method stub
        return items.get(arg0);
    }

    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;
    }

    @Override
    public View getView(int position, View contentView, ViewGroup arg2) {
        contentView=m.get(position);
        if(contentView==null){
        contentView=inflater.inflate(R.layout.link_listview_item, null);
        TextView text=(TextView) contentView.findViewById(R.id.list_item_text_num);
        text.setText(String.valueOf(items.get(position).id)+".");
        TextView textName=(TextView) contentView.findViewById(R.id.list_item_text_name);
        textName.setText(items.get(position).name);
        }
        m.put(position, contentView);
        return contentView;
    }

    

    public void addItem(ModelLinkMain item) { 
        items.add(item); 
    }  

    


}

添加一个名字为LinkActivity的Activity。代码如下：

package com.egojit.crm;

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

import com.egojit.crm.Model.ModelLinkMain;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

public class LinkActivity extends Activity implements OnScrollListener{

      List<ModelLinkMain> items = new ArrayList<ModelLinkMain>(); 
      private ListView listView; 
          private int visibleLastIndex = 0;   //最后的可视项索引 
          private int visibleItemCount;       // 当前窗口可见项总数 
          private AdapterLinkList adapter; 
          private View loadMoreView; 
          private Button loadMoreButton; 
          private Handler handler = new Handler();  
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.activity_link);
        
        
        
        
        loadMoreView = getLayoutInflater().inflate(R.layout.load_more, null); 
        loadMoreButton = (Button) loadMoreView.findViewById(R.id.loadMoreButton); 
        loadMoreButton.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                loadMoreButton.setText("正在加载...");   //设置按钮文字loading 
                handler.postDelayed(new Runnable() { 
                    @Override 
                    public void run() { 
                        loadData(); 
                         
                        adapter.notifyDataSetChanged(); //数据集变化后,通知adapter 
                        listView.setSelection(visibleLastIndex - visibleItemCount + 1); //设置选中项 
                         
                        loadMoreButton.setText("加载更多");    //恢复按钮文字 
                    } 
                }, 1000);  
            }
        });
        
        
        
        listView = (ListView) this.findViewById(R.id.listview_item);
        
        listView.addFooterView(loadMoreView);   //设置列表底部视图 
       // listView.addHeaderView(v)    //设置列表顶部视图
 
        initAdapter(); 
         
        listView.setAdapter(adapter);                //自动为id是list的ListView设置适配器 
         
        listView.setOnScrollListener(this);     //添加滑动监听 
        listView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int position,long arg3) {
                // TODO Auto-generated method stub
                
                Toast.makeText(getApplicationContext(), items.get(position).name,Toast.LENGTH_SHORT).show();
            }
        });
    }


    
    
    
    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        // TODO Auto-generated method stub
        
        this.visibleItemCount = visibleItemCount; 
        visibleLastIndex = firstVisibleItem + visibleItemCount - 1;  
        
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub
        int itemsLastIndex = adapter.getCount() - 1;    //数据集最后一项的索引 
        int lastIndex = itemsLastIndex + 1;             //加上底部的loadMoreView项 
        if (scrollState == OnScrollListener.SCROLL_STATE_IDLE && visibleLastIndex == lastIndex) { 
            //如果是自动加载,可以在这里放置异步加载数据的代码 
            Log.i("LOADMORE", "loading..."); 
        }  
    }
    
    
    
    /**
     * 模拟加载数据
     */ 
    private void loadData() { 
        int count = adapter.getCount(); 
        for (int i = count; i < count + 12; i++) {
            ModelLinkMain m1=new ModelLinkMain();
            m1.id=i+1;
            m1.name="gaolu"+i;
            adapter.addItem(m1); 
        } 
    }

    
    /**
     * 初始化适配器
     */ 
    private void initAdapter() { 
    
        for (int i = 0; i < 12; i++) { 
            
            ModelLinkMain m1=new ModelLinkMain();
            m1.id=i+1;
            m1.name="gaolu"+i;
            items.add(m1); 
        } 
        adapter = new AdapterLinkList(items,this); 
    }  
    
    
}

其中大家看到一个ModelLinkMain类型，这是我定义的类，有id，name字段。通过这些大家很容易去重现代码。