Android 自定义ListView动态加载数据

 我们都知道网络取数据是耗时操作，如果我们一次性请求所有数据，假如数据量不多那还可以接受，但是如果数据量特别多，那么带来的后果就是用户的愤怒（用户是很没有耐心的），所以这时候我们就需要动态的加载数据，分批加载我们所需的数据，提升用户体验，先上图。

         

一般如果一个Activity集成越多的功能，代码量也会随之增多，看起来让人烦，我们可以考虑自定义控件将一些操作集成进去。

自定义ListView

package com.example.listviewdynamicloading;

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;

public class ZdyListView extends ListView implements OnScrollListener {
    private int totalItemCount;// 总数量；
    private int lastVisibleItem;// 最后一个可见的item；
    private boolean isLoading;
    private View footer;
    private LayoutInflater inflater;
    public RefleshDatas refleshDatas;

    public ZdyListView(Context context) {
        super(context);
        initView(context);
    }

    public ZdyListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView(context);
    }

    public ZdyListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView(context);
    }

    private void initView(Context context) {
        footer=inflater.from(context).inflate(R.layout.layout_util_footer, null);
        this.setOnScrollListener(this);
        this.addFooterView(footer);
        this.removeFooterView(footer);
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        this.lastVisibleItem = firstVisibleItem + visibleItemCount;
        this.totalItemCount = totalItemCount;
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        //listview item总数量等于最后一个可见的item并且ListView停下不动了
        if (totalItemCount == lastVisibleItem&& scrollState == SCROLL_STATE_IDLE) {
            if (!isLoading) {
                isLoading = true;
                this.addFooterView(footer);
                if (refleshDatas != null) {      
                    //回调执行向服务器端请求数据
                    refleshDatas.onLoading();
                }  
            }
        }
    };
    public void loadComplete() {
        isLoading = false;
        this.removeFooterView(footer);//加载完毕，移除footView；
    }
    public void setInterface(RefleshDatas refleshDatas) {
        this.refleshDatas = refleshDatas;
    }
    public interface RefleshDatas{
        public void onLoading();
    }
}

MainActivity

package com.example.listviewdynamicloading;

import java.util.ArrayList;

import com.example.listviewdynamicloading.ZdyListView.RefleshDatas;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.Toast;

public class MainActivity extends Activity{
    //一次从服务器端请求十条数据
    private int current=1;  
    private int number=9;
    
    
    private ZdyListView listView; //自定义ListView，将footview，滑动监听等集合在一起，免得Activity代码过多
    private ArrayList<String> listDatas;
    private ListViewAdapter adapter;


    private Handler handler=new Handler(){
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
            case 0x123:
                setlistView((ArrayList<String>)msg.obj,"firstLoading");//firstLoading标志位代表数据是初次加载的
                break;
            case 0x234:
                setlistView((ArrayList<String>)msg.obj,"addLoading");//addLoading标志位代表数据是初次加载之后请求服务器所得
                break;
            case 0x345:
                showMsg((String)msg.obj);
                break;
            default:
                break;
            }
        };
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listDatas=new ArrayList<String>();
        listView=(ZdyListView) this.findViewById(R.id.listview);
        listView.setInterface(new RefleshDatas() {
            @Override
            public void onLoading() {
                getDataThread(current, current+number, "addLoading");
            }
        });
    }



    @Override
    protected void onStart() {
        super.onStart();
        getDataThread(current,number,"firstLoading");
    }

    //.........................模拟开启线程向服务器请求数据.....................................
    private void getDataThread(final int current, final int number,final String type) {
        final Message msg=new Message();
        new Thread(){
            public void run() {
                ArrayList<String> datas=ListViewDatas.returnNum(current, current+number);
                if(datas!=null&&datas.size()>0){
                    switch (type) {
                    case "firstLoading":
                        msg.what=0x123;
                        break;
                    case "addLoading":
                        msg.what=0x234;
                        break;
                    default:
                        break;
                    }    
                    msg.obj=datas;
                }else {
                    msg.what=0x345;
                    msg.obj=datas;
                }
                handler.sendMessage(msg);
            };
        }.start();
    }



    private void setlistView(ArrayList<String> datas,String type) {
        listDatas.addAll(datas);
        if(type.equals("firstLoading")){//初次加载
            adapter=new ListViewAdapter(MainActivity.this, listDatas);
            current=adapter.getCount()+1;
            listView.setAdapter(adapter);
            listView.loadComplete();
        }else if(type.equals("addLoading")){//初次加载后请求的数据，执行notifyDataSetChanged();
            adapter.notifyDataSetChanged();
            current=adapter.getCount()+1;
            listView.loadComplete();
        }
    }


    protected void showMsg(String str) {
        Toast.makeText(MainActivity.this, "已加载完毕", Toast.LENGTH_SHORT).show();
        listView.loadComplete();
    }



}

模拟服务器端数据

package com.example.listviewdynamicloading;

import java.util.ArrayList;

public class ListViewDatas {
    //模拟服务器端数据库中的数据，假设现在只有3条数据
    public static int NUM=53;
    public static ArrayList<String> returnNum(int startNum,int endNum){
        ArrayList<String> list=new ArrayList<String>();
        if(endNum<=NUM){//客户端请求的数据在数据库数据范围之内
            for(int i=startNum;i<=endNum;i++){
                list.add(String.valueOf(i));
            }
            return list;
        }else if(endNum>=NUM&&startNum<=NUM){//客户端请求的数据不全在数据库数据范围之内
            for(int i=startNum;i<=NUM;i++){
                list.add(String.valueOf(i));
            }
            return list;            
        }else if(startNum>NUM){//客户端请求的数据超出数据库数据范围之内
            return null;
        }
        return null;
    }
}

ListView适配器

package com.example.listviewdynamicloading;

import java.util.ArrayList;

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 ListViewAdapter extends BaseAdapter{
    private Context context;
    private ArrayList<String> datas;

    public ListViewAdapter(Context context,ArrayList<String> datas){
        this.context=context;
        this.datas=datas;
    }
    
    @Override
    public int getCount() {
        return datas.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder vh=null;
        if(convertView==null){
            vh=new ViewHolder();
            convertView=LayoutInflater.from(context).inflate(R.layout.listview_item, null);
            vh.tv=(TextView) convertView.findViewById(R.id.tv);
            convertView.setTag(vh);
        }else {
            vh=(ViewHolder) convertView.getTag();
        }
        vh.tv.setText("这是第"+datas.get(position)+"条数据");
        return convertView;
    }
    
    
    
    class ViewHolder{
        TextView tv;
    }


}