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;
     }

 }