Android使用listview实现分页刷新（线程休眠模拟）

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/activity_main"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context="com.example.administrator.day08.MainActivity">
 <ListView
 android:id="@+id/lv"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:layout_alignParentTop="true"
 android:layout_alignParentStart="true" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical" android:layout_width="match_parent"
  android:layout_height="match_parent">
  <TextView
    android:text="Tile"
    android:textSize="30dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textView" />
  <TextView
    android:text="Message"
    android:textSize="20dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textView2" />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="horizontal" android:layout_width="match_parent"
  android:layout_height="match_parent" android:gravity="center">
  <ProgressBar
    style="?android:attr/progressBarStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:id="@+id/progressBar" />
  <TextView
    android:text="玩命加载中"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/textView3" />
</LinearLayout>

 public class News {
   String title;
   String message;
 }

import android.content.DialogInterface;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
/**
 * Created by panchengjia on 2016/11/29.
 */
public class MainActivity extends AppCompatActivity implements AbsListView.OnScrollListener{
  private ListView lv;
  private List<News> news;//声明存储新闻标题与内容的List
  private int total=1;//计数器(设置默认从1开始)用于集合内数据初始化
  MyAdapter adapter;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    lv= (ListView) findViewById(R.id.lv);
    //为当前ListView设置OnScrollListener实现分页刷新
    lv.setOnScrollListener(this);
    //将login_item(下拉刷新效果的item)通过布局 填充器声明
    View v = getLayoutInflater().inflate(R.layout.login_item,null);
    //将login_item设置到ListView页脚
    lv.addFooterView(v);
    //实例化存储内容资源的List
    news = new ArrayList<>();
    //调用初始化List的方法
    initList();
    adapter = new MyAdapter();
    //设置单击item的事件
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
      @Override
      public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        show(view);//事件处理为调用show方法（显示AlertDialog对话框）
      }
    });
    lv.setAdapter(adapter);
  }
  //AlertDialog对话框的调用这里就不多说了，前期有专门的博文解释
  public void show(View v){
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    TextView title = (TextView) v.findViewById(R.id.textView);
    TextView message = (TextView) v.findViewById(R.id.textView2);
    builder.setTitle(title.getText().toString());
    builder.setMessage(message.getText().toString());
    builder.setPositiveButton("已经浏览完毕", new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which) {

      }
    });
    builder.show();
  }
  //初始化List内的元素，模拟每次可刷新10条信息
  private void initList() {
    for(int i=1;i<=10;i++){
      News n = new News();
      //加total是因为total在刷新页面后不会继续从一开始
      n.title = "Title--"+total;
      n.message="Message"+total;
      news.add(n);
      total++;
    }
  }
//  int currenVisibleItemCount;//声明截止当前页面看到的item总数（演示用）
  boolean isLastRow=false;//判断是否到ListView的最后一个item
  @Override
  public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    //firstVisibleItem位可见页面的第一条在Arraylist中的下标，visibleItemCount为当前页面item数
//    currenVisibleItemCount = firstVisibleItem+visibleItemCount-1=totalItemCount;（演示用）
    if(firstVisibleItem+visibleItemCount==totalItemCount&&totalItemCount>0){
      isLastRow=true;//判断已经到最后一个item（即为footerView）
    }
  }
  @Override
  public void onScrollStateChanged(AbsListView view, int scrollState) {
    /*判断是否刷新页面之前，解释一下scrollState的三种状态
    * 1.scrollState = SCROLL_STATE_TOUCH_SCROLL为手指按住屏幕滚动（未脱离屏幕）；
    * 2.scrollState = SCROLL_STATE_FLING可以理解为手指离开屏幕前，用力滑了一下，
    *    手指离开后，页面已然保持滚动；
    * 3.scrollState = SCROLL_STATE_IDLE手指未接触屏幕，且屏幕页面保持静止
    * 开启刷新页面的线程前，确保ListView已经到最后一行（Item）并且屏幕页面保持静止
    * */
    if(isLastRow&&scrollState==SCROLL_STATE_IDLE){
      new Thread(new MyThread()).start();
    }
  }
  //创建分页刷新线程（模拟刷新）
  class MyThread implements Runnable{

    @Override
    public void run() {
      try {
        Thread.sleep(500);//设置线程休眠时间为500毫秒刷新一次
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      initList();//重新初始化List
      //线程内调用Handler执行页面刷新（后面会写文对handler进行详细剖析）
      handler.sendEmptyMessage(1);
    }
  }
  Handler handler = new Handler(){
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      switch (msg.what){
        case 1:
          //强制调用适配器的getView来刷新每个Item的内容。
          adapter.notifyDataSetChanged();
          break;
      }
    }
  };
  //自定义适配器
  class MyAdapter extends BaseAdapter{
    @Override
    public int getCount() {
      return news.size();
    }
    @Override
    public Object getItem(int position) {
      return news.get(position);
    }
    @Override
    public long getItemId(int position) {
      return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
      ViewHolder vh;
      if(convertView==null){
        convertView = getLayoutInflater().inflate(R.layout.item,null);
        vh=new ViewHolder();
        vh.message = (TextView) convertView.findViewById(R.id.textView2);
        vh.title= (TextView) convertView.findViewById(R.id.textView);
        convertView.setTag(vh);
      }
      vh= (ViewHolder) convertView.getTag();
      vh.title.setText(news.get(position).title);
      vh.message.setText(news.get(position).message);
      return convertView;
    }
    class ViewHolder{
      TextView title;
      TextView message;
    }
  }
}