分页加载数据Demo

分页加载数据Demo：当客户端从服务端获取数据量过大，一般为用户考虑流量，我们都需要对数据进行分页加载(譬如图片bitmap等)

 布局代码：listview

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

</LinearLayout>

item布局

<?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="vertical" >
    
    <TextView 
        android:id="@+id/tv_info"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:textColor="@android:color/white"
        android:text="分页加载的数据    10"
        />

</LinearLayout>

footer页脚

<?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="wrap_content"
    android:orientation="horizontal" >
    
    <ProgressBar 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    
    <TextView 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:textColor="@android:color/white"
        android:text="正在加载数据..........."
        android:layout_gravity="center_vertical"
        />

</LinearLayout>

模拟数据

package com.android.hzy.service;

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

public class DataService {

    public List<String> getData(int startPosition, int offset) {
        List<String> data = new ArrayList<String>();
        for (int i = 0; i < 20; i++) {
            data.add("分页加载的数据 " + i);
        }
        return data;
    }
}

MainActivity

package com.android.hzy.pageloaddata;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.util.Log;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.android.hzy.service.DataService;

public class MainActivity extends Activity {
    
    private static final int SUCCESS_GET_DATA = 0;

    private ListView listview;
    private DataService service;
    private List<String> data; // 加载的总数据
    private ArrayAdapter<String> adapter;
    
    private boolean finish = true; // 是否加载完成
    private View footer;
    
    private Handler mHandler = new Handler(){

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case SUCCESS_GET_DATA:
                ArrayList<String> result = (ArrayList<String>)msg.obj;
                data.addAll(result);
                adapter.notifyDataSetChanged(); // 让listview自动刷新
                finish = true; // 加载完成
                if(listview.getFooterViewsCount() > 0){ // 当页脚大于0 就删除页脚
                    listview.removeFooterView(footer);
                }
                break;

            default:
                break;
            }
        }
        
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listview = (ListView) findViewById(R.id.listview);
        service = new DataService();
        data = new ArrayList<String>();

        List<String> result = service.getData(0, 20);
        data.addAll(result);
        adapter = new ArrayAdapter<String>(getApplicationContext(),R.layout.item, R.id.tv_info, data);
        
        footer = View.inflate(getApplicationContext(), R.layout.footer, null);
        
        listview.addFooterView(footer); // 这里必须添加页脚让setAdapter里面满足  if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0)条件
        listview.setAdapter(adapter);
        listview.removeFooterView(footer);// 移除掉
        
        // 设置listview的滚动监听
        listview.setOnScrollListener(new MyOnScrollListener());
        
        
        
    }
    
    private final class MyOnScrollListener implements OnScrollListener{

        
        private int countPage = 5; // 加载的总页数
        private int pageSize = 20; // 每页加载20条数据
        
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            // TODO Auto-generated method stub
            Log.i("i", "  scrollState   " + scrollState);
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            // TODO Auto-generated method stub
            Log.i("i", " firstVisibleItem:" + firstVisibleItem + ",visibleItemCount:" + visibleItemCount
                    + ",totalItemCount:" + totalItemCount);
            
            final int totalCount = firstVisibleItem + visibleItemCount; // 已经加载了多少条目
            int currentPage = totalCount/pageSize; // 当前页
            int nextPage = currentPage + 1; // 下一页
            if (totalCount == totalItemCount && nextPage <= countPage && finish) {// 已经移动到了listview的最后一个条目去加载

                finish = false; // 加载未完成
                // 加载数据时 添加页脚
                listview.addFooterView(footer);
                
                new Thread() {
                    public void run() {
                        SystemClock.sleep(3000);
                        List<String> result = service.getData(totalCount + 1, pageSize);//
                        // 发送消息给hander
                        Message msg = new Message();
                        msg.what = SUCCESS_GET_DATA;
                        msg.obj  = result;
                        mHandler.sendMessage(msg);
                    };
                }.start();
            }
        }
        
    }

}