Android中ListView分页加载数据

         Android 应用开发中,采用ListView组件来展示数据是很常用的功能,当一个应用要展现很多的数据时,一般情况下都不会把所有的数据一次就展示出来,而是通过 分页的形式来展示数据,个人觉得这样会有更好的用户体验。因此,很多应用都是采用分批次加载的形式来获取用户所需的数据。例如:微博客户端可能会在用户滑 动至列表底端时自动加载下一页数据,也可能在底部放置一个"查看更多"按钮,用户点击后,加载下一页数据。

           下面通过一个Demo来展示ListView功能如何实现:该Demo通过在ListView列表的底部添加一个“查看更多...”按钮来加载新闻(模拟 新闻客户端)分页数据。同时限定每次加载10条记录,但完全加载完数据后,就把ListView列表底部视图“查看更多...”删除。假设加载的数据总数 为 38 条记录。先看下该Demo工程的程序结构图:

Android中ListView分页加载数据

其中包 com.andyidea.bean中News.java类是新闻实体类,包com.andyidea.listview中 paginationListViewActivity.java类是用来展示ListView列表。布局layout中包含三个布局文件,分别 为:list_item.xml , loadmore.xml , main.xml 。下面分别贴下源码:

layout中的 list_item.xml源码:

01<span style="font-size:13px;"><?xml version="1.0" encoding="utf-8"?>
02<LinearLayout
03  xmlns:android="http://schemas.android.com/apk/res/android"
04  android:layout_width="fill_parent"
05  android:layout_height="fill_parent"
06  android:orientation="vertical">
07  <TextView
08     android:id="@+id/newstitle"
09     android:layout_width="fill_parent"
10     android:layout_height="wrap_content"/>
11  <TextView
12     android:id="@+id/newscontent"
13     android:layout_width="fill_parent"
14     android:layout_height="wrap_content"/>
15</LinearLayout></span>
layout中loadmore.xml源码:
01<?xml version="1.0" encoding="utf-8"?>
02<LinearLayout
03  xmlns:android="http://schemas.android.com/apk/res/android"
04  android:layout_width="fill_parent"
05  android:layout_height="fill_parent">
06  <Button
07      android:id="@+id/loadMoreButton"
08      android:layout_width="fill_parent"
09      android:layout_height="wrap_content"
10      android:text="查看更多..." />
11</LinearLayout>
layout中main.xml源码:
01<?xml version="1.0" encoding="utf-8"?>
02<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
03    android:orientation="vertical"
04    android:layout_width="fill_parent"
05    android:layout_height="fill_parent">
06    <ListView
07       android:id="@+id/lvNews"
08       android:layout_width="fill_parent"
09       android:layout_height="wrap_content"/>
10</LinearLayou
包 com.andyidea.bean中News.java类源码:
01package com.andyidea.bean;
02
03/**
04 * 新闻实体类
05 * @author Andy.Chen
06 * @mail Chenjunjun.ZJ@gmail.com
07 *
08 */
09public class News {
10   
11    private String title;    //标题
12    private String content;  //内容
13   
14    public String getTitle() {
15        return title;
16    }
17    public void setTitle(String title) {
18        this.title = title;
19    }
20    public String getContent() {
21        return content;
22    }
23    public void setContent(String content) {
24        this.content = content;
25    }
26
27}
包com.andyidea.listview中paginationListViewActivity.java类源码:
001package com.andyidea.listview;
002
003import java.util.ArrayList;
004import java.util.List;
005
006import com.andyidea.bean.News;
007
008import android.app.Activity;
009import android.os.Bundle;
010import android.os.Handler;
011import android.util.Log;
012import android.view.View;
013import android.view.ViewGroup;
014import android.widget.AbsListView;
015import android.widget.AbsListView.OnScrollListener;
016import android.widget.BaseAdapter;
017import android.widget.Button;
018import android.widget.ListView;
019import android.widget.TextView;
020import android.widget.Toast;
021
022public class PaginationListViewActivity extends Activity implements OnScrollListener {
023   
024    private ListView listView; 
025    private int visibleLastIndex = 0;   //最后的可视项索引 
026    private int visibleItemCount;       // 当前窗口可见项总数 
027    private int datasize = 38;          //模拟数据集的条数
028    private PaginationAdapter adapter; 
029    private View loadMoreView; 
030    private Button loadMoreButton; 
031    private Handler handler = new Handler();
032   
033    /** Called when the activity is first created. */
034    @Override
035    public void onCreate(Bundle savedInstanceState) {
036        super.onCreate(savedInstanceState);
037        setContentView(R.layout.main);
038       
039        loadMoreView = getLayoutInflater().inflate(R.layout.loadmore, null);
040        loadMoreButton = (Button)loadMoreView.findViewById(R.id.loadMoreButton);
041        loadMoreButton.setOnClickListener(new View.OnClickListener() {
042           
043            @Override
044            public void onClick(View v) {
045                loadMoreButton.setText("正在加载中...");   //设置按钮文字
046                handler.postDelayed(new Runnable() {
047                   
048                    @Override
049                    public void run() {
050                        loadMoreData();
051                        adapter.notifyDataSetChanged();
052                        loadMoreButton.setText("查看更多...");  //恢复按钮文字
053                    }
054                },2000);
055               
056            }
057        });
058       
059        listView = (ListView)findViewById(R.id.lvNews);
060        listView.addFooterView(loadMoreView);    //设置列表底部视图
061        initializeAdapter();
062        listView.setAdapter(adapter);
063        listView.setOnScrollListener(this);
064    }
065   
066    @Override
067    public void onScrollStateChanged(AbsListView view, int scrollState) {
068        int itemsLastIndex = adapter.getCount()-1//数据集最后一项的索引 
069        int lastIndex = itemsLastIndex + 1;
070        if (scrollState == OnScrollListener.SCROLL_STATE_IDLE
071                && visibleLastIndex == lastIndex) {
072            // 如果是自动加载,可以在这里放置异步加载数据的代码
073        }
074    }
075
076
077    @Override
078    public void onScroll(AbsListView view, int firstVisibleItem,
079            int visibleItemCount, int totalItemCount) {
080        this.visibleItemCount = visibleItemCount;
081        visibleLastIndex = firstVisibleItem + visibleItemCount - 1;
082       
083        Log.e("========================= ","========================");
084        Log.e("firstVisibleItem = ",firstVisibleItem+"");
085        Log.e("visibleItemCount = ",visibleItemCount+"");
086        Log.e("totalItemCount = ",totalItemCount+"");
087        Log.e("========================= ","========================");
088       
089        //如果所有的记录选项等于数据集的条数,则移除列表底部视图
090        if(totalItemCount == datasize+1){
091            listView.removeFooterView(loadMoreView);
092            Toast.makeText(this, "数据全部加载完!", Toast.LENGTH_LONG).show();
093        }
094    }
095   
096    /**
097     * 初始化ListView的适配器
098     */
099    private void initializeAdapter(){
100        List<News> news = new ArrayList<News>();
101        for(int i=1;i<=10;i++){
102            News items = new News();
103            items.setTitle("Title"+i);
104            items.setContent("This is News Content"+i);
105            news.add(items);
106        }
107        adapter = new PaginationAdapter(news);
108    }
109   
110    /**
111     * 加载更多数据
112     */
113    private void loadMoreData(){
114        int count = adapter.getCount();
115       
116        if(count+10 <= datasize){
117            for(int i=count+1; i<=count+10; i++){
118                News item = new News();
119                item.setTitle("Title"+i);
120                item.setContent("This is News Content"+i);
121                adapter.addNewsItem(item);
122            }
123        }else{
124            for(int i=count+1; i<=datasize; i++){
125                News item = new News();
126                item.setTitle("Title"+i);
127                item.setContent("This is News Content"+i);
128                adapter.addNewsItem(item);
129            }
130        }
131       
132    }
133   
134   
135    class PaginationAdapter extends BaseAdapter{
136       
137        List<News> newsItems;
138       
139        public PaginationAdapter(List<News> newsitems){
140            this.newsItems = newsitems;
141        }
142
143        @Override
144        public int getCount() {
145            return newsItems.size();
146        }
147
148        @Override
149        public Object getItem(int position) {
150            return newsItems.get(position);
151        }
152
153        @Override
154        public long getItemId(int position) {
155            return position;
156        }
157
158        @Override
159        public View getView(int position, View view, ViewGroup parent) {
160            if(view == null){
161                view = getLayoutInflater().inflate(R.layout.list_item, null);
162            }
163           
164            //新闻标题
165            TextView tvTitle = (TextView)view.findViewById(R.id.newstitle);
166            tvTitle.setText(newsItems.get(position).getTitle());
167            //新闻内容
168            TextView tvContent = (TextView)view.findViewById(R.id.newscontent);
169            tvContent.setText(newsItems.get(position).getContent());
170           
171            return view;
172        }
173       
174        /**
175         * 添加数据列表项
176         * @param newsitem
177         */
178        public void addNewsItem(News newsitem){
179            newsItems.add(newsitem);
180        }
181       
182    }
183
184}


最后,运行程序的结果截图如下:

 

Android中ListView分页加载数据

通过上面的截图,当我们点击"查看更多..."按钮时,就会加载下10条记录,当加载完所有的记录后,ListView的底部视图将会移除。

转自:http://www.open-open.com/lib/view/open1330132229874.html

posted @ 2012-09-04 22:48  子福当自强  阅读(295)  评论(0编辑  收藏  举报
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