Android中ListView分页加载数据

古城微笑少年丶 2022-06-14 10:38 258阅读 0赞

原文地址：[http://blog.csdn.net/cjjky/article/details/6898871][http_blog.csdn.net_cjjky_article_details_6898871]

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：

![0_1331367378KyQH.gif][]

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：

layout中loadmore.xml源码：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent">
      <Button  
          android:id="@+id/loadMoreButton"  
          android:layout_width="fill_parent"  
          android:layout_height="wrap_content"
          android:text="查看更多..." /> 
    </LinearLayout>

layout中main.xml源码：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
        <ListView
           android:id="@+id/lvNews"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"/>
    </LinearLayou

包 com.andyidea.bean中News.java类源码：

package com.andyidea.bean;
    
    /**
     * 新闻实体类
     * @author Andy.Chen
     * @mail Chenjunjun.ZJ@gmail.com
     *
     */
    public class News {
    	
    	private String title;    //标题
    	private String content;  //内容
    	
    	public String getTitle() {
    		return title;
    	}
    	public void setTitle(String title) {
    		this.title = title;
    	}
    	public String getContent() {
    		return content;
    	}
    	public void setContent(String content) {
    		this.content = content;
    	}
    
    }

包com.andyidea.listview中paginationListViewActivity.java类源码：

package com.andyidea.listview;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import com.andyidea.bean.News;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.os.Handler;
    import android.util.Log;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AbsListView;
    import android.widget.AbsListView.OnScrollListener;
    import android.widget.BaseAdapter;
    import android.widget.Button;
    import android.widget.ListView;
    import android.widget.TextView;
    import android.widget.Toast;
    
    public class PaginationListViewActivity extends Activity implements OnScrollListener {
    	
    	private ListView listView;  
        private int visibleLastIndex = 0;   //最后的可视项索引  
        private int visibleItemCount;       // 当前窗口可见项总数  
        private int datasize = 38;          //模拟数据集的条数
        private PaginationAdapter adapter;  
        private View loadMoreView;  
        private Button loadMoreButton;  
        private Handler handler = new Handler(); 
    	
        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            
            loadMoreView = getLayoutInflater().inflate(R.layout.loadmore, null);
            loadMoreButton = (Button)loadMoreView.findViewById(R.id.loadMoreButton);
            loadMoreButton.setOnClickListener(new View.OnClickListener() {
    			
    			@Override
    			public void onClick(View v) {
    				loadMoreButton.setText("正在加载中...");   //设置按钮文字
    				handler.postDelayed(new Runnable() {
    					
    					@Override
    					public void run() {
    						loadMoreData();
    						adapter.notifyDataSetChanged();
    						loadMoreButton.setText("查看更多...");  //恢复按钮文字
    					}
    				},2000);
    				
    			}
    		});
            
            listView = (ListView)findViewById(R.id.lvNews);
            listView.addFooterView(loadMoreView);    //设置列表底部视图
            initializeAdapter();
            listView.setAdapter(adapter);
            listView.setOnScrollListener(this);
        }
        
        @Override
    	public void onScrollStateChanged(AbsListView view, int scrollState) {
    		int itemsLastIndex = adapter.getCount()-1;  //数据集最后一项的索引  
    		int lastIndex = itemsLastIndex + 1;
    		if (scrollState == OnScrollListener.SCROLL_STATE_IDLE
    				&& visibleLastIndex == lastIndex) {
    			// 如果是自动加载,可以在这里放置异步加载数据的代码
    		}
    	}
    
    
    	@Override
    	public void onScroll(AbsListView view, int firstVisibleItem,
    			int visibleItemCount, int totalItemCount) {
    		this.visibleItemCount = visibleItemCount;
    		visibleLastIndex = firstVisibleItem + visibleItemCount - 1;
    		
    		Log.e("========================= ","========================");
    		Log.e("firstVisibleItem = ",firstVisibleItem+"");
    		Log.e("visibleItemCount = ",visibleItemCount+"");
    		Log.e("totalItemCount = ",totalItemCount+"");
    		Log.e("========================= ","========================");
    		
    		//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
    		if(totalItemCount == datasize+1){
    			listView.removeFooterView(loadMoreView);
    			Toast.makeText(this, "数据全部加载完!", Toast.LENGTH_LONG).show();
    		}
    	}
    	
    	/**
    	 * 初始化ListView的适配器
    	 */
    	private void initializeAdapter(){
    		List<News> news = new ArrayList<News>();
    		for(int i=1;i<=10;i++){
    			News items = new News();
    			items.setTitle("Title"+i);
    			items.setContent("This is News Content"+i);
    			news.add(items);
    		}
    		adapter = new PaginationAdapter(news);
    	}
    	
    	/**
    	 * 加载更多数据
    	 */
    	private void loadMoreData(){
    		int count = adapter.getCount();
    		
    		if(count+10 <= datasize){
    			for(int i=count+1; i<=count+10; i++){
    				News item = new News();
    				item.setTitle("Title"+i);
    				item.setContent("This is News Content"+i);
    				adapter.addNewsItem(item);
    			}
    		}else{
    			for(int i=count+1; i<=datasize; i++){
    				News item = new News();
    				item.setTitle("Title"+i);
    				item.setContent("This is News Content"+i);
    				adapter.addNewsItem(item);
    			}
    		}
    		
    	}
        
        
        class PaginationAdapter extends BaseAdapter{
        	
        	List<News> newsItems;
        	
        	public PaginationAdapter(List<News> newsitems){
        		this.newsItems = newsitems;
        	}
    
    		@Override
    		public int getCount() {
    			return newsItems.size();
    		}
    
    		@Override
    		public Object getItem(int position) {
    			return newsItems.get(position);
    		}
    
    		@Override
    		public long getItemId(int position) {
    			return position;
    		}
    
    		@Override
    		public View getView(int position, View view, ViewGroup parent) {
    			if(view == null){
    				view = getLayoutInflater().inflate(R.layout.list_item, null);
    			}
    			
    			//新闻标题
    			TextView tvTitle = (TextView)view.findViewById(R.id.newstitle);
    			tvTitle.setText(newsItems.get(position).getTitle());
    			//新闻内容
    			TextView tvContent = (TextView)view.findViewById(R.id.newscontent);
    			tvContent.setText(newsItems.get(position).getContent());
    			
    			return view;
    		}
    		
    		/**
    		 * 添加数据列表项
    		 * @param newsitem
    		 */
    		public void addNewsItem(News newsitem){
    			newsItems.add(newsitem);
    		}
        	
        }
    
    }

最后，运行程序的结果截图如下：

![0_1331367534AvRS.gif][]

[http_blog.csdn.net_cjjky_article_details_6898871]: http://blog.csdn.net/cjjky/article/details/6898871
[0_1331367378KyQH.gif]: /images/20220614/7d33d04256344eab9b0c34599dcec676.png
[0_1331367534AvRS.gif]: /images/20220614/501c6e1c709a473cb2cf7b50e13aed45.png