Android中的延迟加载系列（ListView 2）

上一节讲述了Listview延迟加载的封装，本节将讲述如何在Activity中进行调用。

首先定义一个ListView布局

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1. <?xml version="1.0" encoding="utf-8"?>  
2.   
3. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
4.     android:id="@+id/linearLayoutWhole"  
5.     android:layout_width="fill_parent" android:layout_height="fill_parent"  
6.     android:orientation="vertical">  
7.   
8.   
9.     <ListView android:id="@android:id/list" android:layout_width="fill_parent"  
10.         android:layout_height="fill_parent" android:drawSelectorOnTop="false" />  
11.   
12. </LinearLayout>     

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

其次定义一个ListActivity，引入上述布局

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1. public class LazyLoadingActivity extends ListActivity  

public class LazyLoadingActivity extends ListActivity

在onCreate() 方法中加载数据和布局，LongOperation更多的相信信息请参照 页面（Activity）之间的平滑跳转及封 法中加载数据

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1. @Override  
2.     public void onCreate(Bundle savedInstanceState) {  
3.         super.onCreate(savedInstanceState);   
4.         new LongOperation(this,new Excution(){  
5.             @Override  
6.             public void longExcute(){     
7.                 lazyData = new LazyListData<Row>(UIData.getTotalRows(),  
8.                         UIData.getListRows(0,LazyAdapter.PAGE_SIZE_LAZY-1));  
9.                 SystemClock.sleep(3000);//休息3秒，模拟网络延迟  
10.             }  
11.             @Override  
12.             public void uiUpdate(){       
13.                 setContentView(R.layout.empty_list);          
14.                 setListAdapter(new LazyAdapter<Row>(  
15.                         LazyLoadingActivity.this,  
16.                         R.layout.row,//list中的行布局  
17.                         lazyData.getListData(),//得到数据  
18.                         lazyData.getTotalRows(),//得到总行数  
19.                         new LazyLoading(){  
20.                             @Override  
21.                             public void cacheNextPageData(int startIndex, int endIndex) {//加载下一页  
22.                                 Log.d(TAG,"cacheNextPageData() startIndex="+startIndex+", endIndex="+endIndex);  
23.                                 List<Row> nextList = UIData.getListRows(startIndex,endIndex);  
24.                                 lazyData.getListData().addAll(nextList);   
25.                                 SystemClock.sleep(3000);//休息3秒，模拟网络延迟  
26.                             }  
27.                             @Override  
28.                             public void updateItemView(View convertView, Object bean) {//更新每一行  
29.                                 updateItem(convertView, (Row) bean);  
30.                             }     
31.                         }  
32.                 ));  
33.             }  
34.         }).execute(new String[]{});  
35.           
36.     }  

@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);new LongOperation(this,new Excution(){@Overridepublic void longExcute(){lazyData = new LazyListData<Row>(UIData.getTotalRows(),UIData.getListRows(0,LazyAdapter.PAGE_SIZE_LAZY-1));SystemClock.sleep(3000);//休息3秒，模拟网络延迟}@Overridepublic void uiUpdate(){setContentView(R.layout.empty_list); setListAdapter(new LazyAdapter<Row>(LazyLoadingActivity.this,R.layout.row,//list中的行布局lazyData.getListData(),//得到数据lazyData.getTotalRows(),//得到总行数new LazyLoading(){@Overridepublic void cacheNextPageData(int startIndex, int endIndex) {//加载下一页Log.d(TAG,"cacheNextPageData() startIndex="+startIndex+", endIndex="+endIndex);List<Row> nextList = UIData.getListRows(startIndex,endIndex);lazyData.getListData().addAll(nextList); SystemClock.sleep(3000);//休息3秒，模拟网络延迟}@Overridepublic void updateItemView(View convertView, Object bean) {//更新每一行updateItem(convertView, (Row) bean);}}));}}).execute(new String[]{});}

new LazyAdapter()方法是封装之后的延迟加载适配，参见程序代码说明。

下一节将通过一个完整项目进行展示。（待续）