ListActivity 应用之多层列表

ListActivity 的源代码：

public class ListActivity extends Activity {
   
    protected ListAdapter mAdapter;
    protected ListView mList;

    private Handler mHandler = new Handler();
    private boolean mFinishedStart = false;

    private Runnable mRequestFocus = new Runnable() {
        public void run() {
            mList.focusableViewAvailable(mList);
        }
    };

    protected void onListItemClick(ListView l, View v, int position, long id) {
    }
    @Override
    protected void onRestoreInstanceState(Bundle state) {
        ensureList();
        super.onRestoreInstanceState(state);
    }
    @Override
    protected void onDestroy() {
        mHandler.removeCallbacks(mRequestFocus);
        super.onDestroy();
    }

    @Override
    public void onContentChanged() {
        super.onContentChanged();
        View emptyView = findViewById(com.android.internal.R.id.empty);
        mList = (ListView)findViewById(com.android.internal.R.id.list);
        if (mList == null) {
            throw new RuntimeException(
                    "Your content must have a ListView whose id attribute is " +
                    "'android.R.id.list'");
        }
        if (emptyView != null) {
            mList.setEmptyView(emptyView);
        }
        mList.setOnItemClickListener(mOnClickListener);
        if (mFinishedStart) {
            setListAdapter(mAdapter);
        }
        mHandler.post(mRequestFocus);
        mFinishedStart = true;
    }
    public void setListAdapter(ListAdapter adapter) {
        synchronized (this) {
            ensureList();
            mAdapter = adapter;
            mList.setAdapter(adapter);
        }
    }
    public void setSelection(int position) {
        mList.setSelection(position);
    }
    public int getSelectedItemPosition() {
        return mList.getSelectedItemPosition();
    }
    public long getSelectedItemId() {
        return mList.getSelectedItemId();
    }
    public ListView getListView() {
        ensureList();
        return mList;
    }

    public ListAdapter getListAdapter() {
        return mAdapter;
    }

    private void ensureList() {
        if (mList != null) {
            return;
        }
        setContentView(com.android.internal.R.layout.list_content);

    }
    private AdapterView.OnItemClickListener mOnClickListener = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView parent, View v, int position, long id)
        {
            onListItemClick((ListView)parent, v, position, id);
        }
    };
}

从ListActivity 的源代码中我们可以看到其本省含有一个ListView 和一个ListAdapter 成员变量，ListActivity容纳的ListView对象，能够被绑定到不同的数据源，一般是一个数组或者存储了一组查询结果的游标。

ListActivity的默认布局由一个位于屏幕中心的全屏列表构成。但是，如果你不想使用默认的布局，可以在onCreate()方法中通过setContentView()方法设定你自己定制的布局。

"Your content must have a ListView whose id attribute is android.R.id.list"

如果指定你自己定制的布局，你的布局中必须包含一个id为"@android:id/list"(如果是使用代码的形式，则是 list)的ListView 。此外，你自定义的view为空时，能够包含另外一个任何类型的view对象。

"empty list"notifier必须有一个id"android:empty"。要注意的是：Note that when an empty view is present, the list view will be hidden when there is no data to display.

 <?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"  
         android:paddingLeft="8dp"  
         android:paddingRight="8dp">  
   
     <ListView android:id="@id/android:list"  
              android:layout_width="match_parent"  
               android:layout_height="match_parent"  
               android:background="#00FF00"  
               android:layout_weight="1"  
               android:drawSelectorOnTop="false"/>  
   
     <TextView id="@id/android:empty"  
               android:layout_width="match_parent"  
               android:layout_height="match_parent"  
               android:background="#FF0000"  
               android:text="No data"/>  
 </LinearLayout>  

自己写的一个demon

下载地址：http://download.csdn.net/detail/xtlvice/3767088