UI组件之AdapterView及其子类（五）ListView组件和ListActivity

ListView组件是一个显示组件，继承AdapterView基类，前面已经介绍了分别使用ArrayAdapter，SimpleAdapter，扩展BaseAdapter来为LisView提供列表项http://blog.csdn.net/tuke_tuke/article/details/50527018，在其中都要在xml文件中定义ListView组件，然后再Activity.java文件中通过findViewById获取组件设置定义好的adapter即可。

但是ListActivity是直接继承Activity的，在ListActivity的源码中已经定义了一个ListView组件属性，ListActivity的子类无需调用setContentView()来显示某个界面，ListActivity的效果就是整个Activity就是一个列表，没有其他的组件。在使用ListActivity时，只需要继承ListActivity，直接传入一个内容Adapter。ListActivity就是一个列表.

MainActivity.java

<span style="font-size:24px;">public class MainActivity extends ListActivity {//继承ListActivity@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);//无需使用布局文件，-相当于它的布局文件中只有一个ListViewString[] s={"孙悟空","猪八戒","唐僧"};//创建ArrayAdapter对象,这里使用的是android提供的布局文件//ArrayAdapter<String>  ad=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,s);//下面是使用自定义的一个列表项布局ArrayAdapter<String>  ad=new ArrayAdapter<String>(this,R.layout.array_item,s);//设置适配器setListAdapter(ad);}</span>

总结一下：

1，继承ListActivity

2，定义适当的Adapter

3，调用setListAdapter方法设置Adapter

ListActivity的部分源码:

public class ListActivity extends Activity {/*** This field should be made private, so it is hidden from the SDK.* {@hide}*/protected ListAdapter mAdapter;/*** This field should be made private, so it is hidden from the SDK.* {@hide}*/protected ListView mList;private Handler mHandler = new Handler();private boolean mFinishedStart = false;private Runnable mRequestFocus = new Runnable() {public void run() {mList.focusableViewAvailable(mList);}};/*** This method will be called when an item in the list is selected.* Subclasses should override. Subclasses can call* getListView().getItemAtPosition(position) if they need to access the* data associated with the selected item.** @param l The ListView where the click happened* @param v The view that was clicked within the ListView* @param position The position of the view in the list* @param id The row id of the item that was clicked*/protected void onListItemClick(ListView l, View v, int position, long id) {}/*** Ensures the list view has been created before Activity restores all* of the view states.**@see Activity#onRestoreInstanceState(Bundle)*/@Overrideprotected void onRestoreInstanceState(Bundle state) {ensureList();super.onRestoreInstanceState(state);}/*** @see Activity#onDestroy()*/@Overrideprotected void onDestroy() {mHandler.removeCallbacks(mRequestFocus);super.onDestroy();}/*** Updates the screen state (current list and other views) when the* content changes.** @see Activity#onContentChanged()*/@Overridepublic 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;}/*** Provide the cursor for the list view.*/public void setListAdapter(ListAdapter adapter) {synchronized (this) {ensureList();mAdapter = adapter;mList.setAdapter(adapter);}}/*** Set the currently selected list item to the specified* position with the adapter's data** @param position*/public void setSelection(int position) {mList.setSelection(position);}/*** Get the position of the currently selected list item.*/public int getSelectedItemPosition() {return mList.getSelectedItemPosition();}/*** Get the cursor row ID of the currently selected list item.*/public long getSelectedItemId() {return mList.getSelectedItemId();}/*** Get the activity's list view widget.*/public ListView getListView() {ensureList();return mList;}/*** Get the ListAdapter associated with this activity's ListView.*/public ListAdapter getListAdapter() {return mAdapter;}private void ensureList() {if (mList != null) {return;}setContentView(com.android.internal.R.layout.list_content_simple);}private AdapterView.OnItemClickListener mOnClickListener = new AdapterView.OnItemClickListener() {public void onItemClick(AdapterView<?> parent, View v, int position, long id){onListItemClick((ListView)parent, v, position, id);}};
}

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