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

最后更新于:2022-04-01 16:14:11

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](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 @Override protected 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ListView String[] 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) */ @Override protected void onRestoreInstanceState(Bundle state) { ensureList(); super.onRestoreInstanceState(state); } /** * @see Activity#onDestroy() */ @Override protected void onDestroy() { mHandler.removeCallbacks(mRequestFocus); super.onDestroy(); } /** * Updates the screen state (current list and other views) when the * content changes. * * @see Activity#onContentChanged() */ @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; } /** * 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); } }; } ~~~ ![](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-03-10_56e0d9ace787d.jpg)
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