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

發布時間:2025/3/20 编程问答 23 豆豆
生活随笔 收集整理的這篇文章主要介紹了 UI组件之AdapterView及其子类(五)ListView组件和ListActivity 小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

ListView組件是一個顯示組件,繼承AdapterView基類,前面已經介紹了分別使用ArrayAdapter,SimpleAdapter,擴展BaseAdapter來為LisView提供列表項http://blog.csdn.net/tuke_tuke/article/details/50527018,在其中都要在xml文件中定義ListView組件,然后再Activity.java文件中通過findViewById獲取組件設置定義好的adapter即可。

但是ListActivity是直接繼承Activity的,在ListActivity的源碼中已經定義了一個ListView組件屬性,ListActivity的子類無需調用setContentView()來顯示某個界面ListActivity的效果就是整個Activity就是一個列表,沒有其他的組件。在使用ListActivity時,只需要繼承ListActivity,直接傳入一個內容Adapter。ListActivity就是一個列表.

MainActivity.java

<span style="font-size:24px;">public class MainActivity extends ListActivity {//繼承ListActivity@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);//無需使用布局文件,-相當于它的布局文件中只有一個ListViewString[] s={"孫悟空","豬八戒","唐僧"};//創建ArrayAdapter對象,這里使用的是android提供的布局文件//ArrayAdapter<String> ad=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,s);//下面是使用自定義的一個列表項布局ArrayAdapter<String> ad=new ArrayAdapter<String>(this,R.layout.array_item,s);//設置適配器setListAdapter(ad);}</span>

總結一下:

1,繼承ListActivity

2,定義適當的Adapter

3,調用setListAdapter方法設置Adapter

ListActivity的部分源碼:

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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