Android列表视图(List View)
Android列表视图(ListView)
ListView是一个显示滚动项列表的示视图组(viewgroup)，通过使用适配器(Adapter)把这些列表项自动插入到列表中。适配器比如从一个数组或是数据库查询获取到数据，然后转换每一项成为可放入到列表的视图。
列表的显示需要三个元素：
(1) ListView：用来展示列表的view。
(2) 适配器：用来把数据映射到ListView上。
(3) 数据：具体的将被映射的字符串、图片或是基本组件。
图1
对于我们如何使用适配器来动态插入view，参考链接：
http://developer.android.com/guide/topics/ui/declaring-layout.html#AdapterViews
1. 使用加载器(Using a Loader)
为了实现异步加载数据，且为了避免在查询时阻塞APP主线程，从Android3.0开始引入CursorLoader，这是一种查询Cursor的标准方式。当CursorLoader接收到Cursor结果(查询结束)，LoaderCallbacks接收到对onLoadFinished()方法的回调，此方法使用新的Cursor来更新适配器，然后列表视图显示这个结果。
虽然CursorLoader的API是从Android3.0(API 11)开始引入的，但可以通过使用支持的库来使用：http://developer.android.com/tools/extras/support-library.html，但要求Android系统版本在1.6及之后的版本。
public
class ListViewLoader
extends ListActivity
implements
LoaderManager.LoaderCallbacks<Cursor>
{
// This is the Adapter being used to display the list's data
SimpleCursorAdapter mAdapter;
// These are the Contacts rows that we will retrieve
static final
String[] PROJECTION
= new
String[] {ContactsContract.Data._ID,
ContactsContract.Data.DISPLAY_NAME};
// This is the select criteria
static final
String SELECTION =
"((" +
ContactsContract.Data.DISPLAY_NAME
+ " NOTNULL)AND ("
+
ContactsContract.Data.DISPLAY_NAME
+ " != ''))";
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// Create a progress bar to display whilethe list loads
ProgressBar progressBar
= new ProgressBar(this);
progressBar.setLayoutParams(new
LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT,
Gravity.CENTER));
progressBar.setIndeterminate(true);
getListView().setEmptyView(progressBar);
// Must add the progress bar to the root ofthe layout
ViewGroup root
= (ViewGroup) findViewById(android.R.id.content);
root.addView(progressBar);
// For the cursor adapter, specify whichcolumns go into which views
String[] fromColumns
= {ContactsContract.Data.DISPLAY_NAME};
int[] toViews
= {android.R.id.text1};
// The TextViewin simple_list_item_1
// Create an empty adapter we will use todisplay the loaded data.
// We pass null for the cursor, then updateit in onLoadFinished()
mAdapter =
new SimpleCursorAdapter(this,
android.R.layout.simple_list_item_1,
null,
fromColumns, toViews,
0);
setListAdapter(mAdapter);
// Prepare the loader. Eitherre-connect with an existing one,
// or start a new one.
getLoaderManager().initLoader(0,
null,
this);
}
// Called when a new Loader needs to be created
public Loader<Cursor> onCreateLoader(int
id, Bundle args)
{
// Now create and return a CursorLoaderthat will take care of
// creating a Cursor for the data beingdisplayed.
return new
CursorLoader(this,
ContactsContract.Data.CONTENT_URI,
PROJECTION, SELECTION,
null,
null);
}
// Called when a previously created loader has finished loading
public void onLoadFinished(Loader<Cursor>
loader, Cursor data)
{
// Swap the new cursor in. (Theframework will take care of closing the
// old cursor once we return.)
mAdapter.swapCursor(data);
}
// Called when a previously created loader is reset, making the dataunavailable
public void onLoaderReset(Loader<Cursor>
loader) {
// This is called when the last Cursorprovided to onLoadFinished()
// above is about to be closed. We needto make sure we are no
// longer using it.
mAdapter.swapCursor(null);
}
@Override
public void onListItemClick(ListView l,
View v,
int position,
long id) {
// Do something when a list item is clicked
}
}
链接:
Android开发者：
http://developer.android.com/guide/topics/ui/layout/listview.html
Android之ListView原理学习与优化总结
http://mzh3344258.blog.51cto.com/1823534/889879
androidListView详解
http://www.cnblogs.com/allin/archive/2010/05/11/1732200.html
Android的CursorLoader用法小结
http://www.linuxidc.com/Linux/2013-05/84572.htm
