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,
);

        setListAdapter(mAdapter);



        // Prepare the loader.  Eitherre-connect with an existing one,

        // or start a new one.

        getLoaderManager,
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