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android 异步处理采用Thread + Handler + Message

2014-07-08 15:17 141 查看

Handler简介 Handler为Android提供了一种异步消息处理机制，它包含两个队列，一个是线程列队，另一个是消息列队。使用post方法将线程对象添加到线程队列中，使用sendMessage(Message message)将消息放入消息队列中。当向消息队列中发送消息后就立即返回，而从消息队列中读取消息对象时会阻塞，继而回调Handler中public void handleMessage(Message msg)方法。因此在创建Handler时应该使用匿名内部类重写该方法。如果想要这个流程一直执行的话，可以再run方法内部执行postDelay或者
post方法，再将该线程对象添加到消息队列中重复执行。想要停止线程，调用Handler对象的removeCallbacks(Runnable r)从线程队列中移除线程对象，使线程停止执行。

ThreadHandlerActivity.java

01	public class ThreadHandlerActivity extends Activity {

03	private List<String> urlList;

04	private ImageAdapter listItemAdapter;

05	private LinkedList<HashMap<String, Object>> listItem;

06	private Handler handler;

07	private ExecutorService executorService = Executors.newFixedThreadPool( 10 );

@Override

10	public void onCreate(Bundle savedInstanceState) {

11	super .onCreate(savedInstanceState);

12	setContentView(R.layout.activity_main);

13	urlList = new ArrayList<String>();

14	urlList.add( "http://www.baidu.com/img/baidu_sylogo1.gif" );

15	urlList.add( "http://y2.ifengimg.com/2012/06/24/23063562.gif" );

16	urlList.add( "http://himg2.huanqiu.com/statics/images/index/logo.png" );

18	listItem = new LinkedList<HashMap<String, Object>>();

20	listItemAdapter = new ImageAdapter( this , listItem);

21	ListView listView = (ListView) this .findViewById(R.id.listView1);

22	listView.setAdapter(listItemAdapter);

24	handler = new Handler(){

@Override

26	public void handleMessage(Message msg) {

27	HashMap<String, Object> map = (HashMap<String, Object>) msg.obj;

28	listItem.add(map);

29	listItemAdapter.notifyDataSetChanged();

};

32	for ( final String urlStr : urlList) {

33	executorService.submit( new Runnable() {

@Override

35	public void run() {

try

37	URL url = new URL(urlStr);

38	Drawable drawable = Drawable.createFromStream(

39	url.openStream(), "src" );

40	HashMap<String, Object> table = new HashMap<String, Object>();

41	table.put( "ItemImage" , drawable);

42	Message msg = new Message();

43	msg.obj = table;

44	msg.setTarget(handler);

45	handler.sendMessage(msg);

46	} catch (Exception e) {

47	e.printStackTrace();

});

@Override

55	public boolean onCreateOptionsMenu(Menu menu) {

56	getMenuInflater().inflate(R.menu.activity_main, menu);

57	return true ;

三、采用Thread
+ Handler + post方法

使用post方法将Runnable对象放到Handler的线程队列中，该Runnable的执行其实并未单独开启线程，而是仍然在当前Activity的UI线程中执行，Handler只是调用了Runnable对象的run方法。
ThreadHandlerPostActivity.java

01	public class ThreadHandlerPostActivity extends Activity {

03	private List<String> urlList;

04	private ImageAdapter listItemAdapter;

05	private LinkedList<HashMap<String, Object>> listItem;

06	private Handler handler = new Handler();

07	private ExecutorService executorService = Executors.newFixedThreadPool( 10 );

@Override

10	public void onCreate(Bundle savedInstanceState) {

11	super .onCreate(savedInstanceState);

12	setContentView(R.layout.activity_main);

13	urlList = new ArrayList<String>();

14	urlList.add( "http://www.baidu.com/img/baidu_sylogo1.gif" );

15	urlList.add( "http://y2.ifengimg.com/2012/06/24/23063562.gif" );

16	urlList.add( "http://himg2.huanqiu.com/statics/images/index/logo.png" );

18	listItem = new LinkedList<HashMap<String, Object>>();

20	listItemAdapter = new ImageAdapter( this , listItem);

21	ListView listView = (ListView) this .findViewById(R.id.listView1);

22	listView.setAdapter(listItemAdapter);

24	for ( final String urlStr : urlList) {

25	executorService.submit( new Runnable() {

@Override

27	public void run() {

try

29	URL url = new URL(urlStr);

30	Drawable drawable = Drawable.createFromStream(

31	url.openStream(), "src" );

32	final HashMap<String, Object> table = new HashMap<String, Object>();

33	table.put( "ItemImage" , drawable);

34	handler.post( new Runnable(){

@Override

37	public void run() {

38	listItem.add(table);

39	listItemAdapter.notifyDataSetChanged();

});

43	} catch (Exception e) {

44	e.printStackTrace();

});

@Override

52	public boolean onCreateOptionsMenu(Menu menu) {

53	getMenuInflater().inflate(R.menu.activity_main, menu);

54	return true ;

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