一、runOnUiThread的用法

runOnUiThread是Activity的内部方法，使用时最好指定当前的环境变量（Context）。

new Thread(new Runnable() { @Override public void run() { runOnUiThread(new Runnable() { public void run() { Toast.makeText(mainActivity.this,"UI操作。。。",0).show(); } }); } }).start();

执行runOnUiThread这个方法会调用父类中的

public final void runOnUiThread(Runnable action){ if(Thread.currentThread()!=mUiThread){ mHandler.post(action); }else{ action.run(); } }

二、新线程中View直接在UI线程中更新的方法

textView.postDelayed(new Runnable() { @Override public void run() { textView.setText("Test View.post(Runnable)"); } }, 1000); - textView.post(new Runnable() { @Override public void run() { textView.setText("Test View.postDelay(Runnable，long)"); } });

三、Handler(消息传递机制)使用

Handler myHandler = new Handler(){ public void handleMessage(Message msg){ super.handleMessage(msg); } };

也可以继承handler

class MyHandler extends handler{ public MyHandler(){ } @Override public void handleMessage(Message msg){ super.handleMessage(msg); } }

分发Message或者Runnable对象到handler所在的线程中一般handler在主线程中。

handler中一些分发消息的方法：

post（Runnable） postAtTime(Runnable,long) postDelay(Runnable,long) sendEmptyMessage(int what) sendMessage(Message) senMessageAtTime(Message，long) sendMessageDelayed(Message,long)

post方式添加一个实现Runnable接口的匿名对象到消息对列中，在目标收到消息后就可以以回调的方式在自己的线程中执行

Message对象所具有的属性：

Message message = Message.obtain(); message.arg1 = 1; message.arg2 = 2; message.obj = "Demo"; message.what = 3; Bundle bundle = new Bundle(); bundle.putString( "name","Lucy"); message.setData(bundle);

下面贴上一段示例代码（开启新线程实现电子广告牌）

public class MainActivity extends Activity implements Runnable { private ImageView iv; private TextView tv; private Handler handler; private int[] path = new int[]{R.drawable.img01,R.drawable.img02,R.drawable.img03,R.drawable.img04, R.drawable.img05,R.drawable.img06}; private String[] title = new String[]{"编程词典系列","高效开发","快乐分享","用户人群","快速学习","全方位查询"}; private int index =0; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); iv = (ImageView) findViewById(R.id.imageView1); tv = (TextView) findViewById(R.id.textView1); Thread t = new Thread(this); t.start(); handler = new Handler(){ public void handleMessage(Message msg){ if (msg.what ==1) { tv.setText(msg.getData().getString("title")); iv.setImageResource(path[msg.arg1]); } super.handleMessage(msg); } }; } @Override public void run() { while(!Thread.currentThread().isInterrupted()){ index = new Random().nextInt(path.length); Message m = handler.obtainMessage(); m.arg1 = index; Bundle bundle = new Bundle(); m.what = 1; bundle.putString("title", title[index]); m.setData(bundle); handler.sendMessage(m); try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }

四、AsyncTask异步任务的用法

AsyncTask实际上是一个线程池，在代码上比handler要轻量级但是实际上要比Handler要耗资源，Handler仅仅发送了一个消息队列，连线程池对没有开。 onPreExecute()，（可选方法）最新用户调用excute时的接口，任务执行之前调用该方法，可以在这里显示进度对话框。 doInBackground(Params...),后台执行比较好使的操作，不能直接操纵UI。在该方法中使用publishProgress（progress...）来更新任务的进度。 onProgressUpdate(Progress...),在主线程中执行，显示进度条 onPostExecute(Result),此方法可以从doinbackground得到的结果来操作UI，在主线程中执行，执行的结果作为参数返回。 onCancelled(Object)调用此方法可以随时取消操作。

AsyncTask定义的三种泛型

params: 启动任务执行的输入参数，如：http请求的URL progress:后台任务执行的百分比 result:返回结果，如：String、list集合等

private class MyTask extends AsyncTask<params, progress, result> { ... }

示例代码：

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { protected Long doInBackground(URL... urls) { int count = urls.length; long totalSize = 0; for (int i = 0; i < count; i++) { totalSize += Downloader.downloadFile(urls[i]); publishProgress((int) ((i / (float) count) * 100)); // Escape early if cancel() is called if (isCancelled()) break; } return totalSize; } protected void onProgressUpdate(Integer... progress) { setProgressPercent(progress[0]); } protected void onPostExecute(Long result) { showDialog("Downloaded " + result + " bytes"); } }

获取网络图片的示例代码：

public class MainActivity extends ActionBarActivity { private ImageView iv; private Button bt; private String imagePath = "http://192.168.1.1/sa"; private ProgressDialog dialog; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); iv = (ImageView) findViewById(R.id.imageView1); bt = (Button) findViewById(R.id.button1); dialog = new ProgressDialog(this); dialog.setTitle("提示信息："); dialog.setMessage("正在下载。。。"); bt.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { new MyTask().execute(imagePath); } }); } public class MyTask extends AsyncTask<String, Void, Bitmap>{ @Override protected Bitmap doInBackground(String... params) { HttpClient httpClient = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(params[0]); Bitmap bitmap = null; try { HttpResponse httpResponse = httpClient.execute(httpGet); if (httpResponse.getStatusLine().getStatusCode()==200) { HttpEntity httpEntity = httpResponse.getEntity(); byte[] data = EntityUtils.toByteArray(httpEntity); bitmap= BitmapFactory.decodeByteArray(data, 0, data.length); } } catch (Exception e) { e.printStackTrace(); } return bitmap; } @Override protected void onPreExecute() { super.onPreExecute(); dialog.show(); } @Override protected void onPostExecute(Bitmap result) { super.onPostExecute(result); iv.setImageBitmap(result); dialog.dismiss(); } } }

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