实例讲解Android多线程应用开发中Handler的使用

package com.Handler02;  import android.app.Activity; import android.os.Bundle; import android.os.Handler;  public class Handler02Activity extends Activity {   /** Called when the activity is first created. */   private Handler handler=new Handler();   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     handler.post(thread1);     setContentView(R.layout.main);         System.out.println("================Main==============="+Thread.currentThread().getId());     System.out.println("============Main========="+Thread.currentThread().getName());   }   Runnable thread1=new Runnable() {          @Override     public void run() {       System.out.println("======thread1==============="+Thread.currentThread().getId());       System.out.println("========thread1============"+Thread.currentThread().getName());       try {         Thread.sleep(10000);       } catch (Exception e) {         // TODO: handle exception       }            }   }; } 

package com.Handler4;  import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.TextView;  public class Handler4Activity extends Activity {   /** Called when the activity is first created. */   private TextView textView;   private MyHandler myHandler=new MyHandler();   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     textView=(TextView)this.findViewById(R.id.textView1);   }   class MyHandler extends Handler{     //从消息队列中取出并handleMessage处理消息     @Override     public void handleMessage(Message msg) {       textView.setText((String)msg.obj);     }   }   public void download(View view){     Thread thread=new Thread(new Runnable() {              @Override       public void run() {         try {           String s="zhangzhao";           Thread.sleep(5000);           //数据发送出来           //textView.setText(s);           Message message=Message.obtain();//最好不要new，这个obtain会节省资源           message.obj=s;           myHandler.sendMessage(message);//没有指定looper那么就会发送给主线程中的looper                    } catch (InterruptedException e) {           // TODO Auto-generated catch block           e.printStackTrace();         }                }            });     thread.start();//会出错原因是在非UI线程里面直接操作UI     //主线程维护了一个消息对列，当其他的线程有数据需要传递给主线程的时候，你就把数据封装成一个Message对象，然后放在主线程的     //消息队列中去，对应消息的处理由Looper，子线程通过Handler把下载完的数据封装到Message里面，然后把消息取出来交给Handler进行处理     //通过Handle和Message实现两个线程之间达到共享数据   } } 

package com.Handler5;  import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.View; import android.widget.Button; import android.widget.ProgressBar; import android.widget.TextView;  public class Handler5Activity extends Activity {   /** Called when the activity is first created. */   private ProgressBar progressBar;   private Button button;   private TextView textView;   private MyHandler myHandler=new MyHandler();   int i=0;   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);        setContentView(R.layout.main);     progressBar = (ProgressBar)this.findViewById(R.id.progressBar1);     textView=(TextView)this.findViewById(R.id.textView1);   }   class MyHandler extends Handler{     @Override     public void handleMessage(Message msg) {       int pos =(Integer)msg.obj;       progressBar.setProgress(pos);       textView.setText(pos+"%");            }   }   public void downLoad(View view){           new Thread(new Runnable() {              @Override       public void run() {         while(i<=100){           try {             Thread.sleep(300);             i+=10;             Message message=Message.obtain();             message.obj=i;             myHandler.sendMessage(message);           } catch (InterruptedException e) {             // TODO Auto-generated catch block             e.printStackTrace();           }                  }                }     }).start();   } }