实例讲解Android多线程应用开发中Handler的使用

其实可以理解Handler为主线程和另外的线程之间进行数据更新的东东，并且Handler在主线程中，并在Handler直接调用线程的run方法

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 
      } 
       
    } 
  }; 
} 

结果是主线程等待10s后才显示出来，并且线程ID

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(); 
  } 
} 

效果：

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