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：