Handler的使用（一）

程序一:

public class MainActivity extends Activity {
	private Button startButton = null;
	private Button endButton = null;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		startButton = (Button)findViewById(R.id.startButton);
		startButton.setOnClickListener(new StartButtonListener());
		endButton = (Button)findViewById(R.id.endButton);
		endButton.setOnClickListener(new EndButtonListener());
		
	}
	class StartButtonListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			handler.post(updateThread);
			
		}
		
	}
	class EndButtonListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			handler.removeCallbacks(updateThread);
		}
		
	}
	Handler handler = new Handler();
	Runnable updateThread = new Runnable(){

		@Override
		public void run() {
			// TODO Auto-generated method stub
			System.out.println("UpdateThread");
			handler.postDelayed(updateThread, 3000);
		}
	};
}

按下启动按钮之后程序将会每隔3000毫秒打印一句"UpdateThread",直到按下结束按钮。

程序二：

main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

<ProgressBar
	android:id="@+id/bar"
	style="?android:attr/progressBarStyleHorizontal"  //水平方向的进度条
	android:layout_width="200dp"
	android:layout_height="wrap_content"
	android:visibility="gone"                         //进度条处于不可见状态
	/>
<Button 
	android:id="@+id/startButton"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="start"/>
</LinearLayout>

TestBarHandler.java:

public class TestBarHandler extends Activity {
    /** Called when the activity is first created. */
	//声明控件变量
	ProgressBar bar = null;
	Button startButton = null;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //根据控件的ID得到代表控件的对象,并为按钮设置监听器
        bar = (ProgressBar)findViewById(R.id.bar);
        startButton = (Button)findViewById(R.id.startButton);
        startButton.setOnClickListener(new ButtonListener());
    }
    //当点击startButton按钮时，就会执行ButtonListener的onClick方法
    class ButtonListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			bar.setVisibility(View.VISIBLE);
			updateBarHandler.post(updateThread);
		}
    	
    }
    //使用匿名内部类来复写Handler当中的handleMessage方法
    Handler updateBarHandler = new Handler(){

		@Override
		public void handleMessage(Message msg) {    //与sendMessage是异步的消息处理，一个只管发                                                              //送，一个只管接收
			bar.setProgress(msg.arg1);
			Bundle bundle = msg.getData();
			updateBarHandler.post(updateThread);
			System.out.println("test---->" + bundle.getString("test"));
		}
    	
    };
    //线程类，该类使用匿名内部类的方式进行声明
    Runnable updateThread = new Runnable(){
    	int i = 0 ;
		@Override
		public void run() {
			System.out.println("Begin Thread" + i);
			i = i + 10 ;
			//得到一个消息对象，Message类是有Android操作系统提供
			Message msg = updateBarHandler.obtainMessage();
			
			//将msg对象的arg1参数的值设置为i,用arg1和arg2这两个成员变量传递消息，优点是系统性能消耗较少
			msg.arg1 = i ;
			Bundle bundle = new Bundle();
			bundle.putString("test", "test bundle");
			msg.setData(bundle);
			try {
				//设置当前显示睡眠1秒
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			//将msg对象加入到消息队列当中
			if( i > 100){
				//如果当i的值为100时，就将线程对象从handler当中移除
				updateBarHandler.removeCallbacks(updateThread);
				System.out.println(">>>>>>");
			}else{
				updateBarHandler.sendMessage(msg);
				System.out.println("<<<<<<");
			}
		}
    };
    class MyThread extends Thread{
    	public void run(){
    		
    	}
    }
    
}

显示效果：