Handler 的应用

1. Handler 有原理队列

 

 2. main.xml 文件

 

 

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

    <Button 
        android:id="@+id/button_1"
        android:text="first"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />
    <Button 
        android:id="@+id/button_2"
        android:text="stop"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />

</LinearLayout>

 

 

2. 代码实现

 

package com.android.handler.activity;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

/**
 * 
 * @author liuqing
 * @version 1.0
 * @see Handler 的使用
 *
 */
public class Android_chapter14handlerActivity extends Activity {
    
	//开始按扭
	private Button button_1;
	//停止按扭
	private Button button_2;
	//消息队列
	private Handler handler = new Handler();
	
	Runnable postRunnable = new Runnable(){

		@Override
		public void run() {
			System.out.println(" enter successfully...");
			handler.postDelayed(postRunnable, 3000);
		}
	};
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        this.button_1 = (Button) this.findViewById(R.id.button_1);
        this.button_2 = (Button)this.findViewById(R.id.button_2);
        this.button_1.setOnClickListener(new ButtonFirstListener());
        this.button_2.setOnClickListener(new ButtonSecondListener());
    }
    
    private class ButtonFirstListener implements OnClickListener {

		@Override
		public void onClick(View v) {
			handler.post(postRunnable);
			
		}
    	
    }
    
    private class ButtonSecondListener implements OnClickListener {

		@Override
		public void onClick(View v) {
			handler.removeCallbacks(postRunnable);
		}
    	
    }
    
}

 

3. 使用Handler 实现进度条

 

 

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

    <ProgressBar 
        android:id="@+id/progreebar"
        android:layout_width="fill_parent"
        style="@android:style/Widget.ProgressBar.Horizontal"
        android:layout_height="wrap_content"
        />
    <Button 
        android:id="@+id/start"
        android:text="@string/start"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />

</LinearLayout>

 

 

package com.handler.progreebar.activtiy;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;

/**
 * 
 * @author liuqing
 * @version 1.0
 * @see Handler 的使用
 *
 */
public class Android_chapter14handlerProgreeBarActivity extends Activity {
	
	private ProgressBar progressBar;
	
	private Button start;
	
	private Handler handler = new Handler(){

		@Override
		public void handleMessage(Message msg) {
			progressBar.setProgress(msg.arg1);
			handler.post(runnable);
		}
		
	};
	
	Runnable runnable = new Runnable(){
		
		private int a;
		@Override
		public void run() {
			a += 10;
			//Obtain 获得Message
			Message message = handler.obtainMessage();
			//设置参数
			message.arg1 = a;
			try {
				Thread.sleep(2000);
			} 
			catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			//发送消息
			handler.sendMessage(message);
			if (a >= 100) {
				System.out.println("exits !");
				handler.removeCallbacks(runnable);
			}
		}};
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        progressBar = (ProgressBar)findViewById(R.id.progreebar);
        progressBar.setVisibility(0);
        this.progressBar.setMax(100);
        this.start = (Button)findViewById(R.id.start);
        start.setOnClickListener(new StartListener());
    }
    
    private class StartListener implements OnClickListener {

		@Override
		public void onClick(View v) {
			//加入到队列中
			handler.post(runnable);
			
		}
    	
    }
    
    
}

运行结果