自己动手写AsyncTask

   本文依赖上一篇文章：自己动手写消息机制

  在javaSE中模拟Android的AsyncTask异步任务

  

package com.zhanjixun;

public abstract class AsyncTask<Params, Progress, Result> {
	private static final int onProgress = 1;
	private static final int onPost = 2;

	private boolean exeuted = false;// 实现一个任务只能执行一次

	private Handler mHandler = new Handler() {

		@SuppressWarnings("unchecked")
		public void handlerMessage(Message message) {
			if (message.what == onProgress) {
				onProgressUpdate((Progress[]) message.obj);
			}
			if (message.what == onPost) {
				onPostExecute((Result) message.obj);
			}
		}
	};

	/**
	 * 在执行后台任务之前，在主线程调用
	 */
	protected void onPreExecute() {
	}

	/**
	 * 执行后台任务的代码都放在这里
	 * 
	 * @param params
	 */
	protected abstract Result doInBackground(Params... params);

	protected void onProgressUpdate(Progress... progress) {

	}

	/**
	 * 在执行后台任务之后，在主线程调用
	 */
	protected void onPostExecute(Result params) {
	}

	/**
	 * 发送一个消息到主线程中，这是过程是异步的，就是说后台任务发送了消息给主线程之后马上继续往下运行
	 * 
	 * @param progress
	 */
	protected final void publishProgress(Progress... progress) {
		Message msg = new Message();
		msg.what = onProgress;
		msg.obj = progress;
		mHandler.sendMessage(msg);
	}

	public final void execute(Params... params) {
		if (exeuted) {
			throw new RuntimeException("不能运行两次");
		}
		onPreExecute();
		// 简单来就好了，直接启动新的线程，而Android中的AsyncTask的各个子类的任务是同步的，这里是异步的
		new Thread(new Runnable() {

			@Override
			public void run() {
				Result result = doInBackground(params);
				exeuted = true;// 执行完了

				Message msg = new Message();
				msg.what = onPost;
				msg.obj = result;
				mHandler.sendMessage(msg);
			}
		}).start();
	}
}

 

 

 

 

     测试类：

   

package com.zhanjixun.test;

import java.util.Random;

import com.zhanjixun.AsyncTask;
import com.zhanjixun.Looper;

public class AsyncTaskDemo {

	public static void main(String[] args) {
		Looper.prepare();// 将主线程变成轮询线程
		new MyAsyncTask().execute();
		Looper.loop();
	}

	/**
	 * 模拟下载文件
	 * 
	 * @author doudian
	 *
	 */
	public static class MyAsyncTask extends AsyncTask<String, Integer, Boolean> {

		@Override
		protected Boolean doInBackground(String... params) {
			int count = 0;
			Random random = new Random();
			while (count <= 100) {
				String format = String.format("后台中下载文件(%d/100)...（%s线程打印）",
						count, Thread.currentThread().getName());
				System.err.println(format);
				publishProgress(count);
				// 耗时下载
				try {
					Thread.sleep(200);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}

				int nextInt = random.nextInt(20);
				count += nextInt;
			}
			return true;
		}

		@Override
		protected void onProgressUpdate(Integer... progress) {
			String format = String.format("【提示用户】正在下载文件(%d/100)...（%s线程打印）",
					progress[0], Thread.currentThread().getName());
			System.out.println(format);
		}

		@Override
		protected void onPostExecute(Boolean params) {
			String object = params ? "成功" : "失败";
			String format = String.format("任务结束，下载文件%s（%s线程打印）", object, Thread
					.currentThread().getName());
			System.out.println(format);
		}
	}
}

 

 

 

 

测试结果具有随机性：

 

源代码：http://download.youkuaiyun.com/detail/zhanjixun/9583224