JAVA并发:使用Sempare, Handler和线程池写的加载框架

最新推荐文章于 2024-08-27 08:42:43 发布

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最新推荐文章于 2024-08-27 08:42:43 发布

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分类专栏： java

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本文介绍了一个基于Android平台的图像加载示例应用。该应用通过多线程和信号量实现任务调度，利用Handler机制进行UI更新，并采用固定大小的线程池来平衡任务执行效率与系统资源消耗。

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package com.example.imageloaderpratise;

import java.util.LinkedList;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initBackThread();
		for(int i = 0 ; i < 10 ; i++){
			addTask(i);
		}
	}
	
	private void initBackThread() {
		new Thread(new Runnable() {
			
			@Override
			public void run() {
				Looper.prepare();
				backHandler = new Handler(){
					public void handleMessage(Message msg) {
						int tag =  (int) msg.obj;
						threadPool.execute(getTask());	
						Log.e("xxx", "handlerTag:" + tag);
						try {
							semaphore.acquire();
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
						
					};
				};
				backSemaphore.release();
				Looper.loop();
			}
		}).start();
	}

	private void addTask(int i){
		mTask.add(getTask(i));
		if(backHandler == null){
			try {
				backSemaphore.acquire();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		Message message = backHandler.obtainMessage();
		message.obj = i;
		backHandler.sendMessage(message);
	}
	
	private synchronized Runnable getTask(){
		return mTask.removeLast();
	}
	
	LinkedList<Runnable> mTask = new LinkedList<Runnable>();
	Semaphore semaphore = new Semaphore(3);
	Semaphore backSemaphore = new Semaphore(0);
	ExecutorService threadPool = Executors.newFixedThreadPool(2);
	Handler backHandler;

	/*Handler handler = new Handler(){
		public void handleMessage(android.os.Message msg) {
			
		};
	};*/

	protected Runnable getTask(final int tag) {
		return new Runnable() {
			
			@Override
			public void run() {
				try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				Log.e("xxx", Thread.currentThread().getName() + ":" + "执行完将释放..." + "tag:" + tag);
				semaphore.release();
				Log.e("xxx", Thread.currentThread().getName() + ":" + "执行完将释放了***" + "tag:" + tag);
				
			}
		};
	}
}