自定义ThreadPoolExecutor

仍旧沿用ExecutorService的例子， 修改了AsyncImageLoader调用线程管理池的方法。

AsyncImageLoader的思路：
1. 自定义RejectedExecutionHandler， 当线程任务被拒绝时，使其等待线程管理池空余后继续被调用。
2. 自定义线程管理池ThreadPoolExecutor替代ExecutorService
3. 线程的主要任务DownloadThreadTask，加载图片
4. 所有任务完成后，关闭自定义的ThreadPoolExecutor

源码：
自定义的RejectedExecutionHandler

public class RejectedExcutionHandlerImpl implements RejectedExecutionHandler {

	@Override
	public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
		Log.i("test", ((DownloadThreadTask)r).getTask() + " is rejected");
		
                // 如果出现线程任务被拒绝，则等待一段时间后，再次创建并提交到线程池中
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
		executor.execute(r);
		Log.i("test",((DownloadThreadTask)r).getTask() + "再次创建并提交");

	}
}

自定义的ThreadPoolExecutor

public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
	
	public CustomThreadPoolExecutor(
			int corePoolSize, 
			int maximumPoolSize, 
			long keepAliveTime, 
			TimeUnit unit, 
			BlockingQueue<Runnable> workQueue,
			RejectedExecutionHandler handler){
		super(corePoolSize,maximumPoolSize, keepAliveTime, unit, workQueue, handler);
		
		
	}
        
        // beforeExecute， afterExecute方法一般用于日志中，记录任务被调用前和完成后的状态
	@Override
	protected void beforeExecute(Thread t, Runnable r) {
		super.beforeExecute(t, r);
		Log.i("test","perform before execute logic" + ((DownloadThreadTask)r).getTask());
	}

	@Override
	protected void afterExecute(Runnable r, Throwable t) {
		super.afterExecute(r, t);
		
		if (t != null) {
			Log.i("test","Perform exception handler logic" + ((DownloadThreadTask)r).getTask());
		}
		
		Log.i("test","Perform afterExecute() logic" + ((DownloadThreadTask)r).getTask());
	}

}

线程任务DownloadThreadTask

public class DownloadThreadTask implements Runnable {
	
	public Map<String, SoftReference<Drawable>> imageCache = new HashMap<String,SoftReference<Drawable>>();
	
	private String task; // 任务名称
	private String url;  // 加载URL
	private Handler handler;
	private ImageCallback callback;
	
	public DownloadThreadTask(String task, String url, Handler handler, ImageCallback callback){
		this.task = task;
		this.url = url;
		this.handler = handler;
		this.callback = callback;
	}

	public String getTask() {
		return task;
	}
	public void setTask(String task) {
		this.task = task;
	}
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}

	public Handler getHandler() {
		return handler;
	}
	public void setHandler(Handler handler) {
		this.handler = handler;
	}
	@Override
	public void run() {
		try {  
			try{
				Thread.sleep(10);
			}catch(InterruptedException e){
				e.printStackTrace();
			}
			
            final Drawable drawable = loadImageFromUrl(url);
            imageCache.put(url, new SoftReference<Drawable>(drawable));

            handler.post(new Runnable() {  
                public void run() {  
                    callback.imageLoader(drawable);
                }  
            });  
            
            Log.i("test", "加载图片任务完成" + this.task);
        } catch (Exception e) {  
            throw new RuntimeException(e);  
        }  


	}
	
	protected Drawable loadImageFromUrl(String imageUrl){
		 try {  
           return Drawable.createFromStream(new URL(imageUrl).openStream(), "image.png");  
    } catch (Exception e) {  
            throw new RuntimeException(e);  
    }  
		
	}

}

AsyncImageLoader

public class AsyncImageLoader {
	
	public Map<String, SoftReference<Drawable>> imageCache = new HashMap<String,SoftReference<Drawable>>();
	
	private BlockingQueue<Runnable> blockingQueue = new ArrayBlockingQueue<Runnable>(2);
	private RejectedExecutionHandler myReject = new RejectedExcutionHandlerImpl();
	
	CustomThreadPoolExecutor executor = new CustomThreadPoolExecutor(1,2,5,TimeUnit.MILLISECONDS, blockingQueue, myReject);

	private final Handler handler = new Handler();

	public Drawable loadDrawable(final String task, final String imageUrl, final ImageCallback callback){
		
		if(imageCache.containsKey(imageUrl)){
			SoftReference<Drawable> softReference = imageCache.get(imageUrl);
			
			if(softReference.get()!=null){
				return softReference.get();
			}
		}
		Log.i("test","创建任务并提交到线程池中：" + task);
		executor.execute(new DownloadThreadTask(task, imageUrl, handler, callback));	
		
		try {
			Thread.sleep(3);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
		return null;
	}
	
	
	
	public void shutdownAndAwaitTermination() {
		   executor.shutdown(); // Disable new tasks from being submitted

		   try {
		     // Wait a while for existing tasks to terminate
		     if (!executor.awaitTermination(60, TimeUnit.SECONDS)) {
		    	 executor.shutdownNow(); // Cancel currently executing tasks
			       // Wait a while for tasks to respond to being cancelled
		    	 Log.i("test", "i am shutting down...");
			       if (!executor.awaitTermination(60, TimeUnit.SECONDS))
			           System.err.println("Pool did not terminate"); 
		     }
		       
		     
		   }catch (InterruptedException ie) {
		     // (Re-)Cancel if current thread also interrupted
			   Log.e("test","something interrupted happend, and i am shutting down....");
		     executor.shutdownNow();
		     // Preserve interrupt status
		     //Thread.currentThread().interrupt();
		  }
	 }
}

下载的Activity对AsyncImageLoader的调用

public class BatchDownloadActivity extends Activity {
	
	private static final String fileRealName = "我的图片1.gif";
	private String url;
	private int id;
	private List<String> urls = new ArrayList<String>();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
	
		super.onCreate(savedInstanceState);
		
		setContentView(R.layout.batch_download);
		
		String fileName = fileRealName;
		String url = "";
		
		try {
			url = ToolsUtil.getIpAddress() + URLEncoder.encode(fileRealName,"UTF-8");
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		
		Log.i("test","url=" + url);
		
		loadImage("task@1", url, R.id.imageView1);
		loadImage("task@2", url, R.id.imageView2);
		loadImage("task@3", url, R.id.imageView3);
		loadImage("task@4", url,R.id.imageView4);
		loadImage("task$5", url,R.id.imageView5);
		
		loader.shutdownAndAwaitTermination();
	
	}
	
	private AsyncImageLoader loader = new AsyncImageLoader();
	

	private void loadImage(final String task, final String url, final int id) {
		
		Drawable cacheImage = loader.loadDrawable(task, url,new ImageCallback() {  
				@Override
					public void imageLoader(Drawable imageDrawable) {
						
					     ((ImageView) findViewById(id)).setImageDrawable(imageDrawable);
					     Log.i(task, "loading new pic:" +url);
					}  
        });  

		if (cacheImage != null) {  
			((ImageView) findViewById(id)).setImageDrawable(cacheImage);  
			Log.i("test", "loading existing pic");
		}  
	}
	

}

---------------------------------------------------------------

以下使用 Callable 替代Runnable来进行图片的加载。 思路如上述所，只是修改一些源码。
1. 加载图片的 Callable

public class DownloadCallableTask implements Callable<Drawable> {
	
	public Map<String, SoftReference<Drawable>> imageCache = new HashMap<String,SoftReference<Drawable>>();
	
	private String task;
	private String url;
	
	public DownloadCallableTask(String task, String url){
		this.task = task;
		this.url = url;
	}
	public String getTask(){
		return this.task;
	}

	@Override
	public Drawable call() throws Exception {
		  
		try{
			Thread.sleep(10);
		}catch(InterruptedException e){
			e.printStackTrace();
		}
			
		if(imageCache.containsKey(url)){
			SoftReference<Drawable> softReference = imageCache.get(url);
				
			if(softReference.get()!=null){
				return softReference.get();
			}
		}
			
        final Drawable drawable = loadImageFromUrl(url);
        imageCache.put(url, new SoftReference<Drawable>(drawable));
           
        Log.i("test", "加载图片任务完成" + this.task);
          
        return drawable;
        
	}
	
	protected Drawable loadImageFromUrl(String imageUrl){
		 try {  
			 return Drawable.createFromStream(new URL(imageUrl).openStream(), "image.png");  
		 } catch (Exception e) {  
			 throw new RuntimeException(e);  
		 }
	}
	

}

2. AsyncCallableLoader 替代 AsyncImageLoader

public class AsyncCallableLoader {
	
	private BlockingQueue<Runnable> blockingQueue = new ArrayBlockingQueue<Runnable>(2);

	ThreadPoolExecutor executor = new ThreadPoolExecutor(1,2,5,TimeUnit.MILLISECONDS, blockingQueue);
	
	private final Handler handler = new Handler();

	public Drawable loadDrawable(final String task, final String imageUrl) throws InterruptedException, ExecutionException{

		Log.i("test","创建任务并提交到线程池中：" + task);
		final Future<Drawable> future = executor.submit(new DownloadCallableTask(task,imageUrl));
		
	
		try {
			Thread.sleep(3);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		
		return future.get();
		
	}
	
	
	
	public void shutdownAndAwaitTermination() {
		   executor.shutdown(); // Disable new tasks from being submitted

		   try {
		     // Wait a while for existing tasks to terminate
		     if (!executor.awaitTermination(60, TimeUnit.SECONDS)) {
		    	 executor.shutdownNow(); // Cancel currently executing tasks
			       // Wait a while for tasks to respond to being cancelled
		    	 Log.i("test", "i am shutting down...");
			       if (!executor.awaitTermination(60, TimeUnit.SECONDS))
			           System.err.println("Pool did not terminate"); 
		     }
		       
		     
		   }catch (InterruptedException ie) {
		     // (Re-)Cancel if current thread also interrupted
			   Log.e("test","something interrupted happend, and i am shutting down....");
		     executor.shutdownNow();
		     // Preserve interrupt status
		     //Thread.currentThread().interrupt();
		  }
	 }


}

3. Activity调用AsnycCallableLoader

private AsyncCallableLoader loader = new AsyncCallableLoader();
	

	private void loadImage(final String task, final String url, final int id) {
		
		Drawable cacheImage;
		try {
			cacheImage = loader.loadDrawable(task, url);
			if (cacheImage != null) {  
				((ImageView) findViewById(id)).setImageDrawable(cacheImage);  
				Log.i("test", "loading pic");
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (ExecutionException e) {
			e.printStackTrace();
		}
		
	}