public interface HttpDownloader {
public void setDownloadManager(HttpDownloadManager manager);
public HttpDownloadManager getDownloadManager();
public void executeAction();
}
public class MyAsyncTask extends AsyncTask<String, Void, Bitmap> implements HttpDownloader{
private HttpDownloadManager httpDownloadManager;
protected Bitmap doInBackground(String... params) {
httpDownloadManager.downloadStarted();
...
}
protected void onPostExecute(Bitmap bitmap) {
httpDownloadManager.downloadCompleted();
...
}
public void setDownloadManager(HttpDownloadManager httpDownloadManager){
this.httpDownloadManager = httpDownloadManager;
}
public HttpDownloadManager getDownloadManager(){
return httpDownloadManager
}
public void executeAction(){
this.execute();
}
}
public class HttpDownloadManager{
private LinkedList<HttpDownloader> tasks = new LinkedList<HttpDownloader>();
private int mMaxTaskNumber = 1;
private int mActiveTaskNumber = 0;
private boolean isRunning = false;
private ExectorService mService = Executors.newSingleThreadExecutor();
public HttpDownloadManager() {
}
public void addTask(HttpDownloader task) {
try{
task.setDownloadManager(this);
tasks.offer(task);
} catch (Exception e) {
e.printStackTrace();
}
if (!isRunning && !mService.isShutdown()) {
mService.submit(new DoTask());
}
}
public void deleteTasks() {
tasks.clear();
}
public void destroy() {
if (!mService.isShutdown) {
mService.shutdown();
}
}
public final void setMaxTaskNumber(int maxTaskNumber) {
mMaxTaskNumber = maxTaskNumber;
}
public void downloadStarted() {
mActiveTaskNumber++;
}
public void downloadCompleted() {
mActiveTaskNumber--;
}
public boolean isAvailable() {
if (mActiveTaskNumber <= mMaxTaskNumber) {
return true;
} else {
return false;
}
}
private class DoTask implements Runnable {
public void run() {
isRunning = true;
while(!tasks.isEmpty()) {
if (HttpDownloadManager.this.isAvailable()) {
HttpDownloader task = tasks.poll();
task.executeAction();
}
}
isRunning = false;
}
}
}