我有一个Downloader服务，可以加载从我的数据库运行的下载列表。
然后创建一个ASyncTask，它将在后台线程中运行下载。
这一切都运行得很好，但问题是我目前没有办法告诉服务该下载器已经完成。我不得不从ASyncTask的onPostExecute函数（在UIThread上运行）向服务发送消息。
我不能简单地远程关闭服务，因为当ASyncTask完成时，服务还有一些工作要做。
我考虑过从服务中注册一个监听器并在onPostExecute中调用它，但我认为这会导致在Task完成之前关闭服务或一些threadlocking问题等问题。
如何从ASyncTask向我的Downloader服务发送消息（如广播意图）？
修改
这里有一些代码让你对我正在做的事感到困惑。
DownloadService.java（重要位）：
public class DownloadService extends Service implements OnProgressListener {
/** The Downloads. */
private List<Download> mDownloads = new ArrayList<Download>(10);
private DownloadTask mDownloadTask;
/** The Intent receiver that handles broadcasts. */
private BroadcastReceiver mIntentReceiver = new BroadcastReceiver()
{
@Override
public void onReceive(Context context, Intent intent) {
DebugLog.i(TAG, "onRecieve" +intent.toString());
handleCommand(intent);
}
};
/* (non-Javadoc)
* @see android.app.Service#onCreate()
*/
@Override
public void onCreate() {
DebugLog.i(TAG, "onCreate");
mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
IntentFilter commandFilter = new IntentFilter();
commandFilter.addAction(ACTION_PAUSE_DOWNLOADS);
commandFilter.addAction(ACTION_START_DOWNLOADS);
registerReceiver(mIntentReceiver, commandFilter);
}
/* (non-Javadoc)
* @see android.app.Service#onDestroy()
*/
@Override
public void onDestroy(){
DebugLog.i(TAG, "onDestroy");
//Make sure all downloads are saved and stopped
pauseAllDownloads();
//unregister command receiver
unregisterReceiver(mIntentReceiver);
//cancel notifications
closeNotification();
}
/* (non-Javadoc)
* @see android.app.Service#onStartCommand(android.content.Intent, int, int)
*/a
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
handleCommand(intent);
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
}
/**
* Handle command sent via intent.
* <strong>Warning, this function shouldn't do any heavy lifting.
* This will be run in UI thread and should spin off ASyncTasks to do work.</strong>
*
* @param intent the intent
*/
private void handleCommand(Intent intent) {
if(intent != null){
String action = intent.getAction();
Uri data = intent.getData();
if(action.equals(ACTION_START_DOWNLOADS))
{
updateDownloads();//Fetch list of downloads to do from database
startDownloads();//run downloads
}else if(action.equals(ACTION_PAUSE_DOWNLOADS)){
pauseAllDownloads();
}
}
}
/**
* Start all downloads currently in list (in order).
*/
private void startDownloads()
{
pauseAllDownloads();//make sure we don't have a download task running
mDownloadTask = new DownloadTask();
mDownloadTask.setOnProgressListener(this);
Download[] downloads = new Download[mDownloads.size()];
for(int i = 0; i<mDownloads.size(); i++)
{
Download d = mDownloads.get(i);
if(d.getStatus() != Download.COMPLETE)
{
downloads[i] = mDownloads.get(i);
}
}
//must be called on UI thread
mDownloadTask.execute(downloads);
}
/**
* Pause downloads.
*/
private void pauseAllDownloads()
{
if(mDownloadTask == null)
{
//Done. Nothing is downloading.
return;
}
//Cancel download task first so that it doesn't start downloading next
if(mDownloadTask.cancel(true))
{
//Task has been canceled. Pause the active download.
Download activeDownload = mDownloadTask.getActiveDownload();
if(activeDownload != null)
{
activeDownload.pause();
}
}else
{
if(mDownloadTask.getStatus() == AsyncTask.Status.FINISHED)
{
DebugLog.w(TAG, "Download Task Already Finished");
}else{
//Task could not be stopped
DebugLog.w(TAG, "Download Task Could Not Be Stopped");
}
}
}
@Override
public void onProgress(Download download) {
//download progress is reported here from DownloadTask
}
}
DownloadTask：
/**
* The Class DownloadTask.
*/
public class DownloadTask extends AsyncTask<Download, Download, Void> {
/** The On progress listener. */
private OnProgressListener mOnProgressListener;
/**
* The listener interface for receiving onProgress events.
* The class that is interested in processing a onProgress
* event implements this interface and registers it with the component.
*
*/
public static interface OnProgressListener
{
/**
* On progress update.
*
* @param download the download
*/
public void onProgress(Download download);
}
private Download mCurrent;
/**
* Sets the on progress listener.
*
* @param listener the new on progress listener
*/
public void setOnProgressListener(OnProgressListener listener)
{
mOnProgressListener = listener;
}
/**
* Gets the active download.
*
* @return the active download
*/
public Download getActiveDownload()
{
return mCurrent;
}
/* (non-Javadoc)
* @see android.os.AsyncTask#doInBackground(Params[])
*/
@Override
protected Void doInBackground(Download... params) {
int count = params.length;
for (int i = 0; i < count; i++) {
mCurrent = params[i];
if(mCurrent == null)
{
continue;
}
mCurrent.setDownloadProgressListener(new Download.OnDownloadProgressListener() {
@Override
public void onDownloadProgress(Download download, int bytesDownloaded,
int bytesTotal) {
publishProgress(download);
}
});
mCurrent.setOnStatusChangedListener(new Download.OnStatusChangedListener() {
@Override
public void onStatusChanged(Download download, int status) {
publishProgress(download);
}
});
mCurrent.download();
//publishProgress(mCurrent); redundant call
if(this.isCancelled())
break;
}
return null;
}
/* (non-Javadoc)
* @see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
public void onPostExecute(Void v)
{
//TODO notify completion.
}
/* (non-Javadoc)
* @see android.os.AsyncTask#onProgressUpdate(Progress[])
*/
@Override
protected void onProgressUpdate(Download... progress) {
if(mOnProgressListener != null)
{
for(Download d:progress)
{
mOnProgressListener.onProgress(d);
}
}
}
}
答案 0 :(得分：6)
我有一个Downloader Service，可以加载从我的数据库运行的下载列表。 然后它创建一个ASyncTask，它将在后台线程中运行下载。
为什么不使用IntentService，考虑到它已经有了后台线程？ Here is a sample project使用IntentService进行下载演示。
我目前无法告诉服务该下载器已完成。
从stopSelf()致电onPostExecute()。更好的是，使用IntentService，当没有更多的工作要做时，它会自动关闭。