Android DownloadProvider 源码详解

 public static void startingDownload(Activity activity, String url, String userAgent, String contentDisposition, String mimetype, String referer, boolean privateBrowsing, long contentLength, String filename, String downloadPath) { // java.net.URI is a lot stricter than KURL so we have to encode some // extra characters. Fix for b 2538060 and b 1634719 WebAddress webAddress; try { webAddress = new WebAddress(url); webAddress.setPath(encodePath(webAddress.getPath())); } catch (Exception e) { // This only happens for very bad urls, we want to chatch the // exception here Log.e(LOGTAG, "Exception trying to parse url:" + url); return; } String addressString = webAddress.toString(); Uri uri = Uri.parse(addressString); final DownloadManager.Request request; try { request = new DownloadManager.Request(uri); } catch (IllegalArgumentException e) { Toast.makeText(activity, R.string.cannot_download, Toast.LENGTH_SHORT).show(); return; } request.setMimeType(mimetype); // set downloaded file destination to /sdcard/Download. // or, should it be set to one of several Environment.DIRECTORY* dirs // depending on mimetype? try { setDestinationDir(downloadPath, filename, request); } catch (Exception e) { showNoEnoughMemoryDialog(activity); return; } // let this downloaded file be scanned by MediaScanner - so that it can // show up in Gallery app, for example. request.allowScanningByMediaScanner(); request.setDescription(webAddress.getHost()); // XXX: Have to use the old url since the cookies were stored using the // old percent-encoded url. String cookies = CookieManager.getInstance().getCookie(url, privateBrowsing); request.addRequestHeader("cookie", cookies); request.addRequestHeader("User-Agent", userAgent); request.addRequestHeader("Referer", referer); request.setNotificationVisibility( DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED); final DownloadManager manager = (DownloadManager) activity .getSystemService(Context.DOWNLOAD_SERVICE); new Thread("Browser download") { public void run() { manager.enqueue(request); } }.start(); showStartDownloadToast(activity); } 

 public long enqueue(Request request) { ContentValues values = request.toContentValues(mPackageName); Uri downloadUri = mResolver.insert(Downloads.Impl.CONTENT_URI, values); long id = Long.parseLong(downloadUri.getLastPathSegment()); return id; 

 ...... //将相关的请求参数，配置等插入到downloads数据库； long rowID = db.insert(DB_TABLE, null, filteredValues); ...... //将相关的请求参数，配置等插入到request_headers数据库中； insertRequestHeaders(db, rowID, values); ...... if (values.getAsInteger(Downloads.Impl.COLUMN_DESTINATION) == Downloads.Impl.DESTINATION_NON_DOWNLOADMANAGER_DOWNLOAD) { // When notification is requested, kick off service to process all // relevant downloads. //启动DownloadService进行下载及其它工作 if (Downloads.Impl.isNotificationToBeDisplayed(vis)) { context.startService(new Intent(context, DownloadService.class)); } } else { context.startService(new Intent(context, DownloadService.class)); } notifyContentChanged(uri, match); return ContentUris.withAppendedId(Downloads.Impl.CONTENT_URI, rowID); 

 @Override public void onCreate() { super.onCreate(); if (Constants.LOGVV) { Log.v(Constants.TAG, "Service onCreate"); } if (mSystemFacade == null) { mSystemFacade = new RealSystemFacade(this); } mAlarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); mStorageManager = new StorageManager(this); mUpdateThread = new HandlerThread(TAG + "-UpdateThread"); mUpdateThread.start(); mUpdateHandler = new Handler(mUpdateThread.getLooper(), mUpdateCallback); mScanner = new DownloadScanner(this); mNotifier = new DownloadNotifier(this); mNotifier.cancelAll(); mObserver = new DownloadManagerContentObserver(); getContentResolver().registerContentObserver(Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI, true, mObserver); } 

 mUpdateThread = new HandlerThread(TAG + "-UpdateThread"); mUpdateThread.start(); mUpdateHandler = new Handler(mUpdateThread.getLooper(), mUpdateCallback); 

 getContentResolver().registerContentObserver(Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI, true, mObserver) 

 @Override ublic int onStartCommand(Intent intent, int flags, int startId) { int returnValue = super.onStartCommand(intent, flags, startId); if (Constants.LOGVV) { Log.v(Constants.TAG, "Service onStart"); } mLastStartId = startId; enqueueUpdate(); return returnValue; } 

 private void enqueueUpdate() { mUpdateHandler.removeMessages(MSG_UPDATE); mUpdateHandler.obtainMessage(MSG_UPDATE, mLastStartId, -1).sendToTarget(); } 

 private Handler.Callback mUpdateCallback = new Handler.Callback() { @Override public boolean handleMessage(Message msg) { Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); final int startId = msg.arg1; final boolean isActive; synchronized (mDownloads) { isActive = updateLocked(); } ...... if (isActive) { //如果Active，则会在Delayed 5×60000ms后发送MSG_FINAL_UPDATE Message，主要是为了“any finished operations that didn't trigger an update pass.” enqueueFinalUpdate(); } else { //如果没有Active的任务正在进行，就会停止Service以及其它 if (stopSelfResult(startId)) { if (DEBUG_LIFECYCLE) Log.v(TAG, "Nothing left; stopped"); getContentResolver().unregisterContentObserver(mObserver); mScanner.shutdown(); mUpdateThread.quit(); } } return true; } }; 

 private boolean updateLocked() { final long now = mSystemFacade.currentTimeMillis(); boolean isActive = false; long nextActionMillis = Long.MAX_VALUE; //mDownloads初始化是一个空的Map final Set staleIds = Sets.newHashSet(mDownloads.keySet()); final ContentResolver resolver = getContentResolver(); //获取所有的DOWNLOADS任务 final Cursor cursor = resolver.query(Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI, null, null, null, null); try { final DownloadInfo.Reader reader = new DownloadInfo.Reader(resolver, cursor); final int idColumn = cursor.getColumnIndexOrThrow(Downloads.Impl._ID); //迭代Download Cusor while (cursor.moveToNext()) { final long id = cursor.getLong(idColumn); staleIds.remove(id); DownloadInfo info = mDownloads.get(id); //开始时，mDownloads是没有任何内容的，info==null if (info != null) { //从数据库更新最新的Download info信息，来监听数据库的改变并且反应到界面上 updateDownload(reader, info, now); } else { //添加新下载的Dwonload info到mDownloads，并且从数据库读取新的Dwonload info info = insertDownloadLocked(reader, now); } //这里的mDeleted参数表示的是当我删除了正在或者已经下载的内容时，首先数据库会update这个info.mDeleted为true，而不是直接删除文件 if (info.mDeleted) { //不详细解释delete函数，主要是删除数据库内容和现在文件内容 if (!TextUtils.isEmpty(info.mMediaProviderUri)) { resolver.delete(Uri.parse(info.mMediaProviderUri), null, null); } deleteFileIfExists(info.mFileName); resolver.delete(info.getAllDownloadsUri(), null, null); } else { // 开始下载文件 final boolean activeDownload = info.startDownloadIfReady(mExecutor); // 开始media scanner final boolean activeScan = info.startScanIfReady(mScanner); isActive |= activeDownload; isActive |= activeScan; } // Keep track of nearest next action nextActionMillis = Math.min(info.nextActionMillis(now), nextActionMillis); } } finally { cursor.close(); } // Clean up stale downloads that disappeared for (Long id : staleIds) { deleteDownloadLocked(id); } // Update notifications visible to user mNotifier.updateWith(mDownloads.values()); if (nextActionMillis > 0 && nextActionMillis 

 public boolean startDownloadIfReady(ExecutorService executor) { synchronized (this) { final boolean isReady = isReadyToDownload(); final boolean isActive = mSubmittedTask != null && !mSubmittedTask.isDone(); if (isReady && !isActive) { //更新数据库的任务状态为STATUS_RUNNING if (mStatus != Impl.STATUS_RUNNING) { mStatus = Impl.STATUS_RUNNING; ContentValues values = new ContentValues(); values.put(Impl.COLUMN_STATUS, mStatus); mContext.getContentResolver().update(getAllDownloadsUri(), values, null, null); } //开始下载任务 mTask = new DownloadThread( mContext, mSystemFacade, this, mStorageManager, mNotifier); mSubmittedTask = executor.submit(mTask); } return isReady; } } 

 private void transferData(State state, HttpURLConnection conn) throws StopRequestException { ...... in = conn.getInputStream(); ...... //获取InputStream和OutPutStream if (DownloadDrmHelper.isDrmConvertNeeded(state.mMimeType)) { drmClient = new DrmManagerClient(mContext); final RandomAccessFile file = new RandomAccessFile( new File(state.mFilename), "rw"); out = new DrmOutputStream(drmClient, file, state.mMimeType); outFd = file.getFD(); } else { out = new FileOutputStream(state.mFilename, true); outFd = ((FileOutputStream) out).getFD(); } ...... // Start streaming data, periodically watch for pause/cancel // commands and checking disk space as needed. transferData(state, in, out); ...... } 

 private void transferData(State state, InputStream in, OutputStream out) throws StopRequestException { final byte data[] = new byte[Constants.BUFFER_SIZE]; for (;;) { //从InputStream中读取内容信息，“in.read(data)”，并且对数据库中文件下载大小进行更新 int bytesRead = readFromResponse(state, data, in); if (bytesRead == -1) { // success, end of stream already reached handleEndOfStream(state); return; } state.mGotData = true; //利用OutPutStream写入读取的InputStream，"out.write(data, 0, bytesRead)" writeDataToDestination(state, data, bytesRead, out); state.mCurrentBytes += bytesRead; reportProgress(state); } checkPausedOrCanceled(state); } } 

 //这段代码是根据不同的状态设置不同的Notification的icon if (type == TYPE_ACTIVE) { builder.setSmallIcon(android.R.drawable.stat_sys_download); } else if (type == TYPE_WAITING) { builder.setSmallIcon(android.R.drawable.stat_sys_warning); } else if (type == TYPE_COMPLETE) { builder.setSmallIcon(android.R.drawable.stat_sys_download_done); } 

 //这段代码是根据不同的状态来设置不同的notification Intent // Build action intents if (type == TYPE_ACTIVE || type == TYPE_WAITING) { // build a synthetic uri for intent identification purposes final Uri uri = new Uri.Builder().scheme("active-dl").appendPath(tag).build(); final Intent intent = new Intent(Constants.ACTION_LIST, uri, mContext, DownloadReceiver.class); intent.putExtra(DownloadManager.EXTRA_NOTIFICATION_CLICK_DOWNLOAD_IDS, getDownloadIds(cluster)); builder.setContentIntent(PendingIntent.getBroadcast(mContext, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)); builder.setOngoing(true); } else if (type == TYPE_COMPLETE) { final DownloadInfo info = cluster.iterator().next(); final Uri uri = ContentUris.withAppendedId( Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI, info.mId); builder.setAutoCancel(true); final String action; if (Downloads.Impl.isStatusError(info.mStatus)) { action = Constants.ACTION_LIST; } else { if (info.mDestination != Downloads.Impl.DESTINATION_SYSTEMCACHE_PARTITION) { action = Constants.ACTION_OPEN; } else { action = Constants.ACTION_LIST; } } final Intent intent = new Intent(action, uri, mContext, DownloadReceiver.class); intent.putExtra(DownloadManager.EXTRA_NOTIFICATION_CLICK_DOWNLOAD_IDS, getDownloadIds(cluster)); builder.setContentIntent(PendingIntent.getBroadcast(mContext, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)); final Intent hideIntent = new Intent(Constants.ACTION_HIDE, uri, mContext, DownloadReceiver.class); builder.setDeleteIntent(PendingIntent.getBroadcast(mContext, 0, hideIntent, 0)); } 

 //这段代码是更新下载的Progress if (total > 0) { final int percent = (int) ((current * 100) / total); percentText = res.getString(R.string.download_percent, percent); if (speed > 0) { final long remainingMillis = ((total - current) * 1000) / speed; remainingText = res.getString(R.string.download_remaining, DateUtils.formatDuration(remainingMillis)); } builder.setProgress(100, percent, false); } else { builder.setProgress(100, 0, true); }