編輯:關於Android編程
Android DownloadProvider 源碼分析:
Download的源碼編譯分為兩個部分,一個是DownloadProvider.apk, 一個是DownloadProviderUi.apk.
這兩個apk的源碼分別位於
packages/providers/DownloadProvider/ui/src
packages/providers/DownloadProvider/src
其中,DownloadProvider的部分是下載邏輯的實現,而DownloadProviderUi是界面部分的實現。
然後DownloadProvider裡面的下載雖然主要是通過DownloadService進行的操作,但是由於涉及到Notification的更新,下載進度的展示,下載的管理等。
所以還是有不少其它的類來分別進行操作。
DownloadProvider -- 數據庫操作的封裝,繼承自ContentProvider;
DownloadManager -- 大部分邏輯是進一步封裝數據操作,供外部調用;
DownloadService -- 封裝文件download,delete等操作,並且操縱下載的norification;繼承自Service;
DownloadNotifier -- 狀態欄Notification邏輯;
DownloadReceiver -- 配合DownloadNotifier進行文件的操作及其Notification;
DownloadList -- Download app主界面,文件界面交互;
下載一般是從Browser裡面點擊鏈接開始,我們先來看一下Browser中的代碼
在browser的src/com/Android/browser/DownloadHandler.Java函數中,我們可以看到一個很完整的Download的調用,我們在寫自己的app的時候,也可以對這一段進行參考:
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); }
在這個操作中,我們看到添加了request的各種參數,然後最後調用了DownloadManager的enqueue進行下載,並且在開始後,彈出了開始下載的這個toast。manager是一個DownloadManager的實例,DownloadManager是存在與frameworks/base/core/java/android/app/DownloadManager.java。可以看到enqueue的實現為:
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;
enqueue函數主要是將Rquest實例分解組成一個ContentValues實例,並且添加到數據庫中,函數返回插入的這條數據返回的ID;ContentResolver.insert函數會調用到DownloadProvider實現的ContentProvider的insert函數中去,如果我們去查看insert的code的話,我們可以看到操作是很多的。但是我們只需要關注幾個關鍵的部分:
...... //將相關的請求參數,配置等插入到downloads數據庫; long rowID = db.insert(DB_TABLE, null, filteredValues); ...... //將相關的請求參數,配置等插入到request_headers數據庫中; 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. //啟動DownloadService進行下載及其它工作 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);
在這邊,我們就可以看到下載的DownloadService的調用了。因為是一個startService的方法,所以我們在DownloadService裡面,是要去走oncreate的方法的。
@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); }
這邊的話,我們可以看到先去啟動了一個handler去接收callback的處理
mUpdateThread = new HandlerThread(TAG + "-UpdateThread"); mUpdateThread.start(); mUpdateHandler = new Handler(mUpdateThread.getLooper(), mUpdateCallback);
然後去
getContentResolver().registerContentObserver(Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI, true, mObserver)
是去注冊監聽Downloads.Impl.ALL_DOWNLOADS_CONTENT_URI的Observer。
而oncreate之後,就會去調用onStartCommand方法.
@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; }
在enqueueUpdate的函數中,我們會向mUpdateHandler發送一個MSG_UPDATE Message,
private void enqueueUpdate() { mUpdateHandler.removeMessages(MSG_UPDATE); mUpdateHandler.obtainMessage(MSG_UPDATE, mLastStartId, -1).sendToTarget(); }
mUpdateCallback中接收到並且處理:
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,則會在Delayed 5×60000ms後發送MSG_FINAL_UPDATE Message,主要是為了“any finished operations that didn't trigger an update pass.” enqueueFinalUpdate(); } else { //如果沒有Active的任務正在進行,就會停止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; } };
這邊的重點是updateLocked()函數
private boolean updateLocked() { final long now = mSystemFacade.currentTimeMillis(); boolean isActive = false; long nextActionMillis = Long.MAX_VALUE; //mDownloads初始化是一個空的Map<Long, DownloadInfo> final Set<Long> staleIds = Sets.newHashSet(mDownloads.keySet()); final ContentResolver resolver = getContentResolver(); //獲取所有的DOWNLOADS任務 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); //開始時,mDownloads是沒有任何內容的,info==null if (info != null) { //從數據庫更新最新的Download info信息,來監聽數據庫的改變並且反應到界面上 updateDownload(reader, info, now); } else { //添加新下載的Dwonload info到mDownloads,並且從數據庫讀取新的Dwonload info info = insertDownloadLocked(reader, now); } //這裡的mDeleted參數表示的是當我刪除了正在或者已經下載的內容時,首先數據庫會update這個info.mDeleted為true,而不是直接刪除文件 if (info.mDeleted) { //不詳細解釋delete函數,主要是刪除數據庫內容和現在文件內容 if (!TextUtils.isEmpty(info.mMediaProviderUri)) { resolver.delete(Uri.parse(info.mMediaProviderUri), null, null); } deleteFileIfExists(info.mFileName); resolver.delete(info.getAllDownloadsUri(), null, null); } else { // 開始下載文件 final boolean activeDownload = info.startDownloadIfReady(mExecutor); // 開始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 < Long.MAX_VALUE) { final Intent intent = new Intent(Constants.ACTION_RETRY); intent.setClass(this, DownloadReceiver.class); mAlarmManager.set(AlarmManager.RTC_WAKEUP, now + nextActionMillis, PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_ONE_SHOT)); } return isActive; }
重點來看看文件的下載,startDownloadIfReady函數:
public boolean startDownloadIfReady(ExecutorService executor) { synchronized (this) { final boolean isReady = isReadyToDownload(); final boolean isActive = mSubmittedTask != null && !mSubmittedTask.isDone(); if (isReady && !isActive) { //更新數據庫的任務狀態為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); } //開始下載任務 mTask = new DownloadThread( mContext, mSystemFacade, this, mStorageManager, mNotifier); mSubmittedTask = executor.submit(mTask); } return isReady; } }
在DownloadThread的處理中,如果HTTP的狀態是ok的話,會去進行transferDate的處理。
private void transferData(State state, HttpURLConnection conn) throws StopRequestException { ...... in = conn.getInputStream(); ...... //獲取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 (;;) { //從InputStream中讀取內容信息,“in.read(data)”,並且對數據庫中文件下載大小進行更新 int bytesRead = readFromResponse(state, data, in); if (bytesRead == -1) { // success, end of stream already reached handleEndOfStream(state); return; } state.mGotData = true; //利用OutPutStream寫入讀取的InputStream,"out.write(data, 0, bytesRead)" writeDataToDestination(state, data, bytesRead, out); state.mCurrentBytes += bytesRead; reportProgress(state); } checkPausedOrCanceled(state); } }
至此,下載文件的流程就說完了,繼續回到DownloadService的updateLocked()函數中來;重點來分析DownloadNotifier的updateWith()函數,這個方法用來更新Notification
//這段代碼是根據不同的狀態設置不同的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); }
//這段代碼是根據不同的狀態來設置不同的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)); }
//這段代碼是更新下載的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); }
最後調用mNotifManager.notify(tag, 0, notif);根據不同的狀態來設置不同的Notification的title和description
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