Download Manager notes

最新推荐文章于 2025-09-25 03:47:37 发布

原创最新推荐文章于 2025-09-25 03:47:37 发布 · 1.7k 阅读

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#download #manager #null #printing #database #thread

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steps

1.onDownloadStartNoStream

2.3 in BrowserActivity.onDownloadStartNoStream, 3.2 in Controller to DownloadHandler.onDownloadStartNoStream.

2.in onDownloadStartNoStream

check sdcard

generate DownloadManager.Request

set download path and filename.

3.DownloadManager.enque(Request)

in enque of DownloadManager, it will insert the download item to database.

4. since DownloadService regist a ContentObserver on DownloadProvider's uri.

so the DownloadProvider's 'onChange' will be called when the database has changed.

5. in the onChange ot the ContentObserver, call 'DownloadService.updateFromProvider'

and then start a new thread.

mUpdateThread = new UpdateThread();
mSystemFacade.startThread(mUpdateThread);

6. in the thread's 'run' function

traverse the database , get the data into a DownloadInfo class.

and call DownloadInfo.startIfReady() to start a thread to download

DownloadThread downloader = new DownloadThread(mContext, mSystemFacade, this,
                storageManager);
        mHasActiveThread = true;
        mSystemFacade.startThread(downloader);

call RealSystemFacade.startThread()

//mSystemFacade was assigned in

    public void onCreate() {
        super.onCreate();
        if (Constants.LOGVV) {
            Log.v(Constants.TAG, "Service onCreate");
        }

        if (mSystemFacade == null) {
            mSystemFacade = new RealSystemFacade(this);
        }

7 in RealSystemFacade.startThread()

call DownloadThread's run()

start download.

    public void run() {
        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);

        State state = new State(mInfo);
        AndroidHttpClient client = null;
        PowerManager.WakeLock wakeLock = null;
        int finalStatus = Downloads.Impl.STATUS_UNKNOWN_ERROR;

        try {
            PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
            wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, Constants.TAG);
            wakeLock.acquire();


            if (Constants.LOGV) {
                Log.v(Constants.TAG, "initiating download for " + mInfo.mUri);
            }

            client = AndroidHttpClient.newInstance(userAgent(), mContext);

            boolean finished = false;
            while(!finished) {
                Log.i(Constants.TAG, "Initiating request for download " + mInfo.mId);
                HttpGet request = new HttpGet(state.mRequestUri);
                try {
                    executeDownload(state, client, request);
                    finished = true;
                } catch (RetryDownload exc) {
                    // fall through
                } finally {
                    request.abort();
                    request = null;
                }
            }

            if (Constants.LOGV) {
                Log.v(Constants.TAG, "download completed for " + mInfo.mUri);
            }
            finalizeDestinationFile(state);
            finalStatus = Downloads.Impl.STATUS_SUCCESS;
        } catch (StopRequest error) {
            // remove the cause before printing, in case it contains PII
            Log.w(Constants.TAG,
                    "Aborting request for download " + mInfo.mId + ": " + error.getMessage());
            finalStatus = error.mFinalStatus;
            // fall through to finally block
        } catch (Throwable ex) { //sometimes the socket code throws unchecked exceptions
            Log.w(Constants.TAG, "Exception for id " + mInfo.mId + ": " + ex);
            finalStatus = Downloads.Impl.STATUS_UNKNOWN_ERROR;
            // falls through to the code that reports an error
        } finally {
            if (wakeLock != null) {
                wakeLock.release();
                wakeLock = null;
            }
            if (client != null) {
                client.close();
                client = null;
            }
            cleanupDestination(state, finalStatus);
            notifyDownloadCompleted(finalStatus, state.mCountRetry, state.mRetryAfter,
                                    state.mGotData, state.mFilename,
                                    state.mNewUri, state.mMimeType);
            mInfo.mHasActiveThread = false;
        }

webkit download notes

1, ResourceHandle

a class for managing Resource downloading, it's has functions "connection","loadResourceSynchronously" and so forth.

2.ResourceHandleClient

ResourceHandle's client who may really need the data, and using ResourceHandle to download it.

3.ResourceHandleInternal

media class between ReourceHandle and ResourehandleClient.

ResourceHandle use it to find it's client. (so that we can change it's ResourceHandle's real client).

4,ResourceLoader

son of ResourceHandleClient, it will use ResourceHandle to download data, client of ResourceHandle.

5.MainResourceLoader

son of ResourceLoader, same function as it's parent, it will load Main resource, client of ResourceHandle.