library/src/main/java/com/liulishuo/filedownloader/FileDownloader.java
public boolean start(final FileDownloadListener listener, final boolean isSerial) {

        if (listener == null) {
            FileDownloadLog.w(this, "Tasks with the listener can't start, because the listener "
                    + "provided is null: [null, %B]", isSerial);
            return false;
        }


        return isSerial
                ? getQueuesHandler().startQueueSerial(listener)
                : getQueuesHandler().startQueueParallel(listener);
    }
public boolean start(final FileDownloadListener listener, final boolean isSerial) {

        if (listener == null) {
            FileDownloadLog.w(this, "Tasks with the listener can't start, because the listener "
                    + "provided is null: [null, %B]", isSerial);
            return false;
        }


        return isSerial
                ? getQueuesHandler().startQueueSerial(listener)
                : getQueuesHandler().startQueueParallel(listener);
    }
Start the download queue by the same listener.

@param listener Used to assemble tasks which is bound by the same {@code listener}
@param isSerial Whether start tasks one by one rather than parallel.
@return {@code true} if start tasks successfully.