有没有办法从任意点开始在 Phonon 媒体对象中启动流

Question

我正在编写一个应用程序，用于在Mac OS X上收听Qt 4.8.1中的播客。现在，我正在将MediaObject设置为使用播客 RSS 项目中的附件 URL，如下所示：

mediaObj->setCurrentSource(Phonon::MediaSource(QUrl(idx.data(Metadata::Enclosure).toString())));

注意：idx是一个QModelIndex，对应于用户在QTreeView小部件中单击的模型中的QStandardItem。

不过，我现在有两个问题。

1. 每当我暂停流并重新启动它时，它都会从头开始。没那么有帮助。:-(
2. 如果我使用 Phonon::SeekSlider 小部件跳到尚未缓冲的流的一部分，我会被反弹回流的开头。

我(可能有缺陷的(想法是，如果我能找到一种方法让mediaObj从流中的特定时间开始播放，我就可以解决这两个问题。所以，我试过这个：

void BrodCastMainWin::pauseStream()
{
    //save the "left off at" point in the stream
    qDebug() << "current time is:" << currentTime;
    qDebug() << "Saving place at" << currentTimeString
             << "in item" << nowPlaying.data(Qt::DisplayRole).toString();
    //need to use QModelIndex for setData()
    QModelIndex nowPlayingHandle = nowPlaying;
    feed.setData(nowPlayingHandle, QVariant(currentTime), Metadata::LeftOffAt);
    //pause the stream
    mediaObj->pause();
}
void BrodCastMainWin::playStream()
{
    //seek to the "left off at" point in the stream
    qDebug() << "Trying to seek to" << convertTime(nowPlaying.data(Metadata::LeftOffAt).toLongLong())
             << "in item" << nowPlaying.data(Qt::DisplayRole).toString();
    mediaObj->seek(nowPlaying.data(Metadata::LeftOffAt).toLongLong());
    //play the file
    mediaObj->play();
}

注意：currentTime是截至mediaObj发出最后一个tick()信号的时间。我试图在mediaObj中使用currentTime()方法获取这些数据，但没有奏效。但这是另一天的战斗。同样，currentTimeString是人类可读格式的相同信息。

唉，它不起作用：-(。这是我播放流时该代码发生的情况：

current time is: 32153 
Saving place at "00:32" in item "Leo Laporte - The Tech Guy 867" 
switching button to 'play'

槽的。但是当我尝试再次播放时：

Trying to seek to "00:32" in item "Leo Laporte - The Tech Guy 867" 
Playing/Loading/Buffering; switching button to 'pause' 
current time is: 0 
Saving place at "00:00" in item "Leo Laporte - The Tech Guy 867" 
switching button to 'play' 
Trying to seek to "00:00" in item "Leo Laporte - The Tech Guy 867" 
Playing/Loading/Buffering; switching button to 'pause' 

我完全糊涂了。似乎我试图让Phonon以一种它不想的方式行事。我担心这似乎是 Phonon 模块长期存在的问题，我可能不得不以其他方式实现流。帮助？

Answer 1

好吧，看来我太花哨了。我使用一个按钮进行播放/暂停。我只需要改变这个：

void BrodCastMainWin::handleMediaState(Phonon::State state, Phonon::State)
{
    switch (state)
    {
    case Phonon::PlayingState:
    case Phonon::LoadingState:
    case Phonon::BufferingState:
        qDebug() << "Playing/Loading/Buffering; switching button to 'pause'";
        //If we're playing, the button should pause
        ui->playPauseButton->setIcon(QIcon(":/assets/stock_media-pause.svg"));
        connect(ui->playPauseButton, SIGNAL(clicked()),
                this, SLOT(pauseStream()));
        break;
    case Phonon::PausedState:
    case Phonon::StoppedState:
        qDebug() << "switching button to 'play'";
        //if we're paused, the button should play
        ui->playPauseButton->setIcon(QIcon(":/assets/stock_media-play.svg"));
        connect(ui->playPauseButton, SIGNAL(clicked()),
                this, SLOT(playStream()));
    case Phonon::ErrorState:
        //additionally, if there's an error, do error handling.
        break;
    default:
        break;
    }
}

。对此：

void BrodCastMainWin::handleMediaState(Phonon::State state, Phonon::State)
{
    switch (state)
    {
    case Phonon::PlayingState:
        qDebug() << "Playing/Loading/Buffering; switching button to 'pause'";
        //If we're playing, the button should pause
        ui->playPauseButton->setIcon(QIcon(":/assets/stock_media-pause.svg"));
        connect(ui->playPauseButton, SIGNAL(clicked()),
                this, SLOT(pauseStream()));
        break;
    case Phonon::PausedState:
        qDebug() << "switching button to 'play'";
        //if we're paused, the button should play
        ui->playPauseButton->setIcon(QIcon(":/assets/stock_media-play.svg"));
        connect(ui->playPauseButton, SIGNAL(clicked()),
                this, SLOT(playStream()));
        break;
    case Phonon::ErrorState:
        //additionally, if there's an error, do error handling.
        break;
    case Phonon::LoadingState:
    case Phonon::BufferingState:
    case Phonon::StoppedState:
    default:
        break;
    }
}

当然，我最终也会想处理其他状态。但这解决了我的第一个问题。另一个问题可能要等到另一天。