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c++qtmedia-player

Why does QMediaGaplessPlaybackControl not exist?

I have modified the Qt Media Player Example, trying to get QMediaGaplessPlaybackControl for a crossfade effect.

Here is my code:

auto service = m_player->service();
auto cc = service->requestControl("org.qt-project.qt.mediaplayercontrol/5.0");
Q_ASSERT(cc != nullptr);
QMessageBox::information(this, "", cc->metaObject()->className());
QMediaGaplessPlaybackControl* control = qobject_cast<QMediaGaplessPlaybackControl*>(cc);
Q_ASSERT(control != nullptr);

The problem is, that when I request the control, a nullptr is returned. Does anyone know why?

I'm using Qt 5.11 on Windows with MSVC compiler.

Solution

  • The documentation of QMediaService is explicit about how to obtain a pointer to the media service's QMediaControl implementation:

    auto cc = qobject_cast<QMediaPlayerControl *>(service->requestControl("org.qt-project.qt.mediaplayercontrol/5.0"));

    So, in order to get cc as QMediaGaplessPlaybackControl change:

    auto cc = service->requestControl("org.qt-project.qt.mediagaplessplaybackcontrol/5.0");

    to:

    auto *cc = static_cast<QMediaGaplessPlaybackControl *>(qobject_cast<QMediaControl  *>(service->requestControl("org.qt-project.qt.mediaplayercontrol/5.0")));