问题描述
我正在连接 QMediaPlayer :: error（）信号并尝试播放视频文件：
I'm connecting the QMediaPlayer::error() signal and trying to play a video file:
QMediaPlayer *player = new QMediaPlayer;
QMediaPlaylist *playlist = new QMediaPlaylist(player);
playlist->addMedia(QUrl::fromLocalFile("/path/to/file.mp4"));
QVideoWidget *videoWidget = new QVideoWidget;
player->setVideoOutput(videoWidget);
videoWidget->resize(640, 340);
videoWidget->show();
ErrorPrinter *errorPrinter = new ErrorPrinter(player);
QObject::connect(player, SIGNAL(error(QMediaPlayer::Error)), errorPrinter, SLOT(printError(QMediaPlayer::Error)));
player->play();
视频小部件显示，但没有任何播放，所以它必须在某处失败。但是， QMediaPlayer :: error（）信号从不发射！应用程序输出为空，没有声明， play（）函数为 void 成功或失败），并。
The video widget shows, but nothing is playing, so it must have failed somewhere. However, the QMediaPlayer::error() signal is never emitted! The Application Output is empty, there are no asserts, the play() function is void (no return value to indicate success or failure), and playlist->addMedia always returns true.
我应该怎么知道出了什么问题？
How am I supposed to find out what went wrong?
推荐答案
QMediaPlaylist（player） $ c> QObject parent。它不会将播放列表链接到播放器 - 播放器不知道播放列表。
The QMediaPlaylist(player) construction only sets a QObject parent. It doesn't link the playlist to player - the player is unaware of the playlist.
因此，您从未在播放器上设置播放列表。您可能还需要将播放列表索引设置为1或可能为零（？ - 文档不清楚）。
So, you've never set the playlist on the player. You may also need to set the playlist index - to 1 or perhaps zero (? - the docs are not clear on that).
playlist->setCurrentIndex(1);
player->setPlayList(playlist);
player->play();
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