文档说如果QMediaPlaylist :: addMedia失败,则返回false:
bool QMediaPlaylist :: addMedia(const QMediaContent& content )将媒体内容附加到播放列表。 如果操作成功返回true,否则返回false。
但是这个代码将打印为true, 't exists:
QMediaPlayer * player = new QMediaPlayer; QMediaPlaylist * playlist = new QMediaPlaylist(player); qDebug()<< playlist-> addMedia(QUrl(this file does not exist.mp4));如果文件不存在,操作如何才能成功?
$ b在进入Qt源后,我看到QMediaPlaylist :: addMedia()调用 QMediaNetworkPlaylistProvider :: addMedia() code>,它总是返回true: bool QMediaPlaylist :: addMedia(const QMediaContent& content) { return d_func() - > control-> playlistProvider() - > addMedia(content); } bool QMediaNetworkPlaylistProvider :: addMedia(const QMediaContent& content) { Q_D(QMediaNetworkPlaylistProvider); int pos = d-> resources.count(); emit mediaAboutToBeInserted(pos,pos); d-> resources.append(content); emit mediaInserted(pos,pos); return true; }虽然为什么它需要返回一个总是真的bool是一个谜。
The docs say that QMediaPlaylist::addMedia returns false if it fails:
bool QMediaPlaylist::addMedia(const QMediaContent & content) Append the media content to the playlist. Returns true if the operation is successful, otherwise return false.
But this code will print true even though the file doesn't exist:
QMediaPlayer *player = new QMediaPlayer; QMediaPlaylist *playlist = new QMediaPlaylist(player); qDebug() << playlist->addMedia(QUrl("this file doesn't exist.mp4"));If the file doesn't exist how can the operation be considered successful?
解决方案After stepping into the Qt sources, I saw that QMediaPlaylist::addMedia() calls QMediaNetworkPlaylistProvider::addMedia(), which always returns true:
bool QMediaPlaylist::addMedia(const QMediaContent &content) { return d_func()->control->playlistProvider()->addMedia(content); } bool QMediaNetworkPlaylistProvider::addMedia(const QMediaContent &content) { Q_D(QMediaNetworkPlaylistProvider); int pos = d->resources.count(); emit mediaAboutToBeInserted(pos, pos); d->resources.append(content); emit mediaInserted(pos, pos); return true; }Although why it needs to return a bool that's always true is a mystery to me.
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