QPainter::begin: Paint device returned engine == 0, type: 3

 

1. 当页面消息比较多时候，会报错

 

QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::setCompositionMode: Painter not active
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::scale: Painter not active
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::setCompositionMode: Painter not active
QPainter::end: Painter not active, aborted


QThread::start: Failed to create thread (Unknown error 0x00000022.)

 

==========> ExitInstance :gLayerInfo delete 113286984<==============Unload CSProxy from Client.exe...
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

2. 注意观察，总结什么情况下报错

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一秒一条消息进来 10秒刷新一次，10分钟都没有异常 5秒刷新一次，10分钟都没有异常 2秒刷新一次，10分钟都没有异常===>13分钟崩溃 1秒刷新一次，6分钟后有问题   一秒四条消息进来 2秒刷新一次，第4分钟出现异常 5秒刷新一次，第4分钟出现异常 10秒刷新一次，第4分钟出现异常

 

3. 在不确定什么缘由导致时，注释整块、部分代码去排除出问题的代码

出问题的代码如下

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if(!soundName.isEmpty()){     QMediaPlayer    *player = new QMediaPlayer();;//播放器     QMediaPlaylist  *playlist = new QMediaPlaylist();//播放列表     player->setPlaylist(playlist);       if (player->state()!=QMediaPlayer::PlayingState){         playlist->setCurrentIndex(0);     }     playlist->setPlaybackMode(QMediaPlaylist::Sequential); //循环模式       QString audiosPath = QCoreApplication::applicationDirPath() + "/audios/";       playlist->clear();     //放3遍     playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));     playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));     playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));     player->play(); }

 结合网上资料

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class Q_CORE_EXPORT QInternal { public:     enum PaintDeviceFlags {         UnknownDevice = 0x00,         Widget        = 0x01,         Pixmap        = 0x02,         Image         = 0x03,         Printer       = 0x04,         Picture       = 0x05,         Pbuffer       = 0x06,    // GL pbuffer         FramebufferObject = 0x07, // GL framebuffer object         CustomRaster  = 0x08,         MacQuartz     = 0x09,         PaintBuffer   = 0x0a,         OpenGL        = 0x0b     };

QPainter::begin: Paint device returned engine == 0, type: 3

UnknownDevice==>

每条消息会初始化QMediaPlayer，多个QMediaPlayer；播放会造成设备UnknownDevice；并且std::bad_alloc 表示程序分配内存异常。

 

 

 

4.解决方法

使用QMutex mutex，lock()、unlock()对上述代码块加锁，并对QMediaPlayer等复用。

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static QMutex mutex; static QMediaPlayer    *player = new QMediaPlayer();//播放器 static QMediaPlaylist  *playlist = new QMediaPlaylist();//播放列表     void XXX::playSound(QString soundName){     if(!soundName.isEmpty()){         mutex.lock();           qDebug() << "【AlarmMessage::playSound】 start " << soundName;         player->setPlaylist(playlist);           if (player->state()!=QMediaPlayer::PlayingState){             playlist->setCurrentIndex(0);         }         playlist->setPlaybackMode(QMediaPlaylist::Sequential); //循环模式           QString audiosPath = QCoreApplication::applicationDirPath() + "/audios/";           playlist->clear();         //放3遍         playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));         playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));         playlist->addMedia(QUrl::fromLocalFile(audiosPath+soundName+".mp3"));         player->play();           qDebug() << "【AlarmMessage::playSound】 end " << soundName;           mutex.unlock();     } }