为什么PyQt5 QtMultimedia出现错误？

Question

使用操作系统：Linux Ubuntu 18.04

我正在尝试运行包含QtMultimedia模块的不同PyQt示例。 不幸的是，他们给了我同样的错误：

  

defaultServiceProvider :: requestService（）：找不到以下服务：   “ org.qt-project.qt.mediaplayer”

我听说许多使用类似Unix的操作系统的人都遇到了这个问题，但是我仍然找不到任何解决方案。

这是一个代码示例：`

from PyQt5 import QtCore, QtWidgets, QtMultimedia
import sys

class MyWindow(QtWidgets.QWidget):
    def __init__(self, parent=None):
        QtWidgets.QWidget.__init__(self, parent, flags=
        QtCore.Qt.Window | QtCore.Qt.MSWindowsFixedSizeDialogHint)
        self.setWindowTitle("Music PLayer")

        #   Player
        self.mpPlayer = QtMultimedia.QMediaPlayer()
        self.mpPlayer.setVolume(50)
        self.mpPlayer.mediaStatusChanged.connect(self.initPlayer)
        self.mpPlayer.stateChanged.connect(self.setPlayerState)
        vbox = QtWidgets.QVBoxLayout()

        #   File open button
        btnOpen = QtWidgets.QPushButton("File &open")
        btnOpen.clicked.connect(self.openFile)
        vbox.addWidget(btnOpen)

        #   Make components disable at start
        self.sldPosition = QtWidgets.QSlider(QtCore.Qt.Horizontal)
        self.sldPosition.setMinimum(0)
        self.sldPosition.valueChanged.connect(self.mpPlayer.setPosition)
        self.mpPlayer.positionChanged.connect(self.sldPosition.setValue)
        self.sldPosition.setEnabled(False)
        vbox.addWidget(self.sldPosition)

        hbox = QtWidgets.QHBoxLayout()
        self.btnPlay = QtWidgets.QPushButton("&Play")
        self.btnPlay.clicked.connect(self.mpPlayer.play)
        self.btnPlay.setEnabled(False)
        hbox.addWidget(self.btnPlay)

        self.btnPause = QtWidgets.QPushButton("P&ause")
        self.btnPause.clicked.connect(self.mpPlayer.pause)
        self.btnPause.setEnabled(False)
        hbox.addWidget(self.btnPause)

        self.btnStop = QtWidgets.QPushButton("&Stop")
        self.btnStop.clicked.connect(self.mpPlayer.stop)
        self.btnStop.setEnabled(False)
        hbox.addWidget(self.btnStop)

        vbox.addLayout(hbox)

        #    Volume control
        hbox = QtWidgets.QHBoxLayout()

        lblVolume = QtWidgets.QLabel("&Volume")
        hbox.addWidget(lblVolume)

        sldVolume = QtWidgets.QSlider(QtCore.Qt.Horizontal)
        sldVolume.setRange(0, 100)
        sldVolume.setTickPosition(QtWidgets.QSlider.TicksAbove)
        sldVolume.setTickInterval(10)
        sldVolume.setValue(50)
        lblVolume.setBuddy(sldVolume)
        sldVolume.valueChanged.connect(self.mpPlayer.setVolume)
        hbox.addWidget(sldVolume)

        btnMute = QtWidgets.QPushButton("&Mute")
        btnMute.setCheckable(True)
        btnMute.toggled.connect(self.mpPlayer.setMuted)
        hbox.addWidget(btnMute)

        vbox.addLayout(hbox)
        self.setLayout(vbox)
        self.resize(300, 100)


    def openFile(self):
        file = QtWidgets.QFileDialog.getOpenFileUrl(parent=self,
                                                    caption="Choose track file",
                                                    filter="Medial files (*.mp3 *.ac3)")
        self.mpPlayer.setMedia(QtMultimedia.QMediaContent(file[0]))

    def initPlayer(self, state):
        if state == QtMultimedia.QMediaPlayer.LoadedMedia:
            self.mpPlayer.stop()
            self.btnPlay.setEnabled(True)
            self.sldPosition.setEnabled(True)
            self.slfPosition.setMaximum(self.mpPlayer.duration())
        elif state == QtMultimedia.QMediaPlayer.EndOfMedia:
            self.mpPlayer.stop()
        elif state == QtMultimedia.QMediaPlayer.NoMedia or state == QtMultimedia.QMediaPlayer.InvalidMedia:
            self.sldPosition.setValue(0)
            self.sldPosition.setEnabled(False)
            self.btnPlay.setEnabled(False)
            self.btnPause.setEnabled(False)
            self.btnStop.setEnabled(False)


    def setPlayerState(self, state):
        if state == QtMultimedia.QMediaPlayer.StoppedState:
            self.sldPosition.setValue(0)
            self.btnPause.setEnabled(False)
            self.btnStop.setEnabled(False)
        elif state == QtMultimedia.QMediaPlayer.PlayingState:
            self.btnPause.setEnabled(True)
            self.btnStop.setEnabled(True)
        elif state == QtMultimedia.QMediaPlayer.PausedState:
            self.btnPause.setEnabled(False)
            self.btnPlay.setEnabled(True)

def main():
app = QtWidgets.QApplication(sys.argv)
window = MyWindow()
window.show()
sys.exit(app.exec_())

main()

`