PyQt5：QProgressBar不會更新

我有一個應用程式，其中一個功能是使用 pytube 下載 YouTube 視頻。除了使用下載進度更新 QProgressBar 之外，一切都運行良好。請看下面的代碼：

import pytube

import PyQt5.QtWidgets as QtWidgets
import PyQt5.QtCore as QtCore


class Worker(QtCore.QObject):
    finished = QtCore.pyqtSignal()
    progress = QtCore.pyqtSignal(str, int, int)

    def __init__(self, url, save_path, fname):
        super(Worker, self).__init__()
        self.url = url
        self.save_path = save_path
        self.fname = fname
        self.perc_dl = 0

        self.download_video()

    def run(self):
        if self.perc_dl < 100:
            self.progress.emit('Downloading: {}%'.format(str(self.perc_dl)), int(self.perc_dl), 100)
            print(self.perc_dl)

        else:
            self.progress.emit('Done!', 100, 100)
            self.finished.emit()

    def download_video(self):
        yt = pytube.YouTube(self.url, on_progress_callback=self.progress_function)
        stream = yt.streams.filter(progressive=True, file_extension='mp4').get_highest_resolution()
        stream.download(output_path=self.save_path, filename=self.fname)

    def progress_function(self, stream, chunk, bytes_remaining):
        curr = stream.filesize - bytes_remaining
        per_downloaded = round((curr / stream.filesize) * 100, 1)
        self.perc_dl = per_downloaded
        self.run()


class DownloadFromYT(QtWidgets.QDialog):
    def __init__(self, url, save_path, fname):
        super(DownloadFromYT, self).__init__()
        self.url = url
        self.save_path = save_path
        self.fname = fname

        self.vLayoutMaster = QtWidgets.QVBoxLayout()
        self.hLayout = QtWidgets.QHBoxLayout()
        self.hLayout.setAlignment(QtCore.Qt.AlignRight)

        self.label = QtWidgets.QLabel()
        self.label.setText('Downloading video')

        self.pBar = QtWidgets.QProgressBar()
        self.pBar.setInvertedAppearance(True)
        self.pBar.setTextVisible(True)
        self.pBar.setFixedWidth(200)
        self.pBar.setAlignment(QtCore.Qt.AlignCenter)
        self.pBar.setMaximum(100)
        self.pBar.setFormat('Downloading: ')

        self.noButton = QtWidgets.QPushButton('No')
        self.noButton.setFixedWidth(50)
        self.noButton.hide()
        self.yesButton = QtWidgets.QPushButton('Yes')
        self.yesButton.setFixedWidth(50)
        self.yesButton.hide()

        self.vLayoutMaster.addWidget(self.label)
        self.vLayoutMaster.addSpacing(10)
        self.vLayoutMaster.addWidget(self.pBar)
        self.vLayoutMaster.addSpacing(20)
        self.hLayout.addWidget(self.noButton)
        self.hLayout.addWidget(self.yesButton)
        self.vLayoutMaster.addLayout(self.hLayout)

        # Signals / slots
        self.noButton.clicked.connect(self.reject)
        self.yesButton.clicked.connect(self.accept)

        # Widget
        self.setLayout(self.vLayoutMaster)
        self.setWindowTitle('Downloading')
        self.setFixedSize(250, 100)
        self.show()

        # Init download
        self.run_thread(url, save_path, fname)

    def run_thread(self, url, save_path, fname):
        self.thrd = QtCore.QThread()
        self.worker = Worker(url, save_path, fname)
        self.worker.moveToThread(self.thrd)

        self.thrd.start()
        self.thrd.started.connect(self.worker.run)
        self.worker.finished.connect(self.thrd.quit)
        self.worker.finished.connect(self.worker.deleteLater)
        self.worker.progress.connect(self.show_progress)
        self.thrd.finished.connect(self.thrd.deleteLater)

    def show_progress(self, label, n, total):
        self.pBar.setFormat(label)
        self.pBar.setMaximum(total)
        self.pBar.setValue(n)
        QtCore.QCoreApplication.processEvents()

        if label == 'Done!':
            self.thrd.quit()
            self.noButton.show()
            self.yesButton.show()
            self.label.setText('Video has been downloaded. Would you like to set the chosen\n'
                               'file path as the "Local file" path?')

我在我的應用程式的其他部分使用了這個基本結構來顯示和更新進度條，沒有問題，但是由于某種原因，當信號從類發出self.pBar時拒絕更新。如您所見，我在方法中有一個陳述句來檢查代碼是否實際進入該塊并定期將下載進度列印到控制臺，它就是這樣。應用程式在執行緒完成運行時更新，所以我得到了最終的、完全填充的進度條，但在開始和結束之間，進度條沒有按預期更新。progressWorkerprint()runif

任何幫助將不勝感激！

uj5u.com熱心網友回復：

問題似乎是，盡管您努力正確連接所有執行緒作業者組件，但您仍然self.download_video()在主（UI）執行緒中運行。因此它阻止了 UI 的重繪 。如果要在輔助執行緒中運行，則必須在Worker.run()函式中而不是在Worker建構式中啟動它。如果您正確連接了所有執行緒，那么您根本不需要呼叫processEvents()來重繪 UI。

如果您不確定運行下載函式的執行緒，請在列印函式中列印執行緒 ID，并將其與主 UI 執行緒的執行緒 ID 進行比較。看看https://doc.qt.io/qt-5/qthread.html#currentThread

標籤：Python qt pyqt pyqt5 pytube

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