python - 当我希望在两个 setText 之间做某事时，pyqt5 QLineEdit.setText 仅在功能中工作一次

Question

import sys
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QWidget, QLabel, QLineEdit
from PyQt5.QtWidgets import QPushButton
from PyQt5.QtCore import QSize , QTimer
from PyQt5.QtGui import * 
from pytube import YouTube
import os
import time
class MainWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(600, 200))    
        self.setWindowTitle("下載影片程式") 

        self.nameLabel = QLabel(self)
        self.nameLabel.setText('網址:')
        self.line = QLineEdit(self)

        self.line.move(80, 20)
        self.line.resize(500, 32)
        self.nameLabel.move(20, 20)

        pybutton = QPushButton('下載', self)
#        pybutton.clicked.connect(self.clickMethod)
        pybutton.clicked.connect(self.Download)
#        pybutton.clicked.connect(self.Download1)
        pybutton.resize(200,32)
        pybutton.move(80, 60)        

        self.statusline = QLineEdit(self)
        self.statusline.move(80, 100)
        self.statusline.resize(200, 32)

#        self.statusline1 = QLineEdit(self)
#        self.statusline1.move(80, 140)
#        self.statusline1.resize(200, 32)
#        
    def clickMethod(self):
        print('')
    def Download(self):
        self.statusline.setText('開始下載')
        if not os.path.isdir('D:\\下載影片'):
            os.mkdir('D:\\下載影片')
        yt = YouTube(self.line.text())



        video=yt.streams.filter(file_extension='mp4').first()
        video.download(r'D:\\下載影片')
        QTimer.singleShot(1000, lambda: self.statusline.setText('下載完成'))

#    def Download1(self):
#        self.statusline.setText('下載完成')


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    sys.exit( app.exec_() )

我希望它在下载 YouTube 之前显示“开始”，然后显示“结束”。

但它总是只显示“finsh”。

为什么当我点击 QPushButton 时，QLineEdit 只显示“finsh”？

Answer 1

下载文件的任务可能需要很长时间，因此它会阻塞事件循环，导致 GUI 卡住，而卡住的影响是 GUI 无法正确更新。

考虑到上述情况，解决方案是在另一个线程上执行下载。

import functools
import os
import sys

from PyQt5.QtCore import pyqtSignal, pyqtSlot, QObject, QSize, QThread, QTimer
from PyQt5.QtWidgets import (
    QApplication,
    QFormLayout,
    QLabel,
    QLineEdit,
    QMainWindow,
    QPushButton,
    QSizePolicy,
    QWidget,
)

from pytube import YouTube


class DownloadWorker(QObject):
    started = pyqtSignal()
    finished = pyqtSignal()

    @pyqtSlot(str, str)
    def download(self, url, path):
        self.started.emit()
        if not os.path.isdir(path):
            os.mkdir(path)
        try:
            yt = YouTube(url)
            video = yt.streams.filter(file_extension="mp4").first()
            video.download(path)
        except Exception as e:
            print(e)

        self.finished.emit()


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)

        self.setMinimumSize(QSize(600, 200))
        self.setWindowTitle("Download Video Program")

        self.line = QLineEdit()
        self.pybutton = QPushButton("download")
        self.pybutton.setFixedSize(200, 32)
        self.statusline = QLineEdit()
        self.statusline.setFixedSize(200, 32)

        central_widget = QWidget()
        self.setCentralWidget(central_widget)

        lay = QFormLayout(central_widget)
        lay.addRow("URL:", self.line)
        lay.addRow("", self.pybutton)
        lay.addRow("", self.statusline)

        thread = QThread(self)
        thread.start()

        self.worker = DownloadWorker()
        self.worker.started.connect(self.on_started)
        self.worker.finished.connect(self.on_finished)
        self.worker.moveToThread(thread)

    def download(self):
        url = self.line.text()
        # TODO
        path = "/path/of/output.mp4"
        wrapper = functools.partial(self.worker.download, url, path)
        QTimer.singleShot(0, wrapper)

    @pyqtSlot()
    def on_started(self):
        self.statusline.setText("Started")
        self.pybutton.setEnabled(False)

    @pyqtSlot()
    def on_finished(self):
        self.statusline.setText("Finished")
        self.pybutton.setEnabled(True)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())