在函数执行期间在 PyQt5 中显示启动画面

Question

我有一个程序，我用 PyQt5 显示 GUI。从我的 MainWindow 我打开一个 QWidget 从中启动一个功能。虽然此函数是运行，但应该会出现 SplashScreen。一旦函数完成，SplashScreen 应该再次关闭。我试图从函数内部启动 SplashScreen 。但是，SplashScreen 没有出现。

我使用了以下代码：

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QDialog, QProgressBar, QLabel, QFrame, QMainWindow, QVBoxLayout, QPushButton
from PyQt5.QtCore import Qt
import time

class Function:
    def loading(self):
        self.screen = SplashScreen()
        self.screen.show()
        time.sleep(10)
        self.screen.close()

class SplashScreen(QDialog):
    def __init__(self):
        super().__init__()
        self.setWindowTitle('Spash Screen Example')
        self.setFixedSize(1100, 500)
        self.setWindowFlag(Qt.FramelessWindowHint)
        self.setAttribute(Qt.WA_TranslucentBackground)
        self.setWindowFlag(Qt.WindowStaysOnTopHint)
        self.initUI()

    def initUI(self):
        layout = QVBoxLayout()
        self.setLayout(layout)

        self.frame = QFrame()
        layout.addWidget(self.frame)

        self.labelTitle = QLabel(self.frame)
        self.labelTitle.setObjectName('LabelTitle')

        # center labels
        self.labelTitle.resize(self.width() - 10, 150)
        self.labelTitle.move(0, 40)  # x, y
        self.labelTitle.setText('Splash Screen')
        self.labelTitle.setAlignment(Qt.AlignCenter)

        self.labelDescription = QLabel(self.frame)
        self.labelDescription.resize(self.width() - 10, 50)
        self.labelDescription.move(0, self.labelTitle.height())
        self.labelDescription.setObjectName('LabelDesc')
        self.labelDescription.setText('<strong>Working on Task #1</strong>')
        self.labelDescription.setAlignment(Qt.AlignCenter)

        self.progressBar = QProgressBar(self.frame)
        self.progressBar.resize(self.width() - 200 - 10, 50)
        self.progressBar.move(100, self.labelDescription.y() + 130)
        self.progressBar.setAlignment(Qt.AlignCenter)
        self.progressBar.setFormat('%p%')
        self.progressBar.setTextVisible(True)
        self.progressBar.setRange(0, 100)
        self.progressBar.setValue(20)

        self.labelLoading = QLabel(self.frame)
        self.labelLoading.resize(self.width() - 10, 50)
        self.labelLoading.move(0, self.progressBar.y() + 70)
        self.labelLoading.setObjectName('LabelLoading')
        self.labelLoading.setAlignment(Qt.AlignCenter)
        self.labelLoading.setText('loading...')

        self.setStyleSheet('''
                        #LabelTitle {
                            font-size: 60px;
                            color: #93deed;
                        }

                        #LabelDesc {
                            font-size: 30px;
                            color: #c2ced1;
                        }

                        #LabelLoading {
                            font-size: 30px;
                            color: #e8e8eb;
                        }

                        QFrame {
                            background-color: #2F4454;
                            color: rgb(220, 220, 220);
                        }

                        QProgressBar {
                            background-color: #DA7B93;
                            color: rgb(200, 200, 200);
                            border-style: none;
                            border-radius: 10px;
                            text-align: center;
                            font-size: 30px;
                        }

                        QProgressBar::chunk {
                            border-radius: 10px;
                            background-color: qlineargradient(spread:pad x1:0, x2:1, y1:0.511364, y2:0.523, stop:0 #1C3334, stop:1 #376E6F);
                        }
                    ''')

class Window(QWidget):
    def __init__(self):
        super().__init__()
        layout_window = QVBoxLayout()
        self.setLayout(layout_window)
        self.button = QPushButton("Open", self)
        layout_window.addWidget(self.button)
        self.button.clicked.connect(self.open)

    def open(self):
        self.function = Function()
        self.function.loading()


class MyApp(QMainWindow):
    def __init__(self):
        super().__init__()
        self.window_width, self.window_height = 1200, 800
        self.setMinimumSize(self.window_width, self.window_height)

        layout = QVBoxLayout()
        self.setLayout(layout)
        self.button = QPushButton("Open", self)
        layout.addWidget(self.button)
        self.button.clicked.connect(self.open)

    def open(self):
        self.window = Window()
        self.window.show()



if __name__ == '__main__':
    app = QApplication(sys.argv)
    myapp = MyApp()
    myapp.show()

    try:
        sys.exit(app.exec_())
    except SystemExit:
        print('Closing Window...')

我用time.sleep表示了函数（在原始程序中发生了一些耗时的数据处理）。当我省略 close-function 时，'SplashScreen' 在 time.sleep 完成后打开。

Answer 1

time.sleep 将阻塞 event-loop，因此任何 GUI-related 操作都将被挂起，直到它完成。因此，您需要使用 processEvents:

显式强制处理任何未决事件

class Function:
    def loading(self):
        self.screen = SplashScreen()
        self.screen.show()
        for i in range(100):
            self.screen.progressBar.setValue(i)
            QApplication.processEvents()
            time.sleep(0.1)
        self.screen.close()

或者将time-consuming任务移动到工作线程，然后使用信号更新GUI：

from PyQt5.QtCore import pyqtSignal, QThread

class Thread(QThread):
    progressChanged = pyqtSignal(int)

    def run(self):
        for i in range(100):
            QThread.msleep(100)
            self.progressChanged.emit(i)

class Function:
    def loading(self):
        self.screen = SplashScreen()
        self.screen.show()
        self.thread = Thread()
        self.thread.progressChanged.connect(
            self.screen.progressBar.setValue)
        self.thread.finished.connect(self.screen.close)
        self.thread.start()

通常建议采用后一种方法，但如果无法将任务分解为离散的步骤，则可能需要改用 multiprocessing。

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