在函数执行期间在 PyQt5 中显示闪屏

Question

我有一个程序，可以使用 PyQt5 显示 GUI。从我的 MainWindow 中，我打开一个 QWidget，从中启动一个函数。当此函数运行时，应该会出现 SplashScreen。该函数完成后，SplashScreen 应再次关闭。我尝试从函数内启动 SplashScreen 。但是，SplashScreen 不会出现。

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 表示该函数（在原始程序中进行了一些耗时的数据处理）。当我省略 close-function 时，“SplashScreen”会在 time.sleep 完成后打开。

Answer 1

time.sleep 将阻止事件循环，因此任何与 GUI 相关的操作都将暂停，直到完成为止。因此，您需要使用 processEvents 显式强制处理任何待处理事件：

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()

或者将耗时的任务移至工作线程，然后使用信号来更新 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()

通常建议使用后一种方法，但如果任务无法分解为离散的步骤，则可能需要使用 多处理 代替。