PyQt5 無法重繪 QLabel 的文本

Question

我正在嘗試更新 QLabel 以反映日志更改，但它不會重新繪制。 我嘗試了多種方法都沒有成功，代碼中仍然列出了一些。 log_text Label 的值發生變化，它被打印到終端，但從不打印到 GUI。 （灰色區域綁定function改文字）

import sys
from PyQt5 import QtGui, QtCore, QtWidgets
from PyQt5.QtGui import QPainter
from PyQt5.QtCore import QSize
from PyQt5.QtWidgets import (QApplication, QMainWindow, QWidget, QHBoxLayout, QVBoxLayout, QDesktopWidget,
                             QLabel, QAbstractButton, QStackedWidget, QFrame, QTableWidget,)

class MainWindow(QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()

        self.center()

        self.setGeometry(500, 200, 1400, 800)

        layout1 = QHBoxLayout()
        layout2 = QVBoxLayout()
        layout3 = QVBoxLayout()
        layouts = QHBoxLayout()

        layout1.setSpacing(0)
        layout2.setSpacing(0)
        layout3.setSpacing(0)
        layouts.setSpacing(0)

        layout1.setContentsMargins(0, 0, 0, 0)
        layout2.setContentsMargins(0, 0, 0, 0)
        layout3.setContentsMargins(0, 0, 0, 0)
        layouts.setContentsMargins(0, 0, 0, 0)
        self.setContentsMargins(0, 0, 0, 0)

        widget = QWidget()
        widget.setLayout(layout1)
        self.setCentralWidget(widget)

        self.setWindowFlags(QtCore.Qt.FramelessWindowHint)

        self.frameR = QFrame()
        self.frameR.setFrameShape(QFrame.StyledPanel)
        self.frameR.setStyleSheet("background-color: rgb(27, 29, 35); border: 0px solid black")
        self.frameR.setFixedWidth(71)
        self.frameR.setFixedHeight(71)
        layout2.addWidget(self.frameR)

        resize_layout = QVBoxLayout()
        self.frameR.setLayout(resize_layout)

        button5 = PicButtonF(QtGui.QPixmap("validationN.png"), QtGui.QPixmap("validationH.png"),
                             QtGui.QPixmap("validationC.png"))
        button5.clicked.connect(self.widget4)
        layout2.addWidget(button5)

        spacer_m = QFrame()
        spacer_m.setFrameShape(QFrame.StyledPanel)
        spacer_m.setStyleSheet("background-color: rgb(27, 29, 35); border: 0px solid black")
        spacer_m.setFixedWidth(71)
        layout2.addWidget(spacer_m)

        layout1.addLayout(layout2)

        label_title = QLabel("  PG - Programme De Gestion")
        label_title.setStyleSheet('background-color: rgb(37, 39, 44); color: white')
        layouts.addWidget(label_title)

        spacer_m = QFrame()
        spacer_m.setFrameShape(QFrame.StyledPanel)
        spacer_m.setStyleSheet("background-color: rgb(37, 39, 44); border: 0px solid black")
        spacer_m.setFixedHeight(45)
        layouts.addWidget(spacer_m)

        top3 = PicButtonF(QtGui.QPixmap("closeN.png"), QtGui.QPixmap("closeH.png"),
                          QtGui.QPixmap("closeH.png"))
        top3.clicked.connect(self.closeapp)
        top3.setFixedWidth(45)
        top3.setFixedHeight(45)
        layouts.addWidget(top3)

        layout3.addLayout(layouts)

        self.frameS = QFrame()
        self.frameS.setFrameShape(QFrame.StyledPanel)
        self.frameS.setStyleSheet("background-color: rgb(38, 41, 50); border: 0px solid black")
        self.frameS.setFixedHeight(24)
        layout3.addWidget(self.frameS)

        self.layoutS = QHBoxLayout()
        self.layoutS.setSpacing(0)
        self.layoutS.setContentsMargins(5, 5, 5, 5)
        self.frameS.setLayout(self.layoutS)

        self.log_text = QtWidgets.QLabel('Text That Must Change')
        self.log_text.setStyleSheet('color: white')
        self.layoutS.addWidget(self.log_text)

        self.stackedWidget = QStackedWidget()
        self.stackedWidget.addWidget(Validation())

        self.frameC = QFrame()
        self.layoutC = QHBoxLayout()
        self.frameC.setLayout(self.layoutC)
        self.layoutC.setSpacing(0)
        self.layoutC.setContentsMargins(0, 0, 0, 0)
        self.layoutC.addWidget(self.stackedWidget)
        layout3.addWidget(self.frameC)

        frame5 = QFrame()
        frame5.setFrameShape(QFrame.StyledPanel)
        frame5.setStyleSheet("background-color: rgb(37, 39, 44); border: 0px solid black")
        frame5.setFixedHeight(25)
        layout3.addWidget(frame5)

        credit_layout = QHBoxLayout()
        frame5.setLayout(credit_layout)

        layout1.addLayout(layout3)

        self.oldPos = self.pos()

    def logging(self, text):
        print(str('Testing - Text Passed Through Function: ') + str(text))
        print(str('Testing - Text Currently Before Function: ') + str(self.log_text.text()))
        self.log_text.setText(str('New Text From Logging Function'))
        self.log_text.hide()
        self.log_text.show()
        self.log_text.repaint()
        self.log_text.update()
        QtWidgets.qApp.processEvents()
        print(str('Testing - Text Set After Function: ') + str(self.log_text.text()))

    def widget4(self):
        self.stackedWidget.setCurrentIndex(4)

    def center(self):
        qr = self.frameGeometry()
        cp = QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())

    def closeapp(self):
            self.close()

class Validation(QWidget):
    def __init__(self):
        super().__init__()

        self.header = ['CLIENT', 'TYPE']

        header_count = len(self.header)

        self.tableWidget = QTableWidget()
        self.tableWidget.setColumnCount(header_count)
        self.tableWidget.setRowCount(40)
        self.tableWidget.setHorizontalHeaderLabels(self.header)

        layout_tw = QVBoxLayout()
        layout_th = QHBoxLayout()

        frame1 = QFrame()
        frame1.setFrameShape(QFrame.StyledPanel)
        frame1.setStyleSheet("background-color: rgb(144, 149, 160); border: 0px solid black")
        frame1.setFixedHeight(50)
        frame1.setFixedWidth(122)

        frame1l = QHBoxLayout()
        frame1l.setSpacing(0)
        frame1l.setContentsMargins(5, 5, 5, 5)
        frame1.setLayout(frame1l)

        frame1b = PicButtonF(QtGui.QPixmap("query_all.png"), QtGui.QPixmap("query_all.png"),
                             QtGui.QPixmap("query_all.png"))
        frame1b.clicked.connect(self.validation_query)
        frame1l.addWidget(frame1b)

        frame_fill = QFrame()
        frame_fill.setFrameShape(QFrame.StyledPanel)
        frame_fill.setStyleSheet("background-color: rgb(44, 49, 60); border: 0px solid black")
        frame_fill.setFixedHeight(50)

        layout_th.addWidget(frame1)
        layout_th.addWidget(frame_fill)
        layout_tw.addLayout(layout_th)
        layout_tw.addWidget(self.tableWidget)

        layout_tw.setSpacing(0)
        layout_tw.setContentsMargins(0, 0, 0, 0)

        self.setLayout(layout_tw)

    def validation_query(self):
        MainWindow().logging('New Text From The Query Function')

class PicButtonF(QAbstractButton):
    def __init__(self, pixmap, pixmap_hover, pixmap_pressed, parent=None):
        super(PicButtonF, self).__init__(parent)
        self.pixmap = pixmap
        self.pixmap_hover = pixmap_hover
        self.pixmap_pressed = pixmap_pressed

    def paintEvent(self, event):
        pix = self.pixmap_hover if self.underMouse() else self.pixmap
        if self.isDown():
            pix = self.pixmap_pressed

        painter = QPainter(self)
        painter.drawPixmap(event.rect(), pix)

    def enterEvent(self, event):
        self.update()

    def leaveEvent(self, event):
        self.update()

    def sizeHint(self):
        return QSize(71, 71)

class PicButton(QAbstractButton):
    def __init__(self, pixmap, parent=None):
        super(PicButton, self).__init__(parent)
        self.pixmap = pixmap

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(event.rect(), self.pixmap)

    def sizeHint(self):
        return self.pixmap.size()

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

if __name__ == '__main__':
    main()

Answer 1

您不會更改現有 window 的 label，而是每次都創建一個新的 window：

    def validation_query(self):
        MainWindow().logging('New Text From The Query Function')

該行創建一個MainWindow的新實例並調用該實例的logging function，然后立即刪除新實例（收集垃圾），因為沒有創建對它的引用。 即使創建了引用（本地或作為實例屬性），這顯然不是正確的方法。

要正確更改現有window 的 label，您應該使用自定義信號並將其連接到validation_query function。 為此，您也不能只將小部件添加到堆疊布局中，因為您需要參考來連接新信號。

class MainWindow(QMainWindow):
    def __init__(self):
        # ...
        validator = Validation()
        self.stackedWidget.addWidget(validator)
        validator.validateResult.connect(self.logging)
        # ...
 
class Validation(QWidget):
    validateResult = QtCore.pyqtSignal(str)
    # ...
    def validation_query(self):
        self.validateResult.emit('New Text From The Query Function')

我建議您閱讀有關類和實例的更多信息。