无法从 QWidget 更改 QSlider 的值

Posted 2023-03-30

【中文标题】无法从 QWidget 更改 QSlider 的值

【英文标题】：Cannot change value of a QSlider from a QWidget

【发布时间】：2017-05-21 22:51:31

【问题描述】：

我正在尝试从另一个 QWidget 更改 QWidget 的值，但没有任何反应。我正在使用这一行从每个 Filter 对象中调用 changeValue 函数：

self.filter1.valueChanged.connect(self.filter1.changeValue)

我已经把print(value)语句放在changeValue方法里面，看看这个方法有没有被调用，其实没有。

这是我的代码：

import sys
import numpy as np
import cv2
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap, QImage
from PyQt5.QtWidgets import (QWidget, QLabel, QHBoxLayout, QVBoxLayout,
                             QApplication, QPushButton, QSlider,
                             QFileDialog)


class Filter(QSlider):
    """Common base for all filters"""
    defaultK = 3
    filterCount = 0

    def __init__(self):
        super(Filter, self).__init__()

        # Variable for the constant of the OpenCV filter
        self.k = 3

        # Label for the slider
        self.k_lbl = QLabel(str(self.k))

        # Increase the number of filters created
        Filter.filterCount += 1

        # Slider for the first OpenCV filter, with min, max, default and step values
        self.thresh_sld = QSlider(Qt.Horizontal, self)
        self.thresh_sld.setFocusPolicy(Qt.NoFocus)
        self.thresh_sld.setMinimum(3)
        self.thresh_sld.setMaximum(51)
        self.thresh_sld.setValue(self.k)
        self.thresh_sld.setSingleStep(2)

    def changeValue(self, value):
        # Function for setting the value of k1

        print(value)

        if value % 2 == 1:
            self.k = value
        else:
            self.k = value + 1

        self.thresh_sld.setValue(self.k)
        self.k_lbl.setText(str(self.k))

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

        self.filter1 = Filter()
        self.filter2 = Filter()

        # Function sending the slider signal to the processing function
        self.filter1.valueChanged.connect(self.filter1.changeValue)
        self.filter2.valueChanged.connect(self.filter2.changeValue)

        # Creates the main layout (vertical)
        v_main_lay = QVBoxLayout()
        # Adds the sliders and their labels to the bottom of the main layout
        v_main_lay.addWidget(self.filter1.k_lbl)
        v_main_lay.addWidget(self.filter1.thresh_sld)
        v_main_lay.addWidget(self.filter2.k_lbl)
        v_main_lay.addWidget(self.filter2.thresh_sld)

        # Sets the main layout
        self.setLayout(v_main_lay)

        # Sets the geometry, position, window title and window default mode
        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('Review')
        self.showMaximized()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    sys.exit(app.exec_())

【参考方案1】：

问题是您从QSlider 继承，同时在该类中创建了一个名为 thresh_sld 的属性，这是视图中显示的元素，但未连接到changeValue，连接到ChangeValue 的滑块是Filter 类Slider。

使用简单的解决方案是将属性thresh_sld的信号连接到提供的插槽，您必须更改以下内容：

self.filter1.valueChanged.connect(self.filter1.changeValue)
self.filter2.valueChanged.connect(self.filter2.changeValue)

到：

self.filter1.thresh_sld.valueChanged.connect(self.filter1.changeValue)
self.filter2.thresh_sld.valueChanged.connect(self.filter2.changeValue)

更优雅的解决方案是将 Filter 基类从 QSlider 更改为 QWidget，并将标签和 QSlider 添加到其布局中。

class Filter(QWidget):
    """Common base for all filters"""
    defaultK = 3
    filterCount = 0

    def __init__(self):
        super(Filter, self).__init__()
        lay = QVBoxLayout(self)

        # Variable for the constant of the OpenCV filter
        self.k = 3

        # Label for the slider
        self.k_lbl = QLabel(str(self.k))

        # Increase the number of filters created
        Filter.filterCount += 1

        # Slider for the first OpenCV filter, with min, max, default and step values
        self.thresh_sld = QSlider(Qt.Horizontal, self)
        self.thresh_sld.setFocusPolicy(Qt.NoFocus)
        self.thresh_sld.setMinimum(3)
        self.thresh_sld.setMaximum(51)
        self.thresh_sld.setValue(self.k)
        self.thresh_sld.setSingleStep(2)
        self.thresh_sld.valueChanged.connect(self.changeValue)

        lay.addWidget(self.k_lbl)
        lay.addWidget(self.thresh_sld)

    def changeValue(self, value):
        # Function for setting the value of k1

        print(value)

        if value % 2 == 1:
            self.k = value
        else:
            self.k = value + 1

        self.thresh_sld.setValue(self.k)
        self.k_lbl.setText(str(self.k))

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

        self.filter1 = Filter()
        self.filter2 = Filter()

        # Creates the main layout (vertical)
        v_main_lay = QVBoxLayout()
        # Adds the sliders and their labels to the bottom of the main layout
        v_main_lay.addWidget(self.filter1)
        v_main_lay.addWidget(self.filter2)

        # Sets the main layout
        self.setLayout(v_main_lay)

        # Sets the geometry, position, window title and window default mode
        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('Review')
        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    sys.exit(app.exec_())

【讨论】：

非常感谢！这确实是问题所在。感谢您提供有关布局组织的提示，它变得更好了。