如何更改未选中元素的样式？

Question

我正在尝试使用 PyQt5 构建文件夹查看器，但遇到了问题。 为了标记选定的文件或目录，我创建了一个 eventFilter，它设置了 QLabel 元素的“选定”属性并对其应用了一些样式。 问题是，当我将 'selected' 设置为 True - 文件/文件夹被选中（应用到它的样式），但是当我尝试将 'selected' 设置为 None of previous selected element 时，它正在工作（属性更改），但是样式不会应用于它（它不是取消选择，不会返回到未选择状态）。 这是我的代码片段：

import sys
import os

from PyQt5.QtWidgets import (QApplication, QShortcut, QLabel, QPushButton,
                         QGridLayout, QWidget, QMainWindow, QLineEdit,
                         QVBoxLayout, QShortcut, QAction, QMessageBox,
                         QHBoxLayout, QComboBox, QCheckBox, QScrollArea)
from PyQt5.QtGui import QIntValidator, QIcon
from PyQt5.QtCore import Qt, QObject, QEvent, QSize


class MyWindow(QMainWindow):

    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)
        self.setGeometry(600, 300, 700, 500)
        self.setWindowTitle('Folder imitator')
        self.homeDirectory = os.path.splitdrive(os.getcwd())[0]+os.path.sep
        self.currentDirectory = self.homeDirectory
        self.setStyleSheet(open('style.css').read())
        self.selected = None
        self.initUI()

    def initUI(self):
        cenWidget = QWidget(self)
        mainVertLayout = QVBoxLayout(cenWidget)

        scroll = QScrollArea()
        scroll.setWidgetResizable(True)
        viewWidg = QWidget()
        viewVertLayout = QVBoxLayout(viewWidg)
        viewVertLayout.installEventFilter(self)
        viewVertLayout.setAlignment(Qt.AlignTop)
        viewVertLayout.setSpacing(0)
        viewVertLayout.setContentsMargins(3, 3, 3, 3)

        self.files = [QLabel(filename) for filename in self.getDirList()]
        for f in self.files:
            f.installEventFilter(self)
            viewVertLayout.addWidget(f)

        scroll.setWidget(viewWidg)

        mainVertLayout.addWidget(scroll)
        mainVertLayout.setContentsMargins(0, 0, 0, 0)
        mainVertLayout.setSpacing(0)
        mainVertLayout.setAlignment(Qt.AlignLeft)

        self.setCentralWidget(cenWidget)

    def getDirList(self):
        return sorted(os.listdir(self.currentDirectory), 
            key=lambda x : 1 if os.path.isdir(os.path.join(
            self.currentDirectory, x)) and not x.endswith('.BIN') else 2)

    def eventFilter(self, obj, event):
        if event.type() == QEvent.MouseButtonPress:
            # I am interested in this part
            if event.button() == Qt.LeftButton:
                if self.selected and self.files[self.selected] != obj:
                    self.files[self.selected].setProperty('selected', None)
                if obj.property('selected') == None:
                    obj.setProperty('selected', True)
                    self.selected = self.files.index(obj)
                else:
                    obj.setProperty('selected', None)
                    self.selected = None
                obj.setStyleSheet('')

        return QObject.event(obj, event)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MyWindow()
    window.show()
    app.exec_()

这里是 style.css 文件：

QLabel {
    color: black;
    font-size: 12px;
    background-color: none;
}

QLabel[selected=true] {
    color: #fff;
    background-color: blue;
}

未再次单击它所选择的同一文件，似乎正在运行正常，但其他文件不是未选择的自动性，何时选择另一个文件，为什么这是如何解决这个问题？ 提前谢谢你。

Answer 1

你必须调用小部件QStyle的unpolish()和polish()方法：

    def eventFilter(self, obj, event):
        if event.type() == QEvent.MouseButtonPress and obj in self.files:
            if event.button() == Qt.LeftButton:
                if self.selected is None:
                    obj.setProperty("selected", True)
                    self.update_style(obj)
                    self.selected = obj
                elif self.selected is obj:
                    last_state = obj.property("selected")
                    obj.setProperty("selected", None if last_state else True)
                    self.update_style(obj)
                    self.selected = None
                else:
                    self.selected.setProperty("selected", None)
                    obj.setProperty("selected", True)
                    self.update_style(obj)
                    self.update_style(self.selected)
                    self.selected = obj
        return super(MyWindow, self).eventFilter(obj, event)

    @staticmethod
    def update_style(obj):
        obj.style().unpolish(obj)
        obj.style().polish(obj)