python3+PyQt5 自定义窗口部件--使用窗口部件样式表

本文借用HTML的css语法，将样式表应用到窗口部件。这里只是个简单的例子，实际上样式表的语法很丰富。
以下类似于css：

    StyleSheet = """
QComboBox { color: darkblue; }
QLineEdit { color: darkgreen; }
QLineEdit[mandatory="true"] { #mandatory="true"时，QLineEdit的样式会变化
 background-color: rgb(255, 255, 127);
 color: darkblue;
}

如果在选择器的前面加上一个句点，比如.QLineEdit，则选择器就会只应用于指定的类，而不会应用于这个类的子类。如果要求选择器仅用于某一特定窗口部件，则可以对该窗口部件调用setObjectName(),然后用该名字作为选择器的一部分。比如，如果有一个按钮，其对象名字是“findButton”，则应用于这个按钮的选择器就应该是QpushButton#findButton。有些窗口部件会有一些子控件。例如QComboBox会有一个箭头子控件，用户通过点击这个箭头来看到下拉列表。子控件可以指定为选择器的一部分–例如，QComboBox::drop-down。伪状态可以用一个冒号指定–例如，QCheckBox::checked.

#!/usr/bin/env python3

import sys
from PyQt5.QtWidgets import (QApplication, QComboBox, QDialog,
QDialogButtonBox, QGridLayout, QLabel, QLineEdit, QVBoxLayout)


class ContactDlg(QDialog):

StyleSheet = """
QComboBox { color: darkblue; }
QLineEdit { color: darkgreen; }
QLineEdit[mandatory="true"] {
 background-color: rgb(255, 255, 127);
 color: darkblue;
}
"""

def __init__(self, parent=None):
super(ContactDlg, self).__init__(parent)

        forenameLabel = QLabel("&Forename:")
self.forenameEdit = QLineEdit()
        forenameLabel.setBuddy(self.forenameEdit)
        surnameLabel = QLabel("&Surname:")
self.surnameEdit = QLineEdit()
        surnameLabel.setBuddy(self.surnameEdit)
        categoryLabel = QLabel("&Category:")
self.categoryComboBox = QComboBox()
        categoryLabel.setBuddy(self.categoryComboBox)
self.categoryComboBox.addItems(["Business", "Domestic",
"Personal"])
        companyLabel = QLabel("C&ompany:")
self.companyEdit = QLineEdit()
        companyLabel.setBuddy(self.companyEdit)
        addressLabel = QLabel("A&ddress:")
self.addressEdit = QLineEdit()
        addressLabel.setBuddy(self.addressEdit)
        phoneLabel = QLabel("&Phone:")
self.phoneEdit = QLineEdit()
        phoneLabel.setBuddy(self.phoneEdit)
        mobileLabel = QLabel("&Mobile:")
self.mobileEdit = QLineEdit()
        mobileLabel.setBuddy(self.mobileEdit)
        faxLabel = QLabel("Fa&x:")
self.faxEdit = QLineEdit()
        faxLabel.setBuddy(self.faxEdit)
        emailLabel = QLabel("&Email:")
self.emailEdit = QLineEdit()
        emailLabel.setBuddy(self.emailEdit)
self.buttonBox = QDialogButtonBox(QDialogButtonBox.Ok|
QDialogButtonBox.Cancel)
        addButton = self.buttonBox.button(QDialogButtonBox.Ok)
        addButton.setText("&Add")
        addButton.setEnabled(False)

        grid = QGridLayout()
        grid.addWidget(forenameLabel, 0, 0)
        grid.addWidget(self.forenameEdit, 0, 1)
        grid.addWidget(surnameLabel, 0, 2)
        grid.addWidget(self.surnameEdit, 0, 3)
        grid.addWidget(categoryLabel, 1, 0)
        grid.addWidget(self.categoryComboBox, 1, 1)
        grid.addWidget(companyLabel, 1, 2)
        grid.addWidget(self.companyEdit, 1, 3)
        grid.addWidget(addressLabel, 2, 0)
        grid.addWidget(self.addressEdit, 2, 1, 1, 3)
        grid.addWidget(phoneLabel, 3, 0)
        grid.addWidget(self.phoneEdit, 3, 1)
        grid.addWidget(mobileLabel, 3, 2)
        grid.addWidget(self.mobileEdit, 3, 3)
        grid.addWidget(faxLabel, 4, 0)
        grid.addWidget(self.faxEdit, 4, 1)
        grid.addWidget(emailLabel, 4, 2)
        grid.addWidget(self.emailEdit, 4, 3)
        layout = QVBoxLayout()
        layout.addLayout(grid)
        layout.addWidget(self.buttonBox)
self.setLayout(layout)

self.lineedits = (self.forenameEdit, self.surnameEdit,
self.companyEdit, self.phoneEdit, self.emailEdit)
for lineEdit in self.lineedits:
            lineEdit.setProperty("mandatory", True)
            lineEdit.textEdited.connect(self.updateUi)
self.categoryComboBox.activated.connect(self.updateUi)

self.buttonBox.accepted.connect(self.accept)
self.buttonBox.rejected.connect(self.reject)
self.setStyleSheet(ContactDlg.StyleSheet)
self.setWindowTitle("Add Contact")


def updateUi(self):
        mandatory = bool(self.companyEdit.property("mandatory"))
if self.categoryComboBox.currentText() == "Business":
if not mandatory:
self.companyEdit.setProperty("mandatory", True)
        elif mandatory:
self.companyEdit.setProperty("mandatory", False)
if (mandatory !=
            bool(self.companyEdit.property("mandatory"))):
self.setStyleSheet(ContactDlg.StyleSheet)

        enable = True
for lineEdit in self.lineedits:
if (bool(lineEdit.property("mandatory")) and
not lineEdit.text()):
                enable = False
break
self.buttonBox.button(QDialogButtonBox.Ok).setEnabled(enable)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    form = ContactDlg()
    form.show()
    app.exec_()

运行结果：