#!/usr/bin/env python################################################################################# Copyright (C) 2013 Riverbank Computing Limited.## Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).## All rights reserved.#### This file is part of the examples of PyQt.#### $QT_BEGIN_LICENSE:BSD$## You may use this file under the terms of the BSD license as follows:#### "Redistribution and use in source and binary forms, with or without## modification, are permitted provided that the following conditions are## met:##   * Redistributions of source code must retain the above copyright##     notice, this list of conditions and the following disclaimer.##   * Redistributions in binary form must reproduce the above copyright##     notice, this list of conditions and the following disclaimer in##     the documentation and/or other materials provided with the##     distribution.##   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor##     the names of its contributors may be used to endorse or promote##     products derived from this software without specific prior written##     permission.#### THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS## "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT## LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR## A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT## OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,## SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT## LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,## DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY## THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."## $QT_END_LICENSE$###############################################################################from PyQt5.QtCore import Qtfrom PyQt5.QtWidgets import (QApplication, QCheckBox, QDialog,        QDialogButtonBox, QGridLayout, QHBoxLayout, QLabel, QLayout, QLineEdit,        QPushButton, QVBoxLayout, QWidget)class FindDialog(QDialog):    def __init__(self, parent=None):        super(FindDialog, self).__init__(parent)        label = QLabel("Find &what:")        lineEdit = QLineEdit()        label.setBuddy(lineEdit)        caseCheckBox = QCheckBox("Match &case")        fromStartCheckBox = QCheckBox("Search from &start")        fromStartCheckBox.setChecked(True)        findButton = QPushButton("&Find")        findButton.setDefault(True)        moreButton = QPushButton("&More")        moreButton.setCheckable(True)        moreButton.setAutoDefault(False)        extension = QWidget()        wholeWordsCheckBox = QCheckBox("&Whole words")        backwardCheckBox = QCheckBox("Search &backward")        searchSelectionCheckBox = QCheckBox("Search se&lection")        buttonBox = QDialogButtonBox(Qt.Vertical)        buttonBox.addButton(findButton, QDialogButtonBox.ActionRole)        buttonBox.addButton(moreButton, QDialogButtonBox.ActionRole)        moreButton.toggled.connect(extension.setVisible)        extensionLayout = QVBoxLayout()        extensionLayout.setContentsMargins(0, 0, 0, 0)        extensionLayout.addWidget(wholeWordsCheckBox)        extensionLayout.addWidget(backwardCheckBox)        extensionLayout.addWidget(searchSelectionCheckBox)        extension.setLayout(extensionLayout)        topLeftLayout = QHBoxLayout()        topLeftLayout.addWidget(label)        topLeftLayout.addWidget(lineEdit)        leftLayout = QVBoxLayout()        leftLayout.addLayout(topLeftLayout)        leftLayout.addWidget(caseCheckBox)        leftLayout.addWidget(fromStartCheckBox)        mainLayout = QGridLayout()        #关键性的参数设置        mainLayout.setSizeConstraint(QLayout.SetFixedSize)                mainLayout.addLayout(leftLayout, 0, 0)        mainLayout.addWidget(buttonBox, 0, 1)        mainLayout.addWidget(extension, 1, 0, 1, 2)        mainLayout.setRowStretch(2, 1)        self.setLayout(mainLayout)        self.setWindowTitle("Extension")        extension.hide()if __name__ == '__main__':    import sys    app = QApplication(sys.argv)    dialog = FindDialog()    dialog.show()    sys.exit(app.exec_())