ComboBox 函数 currentIndexChanged 无法正常工作 [英] ComboBox function currentIndexChanged not working correctly

问题描述

我采用了两个组合框，即 comboBox1 和 comboBox_2 以及两个函数 test 和 test1 并使用 currentIndexChanged(self.comboBOx1.currentIndexChanged 和 self.comboBOx_2.currentIndexChanged)调用它们.当从 comboBox1 中选择一个值时，它的相应函数(self.comboBOx1.currentIndexChanged)被调用，对于 comboBox_2 也是如此.从 comboBox1 中选择值会更改 comboBox_2 中的值及其工作正常.但是我在这里遇到的问题是，首先当我从 comboBox1 和 comboBox_2 中选择一个值时，我从被调用的函数中获得了预期值(打印hello").第二次当我从 comboBox1 中选择一个值时，只应调用测试函数，但这里两个函数(test 和 test1)都被调用，第二个函数(test1)被调用两次(打印 'hello' 两次)和第三次时间被调用四次(打印你好"四次).请问有人能帮我解决这个问题吗?

I have taken two comboBoxes i.e., comboBox1 and comboBox_2 and two functions test and test1 and calling them using currentIndexChanged (self.comboBOx1.currentIndexChanged and self.comboBOx_2.currentIndexChanged). When a value is selected from comboBox1 its corresponding function(self.comboBOx1.currentIndexChanged) is called and same for comboBox_2. On selection of value from comboBox1 changes the values in comboBox_2 and its working fine. But the problem I have got here is that at first when I select a value from comboBox1 and comboBox_2 I'm getting the expected values from the called function(printing 'hello'). The second time when I select a value from comboBox1 only test function should be called but here both the functions(test and test1) are getting called and the second function (test1) is getting called twice(printing 'hello' twice) and for third time its getting called four times(printing 'hello' four times). Please can anyone help me with this problem.?

代码:

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(800, 600)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.comboBox1 = QtGui.QComboBox(self.centralwidget)
        self.comboBox1.setGeometry(QtCore.QRect(310, 150, 171, 31))
        self.comboBox1.setObjectName(_fromUtf8("comboBox1"))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox_2 = QtGui.QComboBox(self.centralwidget)
        self.comboBox_2.setGeometry(QtCore.QRect(310, 240, 171, 41))
        self.comboBox_2.setObjectName(_fromUtf8("comboBox_2"))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.comboBox1.setItemText(0, _translate("MainWindow", "select", None))
        self.comboBox1.setItemText(1, _translate("MainWindow", "a", None))
        self.comboBox1.setItemText(2, _translate("MainWindow", "b", None))
        self.comboBox1.setItemText(3, _translate("MainWindow", "c", None))
        self.comboBox_2.setItemText(0, _translate("MainWindow", "select", None))
        self.comboBox_2.setItemText(1, _translate("MainWindow", "p", None))
        self.comboBox_2.setItemText(2, _translate("MainWindow", "q", None))
        self.comboBox_2.setItemText(3, _translate("MainWindow", "r", None))
        self.comboBox_2.setEnabled(0)
        self.comboBox1.currentIndexChanged.connect(self.test)

    def test(self):
        s = str(self.comboBox1.currentText())
        res=['aa','bb','cc','dd']

        if (s == "- - select - -"):
            self.comboBox_2.setEnabled(0)
            self.comboBox_2.setCurrentIndex(0)
        elif(len(s)== 0):
            self.comboBox_2.setEnabled(1)
            self.comboBox_2.clear()
            self.comboBox_2.addItem("- - select - -")
            self.comboBox_2.addItem("New Checklist")
        else:
            self.comboBox_2.setEnabled(1)
            self.comboBox_2.clear()
            self.comboBox_2.addItem("- - select - -")
            self.comboBox_2.addItem("New Checklist")
            self.comboBox_2.addItems(res)
            self.comboBox_2.currentIndexChanged.connect(self.test1)

    def test1(self):
        print ("Hello")

if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

推荐答案

为了理解行为，我们将使用以下示例:

To understand the behavior we will use the following examples:

示例 1:

from PyQt4 import QtCore, QtGui


def on_clicked():
    print("clicked")


if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    button = QtGui.QPushButton("Press me")
    for _ in range(4):
        button.clicked.connect(on_clicked)
    button.show()
    sys.exit(app.exec_())

当你按下按钮时，它会打印 4 次，因为 Qt 不记得之前信号和函数之间是否已经存在连接，所以如果同一信号和函数之间有 n 个连接，它们将被调用 n 次，当发出信号.

When you press the button it prints 4 times because Qt does not remember if there was already a connection between signal and a function previously, so if there are n connections between the same signal and function they will be invoked n times when the signal is emitted.

示例 2:

from PyQt4 import QtCore, QtGui


def on_currentIndexChanged(ix):
    print("currentIndex:", ix)


if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    combo = QtGui.QComboBox()
    print("currentIndex:", combo.currentIndex())
    combo.currentIndexChanged.connect(on_currentIndexChanged)
    button_add = QtGui.QPushButton("Add Items")
    button_add.clicked.connect(lambda: combo.addItems("1 2 3".split()))
    button_clear = QtGui.QPushButton("Clear")
    button_clear.clicked.connect(combo.clear)
    w = QtGui.QWidget()
    lay = QtGui.QVBoxLayout(w)
    for widget in (combo, button_add, button_clear):
        lay.addWidget(widget)
    w.show()
    sys.exit(app.exec_())

QComboBox 的默认 currentIndex 为 -1，当您添加项目时，它会更改为 0 的 currentIndex，并且当您清理 QComboBox 时，currentIndex 将恢复为 -1.因此，当您添加或清理项目时，会发出 currentIndexChanged 信号.

The default currentIndex of the QComboBox is -1, when you add items this changes to the currentIndex of 0, and when you clean the QComboBox the currentIndex reverts to -1. So when you add or clean the items, the currentIndexChanged signal is emitted.

基于上述，我将解释您指出的行为:当在 QCombobox 1 中选择新的 currentIndex 时，调用测试方法，如果它在清理和清理后进入 else 语句添加您建立第一个连接的项目，如果现在重复相同的事情，因为有一个连接，则发出 currentIndexChanged 信号两次(一个用于 clear()，另一个用于 addItems())，并且您还创建第二个连接，如果再次重复，信号发出 4 次(1 clear() x 2 个连接 + 1 addItems() x 2 个连接).

Based on the above, I will explain the behavior that you point out: When a new currentIndex is selected in the QCombobox 1 the test method is invoked and if it enters the else statement after cleaning and adding the items you make the first connection, if the same thing is repeated now as there is a connection, the currentIndexChanged signal is emitted twice (one for clear() and another for addItems()) and you also create a second connection, if it is repeated again, the signal is emitted 4 times (1 clear() x 2 connections + 1 addItems() x 2 connections).

解决方案:

• 在只调用一次的函数中建立连接.
• 为了使 clear() 信号和 addItems() 不会发出 currentIndexChanged 信号，您必须使用 blockSignals().
• 另外一点，建议不要修改Qt Designer生成的代码，除了使用装饰@QtCore.pyqtSlot()之外，建议创建另一个使用初始类作为接口的类.

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(800, 600)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.comboBox1 = QtGui.QComboBox(self.centralwidget)
        self.comboBox1.setGeometry(QtCore.QRect(310, 150, 171, 31))
        self.comboBox1.setObjectName(_fromUtf8("comboBox1"))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox1.addItem(_fromUtf8(""))
        self.comboBox_2 = QtGui.QComboBox(self.centralwidget)
        self.comboBox_2.setGeometry(QtCore.QRect(310, 240, 171, 41))
        self.comboBox_2.setObjectName(_fromUtf8("comboBox_2"))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        self.comboBox_2.addItem(_fromUtf8(""))
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.comboBox1.setItemText(0, _translate("MainWindow", "select", None))
        self.comboBox1.setItemText(1, _translate("MainWindow", "a", None))
        self.comboBox1.setItemText(2, _translate("MainWindow", "b", None))
        self.comboBox1.setItemText(3, _translate("MainWindow", "c", None))
        self.comboBox_2.setItemText(0, _translate("MainWindow", "select", None))
        self.comboBox_2.setItemText(1, _translate("MainWindow", "p", None))
        self.comboBox_2.setItemText(2, _translate("MainWindow", "q", None))
        self.comboBox_2.setItemText(3, _translate("MainWindow", "r", None))


class MainWindow(QtGui.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.setupUi(self)

        self.comboBox_2.setEnabled(False)
        self.comboBox1.currentIndexChanged[str].connect(self.test)
        self.comboBox_2.currentIndexChanged.connect(self.test1)

    @QtCore.pyqtSlot(str)
    def test(self, s):
        res=['aa','bb','cc','dd']

        if s == "- - select - -":
            self.comboBox_2.setEnabled(False)
            self.comboBox_2.setCurrentIndex(0)
        elif not s:
            self.comboBox_2.setEnabled(True)
            self.comboBox_2.blockSignals(True)
            self.comboBox_2.clear()
            self.comboBox_2.addItem("- - select - -")
            self.comboBox_2.addItem("New Checklist")
            self.comboBox_2.blockSignals(False)
        else:
            self.comboBox_2.setEnabled(True)
            self.comboBox_2.blockSignals(True)
            self.comboBox_2.clear()
            self.comboBox_2.addItem("- - select - -")
            self.comboBox_2.addItem("New Checklist")
            self.comboBox_2.addItems(res)
            self.comboBox_2.blockSignals(False)


    @QtCore.pyqtSlot(int)
    def test1(self, ix):
        print("Hello", ix)

if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

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