如何在PyQt5中获取变量值，外部事件过滤器方法？

debugcn 发表于 Dev

库玛

Hai，我想打印在“ eventFilter”方法中声明的变量值？在我的代码中，如果focusitem为textbox1，则fitem =“ textbox 1”，如果焦点更改为textbox 2，则fitem为“ textbox2”，依此类推。现在，我想在方法之外打印fitem。（例如，在我的代码第42至44行中，尝试了一些操作，但是什么也不会发生）

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *

item1 = ["Python", "Python 2.7", "Python 2.9", "Python 3.5", "Python 3.7", "National", "Zebra",
        "Apple", "X Ray", "Boat", "Tiger", "Item001", "Item002", "Item003", "Item004", "Item005",
        "001Item", "002Item", "003Item", "004Item", "005Item", "Ball", "Cat", "Dog", "Fish",
        "Gold Fish", "Star Fish", "2821", "2822", "2823", "2811", "2812", "2813"]

item2 = ["India", "America", "Russia", "China", "England", "Iran", "Iraq", "Ice Land"]

item3 = ["Apple","Orange","Bannana","Grapes","Jack Fruit","Black","White","Green","Blue",
         "DarkBlue", "Light Blue","Red","Dark Red","Red Medium","Reddish Blue"]

fitem = None

class Check(QWidget):

    def __init__(self):
        super().__init__()
        self.setWindowTitle("Check Window")
        self.textbox1 = QLineEdit(self)
        self.textbox1.setGeometry(100, 100, 300, 30)
        self.textbox2 = QLineEdit(self)
        self.textbox2.setGeometry(100, 150, 300, 30)
        self.textbox3 = QLineEdit(self)
        self.textbox3.setGeometry(100, 200, 300, 30)

        self.lbox1 = QListWidget()
        self.lbox2 = QListWidget(self)
        self.lbox2.setGeometry(100, 250, 300, 500)
        self.textbox1.setObjectName("textbox1")
        self.textbox2.setObjectName("textbox2")
        self.textbox3.setObjectName("textbox3")

        self.textbox1.installEventFilter(self)
        self.textbox2.installEventFilter(self)
        self.textbox3.installEventFilter(self)
        self.lbox2.installEventFilter(self)

        # Based on focus item, I want to create some codes here.
        if fitem == "textbox1":
            print(" focus item is ", textbox1)


    def eventFilter(self, source, event):
        global fitem
        if event.type() == QEvent.FocusIn:
            if source == self.textbox1:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item1)
                self.lbox2.addItems(item1)
                fitem = "textbox1"
                print("textbox 1")

            elif source == self.textbox2:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item2)
                self.lbox2.addItems(item2)
                fitem = "textbox2"
                print("textbox 2")

            elif source == self.textbox3:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item3)
                self.lbox2.addItems(item3)
                fitem = "textbox3"
                print("textbox 3")

            elif source == self.lbox2:
                fitem = "listbox2"
                print("listbox 2")

        return super(Check, self).eventFilter(source, event)


def main():
    myapp = QApplication(sys.argv)
    mywin = Check()
    mywin.show()
    sys.exit(myapp.exec_())


if __name__ == "__main__":
    main()
    enter code here

永乐

在您的方法中，您有两个问题：

您想要实现的逻辑仅在构造函数中执行一次，而eventFilter在构造对象后执行。
不要滥用变量，因为它们是不好的做法，请阅读为什么全局变量有害？。

逻辑是创建一个存储函数的属性，当您要实现逻辑时会调用该函数：


class Check(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Check Window")
        self.textbox1 = QLineEdit(self)
        self.textbox1.setGeometry(100, 100, 300, 30)
        self.textbox2 = QLineEdit(self)
        self.textbox2.setGeometry(100, 150, 300, 30)
        self.textbox3 = QLineEdit(self)
        self.textbox3.setGeometry(100, 200, 300, 30)

        self.lbox1 = QListWidget()
        self.lbox2 = QListWidget(self)
        self.lbox2.setGeometry(100, 250, 300, 500)
        self.textbox1.setObjectName("textbox1")
        self.textbox2.setObjectName("textbox2")
        self.textbox3.setObjectName("textbox3")

        self.textbox1.installEventFilter(self)
        self.textbox2.installEventFilter(self)
        self.textbox3.installEventFilter(self)
        self.lbox2.installEventFilter(self)

        self.fitem = None

    def eventFilter(self, source, event):
        if event.type() == QEvent.FocusIn:
            if source == self.textbox1:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item1)
                self.lbox2.addItems(item1)
                self.fitem = "textbox1"

            elif source == self.textbox2:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item2)
                self.lbox2.addItems(item2)
                self.fitem = "textbox2"

            elif source == self.textbox3:
                self.lbox1.clear()
                self.lbox2.clear()
                self.lbox1.addItems(item3)
                self.lbox2.addItems(item3)
                self.fitem = "textbox3"

            elif source == self.lbox2:
                self.fitem = "listbox2"
            self.foo()

        return super(Check, self).eventFilter(source, event)

    def foo(self):
        if self.fitem == "textbox1":
            print("test")

即使这样，我也不明白为什么您变得太复杂了，在您的情况下，使用focusChanged信号就足够了：

class Check(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Check Window")
        self.textbox1 = QLineEdit()
        self.textbox2 = QLineEdit()
        self.textbox3 = QLineEdit()
        self.lbox = QListWidget()

        lay = QVBoxLayout(self)
        lay.addWidget(self.textbox1)
        lay.addWidget(self.textbox2)
        lay.addWidget(self.textbox3)
        lay.addWidget(self.lbox)

        self.mapping_list = {
            self.textbox1: item1,
            self.textbox2: item2,
            self.textbox3: item3,
        }

        QApplication.instance().focusChanged.connect(self.on_focusChanged)

    def on_focusChanged(self, old, new):
        item = self.mapping_list.get(new)
        if item is not None:
            self.lbox.clear()
            self.lbox.addItems(item)
            print(" focus item is ", new)

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