python - 如何在 PyQt5 中的外部事件过滤器方法中获取变量值？

Question

嗨，我想打印在“eventFilter”方法中声明的变量的值？。在我的代码中，如果 focusitem 是 textbox1 那么 fitem = "textbox 1"，如果焦点更改为 textbox 2 那么 fitem 是 "textbox2"等等。现在我想在方法之外打印 fitem。 (例如，在我的代码第 42 到 44 行中，尝试了一些操作，但什么也不会发生)

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

Answer 1

在您的方法中，您有两个问题:

• 你想要实现的逻辑只执行一次，因为它在构造函数中，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 Why are global variables evil? .

逻辑是创建一个存储函数的属性，当您想要实现逻辑时调用的函数:

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)

        <b>self.fitem = None</b>

    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)
                <b>self.fitem</b> = "textbox1"

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

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

            elif source == self.lbox2:
                <b>self.fitem</b> = "listbox2"
            <b>self.foo()</b>

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

    <b>def foo(self):
        if self.fitem == "textbox1":
            print("test")</b>

即使如此，我也不明白为什么你变得太复杂，在你的情况下使用 focusChanged 就足够了信号:

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)