如何在 PyQt5 中获取变量值，外部事件过滤器方法？

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"，如果焦点改变到 textbox 2 然后 fitem 是 "textbox2" 等等。现在我想在方法外打印 fitem。（例如，在我的代码第 42 到 44 行中，尝试了一些东西，但没有任何反应）

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

您的方法有两个问题：

你要实现你的逻辑的地方只执行一次，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，当你想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>

即便如此我还是不明白为什么你会变得太复杂，在你的情况下使用 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)

如何在 PyQt5 中获取变量值，外部事件过滤器方法？

How to get a variable value, outside event filter method in PyQt5?

python

pyqt

pyqt5

eventfilter