keyPressEvent 不适用于 PyQt5 中的 Enter 键（但适用于其他所有键）

Question

我有一个 PyQt5 GUI，它有一个带有按钮的主窗口和一个 QLineEdit。

我制作了 keyPressEvent 函数并设置了键盘上的某些键来执行不同的操作。我设置的所有键都可以使用，而不是 Enter 按钮。当您按下 Enter 键时，如果未单击屏幕按钮，则会触发数字 7 屏幕按钮（这是 GUI 中制作的第一个按钮）。单击按钮后，Enter 键将始终触发最后一次单击的屏幕按钮。 所有其他事件工作正常。 有人知道为什么会这样吗？

MRE：

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import QDialog, QPushButton
from PyQt5.QtCore import*
from PyQt5.QtWidgets import*

if hasattr(QtCore.Qt, 'AA_EnableHighDpiScaling'):
    QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling, True)
if hasattr(QtCore.Qt, 'AA_UseHighDpiPixmaps'):
    QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_UseHighDpiPixmaps, True)
    
# I know global variables is bad programming. Just doing this for the example
outputText = ""

class Ui_MainWindow(object):

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        
        MainWindow.setFixedSize(331, 411)
       
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.button_7 = QtWidgets.QPushButton(self.centralwidget)
        self.button_7.setGeometry(QtCore.QRect(20, 190, 71, 41))
        self.button_7.setStyleSheet("QPushButton\n"
"{\n"
"border: none;\n"
"background-color: rgb(255, 255, 255);\n"
"font: 20pt \"Arial\";\n"
"}\n"
"QPushButton:hover{\n"
"background-color: rgb(220, 220, 220);\n"
"}\n"
"QPushButton:pressed\n"
"{\n"
"background-color: rgb(212, 212, 212);\n"
"}\n"
"\n"
"")
        self.button_7.setAutoDefault(True)
        self.button_7.setDefault(False)
        self.button_7.setFlat(True)
        self.button_7.setObjectName("button_7")
        self.button_7.clicked.connect(self.click_and_update)

        self.screenOutput = QtWidgets.QLineEdit(self.centralwidget)
        self.screenOutput.setGeometry(QtCore.QRect(20, 30, 291, 20))
        self.screenOutput.setStyleSheet("border: none; background: transparent;"
        "font: 12pt \"MS Shell Dlg 2\";\n""color: rgb(190, 190, 190);")
        self.screenOutput.setAlignment(QtCore.Qt.AlignCenter)
        self.screenOutput.setObjectName("eqInput")
        

        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 331, 22))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

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

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", " MRE"))
        self.button_7.setText(_translate("MainWindow", "7"))
        self.screenOutput.setText(_translate("MainWindow", "Do Something"))

        # set keyPressEvent to current widgets that we'd like it to be overridden
        self.centralwidget.keyPressEvent = self.keyPressEvent
        self.screenOutput.keyPressEvent = self.keyPressEvent
   
    def keyPressEvent(self,e):
        if e.key() == Qt.Key_Enter:
                self.equal_click()

        if e.key() == Qt.Key_Equal:
                self.equal_click()
   

    def update_screen(self):
        self.screenOutput.setText(outputText)
        return


    def equal_click(self):
        global outputText
        outputText = "Pressed Key"
        self.update_screen()
        return

    def click_and_update(self):
        global outputText
        outputText+=" 7"
        self.update_screen()
        return

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

Equal 键可以正常工作，Enter 键不行。

Answer 1

问题是 Enter 键与 Qt.Key_Return 相关联，并且仅在键盘中是 Qt.Key_Enter。所以一个通用的解决方案是检查两个键：

if e.key() in (Qt.Key_Return, Qt.Key_Enter):
    self.equal_click()

但是，它并没有纠正真正的错误，因为问题在于按钮具有焦点，因此 keypress 事件不会传播到其父级。

此外，不建议使用foo.keyPressEvent = bar，因为在许多情况下它可能会失败，如果您有“n”个小部件，您将不得不为所有这些小部件实现该逻辑。更优雅的解决方案是在窗口上使用事件过滤器。所以你必须恢复 .py 文件，因为不建议修改它（参见这篇文章：QtDesigner changes will be lost after redesign User Interface），我假设它被称为 main_ui.py

from PyQt5 import QtCore, QtWidgets

from main_ui import Ui_MainWindow


class KeyHelper(QtCore.QObject):
    keyPressed = QtCore.pyqtSignal(QtCore.Qt.Key)

    def __init__(self, window):
        super().__init__(window)
        self._window = window

        self.window.installEventFilter(self)

    @property
    def window(self):
        return self._window

    def eventFilter(self, obj, event):
        if obj is self.window and event.type() == QtCore.QEvent.KeyPress:
            self.keyPressed.emit(event.key())
        return super().eventFilter(obj, event)


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

    def handle_key_pressed(self, key):
        if key in (QtCore.Qt.Key_Enter, QtCore.Qt.Key_Return):
            self.update_text()

    def update_text(self):
        text = self.ui.screenOutput.text() + "7"
        self.ui.screenOutput.setText(text)


if hasattr(QtCore.Qt, "AA_EnableHighDpiScaling"):
    QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling, True)
if hasattr(QtCore.Qt, "AA_UseHighDpiPixmaps"):
    QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_UseHighDpiPixmaps, True)


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)

    w = MainWindow()
    w.show()

    helper = KeyHelper(w.windowHandle())
    helper.keyPressed.connect(w.handle_key_pressed)

    sys.exit(app.exec_())