keyPressEvent 方法在这个程序中是如何工作的? [英] How does the keyPressEvent method work in this program?

问题描述

我无法理解 keyPressEvent 方法在此程序中的工作原理.具体来说，这里的e"是什么?keyPressEvent 是使用预先存在的实例e"重新定义的方法吗?

I'm having trouble understanding how the keyPressEvent method works in this program. Specifically, what is "e" here? Is keyPressEvent a redefined method using a pre-existing instance "e"?

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):

        self.setGeometry(300,300,250,150)
        self.setWindowTitle('Event handler')
        self.show()

    def keyPressEvent(self, e):

        if e.key() == QtCore.Qt.Key_Escape:
            self.close()

def main():

    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

推荐答案

e 是用户按下某个键时生成的事件".这在事件处理程序中很常见，这是将信息(例如按下哪个键 - 使用 e.key() 拉出的内容)传递给事件处理程序的好方法，以便我们可以组合相关事件并使用单一功能.

e is the "event" that is generated when a user presses a key. This is pretty common in event handlers, it's a great way to pass information (such as which key got pressed - which is what's getting pulled with e.key()) to event handlers, so that we can combine related events and handle them with a single function.

# A key has been pressed!
def keyPressEvent(self, event):
    # Did the user press the Escape key?
    if event.key() == QtCore.Qt.Key_Escape: # QtCore.Qt.Key_Escape is a value that equates to what the operating system passes to python from the keyboard when the escape key is pressed.
        # Yes: Close the window
        self.close()
    # No:  Do nothing.

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