PyQt5.QtCore.QEvent的MouseButtonRelease()方法详解

The MouseButtonRelease() method is a predefined event type in PyQt5.QtCore.QEvent, which represents the release of a mouse button.

Syntax:

event = QEvent(QEvent.MouseButtonRelease)

This method is commonly used in conjunction with the eventFilter() method to handle the mouse button release event for a particular widget.

Example:

Let's say we have a custom widget called MyWidget and we want to handle the release of a mouse button for that widget. Here's an example implementation:

from PyQt5.QtWidgets import QApplication, QWidget
from PyQt5.QtCore import QEvent

class MyWidget(QWidget):
    def __init__(self):
        super().__init__()

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            print("Left mouse button released")
        elif event.button() == Qt.RightButton:
            print("Right mouse button released")

        # Call the base class implementation to ensure normal behavior
        super().mouseReleaseEvent(event)

    def eventFilter(self, object, event):
        if event.type() == QEvent.MouseButtonRelease:
            self.handleMouseButtonRelease(event)
            return True

        # Call the base class implementation to ensure normal behavior
        return super().eventFilter(object, event)

    def handleMouseButtonRelease(self, event):
        if event.button() == Qt.LeftButton:
            print("Mouse button released")

if __name__ == '__main__':
    app = QApplication([])
    widget = MyWidget()
    widget.installEventFilter(widget)
    widget.show()
    app.exec_()

In the above example, we have subclassed the QWidget class to create our custom widget called MyWidget. We override the mouseReleaseEvent() method to handle the release of a mouse button within the widget. We check for the button type using event.button() and print an appropriate message.

We also override the eventFilter() method to handle the MouseButtonRelease event for the widget. Within this method, we call our custom method handleMouseButtonRelease() to handle the event. We return True to indicate that we have handled the event.

Finally, we create an instance of MyWidget, install it as an event filter for itself using the installEventFilter() method, and show the widget.

When we run the above code, if we click and release the left mouse button on the MyWidget widget, it will print "Left mouse button released". Similarly, if we click and release the right mouse button, it will print "Right mouse button released".