为什么 mouseMoveEvent 在 PyQt5 中什么都不做

Question

我尝试在PyQt5和Python3.5中使用mouseMoveEvent和mousePressEvent，但是当我点击鼠标时没有任何反应。我的代码如下，有什么问题吗？

from PyQt5 import QtWidgets, QtGui, QtCore

class Window(QtWidgets.QMainWindow):
    def __init__(self):
        QtWidgets.QMainWindow.__init__(self)
        widget = QtWidgets.QWidget(self)
        layout = QtWidgets.QVBoxLayout(widget)
        self.graphicsView = QtWidgets.QGraphicsView()
        self.graphicsView.setCursor(QtCore.Qt.CrossCursor)
        self.graphicsView.setObjectName("graphicsView")
        layout.addWidget(self.graphicsView)
        self.setCentralWidget(widget)

    def mouseMoveEvent(self, event):
        if event.buttons() == QtCore.Qt.NoButton:
            print("Simple mouse motion")
        elif event.buttons() == QtCore.Qt.LeftButton:
            print("Left click drag")
        elif event.buttons() == QtCore.Qt.RightButton:
            print("Right click drag")

    def mousePressEvent(self, event):
        if event.button() == QtCore.Qt.LeftButton:
            print("Press!")

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    win = Window()
    win.show()
    sys.exit(app.exec_())

Answer 1

我确定您的事件是在 QGraphicsView 内部处理的。您必须阅读有关事件传播的更多信息。尝试在 Window 之上不添加任何其他小部件。并且不要忘记 abt MouseTracking 属性，默认情况下它是 false 并且根本不会发生没有按钮的鼠标移动事件。

我建议阅读 this article. It's is quite old, but still relevant. Also mouse events in QGraphicsView handled in a different way, read docs 了解更多详情。

抱歉没有代码示例，因为我是 C++ 开发人员。

Answer 2

首先，您必须启用mouse-tracking:

        self.graphicsView.setMouseTracking(True)

那么你可以使用 QGraphicsView 的子类:

class GraphicsView(QtWidgets.QGraphicsView):   
    def mouseMoveEvent(self, event):
        if event.buttons() == QtCore.Qt.NoButton:
            print("Simple mouse motion")
        elif event.buttons() == QtCore.Qt.LeftButton:
            print("Left click drag")
        elif event.buttons() == QtCore.Qt.RightButton:
            print("Right click drag")
        super(GraphicsView, self).mouseMoveEvent(event)

    def mousePressEvent(self, event):
        if event.button() == QtCore.Qt.LeftButton:
            print("Press!")
        super(GraphicsView, self).mousePressEvent(event)

或者安装一个事件过滤器：

        self.graphicsView.viewport().installEventFilter(self)
        ...

    def eventFilter(self, source, event):
        if event.type() == QtCore.QEvent.MouseMove:
            if event.buttons() == QtCore.Qt.NoButton:
                print("Simple mouse motion")
            elif event.buttons() == QtCore.Qt.LeftButton:
                print("Left click drag")
            elif event.buttons() == QtCore.Qt.RightButton:
                print("Right click drag")
        elif event.type() == QtCore.QEvent.MouseButtonPress:
            if event.button() == QtCore.Qt.LeftButton:
                print("Press!")
        return super(Window, self).eventFilter(source, event)

为什么 mouseMoveEvent 在 PyQt5 中什么都不做

Why mouseMoveEvent does nothing in PyQt5

python

python-3.x

pyqt

pyqt5