Pyqt5：如何限制QMainWindow中QPushButton的拖动区域？

Question

在 QWidget 中拖动 QPushButton 时，直到它消失一旦它通过（越过）MainWindow (QWidget) 的边界

我想限制这个 QPushButton 不越过它的容器的边界，但在 QWidget 内保持可见

from PyQt5.QtWidgets import QApplication, QWidget, QPushButton
from PyQt5.QtCore import Qt

class DragButton(QPushButton):
    def mousePressEvent(self, event):
        self.__mousePressPos = None
        self.__mouseMovePos = None
        if event.button() == Qt.LeftButton:
            self.__mousePressPos = event.globalPos()
            self.__mouseMovePos = event.globalPos()
        super(DragButton, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if event.buttons() == Qt.LeftButton:
            # adjust offset from clicked point to origin of widget
            currPos = self.mapToGlobal(self.pos())
            globalPos = event.globalPos()
            diff = globalPos - self.__mouseMovePos
            newPos = self.mapFromGlobal(currPos + diff)
            self.move(newPos)
            self.__mouseMovePos = globalPos
        super(DragButton, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        if self.__mousePressPos is not None:
            moved = event.globalPos() - self.__mousePressPos 
            if moved.manhattanLength() > 3:
                event.ignore()
                return
        super(DragButton, self).mouseReleaseEvent(event)

def clicked():
    print ("click as normal!")

if __name__ == "__main__":
    app = QApplication([])
    w   = QWidget()
    w.resize(800,600)
    button = DragButton("Drag", w)
    button.clicked.connect(clicked)
    w.show()
    app.exec_() 

有没有办法做到这一点？

Answer 1

由于要求是确保子级在父级边界内，您需要检查子级rect()（翻译到新位置）是否在该区域内，在移动之前它。

请注意，要实现“自我”运动，不必不断平移全局位置。

class DragButton(QPushButton):
    def mousePressEvent(self, event):
        self.__mousePressPos = None
        self.__mouseMovePos = None
        if event.button() == Qt.LeftButton:
            self.__mousePressPos = event.globalPos()
            self.__mouseMovePos = event.pos()
        super(DragButton, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if event.buttons() == Qt.LeftButton:
            delta = event.pos() - self.__mouseMovePos
            newPos = self.pos() + delta
            if self.parent():
                geo = self.rect().translated(newPos)
                parentRect = self.parent().rect()
                if geo.x() < 0:
                    geo.moveLeft(0)
                elif geo.right() > parentRect.right():
                    geo.moveRight(parentRect.right())
                if geo.y() < 0:
                    geo.moveTop(0)
                elif geo.bottom() > parentRect.bottom():
                    geo.moveBottom(parentRect.bottom())
                self.move(geo.topLeft())
            else:
                self.move(newPos)
        super(DragButton, self).mouseMoveEvent(event)

还要考虑拖动已启用的按钮不是一个好主意，因为它可能会导致不需要的、不直观的和意外的行为。您的实现显示了这一点，因为如果按钮移动超过 3 像素限制，它将保持按下状态。