限制父小部件中的子小部件移动范围

Question

我正在做一个拖放小部件功能。我在网上复制了一段代码，重写了三个类mousePressEvent、mouseReleaseEvent和mouseMoveEvent。

当子部件移动到父部件的边框时，它会覆盖父部件的边框。我不希望它变成这样。我想保留父小部件的边框。有没有办法让子widget只在父widget的内容区移动

我尝试了几种方法，但都失败了

首先：设置父控件布局的setContentsMargins属性

第二：设置父控件的内边距

第三：设置子控件的边距

import sys
from PyQt4 import QtGui, QtCore
from PyQt4.QtCore import Qt, QMimeData, QDataStream, QIODevice, QByteArray, QPoint, QSize
from PyQt4.QtGui import QLabel, QWidget, QHBoxLayout, QStyleOption, QPainter, QStyle, QDrag, QListWidgetItem, QIcon, \
    QFontMetricsF, QColor


class Label(QWidget):
    def __init__(self):
        super(Label, self).__init__()

        self.setStyleSheet("""
            *{             border-width: 1px;
             border-style: solid;
             border-color: #cdcdcd;
             background-color:blue
             }
        """)
        self.setFixedSize(300, 300)

    def paintEvent(self, event):
        super(Label, self).paintEvent(event)
        opt = QStyleOption()
        opt.initFrom(self)
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)
        self.style().drawPrimitive(QStyle.PE_Widget, opt, painter, self)

    def mousePressEvent(self, event):
        self.__mousePressPos = None
        self.__mouseMovePos = None
        if event.button() == QtCore.Qt.LeftButton:
            self.__mousePressPos = event.globalPos()
            self.__mouseMovePos = event.globalPos()

        super(Label, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if event.buttons() == QtCore.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(Label, 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(Label, self).mouseReleaseEvent(event)


class Widget(QWidget):
    def __init__(self):
        super(Widget, self).__init__()
        box = QHBoxLayout()
        box.setContentsMargins(20, 20, 20, 20)
        self.setLayout(box)
        box.addWidget(Label())
        self.setFixedSize(500, 500)

        self.setStyleSheet("""
            *{             border-width: 10px;
             border-style: solid;
             border-color: red;}
        """)

    def paintEvent(self, event):
        super(Widget, self).paintEvent(event)
        opt = QStyleOption()
        opt.initFrom(self)
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)
        self.style().drawPrimitive(QStyle.PE_Widget, opt, painter, self)


class Example(QtGui.QWidget):

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

        self.initUI()

    def initUI(self):
        h = QtGui.QHBoxLayout()
        h.addWidget(Widget())
        self.setLayout(h)
        self.setGeometry(100, 100, 900, 000)
        self.setWindowTitle("PyQt")
        self.show()


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


if __name__ == '__main__':
    main()

Answer 1

父 QWidget 始终绘制在子元素下方，因此您可以看到这种效果。解决方案是在包含红色边框的蓝色子项之上创建另一个子项，该子项占用与父项相同的大小（这是通过布局实现的）并且不会阻止鼠标事件（因为默认情况下小部件将鼠标锁定到较低的小部件，但可以使用 Qt::WA_TransparentForMouseEvents 标志禁用）。

class Widget(QWidget):
    def __init__(self):
        super(Widget, self).__init__()
        self.setFixedSize(500, 500)

        container = QWidget()
        container.setAttribute(Qt.WA_TransparentForMouseEvents)
        container.setStyleSheet(
            """
            *{             border-width: 10px;
             border-style: solid;
             border-color: red;}
        """
        )

        box = QHBoxLayout(self)
        box.setContentsMargins(0, 0, 0, 0)
        box.addWidget(container)

        label = Label()
        label.setParent(self)

        container.raise_()