如何在PyQt5 Python中显示QDial上的标记

问题描述

我正在qt-desginer中设计一个用户界面，在其中添加了dial。如下图所示：

它没有任何标记。是否可以添加一些标记以更好地理解它。如下所示：

解决方法

不幸的是，QDial是一个从未真正关心过的小部件，主要是因为它很少使用，而且还因为许多功能需求可能会以不一致的方式改变其行为。无论如何，Designer都无法做到这一点。

可以通过对QDial进行子类化并在设计器中进行推广来部分完成 ，但是最终您会在 槽口或表盘本身上绘制数字，这将看起来很丑。

为了实现所需的功能，您需要使用包含表盘 的自定义小部件，并最终升级那个小部件，但是您将无法在Designer中查看它或设置其属性（除非您创建Designer插件，这不是一件容易的事）。这是通过设置容器布局边距来实现的，以便始终有足够的空间将值显示为文本。

这是可能的实现。出于显而易见的原因，请考虑一下，如果您的值范围较大且表盘较小，则数字将重叠。

class ValueDial(QtWidgets.QWidget):
    _dialProperties = ('minimum','maximum','value','singleStep','pageStep','notchesVisible','tracking','wrapping','invertedAppearance','invertedControls','orientation')
    _inPadding = 3
    _outPadding = 2
    valueChanged = QtCore.pyqtSignal(int)

    def __init__(self,*args,**kwargs):
        # remove properties used as keyword arguments for the dial
        dialArgs = {k:v for k,v in kwargs.items() if k in self._dialProperties}
        for k in dialArgs.keys():
            kwargs.pop(k)
        super().__init__(*args,**kwargs)
        layout = QtWidgets.QVBoxLayout(self)
        self.dial = QtWidgets.QDial(self,**dialArgs)
        layout.addWidget(self.dial)
        self.dial.valueChanged.connect(self.valueChanged)
        # make the dial the focus proxy (so that it captures focus *and* key events)
        self.setFocusProxy(self.dial)

        # simple "monkey patching" to access dial functions
        self.value = self.dial.value
        self.setValue = self.dial.setValue
        self.minimum = self.dial.minimum
        self.maximum = self.dial.maximum
        self.wrapping = self.dial.wrapping
        self.notchesVisible = self.dial.notchesVisible
        self.setNotchesVisible = self.dial.setNotchesVisible
        self.setNotchTarget = self.dial.setNotchTarget
        self.notchSize = self.dial.notchSize
        self.invertedAppearance = self.dial.invertedAppearance
        self.setInvertedAppearance = self.dial.setInvertedAppearance

        self.updateSize()

    def inPadding(self):
        return self._inPadding

    def setInPadding(self,padding):
        self._inPadding = max(0,padding)
        self.updateSize()

    def outPadding(self):
        return self._outPadding

    def setOutPadding(self,padding):
        self._outPadding = max(0,padding)
        self.updateSize()

    # the following functions are required to correctly update the layout
    def setMinimum(self,minimum):
        self.dial.setMinimum(minimum)
        self.updateSize()

    def setMaximum(self,maximum):
        self.dial.setMaximum(maximum)
        self.updateSize()

    def setWrapping(self,wrapping):
        self.dial.setWrapping(wrapping)
        self.updateSize()

    def updateSize(self):
        # a function that sets the margins to ensure that the value strings always
        # have enough space
        fm = self.fontMetrics()
        minWidth = max(fm.width(str(v)) for v in range(self.minimum(),self.maximum() + 1))
        self.offset = max(minWidth,fm.height()) / 2
        margin = self.offset + self._inPadding + self._outPadding
        self.layout().setContentsMargins(margin,margin,margin)

    def translateMouseEvent(self,event):
        # a helper function to translate mouse events to the dial
        return QtGui.QMouseEvent(event.type(),self.dial.mapFrom(self,event.pos()),event.button(),event.buttons(),event.modifiers())

    def changeEvent(self,event):
        if event.type() == QtCore.QEvent.FontChange:
            self.updateSize()

    def mousePressEvent(self,event):
        self.dial.mousePressEvent(self.translateMouseEvent(event))

    def mouseMoveEvent(self,event):
        self.dial.mouseMoveEvent(self.translateMouseEvent(event))

    def mouseReleaseEvent(self,event):
        self.dial.mouseReleaseEvent(self.translateMouseEvent(event))

    def paintEvent(self,event):
        radius = min(self.width(),self.height()) / 2
        radius -= (self.offset / 2 + self._outPadding)
        invert = -1 if self.invertedAppearance() else 1
        if self.wrapping():
            angleRange = 360
            startAngle = 270
            rangeOffset = 0
        else:
            angleRange = 300
            startAngle = 240 if invert > 0 else 300
            rangeOffset = 1
        fm = self.fontMetrics()

        # a reference line used for the target of the text rectangle
        reference = QtCore.QLineF.fromPolar(radius,0).translated(self.rect().center())
        fullRange = self.maximum() - self.minimum()
        textRect = QtCore.QRect()

        qp = QtGui.QPainter(self)
        qp.setRenderHints(qp.Antialiasing)
        for p in range(0,fullRange + rangeOffset,self.notchSize()):
            value = self.minimum() + p
            if invert < 0:
                value -= 1
                if value < self.minimum():
                    continue
            angle = p / fullRange * angleRange * invert
            reference.setAngle(startAngle - angle)
            textRect.setSize(fm.size(QtCore.Qt.TextSingleLine,str(value)))
            textRect.moveCenter(reference.p2().toPoint())
            qp.drawText(textRect,QtCore.Qt.AlignCenter,str(value))


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    dial = ValueDial(minimum=1,maximum=11)
    dial.setNotchesVisible(True)
    dial.show()
    sys.exit(app.exec_())