使用 PyQt 自定义 QDial 刻度

Question

目前我有这个自定义旋转的QDial() 小部件，拨号手柄向上指向0 位置，而不是默认的180 值位置。

要更改刻度间距，setNotchTarget() 用于分隔凹槽，但这会创建均匀分布的刻度（左）。我想创建一个只有 三个 可调节刻度的自定义表盘（右）。

中心刻度永远不会移动，并且始终位于0 的北方位置。但其他两个刻度可以调整，并且应该均匀分布。例如，如果刻度设置为70，它会将左/右刻度从中心放置35 个单位。同样，如果刻度更改为120，它会将刻度间隔60。

我该怎么做？如果使用QDial() 无法做到这一点，那么还有什么其他小部件能够做到这一点？我正在使用 PyQt4 和 Python 3.7

import sys
from PyQt4 import QtGui, QtCore

class Dial(QtGui.QWidget):
    def __init__(self, rotation=0, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.dial = QtGui.QDial()
        self.dial.setMinimumHeight(160)
        self.dial.setNotchesVisible(True)
        # self.dial.setNotchTarget(90)
        self.dial.setMaximum(360)
        self.dial.setWrapping(True)

        self.label = QtGui.QLabel('0')
        self.dial.valueChanged.connect(self.label.setNum)

        self.view = QtGui.QGraphicsView(self)
        self.scene = QtGui.QGraphicsScene(self)
        self.view.setScene(self.scene)
        self.graphics_item = self.scene.addWidget(self.dial)
        self.graphics_item.rotate(rotation)

        # Make the QGraphicsView invisible
        self.view.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.view.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.view.setFixedHeight(self.dial.height())
        self.view.setFixedWidth(self.dial.width())
        self.view.setStyleSheet("border: 0px")

        self.layout = QtGui.QVBoxLayout()
        self.layout.addWidget(self.view)
        self.layout.addWidget(self.label)
        self.setLayout(self.layout)

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialexample = Dial(rotation=180)
    dialexample.show()
    sys.exit(app.exec_())

Answer 1

首先。 Qt 的表盘一团糟。它们是不错的小部件，但它们主要是为简单的用例而开发的。

如果您需要“特殊”行为，则需要重写一些重要的方法。这个例子显然需要paintEvent 覆盖，但最重要的部分是鼠标事件和滚轮事件。跟踪将单步和页步设置为值范围所需的键盘事件，并“覆盖”原始valueChanged 信号以确保发出的值范围始终在 -1 和 1 之间。显然，您可以通过添加专用功能。
从理论上讲，QDial 小部件应该始终使用 240|-60 度角，但将来可能会改变，因此我决定启用环绕以将度数保持为“内部”值。请记住，您可能还需要提供自己的 value() 属性实现。

from PyQt4 import QtCore, QtGui
from math import sin, cos, atan2, degrees, radians
import sys

class Dial(QtGui.QDial):
    MinValue, MidValue, MaxValue = -1, 0, 1
    __valueChanged = QtCore.pyqtSignal(int)

    def __init__(self, valueRange=120):
        QtGui.QDial.__init__(self)
        self.setWrapping(True)
        self.setRange(0, 359)
        self.valueChanged.connect(self.emitSanitizedValue)
        self.valueChanged = self.__valueChanged
        self.valueRange = valueRange
        self.__midValue = valueRange / 2
        self.setPageStep(valueRange)
        self.setSingleStep(valueRange)
        QtGui.QDial.setValue(self, 180)
        self.oldValue = None
        # uncomment this if you want to emit the changed value only when releasing the slider
        # self.setTracking(False)
        self.notchSize = 5
        self.notchPen = QtGui.QPen(QtCore.Qt.black, 2)
        self.actionTriggered.connect(self.checkAction)

    def emitSanitizedValue(self, value):
        if value < 180:
            self.valueChanged.emit(self.MinValue)
        elif value > 180:
            self.valueChanged.emit(self.MaxValue)
        else:
            self.valueChanged.emit(self.MidValue)

    def checkAction(self, action):
        value = self.sliderPosition()
        if action in (self.SliderSingleStepAdd, self.SliderPageStepAdd) and value < 180:
            value = 180 + self.valueRange
        elif action in (self.SliderSingleStepSub, self.SliderPageStepSub) and value > 180:
            value = 180 - self.valueRange
        elif value < 180:
            value = 180 - self.valueRange
        elif value > 180:
            value = 180 + self.valueRange
        else:
            value = 180
        self.setSliderPosition(value)

    def valueFromPosition(self, pos):
        y = self.height() / 2. - pos.y()
        x = pos.x() - self.width() / 2.
        angle = degrees(atan2(y, x))
        if angle > 90 + self.__midValue or angle < -90:
            value = self.MinValue
            final = 180 - self.valueRange
        elif angle >= 90 - self.__midValue:
            value = self.MidValue
            final = 180
        else:
            value = self.MaxValue
            final = 180 + self.valueRange
        self.blockSignals(True)
        QtGui.QDial.setValue(self, final)
        self.blockSignals(False)
        return value

    def value(self):
        rawValue = QtGui.QDial.value(self)
        if rawValue < 180:
            return self.MinValue
        elif rawValue > 180:
            return self.MaxValue
        return self.MidValue

    def setValue(self, value):
        if value < 0:
            QtGui.QDial.setValue(self, 180 - self.valueRange)
        elif value > 0:
            QtGui.QDial.setValue(self, 180 + self.valueRange)
        else:
            QtGui.QDial.setValue(self, 180)

    def mousePressEvent(self, event):
        self.oldValue = self.value()
        value = self.valueFromPosition(event.pos())
        if self.hasTracking() and self.oldValue != value:
            self.oldValue = value
            self.valueChanged.emit(value)

    def mouseMoveEvent(self, event):
        value = self.valueFromPosition(event.pos())
        if self.hasTracking() and self.oldValue != value:
            self.oldValue = value
            self.valueChanged.emit(value)

    def mouseReleaseEvent(self, event):
        value = self.valueFromPosition(event.pos())
        if self.oldValue != value:
            self.valueChanged.emit(value)

    def wheelEvent(self, event):
        delta = event.delta()
        oldValue = QtGui.QDial.value(self)
        if oldValue < 180:
            if delta < 0:
                outValue = self.MinValue
                value = 180 - self.valueRange
            else:
                outValue = self.MidValue
                value = 180
        elif oldValue == 180:
            if delta < 0:
                outValue = self.MinValue
                value = 180 - self.valueRange
            else:
                outValue = self.MaxValue
                value = 180 + self.valueRange
        else:
            if delta < 0:
                outValue = self.MidValue
                value = 180
            else:
                outValue = self.MaxValue
                value = 180 + self.valueRange
        self.blockSignals(True)
        QtGui.QDial.setValue(self, value)
        self.blockSignals(False)
        if oldValue != value:
            self.valueChanged.emit(outValue)

    def paintEvent(self, event):
        QtGui.QDial.paintEvent(self, event)
        qp = QtGui.QPainter(self)
        qp.setRenderHints(qp.Antialiasing)
        qp.translate(.5, .5)
        rad = radians(self.valueRange)
        qp.setPen(self.notchPen)
        c = -cos(rad)
        s = sin(rad)
        # use minimal size to ensure that the circle used for notches
        # is always adapted to the actual dial size if the widget has
        # width/height ratio very different from 1.0
        maxSize = min(self.width() / 2, self.height() / 2)
        minSize = maxSize - self.notchSize
        center = self.rect().center()
        qp.drawLine(center.x(), center.y() -minSize, center.x(), center.y() - maxSize)
        qp.drawLine(center.x() + s * minSize, center.y() + c * minSize, center.x() + s * maxSize, center.y() + c * maxSize)
        qp.drawLine(center.x() - s * minSize, center.y() + c * minSize, center.x() - s * maxSize, center.y() + c * maxSize)


class Test(QtGui.QWidget):
    def __init__(self, *sizes):
        QtGui.QWidget.__init__(self)
        layout = QtGui.QGridLayout()
        self.setLayout(layout)
        if not sizes:
            sizes = 70, 90, 120
        self.dials = []
        for col, size in enumerate(sizes):
            label = QtGui.QLabel(str(size))
            label.setAlignment(QtCore.Qt.AlignCenter)
            dial = Dial(size)
            self.dials.append(dial)
            dial.valueChanged.connect(lambda value, dial=col: self.dialChanged(dial, value))
            layout.addWidget(label, 0, col)
            layout.addWidget(dial, 1, col)

    def dialChanged(self, dial, value):
        print('dial {} changed to {}'.format(dial, value))

    def setDialValue(self, dial, value):
        self.dials[dial].setValue(value)

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialexample = Test(70, 90, 120)
    # Change values here
    dialexample.setDialValue(1, 1)
    dialexample.show()
    sys.exit(app.exec_())

编辑：我更新了代码以实现键盘导航并避免不必要的多重信号发射。