Qt编写自定义控件：环形颜色选择控件

效果：

代码：

#ifndef COLORSELECTIONRINGWIDGET_H
#define COLORSELECTIONRINGWIDGET_H

#include <QWidget>

class ColorSelectionRingWidget : public QWidget
{
    Q_OBJECT

public:
    ColorSelectionRingWidget(QWidget *parent = nullptr);
    ~ColorSelectionRingWidget()override;

protected:
    void paintEvent(QPaintEvent *event)override;
    void mousePressEvent(QMouseEvent *event)override;
    void mouseReleaseEvent(QMouseEvent* event)override;
    void mouseMoveEvent(QMouseEvent *event)override;
    void showEvent(QShowEvent *event) override;

private:
    qreal ballAngle{0};
    bool isPressed{false};
    void getColorInWidget(const QPoint & pos);
    QColor selectColor;//当前颜色
};
#endif // COLORSELECTIONRINGWIDGET_H

#include "colorselectionringwidget.h"
#include <QPaintEvent>
#include <QPainter>
#include <QPainterPath>
#include <QDebug>
#include <QtMath>
#include <QGuiApplication>
#include <QScreen>

ColorSelectionRingWidget::ColorSelectionRingWidget(QWidget *parent)
    : QWidget(parent)
{
    setPalette(Qt::white);
    setMinimumSize(150,150);
}

ColorSelectionRingWidget::~ColorSelectionRingWidget()
{
}

void ColorSelectionRingWidget::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
    {
        auto pressPos = event->pos();
        QPoint centerPoint = rect().center();
        ballAngle = atan2(pressPos.y()-centerPoint.y(),pressPos.x()-centerPoint.x()) * (180 / M_PI); //两点之间的角度（弧度）
        qDebug()<<"角度 "<<ballAngle;
        isPressed = true;
        update();
    }
    QWidget::mousePressEvent(event);
}

void ColorSelectionRingWidget::mouseReleaseEvent(QMouseEvent* event)
{
    if(isPressed)
    {
        isPressed = false;
    }
    return QWidget::mouseReleaseEvent(event);
}

void ColorSelectionRingWidget::mouseMoveEvent(QMouseEvent* event)
{
    if(isPressed)
    {
        auto nowPos = event->pos();
        QPoint centerPoint = rect().center();
        ballAngle = atan2(nowPos.y()-centerPoint.y(),nowPos.x()-centerPoint.x()) * (180 / M_PI); //两点之间的角度（弧度）
        update();
    }
    return QWidget::mouseMoveEvent(event);
}

void ColorSelectionRingWidget::showEvent(QShowEvent *event)
{
    update();
    return QWidget::showEvent(event);
}

void ColorSelectionRingWidget::getColorInWidget(const QPoint &pos)
{
    static QScreen *screen = QGuiApplication::screenAt(pos);
    if (!screen)
        screen = QGuiApplication::primaryScreen();
    auto gpos = mapToGlobal(pos);
    selectColor = screen->grabWindow(0, gpos.x(), gpos.y(), 1, 1).toImage().pixel(0, 0);
}

void ColorSelectionRingWidget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);
    painter.setPen(Qt::transparent);

    auto rect = event->rect();
    auto standardLength = std::min(rect.width(),rect.height());
    auto radius = standardLength / 2 - standardLength * 0.1;

    QConicalGradient conicalGradient(0, 0, 0); //创建渐变 前两个参数是渐变的中心点  第三个参数是渐变的角度
    QList<Qt::GlobalColor> list{Qt::red,
                                Qt::yellow,
                                Qt::green,
                                Qt::cyan,
                                Qt::blue,
                                Qt::magenta};

    for(int i = 0;i < list.size();++i)
    {
        conicalGradient.setColorAt(60.0 * i/360.0, list[i]);
    }
    conicalGradient.setColorAt(1.0, list[0]);
    painter.translate(rect.center());

    QBrush brush(conicalGradient);
    painter.setPen(Qt::NoPen);
    painter.setBrush(brush);

    QPainterPath path1;
    path1.addEllipse(QPoint(0, 0), radius, radius);
    QPainterPath path2;
    path1.addEllipse(QPoint(0, 0), radius * 0.8, radius * 0.8);
    painter.drawPath(path1 - path2);

    QPointF ballPos = QPointF(cos(ballAngle * M_PI/180) * radius * 0.9,sin(ballAngle * M_PI/180) * radius * 0.9);//小球圆心
    painter.setPen(QColor("#128bf1"));
    painter.drawEllipse(ballPos, radius*0.2, radius*0.2);

    getColorInWidget(ballPos.toPoint() + QPoint(rect.width()/2,rect.height()/2));
    painter.setBrush(selectColor);
    painter.setPen(Qt::transparent);
    painter.drawEllipse(QPoint(0, 0), radius * 0.6, radius * 0.6);
}