Qt?Qml實現(xiàn)任意角為圓角的矩形

更新時間：2025年01月16日 08:59:53 作者：夢起丶

在?Qml?中,矩形（Rectangle）是最常用的元素之一,本文將介紹如何通過自定義?Qml?元素實現(xiàn)一個任意角可為圓角的矩形,感興趣的可以了解下

效果圖

自定義 Qml 元素：DelRectangle

我們將創(chuàng)建一個名為 DelRectangle 的自定義 Qml 元素，它繼承自 QQuickPaintedItem，并重寫其 paint() 方法來自定義繪制邏輯。

頭文件（delrectangle.h）

#ifndef DELRECTANGLE_H
#define DELRECTANGLE_H

#include <QQuickPaintedItem>

class DelPen: public QObject
{
    Q_OBJECT
    Q_PROPERTY(qreal width READ width WRITE setWidth NOTIFY widthChanged FINAL)
    Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged FINAL)
    QML_NAMED_ELEMENT(DelPen)
public:
    DelPen(QObject *parent = nullptr);
    qreal width() const;
    void setWidth(qreal width);
    QColor color() const;
    void setColor(const QColor &color);
    bool isValid() const;
signals:
    void widthChanged();
    void colorChanged();
private:
    qreal m_width = 1;
    QColor m_color = Qt::transparent;
};

class DelRectangle: public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(qreal radius READ radius WRITE setRadius NOTIFY radiusChanged FINAL)
    Q_PROPERTY(qreal topLeftRadius READ topLeftRadius WRITE setTopLeftRadius NOTIFY topLeftRadiusChanged FINAL)
    Q_PROPERTY(qreal topRightRadius READ topRightRadius WRITE setTopRightRadius NOTIFY topRightRadiusChanged FINAL)
    Q_PROPERTY(qreal bottomLeftRadius READ bottomLeftRadius WRITE setBottomLeftRadius NOTIFY bottomLeftRadiusChanged FINAL)
    Q_PROPERTY(qreal bottomRightRadius READ bottomRightRadius WRITE setBottomRightRadius NOTIFY bottomRightRadiusChanged FINAL)
    Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged FINAL)
    Q_PROPERTY(DelPen* border READ border CONSTANT)
    QML_NAMED_ELEMENT(DelRectangle)
public:
    explicit DelRectangle(QQuickItem *parent = nullptr);
    ~DelRectangle();
    qreal radius() const;
    void setRadius(qreal radius);
    qreal topLeftRadius() const;
    void setTopLeftRadius(qreal radius);
    qreal topRightRadius() const;
    void setTopRightRadius(qreal radius);
    qreal bottomLeftRadius() const;
    void setBottomLeftRadius(qreal radius);
    qreal bottomRightRadius() const;
    void setBottomRightRadius(qreal radius);
    QColor color() const;
    void setColor(QColor color);
    DelPen *border();
    void paint(QPainter *painter) override;
signals:
    void radiusChanged();
    void topLeftRadiusChanged();
    void topRightRadiusChanged();
    void bottomLeftRadiusChanged();
    void bottomRightRadiusChanged();
    void colorChanged();
private:
    Q_DECLARE_PRIVATE(DelRectangle);
    QSharedPointer<DelRectanglePrivate> d_ptr;
};

#endif // DELRECTANGLE_H

實現(xiàn)文件（delrectangle.cpp）

#include "delrectangle.h"

#include <QPainter>
#include <QPainterPath>
#include <private/qqmlglobal_p.h>

class DelRectanglePrivate
{
public:
    QColor m_color = { 0xffffff };
    DelPen *m_pen = nullptr;
    qreal m_radius = 0;
    qreal m_topLeftRadius = 0;
    qreal m_topRightRadius = 0;
    qreal m_bottomLeftRadius = 0;
    qreal m_bottomRightRadius = 0;
};

DelRectangle::DelRectangle(QQuickItem *parent)
    : QQuickPaintedItem{parent}
    , d_ptr(new DelRectanglePrivate)
{
}

DelRectangle::~DelRectangle()
{
}

qreal DelRectangle::radius() const
{
    Q_D(const DelRectangle);
    return d->m_radius;
}

void DelRectangle::setRadius(qreal radius)
{
    Q_D(DelRectangle);
    if (d->m_radius != radius) {
        d->m_radius = radius;
        d->m_topLeftRadius = radius;
        d->m_topRightRadius = radius;
        d->m_bottomLeftRadius = radius;
        d->m_bottomRightRadius = radius;
        emit radiusChanged();
        update();
    }
}

// 其他 getter 和 setter 方法省略...

QColor DelRectangle::color() const
{
    Q_D(const DelRectangle);
    return d->m_color;
}

void DelRectangle::setColor(QColor color)
{
    Q_D(DelRectangle);
    if (d->m_color != color) {
        d->m_color = color;
        emit colorChanged();
        update();
    }
}

DelPen *DelRectangle::border()
{
    Q_D(DelRectangle);
    if (!d->m_pen) {
        d->m_pen = new DelPen;
        QQml_setParent_noEvent(d->m_pen, this);
        connect(d->m_pen, &DelPen::colorChanged, this, [this]{ update(); });
        connect(d->m_pen, &DelPen::widthChanged, this, [this]{ update(); });
        update();
    }
    return d->m_pen;
}

void DelRectangle::paint(QPainter *painter)
{
    Q_D(DelRectangle);
    painter->save();
    painter->setRenderHint(QPainter::Antialiasing);
    QRectF rect = boundingRect();
    if (d->m_pen && d->m_pen->isValid()) {
        rect = boundingRect();
        if (rect.width() > d->m_pen->width() * 2) {
            auto dx = d->m_pen->width() * 0.5;
            rect.adjust(dx, 0, -dx, 0);
        }
        if (rect.height() > d->m_pen->width() * 2) {
            auto dy = d->m_pen->width() * 0.5;
            rect.adjust(0, dy, 0, -dy);
        }
        painter->setPen(QPen(d->m_pen->color(), d->m_pen->width(), Qt::SolidLine, Qt::SquareCap, Qt::SvgMiterJoin));
    }
    QPainterPath path;
    path.moveTo(rect.bottomRight() - QPointF(0, d->m_bottomRightRadius));
    path.lineTo(rect.topRight() + QPointF(0, d->m_topRightRadius));
    path.arcTo(QRectF(QPointF(rect.topRight() - QPointF(d->m_topRightRadius * 2, 0)), QSize(d->m_topRightRadius * 2, d->m_topRightRadius * 2)), 0, 90);
    path.lineTo(rect.topLeft() + QPointF(d->m_topLeftRadius, 0));
    path.arcTo(QRectF(QPointF(rect.topLeft()), QSize(d->m_topLeftRadius * 2, d->m_topLeftRadius * 2)), 90, 90);
    path.lineTo(rect.bottomLeft() - QPointF(0, d->m_bottomLeftRadius));
    path.arcTo(QRectF(QPointF(rect.bottomLeft().x(), rect.bottomLeft().y() - d->m_bottomLeftRadius * 2), QSize(d->m_bottomLeftRadius * 2, d->m_bottomLeftRadius * 2)), 180, 90);
    path.lineTo(rect.bottomRight() - QPointF(d->m_bottomRightRadius, 0));
    path.arcTo(QRectF(QPointF(rect.bottomRight() - QPointF(d->m_bottomRightRadius * 2, d->m_bottomRightRadius * 2)), QSize(d->m_bottomRightRadius * 2, d->m_bottomRightRadius * 2)), 270, 90);
    painter->setBrush(d->m_color);
    painter->drawPath(path);
    painter->restore();
}

關(guān)鍵點解析

自定義 Qml 元素：通過繼承 QQuickPaintedItem 并使用 QML_NAMED_ELEMENT 宏，我們可以將自定義的 C++ 類注冊為 Qml 元素。

屬性定義：我們定義了多個屬性來控制矩形的圓角半徑和顏色，例如 radius、topLeftRadius、color 等，并提供了相應(yīng)的 getter 和 setter 方法。

邊框管理：通過 DelPen 類來管理矩形的邊框樣式，包括邊框顏色和寬度。

繪制邏輯：在 paint() 方法中，我們使用 QPainterPath 來繪制具有不同圓角的矩形。通過組合使用直線和弧線，我們可以實現(xiàn)任意角的圓角效果。

使用示例

在 Qml 文件中，我們可以像使用標準的 Rectangle 元素一樣使用 DelRectangle：

import QtQuick 2.15
import QtQuick.Window 2.15
import DelegateUI.Controls 1.0

Window {
    visible: true
    width: 400
    height: 300
    title: "DelRectangle Example"

    DelRectangle {
        anchors.centerIn: parent
        width: 200
        height: 150
        color: "lightblue"
        topLeftRadius: 20
        bottomRightRadius: 30
        border {
            width: 2
            color: "blue"
        }
    }
}