一、概述

最近想做一个炫酷的悬浮式菜单，考虑到菜单展开和美观，所以考虑学习下Qt的动画系统和状态机内容，打开QtCreator的示例教程浏览了下，大致发现教程中2D Painting程序和Animated Tiles程序有所帮助，如下图所示，这两个demo讲述了怎么做一个展开动画，感兴趣的同学也可以直接参考

有了这两个demo之后，就可以开始动工写咱们自己的程序。

二、效果展示

如下两幅图就是作者失效的两个悬浮菜单效果图，展示图1代码已上传至CSDN，不需要积分即可下载，效果图2代码暂时不开源，有需要的朋友可以进一步咨询

基础圆形菜单功能，代码已上传CSDN - Qt 失效的 PC 端环形菜单、悬浮球菜单、展开动画

高级悬浮球菜单、支持二级菜单打开

三、实现代码

实现文件比较简单，只有头文件和实现文件，这里先主要放出头文件，然后讲解实现思路，具体实现细节可以通过下载源码进行具体了解

1、菜单项

PopRingItem为菜单展开项、可以通过绑定外部QAction实现与普通菜单相同功能

class PopRingItem : public QLabel
{Q_OBJECTpublic:PopRingItem(QWidget *parent = 0);~PopRingItem();void SetRadius(int radius);int GetRadius() const;void BindAction(QAction * action);signals:void MouseEvent(bool);protected:virtual void enterEvent(QEvent * event) override;virtual void leaveEvent(QEvent * event) override;virtual void paintEvent(QPaintEvent * event) override;protected:int m_iRadius = 50;QAction * m_actAction = nullptr;
};

2、悬浮球

悬浮球为菜单入口，继承自菜单项，与菜单项有相似功能

class QVariantAnimation;
class QPropertyAnimation;
class PopRingMenu : public PopRingItem
{Q_OBJECTpublic:PopRingMenu(QWidget *parent = 0);~PopRingMenu();signals:void DoubleClicked();public:void SetActions(const QVector<QAction *> & acts);void SetIcons(const QVector<QString> & icons);void SetAnimationEnabled(bool enabled);bool IsAnimationEnabled() const;void SetSlowlyFade(bool enabled);bool IsSlowlyFade() const;void SetDistanced(int distance);int GetDistanced() const;void SetStartAngle(int angle);int GetStartAngle() const;void SetStepAngle(int angle);int GetStepAngle() const;void SetNormalMenuSize(int size);int GetNormalMenuSize() const;void SetNormalItemSize(int size);int GetNormalItemSize() const;protected:virtual void enterEvent(QEvent * event) override;virtual void leaveEvent(QEvent * event) override;virtual void mouseDoubleClickEvent(QMouseEvent * event) override;virtual void timerEvent(QTimerEvent * event) override;virtual bool event(QEvent * event) override;private slots:void OnMouseEvent(bool);private:void UpdateActions(int msecond);void ExpandMenu();void CollapseMenu();void SlowlyFade();void QuicklyLighter();bool IsUnderMouse() const;void TryCollapseMenu();void KillHideTimer();private:int m_iDistance = 70;int m_iStartAngle = 0;int m_iStepAngle = 60;int m_iMenuSize = 70;int m_iItemSize = 60;int m_iTimerID = -1;QPropertyAnimation * m_pOpacityAnimation = nullptr;QVariantAnimation * m_pItemAnimation = nullptr;QVector<PopRingItem *> m_items;
};

3、关键点

初始化动画对象，指定动画时长和动画起始、终止值

动画具体实现函数未UpdateAction，根据当前动画进度值在动画起始值和终止值所占比例，进行计算当前动画时刻菜单项的位置和大小

m_pItemAnimation = new QVariantAnimation(this);m_pItemAnimation->setEasingCurve(QEasingCurve::InCubic);
m_pItemAnimation->setStartValue(ShowMenuStartValue);
m_pItemAnimation->setEndValue(ShowMenuEndValue);
m_pItemAnimation->setDuration(ShowMenuDuration);connect(m_pItemAnimation, &QVariantAnimation::valueChanged, this, [this](const QVariant & v){UpdateActions(v.toInt());
});

鼠标进入悬浮球时，执行展开动画

void PopRingMenu::ExpandMenu()
{if (m_pItemAnimation){if (m_pItemAnimation->state() != QAbstractAnimation::Running&& m_pItemAnimation->currentValue().toInt() != ShowMenuEndValue){m_pItemAnimation->setDirection(QVariantAnimation::Forward);m_pItemAnimation->start();}}else{UpdateActions(ShowMenuEndValue);}KillHideTimer();QuicklyLighter();
}

鼠标离开悬浮球时，执行收起动画，与展开动画相反方向收起动画时有一个细节点，那就是鼠标hover在菜单项上时，也不能收起

void PopRingMenu::CollapseMenu()
{if (false == IsUnderMouse()){if (m_pItemAnimation){m_pItemAnimation->setDirection(QVariantAnimation::Backward);m_pItemAnimation->start();}else{UpdateActions(ShowMenuStartValue);}KillHideTimer();SlowlyFade();}
}

展开和收起动画实现细节，根据动画指定帧数，按比例进行缩放和移动菜单项

void PopRingMenu::UpdateActions(int msecond)
{int curDistance = msecond * m_iDistance / ShowMenuEndValue;for (int i = 0; i < m_items.size(); ++i){PopRingItem * item = m_items.at(i);double radians = qDegreesToRadians(m_iStepAngle * i * 1.0 + m_iStartAngle);int offx = curDistance * qCos(radians);int offy = curDistance * qSin(radians);item->move(pos() + QPoint(offx, offy));int curSize = msecond * m_iItemSize / ShowMenuEndValue;item->SetRadius(curSize);item->setVisible(ShowMenuStartValue != msecond);};::SetWindowPos(HWND(winId()), HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
}

悬浮球指定时间未激活时，淡出，减少对用户视觉冲击

void PopRingMenu::SetSlowlyFade(bool enabled)
{if (enabled){if (nullptr == m_pOpacityAnimation){m_pOpacityAnimation = new QPropertyAnimation(this, "opacity");m_pOpacityAnimation->setEasingCurve(QEasingCurve::OutCubic);m_pOpacityAnimation->setStartValue(SlowlyStartValue);m_pOpacityAnimation->setEndValue(SlowLyEndValue);m_pOpacityAnimation->setDuration(SlowlyFadeDuration);}}else{if (m_pOpacityAnimation){delete m_pOpacityAnimation;m_pOpacityAnimation = nullptr;}}
}