前文链接：Qt动态多级导航菜单（二）
本次更新，主要将原导航项NavItem抽象为基类NavItemBase, 并派生出带有图标样式的动态多级导航菜单。至此，关于想要增加自定义的导航菜单样式，只需要从NavItemBase类派生即可。
效果图

核心代码

#pragma once
#include "NavItemBase.h"

class NavItem2 : public NavItemBase
{
	Q_OBJECT
public:
	NavItem2(const QString &text, NavItemBase *parent = nullptr);
	~NavItem2();

protected:
	virtual void paintEvent(QPaintEvent *event) override;
};

#include "NavItem2.h"
#include "QWHNavTreeView.h"
#include <QPainter>

NavItem2::NavItem2(const QString &text, NavItemBase *parent /*= nullptr*/)
	: NavItemBase(text, parent)
{

}

NavItem2::~NavItem2()
{

}

void NavItem2::paintEvent(QPaintEvent *event)
{
	Q_UNUSED(event)

	int width = this->width();
	int height = this->height();

	QPainter painter(this);
	painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);

	// 绘制背景
	painter.setPen((m_view->m_showTopItemBorder && 0 == m_level) ? QPen(m_selected ? m_view->m_borderSelectedColor : (m_hover ? m_view->m_borderHoverColor : m_view->m_borderColor), m_view->m_borderWidth) : Qt::NoPen);
	painter.setBrush(m_selected ? m_view->m_bgSelectedColor : (m_hover ? m_view->m_bgHoverColor : m_view->m_bgColor));

	// 判断是否是第一个顶层节点
	QPoint p = m_view->m_contentWidget->mapFromGlobal(this->mapToGlobal(QPoint(0, 0)));
	bool topFirst = p.y() == 0;
	painter.drawRect(rect().adjusted(-m_view->m_borderWidth, topFirst ? -m_view->m_borderWidth : -m_view->m_borderWidth / 2, m_view->m_borderWidth, 0));

	int iconSize = m_view->m_showIcon ? m_view->m_iconSize : 10;

	// 绘制折叠标志
	if (m_view->m_branchType == QWHNavTreeView::TRIANGLE)
	{
		// 只有顶层节点绘制
		if (!m_parent)
		{
			painter.save();
			int offsetY = 1;
			painter.translate(width - m_view->m_paddingLR - m_view->m_branchSize, height / 2 - offsetY);
			painter.rotate(m_childNum > 0 ? m_angle : -90);
			QPainterPath path;
			path.moveTo(-m_view->m_branchSize / 2, -m_view->m_branchSize * 0.3);
			path.lineTo(m_view->m_branchSize / 2, -m_view->m_branchSize * 0.3);
			path.lineTo(0, m_view->m_branchSize * 0.6);
			path.closeSubpath();
			painter.setPen(Qt::NoPen);
			painter.setBrush(m_selected ? m_view->m_branchSelectedColor : (m_hover ? m_view->m_branchHoverColor : m_view->m_branchColor));
			painter.drawPath(path);
			painter.restore();
		}
	}
	else// m_view->m_branchColor == QWHNavTreeView::CROSS
	{
		// 只有顶层节点绘制
		if (!m_parent)
		{
			painter.save();
			painter.translate(width - m_view->m_paddingLR - m_view->m_branchSize, height / 2);
			painter.rotate(m_childNum > 0 ? m_angle : -90);
			QPainterPath path;
			path.addRect(-m_view->m_branchSize / 2, -NavContentWidget::LINE_WIDTH / 2, m_view->m_branchSize, NavContentWidget::LINE_WIDTH);
			if (0 != m_angle)
				path.addRect(-NavContentWidget::LINE_WIDTH / 2, -m_view->m_branchSize / 2, NavContentWidget::LINE_WIDTH, m_view->m_branchSize);
			painter.setPen(Qt::NoPen);
			painter.setBrush(m_selected ? m_view->m_branchSelectedColor : (m_hover ? m_view->m_branchHoverColor : m_view->m_branchColor));
			painter.drawPath(path);
			painter.restore();
		}
	}

	// 绘制文本
	int offsetX = 6;
	int textW = width - (m_view->m_paddingLR + m_view->m_branchSize + iconSize + offsetX);
	QRect textRect(m_view->m_paddingLR + iconSize / 2 * 5, 0, textW, height);
	QFont font = painter.font();
	font.setPixelSize(20);
	painter.setFont(font);
	painter.setPen(QPen(m_selected ? m_view->m_selectedColor : (m_hover ? m_view->m_hoverColor : m_view->m_color), 2));
	painter.drawText(textRect, Qt::AlignLeft | Qt::AlignVCenter, m_text);

	// 绘制图标
	if (m_view->m_showIcon)
	{
		QRect iconRect(m_view->m_paddingLR + QWHNavTreeView::LEVEL_X * m_level + iconSize / 2, (height - iconSize) / 2, iconSize, iconSize);
		painter.drawPixmap(iconRect, m_icon);
	}
}