分享按钮栏实现小例子

class Line : public QLabel {
    Q_OBJECT
public:
    Line(QWidget *parent = NULL) : QLabel(parent) { }

    /* 绘图事件 */
    void paintEvent(QPaintEvent *)
    {
        QPainter painter(this);
        /* 设置画笔 */
        painter.setPen(QPen(Qt::black, height()));
        /* 画线 */
        painter.drawLine(0, 0, width(), 0);
    }
};

class Button : public QPushButton {
    Q_OBJECT
public:
    Button(const QString &text, QWidget *parent = NULL) :
        QPushButton(text, parent)
    {
        m_line = new Line(this);
        m_line->setVisible(false);
        QString styleSheet = R"(
                             QPushButton {
                                 border: 0px;
                                 border-radius: 5px;
                                 margin: 0px;
                                 padding: 0px;
                                 font-size: 16px;
                                 background: white;
                                 color: black;
                                 outline: none;
                             }
                             QPushButton:pressed{
                                 outline: none;
                                 background: #1ABC9C;
                                 color: white;
                             }
                             )";
        this->setStyleSheet(styleSheet);
    }

    void focusInEvent(QFocusEvent *)
    {
        /* 焦点进入则显示底部线条 */
        m_line->setVisible(true);
    }

    void focusOutEvent(QFocusEvent *)
    {
        /* 焦点离开则隐藏底部线条 */
        m_line->setVisible(false);
    }

    void resizeEvent(QResizeEvent *event)
    {
        /* 按按钮大小变化时ye也要自动适应其底部线条的大小与位置 */
        m_line->resize(event->size().width()*0.75, 5);
        int lineX = (event->size().width() - m_line->width())/2;
        int lineY = event->size().height() * 0.85;
        m_line->move(lineX, lineY);
    }

private:
    Line *m_line;
};

QHBoxLayout *layout = new QHBoxLayout;
for (int i = 0; i < 5; i++) {
    Button *btn = new Button(QString::fromLocal8Bit("标题") + QString::number(i+1));
    btn->setFixedSize(80, 50);
    layout->addWidget(btn);
}

QWidget w;
w.setWindowTitle(QString::fromLocal8Bit("按钮栏@Qt君"));
w.setLayout(layout);
w.show();