Qt——仿bilibili直播的调音量控件

.h

/////////////////////////////////////////////////////////
//BIG_C_GOD
/////////////////////////////////////////////////////////
class VolumeController : public QWidget
{
    Q_OBJECT
public:
    explicit VolumeController(QWidget *parent = 0);

    void setMaxValue(int value);
protected:
    int m_maxValue;
    int m_value;
    int m_mouseCurPos;
    int m_isPress;

    void mousePressEvent(QMouseEvent *);
    void mouseMoveEvent(QMouseEvent *);
    void mouseReleaseEvent(QMouseEvent *);
    void leaveEvent(QEvent *);
    void paintEvent(QPaintEvent *);

signals:
    void valueChange(int value);
};

.cpp

VolumeController::VolumeController(QWidget *parent) :
    QWidget(parent),m_maxValue(100),m_value(0),m_mouseCurPos(0),m_isPress(0)
{
    setMouseTracking(true);//在任何情况下启用mouseMoveEvent
}

void VolumeController::setMaxValue(int value)
{
    m_maxValue = value;
}

void VolumeController::mousePressEvent(QMouseEvent *e)
{
    m_isPress = 1;

    if(e->pos().x() >= 0 && e->pos().x() <= width())
    {
        m_mouseCurPos = e->pos().x();
        m_value = e->pos().x();
    }

    emit valueChange(m_value*m_maxValue/width());

    update();
}

void VolumeController::mouseMoveEvent(QMouseEvent *e)
{
    if(e->pos().x() >= 0 && e->pos().x() <= width())
    {
        //鼠标滑过生效
        m_mouseCurPos = e->pos().x();

        //鼠标按下生效
        if(m_isPress)
            m_value = e->pos().x();
    }

    emit valueChange(m_value*m_maxValue/width());

    update();
}

void VolumeController::mouseReleaseEvent(QMouseEvent *)
{
    m_isPress = 0;
}

void VolumeController::leaveEvent(QEvent *)
{
    m_mouseCurPos = 0;

    update();
}

void VolumeController::paintEvent(QPaintEvent *)
{
    QPainter painter;

    painter.begin(this);
    painter.fillRect(rect(),QColor(0,0,0,100));
    painter.end();

    QImage mask(width(),height(),QImage::Format_ARGB32);
    painter.begin(&mask);
    painter.setPen(Qt::NoPen);
    painter.setBrush(QColor(0,0,0));
    mask.fill(QColor(255,255,255,0));

    int scaling_flag = m_mouseCurPos*10/width();//找出鼠标悬停的位置

    for(int i = 0; i < 10; ++i)
        if(i == scaling_flag)
        {
            double parameter = qAbs(width()/20 - m_mouseCurPos%(width()/10))/(double)width()*20;//参数为0时最大
            painter.drawRoundedRect(QRect(width()/10*i + width()/40,parameter*height()/5,
                                          width()/20,height() - parameter*height()/5),
                                    width()/20,width()/20);
        }
        else
            painter.drawRoundedRect(QRect(width()/10*i + width()/40,height()/5,width()/20,height()/5*4),
                                    width()/20,width()/20);
    painter.end();

    painter.begin(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    QRegion region(QBitmap::fromImage(mask));
    painter.setClipRegion(region);

    painter.fillRect(QRect(0,0,width(),height()),QColor(255,255,255));
    painter.fillRect(QRect(0,0,m_value,height()),QColor(242,156,177));
    painter.end();
}