Qt DoubleSlider 双滑块支持float变化的控件，以及单滑块float控件

最近做到一个项目，需要设置一个参数的上下限，最开始考虑的办法是用QSlider控件来实现，发现有两个不太合适的地方。

• 一个参数需要用两个控件来设置，而且两者之间还有大小关系的限制，比较麻烦；
• QSlider只支持int类型的输入与改变。

因此，决定自己写一个，本着资源共享的精神，特将代码贴出，供大家参考，如有更好的想法，也欢迎指正与交流。

双滑块的代码

#ifndef DOUBLESLIDER_H
#define DOUBLESLIDER_H
 
#include 
 
class DoubleSlider : public QWidget
{
    Q_OBJECT
public:
    DoubleSlider(QWidget* parent = 0);
    void setRange(float min, float max);
    void setSingleStep(float step);
 
    enum State{ MinHandle,MaxHandle,None};
 
    float minValue() const;
    float maxValue() const;
 
    float minRange() const;
    float maxRange() const;
 
public slots:
    void setLabel(const QString& label);
    void setMaxValue(float val);
    void setMinValue(float val);
 
signals:
    void minValueChanged(float);
    void maxValueChanged(float);
 
private:
    float m_min;
    float m_max;
    float m_singleStep;
 
    float m_minValue;
    float m_maxValue;
 
    QRect minHandleRegion;
    QRect maxHandleRegion;
 
    State m_state;
 
    QString m_label;
 
protected:
    void paintEvent(QPaintEvent* event);
    void paintColoredRect(QRect rect, QColor color, QPainter* painter);
    void paintValueLabel(QPainter* painter);
 
    void mousePressEvent(QMouseEvent* event);
    void mouseMoveEvent(QMouseEvent* event);
 
    void keyPressEvent(QKeyEvent *event);
    void leaveEvent(QEvent* event);
 
};
 
#endif // DOUBLESLIDER_H

#include "doubleslider.h"
#include 
#include 
 
DoubleSlider::DoubleSlider(QWidget* parent)
    : QWidget(parent)
    , m_min(0.0f)
    , m_max(99.0f)
    , m_singleStep(0.1f)
    , m_minValue(0.0f)
    , m_maxValue(99.0f)
    , m_state(None)
{
    setFixedHeight(50);
    setFocusPolicy(Qt::StrongFocus);
}
 
void DoubleSlider::paintEvent(QPaintEvent* event)
{
    QWidget::paintEvent(event);
    QPainter painter(this);
    paintValueLabel(&painter);
}
 
void DoubleSlider::paintColoredRect(QRect rect, QColor color ,QPainter* painter)
{
    painter->fillRect(rect,QBrush(color));
}
 
void DoubleSlider::paintValueLabel(QPainter* painter)
{
    painter->setBrush(Qt::NoBrush);
    painter->setPen(Qt::black);
    painter->setFont(QFont("Arial",12));
 
    QString minValueString = QString::number(m_minValue,'f',3);
    QString maxValueString = QString::number(m_maxValue,'f',3);
 
    QFontMetrics metrics = painter->fontMetrics();
    int mintextWidth = metrics.width(minValueString);
    int maxtextWidth = metrics.width(maxValueString);
    int textHeight = metrics.height();
 
    //---- paint text
    painter->drawText(QRectF(2,4,mintextWidth,textHeight),minValueString);
    painter->drawText(QRectF(width() - maxtextWidth -2, 4, maxtextWidth,textHeight), maxValueString);
 
 
    //----- paint label
    painter->setFont(QFont("Arial",12));
    metrics = painter->fontMetrics();
    int labelWidth = metrics.width(m_label);
    int labelHeight = metrics.height();
 
    QRectF textRect = QRectF((width()/2 - labelWidth/2), 0,labelWidth,labelHeight);
 
    painter->drawText(textRect,m_label);
 
 
    int minPos = ( m_minValue - m_min ) * width() / (m_max - m_min);
    int maxPos = (m_maxValue - m_min ) * width() /  (m_max - m_min);
 
    if(minPos <= 4){
        minPos = 4;
    }else if(minPos >= width() - 8){
        minPos = width() - 8;
    }else{}
 
    if(maxPos <= 4){
        maxPos = 4;
    }else if(maxPos >= width() -8){
        maxPos = width() - 8;
    }else{}
 
 
    //----- paint groove
    paintColoredRect(QRect(4,37,width() - 8,2),Qt::gray,painter);
    paintColoredRect(QRect(minPos + 4,37,maxPos - minPos,2),QColor(51,153,155),painter);
 
    //----- handle
 
    minHandleRegion = QRect(minPos ,30,8,16);
    maxHandleRegion = QRect(maxPos ,30,8,16);
 
    //-----paint Handle
    QColor minColor  = (m_state == MinHandle) ? QColor(51,153,155) : Qt::darkGray;
    QColor maxColor  = (m_state == MaxHandle) ? QColor(51,153,155) : Qt::darkGray;
    paintColoredRect(minHandleRegion,minColor,painter);
    paintColoredRect(maxHandleRegion,maxColor,painter);
}
 
inline float getValidValue(float val, float min, float max)
{
    float tmp = std::max(val, min);
    return std::min(tmp, max);
}
 
 
void DoubleSlider::setRange(float min, float max)
{
    m_min = min;
    m_max = max;
 
    if(minValue() < m_min)
        setMinValue(m_min);
 
    if(maxValue() > m_max){
        setMaxValue(m_max);
    }
}
 
void DoubleSlider::setSingleStep(float step)
{
    m_singleStep = step;
}
 
float DoubleSlider::minValue() const
{
    return m_minValue;
}
void DoubleSlider::setMinValue(float val)
{
    if(fabs( m_minValue - val ) > 0.0001 ){
        m_minValue = val;
        emit minValueChanged(val);
    }
}
 
float DoubleSlider::maxValue() const
{
    return m_maxValue;
}
void DoubleSlider::setMaxValue(float val)
{
    if(fabs(m_maxValue - val) > 0.0001){
        m_maxValue = val;
        emit maxValueChanged(val);
    }
}
 
void DoubleSlider::setLabel(const QString& label)
{
   m_label = label;
   update();
}
 
void DoubleSlider::leaveEvent(QEvent* event)
{
    QWidget::leaveEvent(event);
    m_state = None;
    update();
}
 
float DoubleSlider::minRange() const
{
    return m_min;
}
float DoubleSlider::maxRange() const
{
    return m_max;
}
 
 
void DoubleSlider::mousePressEvent(QMouseEvent* event)
{
    if(minHandleRegion.contains(event->pos())){
        m_state = MinHandle;
    }else if(maxHandleRegion.contains(event->pos())){
        m_state = MaxHandle;
    }else{
        m_state = None;
    }
 
    if(fabs(minValue() - maxValue()) < 0.001){
        if(fabs(minValue() - m_min) < 0.001){
            m_state = MaxHandle;
        }else if(fabs(minValue() - m_max) < 0.001){
            m_state = MinHandle;
        }else{}
    }
 
    update();
}
 
void DoubleSlider::mouseMoveEvent(QMouseEvent* event)
{
    if(event->buttons() & Qt::LeftButton){
        float move = event->x() * (m_max - m_min) * 1.0/ width() + m_min;
 
        switch(m_state){
            case MinHandle:{
                float val = getValidValue( move, m_min,maxValue());
                setMinValue(val);
                break;
            }
 
            case MaxHandle:{
                    float val = getValidValue(move, minValue(), m_max);
                    setMaxValue(val);
                    break;
            }
            case None:default: break;
        }
    }
    update();
}
 
 
void DoubleSlider::keyPressEvent(QKeyEvent *event)
{
    QWidget::keyPressEvent(event);
 
    if(event->key() == Qt::Key_Left){
        if(m_state == MinHandle){
            float val = getValidValue(minValue()- m_singleStep, m_min ,maxValue());
            setMinValue(val);
        }else if(m_state == MaxHandle) {
            float val = getValidValue(maxValue()- m_singleStep, minValue() ,m_max);
            setMaxValue(val);
        }else{}
    }else if(event->key() == Qt::Key_Right){
        if(m_state == MinHandle){
            float val = getValidValue(minValue() + m_singleStep, m_min ,maxValue());
            setMinValue(val);
        }else if(m_state == MaxHandle) {
            float val = getValidValue(maxValue() + m_singleStep, minValue() ,m_max);
            setMaxValue(val);
        }else{}
    }
 
    update();
 
}