Qt自定义带游标的slider，在滑块正上方显示当前值（类似于进度条，用一个额外的QLabel冒充QSilder的一部分，然后move就行了）

首先自定义QSlider的子类MyCustomSlider，如下所示。

mycustomslider.h

#ifndef MYCUSTOMSLIDER_H
#define MYCUSTOMSLIDER_H
#include <QSlider>
#include <QLabel>
#include <QMouseEvent>
class MyCustomSlider : public QSlider
{
public:
    MyCustomSlider(QWidget *parent=0);
    ~MyCustomSlider();

protected:
    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);

private:
    QLabel* m_displayLabel;
};

#endif // MYCUSTOMSLIDER_H

mycustomslider.cpp

#include "mycustomslider.h"
#include <QPalette>

MyCustomSlider::MyCustomSlider(QWidget *parent):QSlider(parent)
{
   m_displayLabel=new QLabel(this);
   m_displayLabel->setFixedSize(QSize(20,20));
   //设置游标背景为白色
   m_displayLabel->setAutoFillBackground(true);
   QPalette palette;
   palette.setColor(QPalette::Background, Qt::white);
   m_displayLabel->setPalette(palette);

   m_displayLabel->setAlignment(Qt::AlignCenter);

   m_displayLabel->setVisible(false);
   m_displayLabel->move(0,3);
}

MyCustomSlider::~MyCustomSlider()
{

}

void MyCustomSlider::mousePressEvent(QMouseEvent *event)
{
    if(!m_displayLabel->isVisible())
    {
        m_displayLabel->setVisible(true);
        m_displayLabel->setText(QString::number(this->value()));
    }
    QSlider::mousePressEvent(event);
}

void MyCustomSlider::mouseReleaseEvent(QMouseEvent *event)
{
    if(m_displayLabel->isVisible())
    {
        m_displayLabel->setVisible(false);
    }
    QSlider::mouseReleaseEvent(event);
}

void MyCustomSlider::mouseMoveEvent(QMouseEvent *event)
{
    m_displayLabel->setText(QString::number(this->value()));
    m_displayLabel->move((this->width()-m_displayLabel->width())*this->value()/(this->maximum()-this->minimum()),3);
    QSlider::mouseMoveEvent(event);
}

然后将界面QSlider控件提升为MyCustomSlider，提升方法如下所示。

Qt中控件类的提升

最后的效果如下图所示，当鼠标点击滑块或者拖动滑块时，滑块正上方的游标实时显示当前值，松开鼠标时，游标隐藏。

源码链接：见http://blog.csdn.net/caoshangpa/article/details/51973902的评论

http://blog.csdn.net/caoshangpa/article/details/51973902