记录一个问题：
我重写了一个类myslider继承自QSlider，然后重写了paintEvent(QPaintEvent *)方法。
然后从工具栏拖一个QSlider工具到主界面上，名字为verticalSlider，然后将这个QSlider提升为自己的myslider
然后运行的时候发现不会执行myslider::paintEvent(QPaintEvent *)函数。也就是界面上不显示这个QSlider。
解决方案：
主界面构造函数中添加如下代码：
ui->verticalSlider->setParent(this);
ui->verticalSlider->show();
我自己重写的qslider具体如下，有兴趣的可以看看：
#include "myslider.h"
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MySlider::MySlider(QWidget *parent):
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m_SliderDir(VERTICAL_SLIDER),
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m_nMarkNum(5),
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m_fTopleftScale(0),
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m_fBottomleftScale(1)
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{
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}
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MySlider::~MySlider()
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{
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}
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void MySlider::paintEvent(QPaintEvent *)
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{
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//启用反锯齿
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QPainter painter(this);
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painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
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//绘制标尺
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QFont font = QFont("Microsoft YaHei");
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font.setPointSizeF(8);
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painter.setFont(font);
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int height = this->height();
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int width = this->width();
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qint64 nTotalTime= m_iStartDateTime.secsTo(m_iEndDateTime);//计算总时间(秒)
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qint64 nStepTime = nTotalTime*(m_fBottomleftScale-m_fTopleftScale)/(m_nMarkNum-1);//计算相邻刻度之间的时间间隔
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QDateTime iStartDateTime = m_iStartDateTime.addSecs(nTotalTime*m_fTopleftScale);//计算缩放后的开始时间
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if(m_SliderDir==VERTICAL_SLIDER)//垂直slider
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{
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qreal fStep = (height-10)*1.0f/(m_nMarkNum-1);//计算相邻刻度之间的距离
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for(int i=0;i<m_nMarkNum;i++)//绘制每一个刻度的时间与刻度标记
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{
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qreal fY = 10+fStep*i;
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QPointF ptText=QPointF(0,fY);
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QDateTime iCurDateTime = iStartDateTime.addSecs(nStepTime*i);
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QString strTime = iCurDateTime.toString("hh:mm");
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painter.setPen(QPen(Qt::red,1));
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painter.drawText(ptText,strTime);
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painter.setPen(QPen(Qt::blue,2));
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//绘制大刻度
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painter.drawLine(QPointF(width,fY-5),QPointF(width-4,fY-5));
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//绘制小刻度
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painter.setPen(QPen(Qt::blue,1));
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for(int j = 1;j<4;j++)
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{
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painter.drawLine(QPointF(width,fY-3+j*(fStep/4)),QPointF(width-4,fY-3+j*(fStep/4)));
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}
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}
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painter.setPen(QPen(Qt::blue,2));
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painter.drawLine(QPointF(width,0),QPointF(width,height));
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}
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else if(m_SliderDir == HORIZONTAL_SLIDER)//水平slider
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{
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//TODO:如果要让标尺横向显示，则需要在此处完善代码
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}
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}
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void MySlider::setStartStamp(qint64 nStartStamp)
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{
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QDateTime iOriginTime = QDateTime::fromString("1970-01-01 08:00:00","yyyy-MM-dd hh:mm:ss");
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m_iStartDateTime = iOriginTime.addSecs(nStartStamp);
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}
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void MySlider::setEndStamp(qint64 nEndStamp)
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{
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QDateTime iOriginTime = QDateTime::fromString("1970-01-01 08:00:00","yyyy-MM-dd hh:mm:ss");
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m_iEndDateTime = iOriginTime.addSecs(nEndStamp);
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}
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void MySlider::setScale(qreal topleftScale, qreal bottomleftScale)
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{
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m_fTopleftScale = topleftScale;
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m_fBottomleftScale = bottomleftScale;
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this->update();
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}
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```
