qt 文本滚动条

开发项目中学习到的知识，记录一下。文本在qlabel控件中来回滚动

#ifndef SCROLLLABEL_H
#define SCROLLLABEL_H

#include 
#include 
#include 
#include 
class ScrollLabel : public QLabel
{
public:
    ScrollLabel(QWidget *parent = nullptr);

public:
    void paintEvent(QPaintEvent *);
    void UpdateIndex();
    void StartScroll(int p_IsUp, QString p_Str1, QString p_Str2);
    void SetFont(QFont p_Font);
    void SetText(QString p_Str);

private:
    QTimer *m_Timer;
    int m_CurIndex;
    int m_IsUp;
    QString m_Str1;
    QString m_Str2;
    QFont m_Font;
};

#endif // SCROLLLABEL_H

#include "scrolllabel.h"
#include 
#include 
#include 

ScrollLabel::ScrollLabel(QWidget *parent): QLabel(parent)
{
    m_CurIndex = 0;
    m_Timer = new QTimer(this);
    m_Timer->setInterval(20);
    connect(m_Timer, &QTimer::timeout, this, &ScrollLabel::UpdateIndex);
}

void ScrollLabel::paintEvent(QPaintEvent *)
{
    QPen pen;
    pen.setColor(QColor(255,255,255));

    QPainter painter(this);
    painter.setPen(pen);
    painter.setFont(m_Font);

    QFontMetrics FontMetrics(m_Font);

    int Str1Width = FontMetrics.width(m_Str1);//字符的宽度
    int Str2Width = FontMetrics.width(m_Str2);//字符的宽度
    int CharWidth = FontMetrics.width("a");//每个字符的宽度

    int Interval = (width() - Str1Width)/2;
    int Interval2 = (width() - Str2Width)/2;

    if(0 == m_CurIndex)
    {
        painter.drawText(Interval , 22, m_Str1);
    }
    else
    {
        if(m_IsUp)
        {
            painter.drawText(Interval+CharWidth*m_CurIndex, 22, m_Str1);
            painter.drawText(CharWidth*m_CurIndex - Str2Width + (Interval - Interval2), 22, m_Str2);

            if(Interval + CharWidth*m_CurIndex > width())
            {
                m_Timer->stop( );
                m_CurIndex = 0;
            }
        }
        else
        {
            painter.drawText((width() -Str1Width)/2-CharWidth*m_CurIndex, 22, m_Str1);
            painter.drawText(width() - CharWidth*m_CurIndex+(Interval2 - Interval), 22, m_Str2);

            if(Interval + Str1Width < CharWidth*m_CurIndex)
            {
                m_Timer->stop( );
                m_CurIndex = 0;
            }
        }

    }
}

void ScrollLabel::UpdateIndex()
{
    update();
    m_CurIndex++;
}


void ScrollLabel::SetFont(QFont p_Font)
{
    m_Font = p_Font;
}

void ScrollLabel::SetText(QString p_Str)
{
    m_Str1 = p_Str;
    update();
}

void ScrollLabel::StartScroll(int p_IsUp, QString p_Str1, QString p_Str2)
{
    m_IsUp = p_IsUp;
    m_Str1 = p_Str1;
    m_Str2 = p_Str2;
    m_Timer->start( );
}

调用方法：

m_total_mileage_text_label = new ScrollLabel(this);

//开始滚动
m_total_mileage_text_label->StartScroll(IsUp, Str1, Str2);

IsUp 1：指滚向上一条 0：滚向下一条
str1和str2分别指滚动前的字符串和滚动后的字符串