qt 自定義窗口繪制正弦曲線

circlewidget.h

#ifndef CIRCLAWIDGET_H
#define CIRCLAWIDGET_H
#include <QFrame>
#include<QVector>
#include<QMouseEvent>

class CircleWidget:public QFrame
{
    Q_OBJECT
public:
    CircleWidget(QWidget *parent);
    ~CircleWidget();
private:
    void paintEvent(QPaintEvent *event);


public:
    void Adjust(int period, int grain, int radius);
    QPoint origin();            // 坐標原點位置
    QPoint toCoord(QPoint p);   // 將GUI窗口的點(x,y)轉換成坐標系統里的點
    QPoint fromCoord(QPoint p); // 將坐標系內的(x,y)轉成GUI的坐標
private:

    int m_period, m_grain, m_radius;

};

#endif // CIRCLAWIDGET_H

circlewidget.cpp

# include"circlewidget.h"
#include<QPainter>
#include<QDebug>
#include<math.h>

CircleWidget::CircleWidget(QWidget *parent):QFrame(parent)
{
        m_period = 20;  //周期
        m_grain = 1;    //粒度
        m_radius = 10; // 振幅
}
CircleWidget::~CircleWidget()
{

}
void CircleWidget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);

        int width = this->width();
        int height = this->height();
        QRect rect(0,0, width, height);

        // 設置背景為黑色
        painter.setBrush(QBrush(QColor(0x00,0x00, 0x00)));
        painter.drawRect(rect);

        painter.setPen(QPen(QColor(0, 255, 0))); // 設置線條為綠色

        QPoint o = origin();
        painter.drawLine(QPoint(0, o.y()), QPoint(width, o.y())); // x軸
        painter.drawLine(QPoint(o.x(), 0), QPoint(o.x(), height));// y軸


        // 正弦曲線: 從坐標原點，向左、向右伸展
        QPoint p1(0,0);
        for(int x=0; x<width/2; x+=m_grain)
        {
            // y=sin(x)
            double angle = (double) x / m_period * 2 * 3.1415926;
            double y = m_radius * sin(angle);
            QPoint p2(x, y);

            // 右側
            painter.drawLine(fromCoord(p1), fromCoord(p2));

            // 左側
            QPoint base(0,0);
            painter.drawLine(fromCoord(base-p1), fromCoord(base-p2));

            p1 = p2;
        }

}

void CircleWidget::Adjust(int period, int grain, int radius)
{
    m_period = period;
    m_grain = grain;
    m_radius = radius;
    update(); // 更新重繪
}

QPoint CircleWidget::origin()
{
    QRect r = this->rect();
    return r.center();
}
// 將GUI窗口的點(x,y)轉換成數學坐標系統里的點
QPoint CircleWidget::toCoord(QPoint p)
{
    // 圓心
    QPoint o = this->origin();
    QPoint result =  p - o;
    result.setY(0 - result.y()); // y坐標反轉
    return result;
}
// 將數學坐標系內的(x,y)轉成GUI的坐標
QPoint CircleWidget::fromCoord(QPoint p)
{
    // 圓心
    QPoint o = this->origin();
    p.setY(0 - p.y()); // y坐標反轉
    return p + o;

}

結果：