qt 简单实验 画一个等边三角形

1.概要

2.代码

2.1 widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPainter>

QT_BEGIN_NAMESPACE
namespace Ui {
class Widget;
}
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
protected:
    void paintEvent(QPaintEvent *event);

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

2.2 widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::paintEvent(QPaintEvent *event){
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);

    // 设置画笔颜色
    painter.setPen(Qt::black);

    // 设置画刷颜色（如果需要填充）
    painter.setBrush(Qt::lightGray);

    // 计算等边三角形的大小和位置
    int side = qMin(width(), height()) * 0.7; // 边长取窗口宽度和高度中较小值的70%
    int centerX = width() / 2;
    int centerY = height() / 2;

    // 计算等边三角形顶点的位置
    QPointF point1(centerX, centerY - side / 2.0 * sqrt(3.0) / 2.0);
    QPointF point2(centerX + side / 2.0, centerY + side / 2.0 * sqrt(3.0) / 2.0);
    QPointF point3(centerX - side / 2.0, centerY + side / 2.0 * sqrt(3.0) / 2.0);

    // 绘制等边三角形
    QPolygonF triangle;
    triangle << point1 << point2 << point3;
    painter.drawPolygon(triangle);
}

2.3 main.cpp

#include "widget.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}

3.运行结果