QTpainter 程序

#ifndef WIDGET_H
#define WIDGET_H

#include

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

    void paintEvent(QPaintEvent *event);

private slots:
    void on_pushButton_clicked();

private:
    Ui::Widget *ui;

    qreal x,y,r;

};
#endif // WIDGET_H

-------------------------------------------------

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

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    x = 200;
    y = 300;
    r = 0;
}

Widget::~Widget()
{
    delete ui;
}

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.save();//Save current position

    painter.setPen(QColor(255,0,0));
    painter.setBrush(QColor(0,255,255));
    painter.translate(x,y);//Move from the current position
    painter.rotate(r);

    QPoint polygonPoint[] = {{-10,0},{0,30},{10,0}};
    painter.drawPolygon(polygonPoint,3);

    QPoint linePointA = {0,20};
    QPoint linePointB = {-50,0};
    painter.drawLine(linePointA,linePointB);

    QRectF rect = {50,0,50,100};
    painter.drawRect(rect);

    int ellipseX = 0;
    int ellipseY = 50;
    int ellipseWidth = 50;
    int ellipseHeight = 100;
    painter.drawEllipse(ellipseX,ellipseY,ellipseWidth,ellipseHeight);

    painter.restore();//Restore current position
}

void Widget::on_pushButton_clicked()
{
    x = ui->lineEdit->text().toDouble();
    y = ui->lineEdit_2->text().toDouble();
    r += ui->lineEdit_3->text().toDouble();

    update();
}