qt 使用QPainter绘图

QPainter 绘制一些简单的图形，也可以设置文字，设置笔，路径等。需要实现paintEvent这个方法，然后使用QPainter需要传入this指针，表示父类会调用。

#include "basicshapewindow.h"
#include "ui_basicshapewindow.h"

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

void BasicShapeWindow::paintEvent(QPaintEvent *event)
{
    QPainter textPainter(this);
    textPainter.setFont(QFont("Times", 14, QFont::Bold));
    textPainter.drawText(QPoint(40, 60), "Testing");

    QPainter linePainter(this);
    linePainter.drawLine(QPoint(50, 60), QPoint(100, 100));

    QPainter rectPainter(this);
    rectPainter.setBrush(Qt::BDiagPattern);
    rectPainter.drawRect(QRect(40, 120, 80, 130));

    QPen ellipsePen;
    ellipsePen.setColor(Qt::red);
    ellipsePen.setStyle(Qt::DashDotLine);

    QPainter ellipsePainter(this);
    ellipsePainter.setPen(ellipsePen);
    ellipsePainter.drawEllipse(QPoint(200, 100), 150, 70);

    QPainterPath rectPath;
    rectPath.addRect(QRect(150, 60, 100, 50));
    QPainter pathPainter(this);
    pathPainter.setPen(QPen(Qt::red, 3, Qt::DashDotLine, Qt::FlatCap, Qt::MiterJoin));
    pathPainter.setBrush(Qt::yellow);
    pathPainter.drawPath(rectPath);

    QPainterPath ellipsePath;
    ellipsePath.addEllipse(QPoint(200, 120), 50, 120);
    QPainter ellipsePathPainter(this);
    ellipsePathPainter.setPen(QPen(QColor(79, 106, 25), 5,
                                            Qt::SolidLine, Qt::FlatCap, Qt::MiterJoin));
    ellipsePathPainter.setBrush(QColor(122, 163, 39));
    ellipsePathPainter.drawPath(ellipsePath);

    QImage image;
    image.load(":/head.png");
    QPainter imagePainter(this);
    imagePainter.drawImage(QPoint(100, 150), image);
}

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