下图绘制的是矩形对象,但是将绘制矩形函数(drawRect)更改为绘制圆形(drawEllipse)即可绘制圆形。
#ifndef CMAINWINDOW_H
#define CMAINWINDOW_H#include
#include
#include QT_BEGIN_NAMESPACE
namespace Ui { class CMainWindow; }
QT_END_NAMESPACEclass CMainWindow : public QMainWindow
{Q_OBJECTpublic:CMainWindow(QWidget *parent = nullptr);~CMainWindow();private:Ui::CMainWindow *ui;// QWidget interface
protected:/*** @brief paintEvent 绘制事件* @param event 绘制事件对象*/void paintEvent(QPaintEvent *event);// QWidget interface
protected:/*** @brief mouseReleaseEvent 鼠标释放事件* @param event 鼠标事件对象*/void mouseReleaseEvent(QMouseEvent *event);/*** @brief mouseMoveEvent 鼠标移动事件* @param event 鼠标事件对象*/void mouseMoveEvent(QMouseEvent *event);/*** @brief mouseMoveEvent 鼠标按下事件* @param event 鼠标事件对象*/void mousePressEvent(QMouseEvent *event);private:QPoint m_startPos; // 鼠标按下起始位置QRect m_tmpRect; // 当前rect对象QList m_listRect; // 历史rect容器};
#endif // CMAINWINDOW_H
#include "CMainWindow.h"
#include "ui_CMainWindow.h"#include
#include CMainWindow::CMainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::CMainWindow)
{ui->setupUi(this);
}CMainWindow::~CMainWindow()
{delete ui;
}void CMainWindow::paintEvent(QPaintEvent *event)
{// 创建画笔对象QPainter painter(this);// 设置绘制对象抗锯齿painter.setRenderHint(QPainter::Antialiasing);// 绘制当前rect对象painter.drawRect(m_tmpRect);// 遍历绘制历史rect对象foreach(const QRect &rect, m_listRect){painter.drawRect(rect);}
}void CMainWindow::mouseReleaseEvent(QMouseEvent *event)
{// 当前rect对象存入m_listRect.append(m_tmpRect);// 当前rect对象置空m_tmpRect = QRect();// 重绘界面this->repaint(this->rect());
}void CMainWindow::mouseMoveEvent(QMouseEvent *event)
{// 当前rect对象赋值m_tmpRect = QRect(m_startPos, event->pos());// 更新界面this->update(this->rect());
}void CMainWindow::mousePressEvent(QMouseEvent *event)
{// 其实点赋值m_startPos = event->pos();
}
文章较简单,练手即可,下章为QPainter实现画笔功能。
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