Qt实现画笔功能

用Qt实现在窗口上画线，类似于画笔功能。头文件#ifndefMyPaint_h__#defineMyPaint_h__#includeQtWidgets/QWidgetclassMyPaint...

用Qt实现在窗口上画线，类似于画笔功能。

头文件

#ifndef MyPaint_h__
#define MyPaint_h__

#include <QtWidgets/QWidget>

class MyPaint :public QWidget
{
 Q_OBJECT
public:
 MyPaint(QWidget *parent = nullptr);

 void mousePressEvent(QMouseEvent *event);
 void mouseMoveEvent(QMouseEvent *event);
 void mouseReleaseEvent(QMouseEvent *event);
 void paintEvent(QPaintEvent *event);

private:
 std::vector<std::vector<QPoint>> _lines;

};

#endif // MyPaint_h__

实现

#include "MyPaint.h"
#inclupythonde <QPainter>
#编程include <QMouseEvent>


MyPaint::MyPaint(QWidget *parent):QWidget(parent)
{

}

void MyPaint::mousePressEvent(QMouseEvent *event) //鼠标按下的时候新增加一条线，并记录起点
{
 std::vector<QPoint> line; 
 line.push_back(event->pos());
 _lines.push_back(line);
}

void MyPaint::mouseMoveEvent(QMouseEvent *event)//鼠标移动的时候新增加点
{
 auto &line = _lines[_lines.size() - 1];
 line.push_back(event->pos());

 update(); //更新，重新绘制窗口，自动调用paintEvent
}

void MyPaint::mouseReleaseEvent(QMouseEvent *event)
{
 auto &line = _lines[_lines.size() - 1];
 line.push_back(event->pos());
}

void MyPaint::paintEvent(QPaintEvent *event) //绘制所有android的线
{
 //QPainter painter(this);
 //painter.setPen(QPen(Qt::red, 3, Qt::DashLine));
 //painter.setBrush(Qt::blue);
 //painter.drawRect(QRect(10, 10, 100, 30));
 //painter.drawEllipse(130, 10, 50, 50);
 //painter.drawLine(QLine(200, 10, 300, 20));
 //painter.drawTextphp(QPoint(10, 70), "hello" );
 QPainter painter(this);
 painter.setPen(QPen(Qt::green, 3));
 for (const auto &line : _lines)
 {
  for (int i=0;i<line.size()-1;i++)
  {
   painter.drawLine(line.at(i), line.at(i + 1));
  }
 }
}

效果

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