qt 一个可以拖拽的矩形

1.概要

2.代码

2.1 mycotrl.h

#ifndef MYCOTRL_H
#define MYCOTRL_H#include <QWidget>
#include <QMouseEvent>class MyCotrl: public QWidget
{Q_OBJECT
public://MyCotrl();MyCotrl(QWidget *parent = nullptr);
protected:void paintEvent(QPaintEvent *event);void mousePressEvent(QMouseEvent *event);void mouseMoveEvent(QMouseEvent *event);void mouseReleaseEvent(QMouseEvent *event);
private:bool dragging;QPoint oldPos;
};

2.2 widget.h 

 

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>QT_BEGIN_NAMESPACE
namespace Ui {
class Widget;
}
QT_END_NAMESPACEclass Widget : public QWidget
{Q_OBJECTpublic:Widget(QWidget *parent = nullptr);~Widget();private:Ui::Widget *ui;
};
#endif // WIDGET_H

2.3 mycotrl.cpp 

 

#include "mycotrl.h"
#include <QPainter>//MyCotrl::MyCotrl() {}MyCotrl::MyCotrl(QWidget *parent) : QWidget(parent), dragging(false)
{}void MyCotrl::paintEvent(QPaintEvent *event)  {QPainter painter(this);painter.setRenderHint(QPainter::Antialiasing);painter.setBrush(Qt::blue);painter.drawRect(rect()); // 绘制一个矩形，其大小由QWidget的size决定
}void MyCotrl::mousePressEvent(QMouseEvent *event){if (event->button() == Qt::LeftButton) {dragging = true;oldPos = event->pos();}
}void MyCotrl::mouseMoveEvent(QMouseEvent *event){if (dragging) {move(mapToParent(event->pos()) - oldPos);oldPos = event->pos();}
}void MyCotrl::mouseReleaseEvent(QMouseEvent *event) {Q_UNUSED(event)dragging = false;
}

 

2.4 widget.cpp 

 

#include "widget.h"
#include "ui_widget.h"
#include <QPushButton>
#include "mycotrl.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);QPushButton *button = new QPushButton("My Button", this);// 设置按钮的位置和大小（可选）// 注意：在 QMainWindow 中，你可能需要先设置一个 central widget 或其他容器button->setGeometry(QRect(10, 10, 100, 30));MyCotrl* my = new MyCotrl(this);button->setGeometry(QRect(100, 100, 100, 30));
}Widget::~Widget()
{delete ui;
}

2.5 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