| jdwx |
2013-04-01 20:50 |
在QWidget上用鼠标画方框
如何在QWidget上用鼠标画方框
很简单，只是为初学者提供一个最基本的鼠标画图的例子，代码很少很容易看懂。
直接上代码，附件里有全部的代码下载，这里只显示主要的部分：
win7 + Qt5 + VS2010，编译运行。
- #ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
namespace Ui {
class Widget;
}
class Widget : public QWidget
{
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
~Widget();
protected:
void mousePressEvent(QMouseEvent *e);
void mouseMoveEvent(QMouseEvent *e);
void mouseReleaseEvent(QMouseEvent *e);
void paintEvent(QPaintEvent *);
private slots:
private:
Ui::Widget *ui;
bool m_isDown;
QPoint m_start;
QPoint m_stop;
};
#endif // WIDGET_H
- #include "widget.h"
#include "ui_widget.h"
#include <QtWidgets>
Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
m_isDown = false;
}
Widget::~Widget()
{
delete ui;
}
void Widget::mousePressEvent(QMouseEvent *e)
{
if(e->button() && Qt::LeftButton){
m_isDown = true;
m_start = e->pos();
m_stop = e->pos();
}
}
void Widget::mouseMoveEvent(QMouseEvent *e)
{
if(m_isDown){
m_stop = e->pos();
}
update();
}
void Widget::mouseReleaseEvent(QMouseEvent *e)
{
if(e->button() && Qt::LeftButton){
m_isDown = false;
}
}
void Widget::paintEvent(QPaintEvent *)
{
if(!m_isDown){
return;
}
QPainter p(this);
p.drawRect(QRect(m_start,m_stop));
}
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