我是Qt和C++的初学者,想了解如何在Qt中使用QPainter和事件,但因执行时出现错误消息而卡住了,这是我的原始代码:
主.cpp
#include "customwidget.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QScopedPointer<QWidget> widget(new customWidget());
widget->resize(240, 120);
widget->show();
return a.exec();
}
并且还有标题:
#ifndef CUSTOMWIDGET_H
#define CUSTOMWIDGET_H
#include <QWidget>
#include <QMouseEvent>
#include <QPoint>
#include <QPainter>
class customWidget : public QWidget
{
Q_OBJECT
public:
explicit customWidget(QWidget *parent = 0);
void paintEvent(QPaintEvent *);
void mouseMoveEvent(QMouseEvent *event);
void mousePressEvent(QMouseEvent *event);
private:
QPoint m_mousePos;
QRect m_r2;
signals:
void needToRepaint();
public slots:
};
#endif // CUSTOMWIDGET_H
还有 .cpp 文件:
#include "customwidget.h"
customWidget::customWidget(QWidget *parent) : QWidget(parent)
{
QRect m_r2;
QPoint m_mousePos;
QObject::connect(this, SIGNAL(needToRepaint()), this, SLOT(repaint()));
}
void customWidget::paintEvent(QPaintEvent *)
{
QPainter painter(this);
// ############ First Rectangle ****************************************
QRect r1 = rect().adjusted(10, 10, -10, -10);
painter.setPen(QColor("#FFFFFF"));
painter.drawRect(r1);
// ############ Seconde Rectangle ****************************************
QRect r2(QPoint(0, 0), QSize(100, 100));
m_r2.moveCenter(m_mousePos);
QPainter painter2;
QPen pen;
painter2.setPen(QColor("#000000"));
pen.setWidth(3);
painter2.setPen(pen);
painter2.drawRect(m_r2);
update();
}
void customWidget::mouseMoveEvent(QMouseEvent *event)
{
m_mousePos = event->pos();
emit needToRepaint();
}
我试图在网络上搜索,发现这是因为QPainter不在paintEvent中而无法正常工作,但在我的代码中不是这种情况,感谢你的帮助。
painter2.begin(objectWhereToDraw)
和painter2.end()
。或者直接创建QPainter painter2(objectWhereToDraw)
。 - ilotXXI