QT编译错误：XXX does not name a type【如图】

Question

Answer 1

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include

namespace Ui {
class widget;
}

class widget : public QWidget
{
Q_OBJECT

public:
explicit widget(QWidget *parent = 0);
~widget();

private:
Ui::widget *ui;
};

#endif // WIDGET_H