Qt -- 输出hello world

界面设计：

.h中定义slots

#include <QtWidgets/QMainWindow>
#include "ui_QtGuiApplication2.h"

class QtGuiApplication2 : public QMainWindow
{
    Q_OBJECT

public:
    QtGuiApplication2(QWidget *parent = Q_NULLPTR);
    void init();

private:
    Ui::QtGuiApplication2Class ui;

private slots:
    void onshow();
};

.cpp中实现