单例类Test

#pragma once
#include <qwidget.h>
class Test :public QWidget
{
public:static Test& instance(){static Test test;return test;}void set(int a, int b){c = a;d = b;}void get(int& a, int& b){a = c;b = d;}
private:int c=0;int d=0;Test() {}Test(const Test&) {}Test& operator==(const Test&) {}
};

SingleInstance单例类

#pragma once#include <QtWidgets/QMainWindow>
#include "ui_SingleInstance.h"class SingleInstance : public QMainWindow
{Q_OBJECTpublic:SingleInstance(QWidget *parent = Q_NULLPTR);static SingleInstance& instance(){static SingleInstance qinstance;return qinstance;}
private:Ui::SingleInstanceClass ui;
};

main.cpp

#include "SingleInstance.h"
#include <QtWidgets/QApplication>
#include "Test.h"int main(int argc, char *argv[])
{QApplication a(argc, argv);Test::instance().set(3,5);//此处将Test类中的c、d设置为3、5SingleInstance::instance().show();return a.exec();
}

SingleInstance.cpp

#include "SingleInstance.h"
#include <qpushbutton.h>
#include "Test.h"
#include <qmessagebox.h>
#include <qdebug.h>SingleInstance::SingleInstance(QWidget *parent): QMainWindow(parent)
{ui.setupUi(this);int a=0, b=0;Test::instance().get(a,b);qDebug() << "a:" << a << " b:" << b << endl;//此处打印3,5
}