效果:

核心代码:

#include "simpleapp.h"
#include "ui_simpleapp.h"
#include <QMessageBox>

SimpleApp::SimpleApp(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::SimpleApp)
{
    ui->setupUi(this);
}

SimpleApp::~SimpleApp()
{
    delete ui;
}

void SimpleApp::on_btnExit_clicked()
{
    close();

}


// 此项目参考地址:
// https://www.youtube.com/watch?v=6FjOY28Nl5g&ab_channel=HelloC%26CPPByProgrammingKnowledge


void SimpleApp::on_btnLongin_clicked()
{
    QString name = ui->usernameTxt->text();
    QString pass = ui->passwordTxt->text();


    if (name == "admin" && pass == "123") {
        QMessageBox::information(this, "Login", "账号密码都正确！");

        // 先隐藏登录窗口。
        hide();

        // 显示一个新的窗口。
        secDialog = new SecDialog(this);
        secDialog->show();

    } else {
        QMessageBox::warning(this, "Login", "账号或密码不正确！请检查！");
    }
}

完整项目已经上传， 免积分下载，https://download.csdn.net/download/waterHBO/89547456