main.cpp

#include "widget.h"
#include "second.h"#include <QApplication>int main(int argc, char *argv[])
{QApplication a(argc, argv);Widget w;w.show();//实例化第二个界面Second s;QObject::connect(&w, &Widget::my_jump, &s, &Second::jump_slot);return a.exec();
}

second.cpp

#include "second.h"
#include "ui_second.h"Second::Second(QWidget *parent) :QWidget(parent),ui(new Ui::Second)
{ui->setupUi(this);
}Second::~Second()
{delete ui;
}//第二个界面自定义的槽函数的实现
void Second::jump_slot()
{this->show();
}void Second::on_sendBtn_clicked()
{QString msg = ui->msgEdit->text();ui->msgWidget->addItem(msg);
}

widget.cpp

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);ui->setupUi(this);this->setWindowFlag(Qt::FramelessWindowHint);this->setAttribute(Qt::WA_TranslucentBackground);connect(ui->exit_btn, &QPushButton::clicked, this, &Widget::on_exit_btn_clicked);connect(ui->login_btn, &QPushButton::clicked, this, &Widget::on_login_btn_clicked);}Widget::~Widget()
{delete ui;
}void Widget::on_login_btn_clicked()
{if(ui->name_edit->text() == "admin" && ui->code_edit->text() == "123456"){QMessageBox::information(this,"提示","登录成功",QMessageBox::Ok);this->close();emit my_jump();}else{QMessageBox msg(QMessageBox::Warning,"警告","账号和密码不匹配,是否重新登陆",QMessageBox::Yes | QMessageBox::No,this);int ret = msg.exec();if(ret == QMessageBox::Yes){  //判断警报this->show();ui->code_edit->clear();   //清除}else{this->close();   //关闭}}
}void Widget::on_exit_btn_clicked()
{this->close();
}

second.ui

widget.ui