mainwindow.h

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
 
signals:
    void jump();           //自定义跳转信号函数
 
private slots:
 
    void on_pushButton_clicked();
 
    void on_pushButton_2_clicked();
 
private:
    Ui::MainWindow *ui;
 
    Second *s1;  //定义另一个界面的指针
};
#endif // MAINWINDOW_H

second.h

#ifndef SECOND_H
#define SECOND_H
 
#include <QDialog>
 
namespace Ui {
class Second;
}
 
class Second : public QDialog
{
    Q_OBJECT
 
public:
    explicit Second(QWidget *parent = nullptr);
    ~Second();
 
public slots:
    void jump_slot();         //接收跳转信号的槽函数
 
private:
    Ui::Second *ui;
};
 
#endif // SECOND_H

mianwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    ui->label->setPixmap(QPixmap("D:\\QTtupian\\jimoaqing.gif"));
    ui->label->setScaledContents(true);
 
    ui->label_2->setPixmap(QPixmap("D:\\QTtupian\\zhanghao.jpg"));
    ui->label_2->setScaledContents(true);
    ui->label_3->setPixmap(QPixmap("D:\\QTtupian\\mima.jpg"));
    ui->label_3->setScaledContents(true);
 
    s1 = new Second;            //给另一个界面实例化空间
 
    //将当前界面的信号，与s1界面的槽函数进行连接
    connect(this,&MainWindow::jump, s1, &Second::jump_slot);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
 
void MainWindow::on_pushButton_clicked()
{
    if(ui->lineEdit->text()=="admin"&&ui->lineEdit_2->text()=="123456")
    {
        //信息对话框
        QMessageBox box(QMessageBox::Question,"信息对话框","登录成功",
                        QMessageBox::Ok,this);
        box.setDefaultButton(QMessageBox::Ok);  //默认到ok上
 
        int ret = box.exec();  //运行对话框
        if(ret == QMessageBox::Ok)
        {
            emit jump();  //发送跳转信息
 
            this->hide();        //将当前界面隐藏
        }
    }
    else
    {
        //错误对话框
        QMessageBox box(QMessageBox::Question,"错误对话框","账号密码不匹配，是否重新登录",
                        QMessageBox::Ok|QMessageBox::Cancel,this);
        box.setDefaultButton(QMessageBox::Ok);  //默认到ok上
        int ret = box.exec();  //运行对话框
        switch(ret)
        {
        case QMessageBox::Ok:
            ui->lineEdit->clear();  //清楚账号密码内容
            ui->lineEdit_2->clear();
            break;
        case QMessageBox::Cancel:
            //ret=box.close();
            break;
        }
    }
 
}
 
void MainWindow::on_pushButton_2_clicked()
{
    //问题对话框
    int ret = QMessageBox::question(this,"问题对话框","是否确定要退出登录",
                                    QMessageBox::Yes|QMessageBox::No,
                                    QMessageBox::No);
 
    switch(ret)
    {
        case QMessageBox::Yes:
            this->close();  //关闭窗口
            break;
        case QMessageBox::No:
            break;
    }
}

second.cpp

#include "second.h"
#include "ui_second.h"
 
Second::Second(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Second)
{
    ui->setupUi(this);
}
 
Second::~Second()
{
    delete ui;
}
 
//接收跳转信号对应的槽函数
void Second::jump_slot()
{
    this->show();            //将自己界面进行展示
}

main.cpp

#include "mainwindow.h"
 
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}