1>使用手动连接，将登录框中的取消按钮使用qt4版本的连接到自定义的槽函数中，在自定义的槽函数中调用关闭函。将登录按钮使用qt5版本的连接到自定义的槽函数中，在槽函数中判断ui界面上输入的账号是否为"admin"，密码是否为"123456",如果账号密码匹配成功，则输出“登录成功”，并关闭该界面，如果匹配失败，则输出登录失败，并将密码框中的内容清空

代码：

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPushButton>
#include <QDebug>
QT_BEGIN_NAMESPACE
namespace Ui {
class Widget;
}
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

signals:
    void jump_success_signal();
    void jump_failure_signal();
    void jump_signal();

private slots:
    void on_Login_clicked();

    void on_Cancel_clicked();

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

success.h

#ifndef SUCCESS_H
#define SUCCESS_H

#include <QWidget>

namespace Ui {
class Success;
}

class Success : public QWidget
{
    Q_OBJECT

public:
    explicit Success(QWidget *parent = nullptr);
    ~Success();

public slots:
    void jump_slot();

private:
    Ui::Success *ui;
};

#endif // SUCCESS_H

failure.h

#ifndef FAILURE_H
#define FAILURE_H

#include <QWidget>

namespace Ui {
class Failure;
}

class Failure : public QWidget
{
    Q_OBJECT

public:
    explicit Failure(QWidget *parent = nullptr);
    ~Failure();

public slots:
    void jump_slot();//界面2-槽函数声明

private:
    Ui::Failure *ui;
};

#endif // FAILURE_H

main.cpp

#include "widget.h"
#include "success.h"
#include "failure.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    Success s;
    Failure f;

    QObject::connect(&w,&Widget::jump_success_signal,&s,&Success::jump_slot);
    QObject::connect(&w,&Widget::jump_failure_signal,&f,&Failure::jump_slot);
    return a.exec();
}

widget.cpp

#include "widget.h"
#include "ui_widget.h"
Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    connect(ui->Cancel,SIGNAL(clicked()),this,SLOT(on_Cancel_clicked()));
}

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



void Widget::on_Login_clicked()
{
    QString user=ui->User->text();
    QString passwd=ui->Passwd->text();
    if(user == "admin" && passwd == "123456")
        emit jump_success_signal();
    else
    {
        ui->User->clear();
        ui->Passwd->clear();
        emit jump_failure_signal();

    }
}



void Widget::on_Cancel_clicked()
{
    this->close();
}

success.cpp

#include "success.h"
#include "ui_success.h"

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

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

void Success::jump_slot()
{
    this->show();
}

failure.cpp

#include "failure.h"
#include "ui_failure.h"

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

Failure::~Failure()
{
    delete ui;
}
void Failure::jump_slot()
{
    this->show();
}

结果：

2>自己完成一个使用qss的登陆窗口界面。

*{

	background-color: rgb(255, 255, 255);
}

QFrame#frame{
	border-radius:30px;
	border-image: url(:/Logo/shanChuan.jpg);
}

#frame_2{
	border-radius:30px;
	background-color: rgba(112, 112, 112,120);
}

QLabel#label{
	border-radius:30px;
	background-color: rgba(130, 130, 130,120);
}

#label_2{
	background:transparent;/*完全透明*/
	font: 30pt "Hiragino Sans GB";
	
	color: rgba(255, 255, 255,120);
}

QLineEdit {
	background:transparent;
	border:none;/*无边框*/
	
	border-bottom:1px solid rgba(255, 255, 255, 110);
}

QPushButton{
	border-radius:10px;
	color: rgba(255,255,255,180);
	background-color: qlineargradient(spread:pad, x1:0, y1:0, x2:1, y2:0, stop:0 rgba(40, 97, 229, 255), stop:1 rgba(255, 255, 255, 255));
}

QPushButton:hover{ 	/*鼠标移动*/
	border-radius:10px;
	color: rgba(255,255,255,180);
	background-color: qlineargradient(spread:pad, x1:0, y1:0, x2:1, y2:0, stop:0 rgba(40, 97, 229, 255), stop:1 rgba(255, 255, 255, 255));
}

QPushButton:pressed{	/*鼠标点击*/
	border-radius:10px;
	color: rgba(255,255,255,180);
	background-color: qlineargradient(spread:pad, x1:0, y1:0, x2:1, y2:0, stop:0 rgba(60, 97, 229, 255), stop:1 rgba(255, 255, 255, 255));

	padding-top:5px;
	padding-left:5px;
}