登录窗口

#include "widget.h"
#include "ui_widget.h"



Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    this -> setFixedSize(540, 410); //固定窗口大小
    this -> setWindowTitle("啊啊啊");  //设置窗口标题
    this -> setWindowIcon(QIcon(":/icon/1.png"));    //设置窗口图标

    lab1 = new QLabel(this);    //构造一个标签
    lab1 -> setPixmap(QPixmap(":/icon/logo.png"));    //标签中添加图片
    lab1 -> setScaledContents(true);    //设置图片自适应
    lab1 -> move(0, 0); //标签位置
    lab1 -> resize(540,150);    //标签大小

    lab2 = new QLabel(this);    //构建账户标签
    lab2 -> setPixmap(QPixmap(":/icon/userName.jpg"));    //标签中添加图片
    lab2 -> setScaledContents(true);    //设置图片自适应
    lab2 -> move(80, 200); //标签位置
    lab2 -> resize(50,50);    //标签大小

    lab3 = new QLabel(this);    //构建密码标签
    lab3 -> setPixmap(QPixmap(":/icon/passwd.jpg"));    //标签中添加图片
    lab3 -> setScaledContents(true);    //设置图片自适应
    lab3 -> move(80, 280); //标签位置
    lab3 -> resize(50,50);    //标签大小

    lab4 = new QLabel(this);
    lab4 -> move(80, 350); //标签位置
    lab4 -> resize(100,20);    //标签大小

    edit1 = new QLineEdit(this);
    edit1 -> setPlaceholderText("QQ号码/手机号/邮箱");
    edit1 -> move(180, 200);
    edit1 -> resize(300,50);

    edit2 = new QLineEdit(this);
    edit2 -> setPlaceholderText("密码");
    edit2 -> setEchoMode(QLineEdit::Password);
    edit2 -> move(180, 280);
    edit2 -> resize(300,50);

    btn1 = new QPushButton(QIcon(":/icon/login.png"),"登录",this);
    btn1 -> move(260, 350);
    btn1 -> resize(100, 40);

    btn2 = new QPushButton(QIcon(":/icon/cancel.png"),"取消",this);
    btn2 -> move(380, 350);
    btn2 -> resize(100, 40);

    /******************************************************************/
    connect(btn1, &QPushButton::clicked, this, &Widget::Loging);
    connect(btn2, SIGNAL(clicked()), this, SLOT(close()));
}

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

void Widget::Loging()
{
    if("admin" == edit1->text() && "123456" == edit2->text()){
        qDebug() << "登录成功";
        lab4 -> setText("登陆成功");
        emit jump();
        this -> close();
    }
    else if("admin" == edit1->text()){
        qDebug() << "密码错误登录失败";
        lab4 -> setText("密码错误登录失败");
        emit jump_err();
        edit2 -> clear();
    }
    else{
        qDebug() << "账号错误";
        lab4 -> setText("账号错误");
        emit jump_err();
        edit2 -> clear();
    }
}

主函数 

#include "widget.h"
#include"form.h"    //第二个界面的头文件
#include"error.h"

#include <QApplication>

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

    Form f;

    error e;

    QObject::connect(&w, &Widget::jump_err, &e, &error::jump_slot);

    QObject::connect(&w, &Widget::jump, &f, &Form::jump_slot);  //将第一个界面的信号函数与第二个界面的槽函数连接

    return a.exec();
}

登录成功后的窗口 

#include "form.h"
#include "ui_form.h"


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

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

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

登录失败后的窗口

#include "error.h"
#include "ui_error.h"

void error::jump_slot()
{
    ui -> lab1 ->setText("登录错误");
    connect(ui->btn1, &QPushButton::clicked, this, &error::close);
    this -> show();
}

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

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