基于pyqt6和mysql实现用户登录注册功能和界面跳转

以下是基于PyQt6和MySQL实现用户登录注册功能和界面跳转的示例代码，包括登录界面、注册界面和主界面三个界面，实现了用户注册、登录、注销和界面之间的跳转。

from PyQt6 import QtCore, QtGui, QtWidgets, QtSql
import mysql.connector

class Login(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("Login")

        # layout
        layout = QtWidgets.QVBoxLayout(self)

        # username input
        self.username_input = QtWidgets.QLineEdit()
        self.username_input.setPlaceholderText("Username")
        layout.addWidget(self.username_input)

        # password input
        self.password_input = QtWidgets.QLineEdit()
        self.password_input.setEchoMode(QtWidgets.QLineEdit.EchoMode.Password)
        self.password_input.setPlaceholderText("Password")
        layout.addWidget(self.password_input)

        # login button
        login_button = QtWidgets.QPushButton("Login")
        login_button.clicked.connect(self.login)
        layout.addWidget(login_button)

        # register button
        register_button = QtWidgets.QPushButton("Register")
        register_button.clicked.connect(self.show_register)
        layout.addWidget(register_button)

    def login(self):
        username = self.username_input.text()
        password = self.password_input.text()

        # connect to database
        mydb = mysql.connector.connect(
          host="localhost",
          user="yourusername",
          password="yourpassword",
          database="mydatabase"
        )

        mycursor = mydb.cursor()

        # check if user exists
        sql = "SELECT * FROM users WHERE username = %s AND password = %s"
        val = (username, password)
        mycursor.execute(sql, val)

        result = mycursor.fetchone()

        if result:
            # login successful, open main window
            self.main = MainWindow()
            self.main.show()
            self.close()
        else:
            # login failed, show error message
            QtWidgets.QMessageBox.warning(self, "Error", "Invalid username or password")

    def show_register(self):
        # show register window
        self.register = Register()
        self.register.show()
        self.close()


class Register(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("Register")

        # layout
        layout = QtWidgets.QVBoxLayout(self)

        # username input
        self.username_input = QtWidgets.QLineEdit()
        self.username_input.setPlaceholderText("Username")
        layout.addWidget(self.username_input)

        # password input
        self.password_input = QtWidgets.QLineEdit()
        self.password_input.setEchoMode(QtWidgets.QLineEdit.EchoMode.Password)
        self.password_input.setPlaceholderText("Password")
        layout.addWidget(self.password_input)

        # confirm password input
        self.confirm_password_input = QtWidgets.QLineEdit()
        self.confirm_password_input.setEchoMode(QtWidgets.QLineEdit.EchoMode.Password)
        self.confirm_password_input.setPlaceholderText("Confirm Password")
        layout.addWidget(self.confirm_password_input)

        # register button
        register_button = QtWidgets.QPushButton("Register")
        register_button.clicked.connect(self.register)
        layout.addWidget(register_button)

        # back button
        back_button = QtWidgets.QPushButton("Back")
        back_button.clicked.connect(self.show_login)
        layout.addWidget(back_button)

    def register(self):
        username = self.username_input.text()
        password = self.password_input.text()
        confirm_password = self.confirm_password_input.text()

        if password != confirm_password:
            # password and confirm password do not match, show error message
            QtWidgets.QMessageBox.warning(self, "Error", "Passwords do not match")
            return

        # connect to database
        mydb = mysql.connector.connect(
          host="localhost",
          user="yourusername",
          password="yourpassword",
          database="mydatabase"
        )

        mycursor = mydb.cursor()

        # check if user exists
        sql = "SELECT * FROM users WHERE username = %s"
        val = (username,)
        mycursor.execute(sql, val)

        result = mycursor.fetchone()

        if result:
            # user already exists, show error message
            QtWidgets.QMessageBox.warning(self, "Error", "User already exists")
            return

        # insert new user to database
        sql = "INSERT INTO users (username, password) VALUES (%s, %s)"
        val = (username, password)
        mycursor.execute(sql, val)
        mydb.commit()

        # registration successful, show success message and go back to login window
        QtWidgets.QMessageBox.information(self, "Success", "User registered successfully")
        self.show_login()

    def show_login(self):
        # show login window
        self.login = Login()
        self.login.show()
        self.close()


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("Main")

        # layout
        central_widget = QtWidgets.QWidget()
        self.setCentralWidget(central_widget)
        layout = QtWidgets.QVBoxLayout(central_widget)

        # welcome label
        welcome_label = QtWidgets.QLabel("Welcome!")
        welcome_label.setAlignment(QtCore.Qt.AlignmentFlag.AlignCenter)
        welcome_label.setFont(QtGui.QFont("Arial", 20))
        layout.addWidget(welcome_label)

        # logout button
        logout_button = QtWidgets.QPushButton("Logout")
        logout_button.clicked.connect(self.logout)
        layout.addWidget(logout_button)

    def logout(self):
        # logout and go back to login window
        self.login = Login()
        self.login.show()
        self.close()


if __name__ == "__main__":
    app = QtWidgets.QApplication([])

    # connect to database
    db = QtSql.QSqlDatabase.addDatabase("QMYSQL")
    db.setHostName("localhost")
    db.setUserName("yourusername")
    db.setPassword("yourpassword")
    db.setDatabaseName("mydatabase")
    if not db.open():
        QtWidgets.QMessageBox.warning(None, "Error", "Database connection failed")
        exit(-1)

    # show login window
    login = Login()
    login.show()

    app.exec()

在这段代码中，我们首先创建了三个界面：登录界面、注册界面和主界面。登录界面包含了用户名和密码的输入框和登录按钮，点击登录按钮后会检查用户是否存在于数据库中，如果存在则跳转到主界面，否则弹出错误提示。注册界面包含了用户名、密码和确认密码的输入框和注册按钮，点击注册按钮后会检查用户名是否已经存在于数据库中，如果不存在则将用户信息插入到数据库中，注册成功后回到登录界面。主界面包含了欢迎标签和注销按钮，点击注销按钮后回到登录界面。

在主程序中，我们首先连接到数据库，如果连接失败则弹出错误提示。然后显示登录界面，进入主程序循环。