如果条件为真JavaFX如何在场景之间切换

Question

我正在使用 javaFX 创建登录系统。当用户输入正确的用户名和密码时，系统应打开一个名为“Dashbord”的新场景。 这是我的登录功能

public void validatelogin() throws SQLException, ClassNotFoundException, IOException {
    String jdbcURL = "jdbc:mysql://localhost/medibase";
    String username = "root";
    String password = "0852";
    Connection connection = DriverManager.getConnection(jdbcURL,username,password);
    Class.forName("com.mysql.jdbc.Driver");
    String uname = username1.getText();
    String psd = password1.getText();
    pst=connection.prepareStatement("SELECT * FROM user_account WHERE username=? and password=?");
    pst.setString(1, uname);
    pst.setString(2, psd);
    rs = pst.executeQuery();
    if(rs.next()){
    //loginmessagelabel.setText("Congratulations");
        switchtoSC1(null);
        
    } else{
        loginmessagelabel.setText("Login failed");
    }

}

当用户输入正确的用户名和密码时，我调用了 switchtoSC1 方法，但这不起作用。这是方法，，

public void switchtoSC1(ActionEvent event)throws IOException {
    Parent root = FXMLLoader.load(getClass().getResource("Dashboard.fxml"));
    stage = (Stage)((Node)event.getSource()).getScene().getWindow();
    scene=new Scene(root);
    stage.setScene(scene);
    stage.show();


}

Answer 1

正如@James_D已经说过的，你必须传递一个非空事件来获取阶段变量，并且你还应该在同一个阶段中更改场景而不是再次创建一个新阶段，因为这不会照顾资源和会减慢应用程序的速度。

另外，查看您的登录代码，我建议您仅通过用户名获取数据库行，然后将密码（如果是密码哈希值更好，或者使用加盐哈希值更好）作为变量进行比较。这是因为结果集可能很棘手，并且您不想将身份验证基于它。

public void validateLogin(Connection conn) {

    String username = username1.getText(); // you should obviously prevent username 
                                           // duplication in the signin page code
    String password = password1.getText();

    String queryStr = "select * from user_account where username=?";

    try (PreparedStatement prepStmt = conn.prepareStatement(queryStr)) {

        prepStmt.setString(1, username);
        ResultSet rset = prepStmt.executeQuery();

        if (!rset.next())
            throw new LoginFailedException(); // the username doesn't match any database 
                                              // row

        byte[] passwordHash = rset.getBytes("passwordColumn"); // get the password hash from 
                                                               // the resultset

        byte[] inputHash = someHashingFunction(password); // get the input hash with the same 
                                                          // function used to store passwords, 
                                                          // so that you get the same result 
                                                          // inputting the same password

        checkHashes(passwordHash, inputHash))
        switchScene(); // some method or block to switch scenes

    } catch (LoginFailedException e) {
        // show some error scene here
    }
}

public void checkHashes(byte[] passwordHash, byte[] inputHash) throw LoginFailedException {

    for (int x = 0; x < inputHash.length; x++) {
        if (passwordHash[x] != inputHash[x]) {
            throw new LoginFailedException();
    }        
}

Answer 2

这就是我在场景之间切换的方法。 当用户输入正确的用户凭证时，场景将更改为 SalaryCalcForm.fxml

HelloApplication.java

package org.xxxxx;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.io.IOException;

public class HelloApplication extends Application {
    @Override
    public void start(Stage primaryStage) throws IOException {

        Parent root = FXMLLoader.load(getClass().getResource("login.fxml"));
        primaryStage.setTitle("Login");
        primaryStage.setScene(new Scene(root, 520, 400));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch();
    }
}

HelloController.java

package org.jayathilakariceproducts.jayathilakarice;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextArea;
import javafx.stage.Stage;
import javafx.stage.Window;
import org.jayathilakariceproducts.jayathilakarice.login.LoginDAO;

import java.io.IOException;

public class HelloController {

    private Stage stage;
    private Scene scene;
    private Parent root;



    @FXML
    private Button loginButton;

    @FXML
    private Label loginMessageLabel;

    @FXML
    private TextArea userNameTextArea;

    @FXML
    private PasswordField passwordPasswordField;

    public void switchToSalaryCalcForm(ActionEvent event) throws IOException {
        root = FXMLLoader.load(getClass().getResource("salaryCalcForm.fxml"));
        stage = (Stage)((Node)event.getSource()).getScene().getWindow();
        stage.setScene(new Scene(root));
        stage.show();
    }

    // use for future redirections
    public void switchToXXXXXXXXX(ActionEvent event) throws IOException {
        root = FXMLLoader.load(getClass().getResource("yourfxmlFile.fxml"));
        stage = (Stage)((Node)event.getSource()).getScene().getWindow();
        stage.setScene(new Scene(root));
        stage.show();
    }

//When the login button is clicked, this method executes.
// LoginDAO does the database operations.
    public void loginButtonOnAction(ActionEvent e) throws IOException {
        LoginDAO loginDAO = new LoginDAO();
         //validate inputs
        if (userNameTextArea.getText() == null || userNameTextArea.getText().isBlank()){
            loginMessageLabel.setText("User Name is Empty. Please enter the user name");
        }
        else if (passwordPasswordField.getText() == null || passwordPasswordField.getText().isBlank()){
            loginMessageLabel.setText("Password is Empty. Please enter the password");
        }
        else {
            boolean isValidate = loginDAO.isUserAuthorized(userNameTextArea.getText() , passwordPasswordField.getText());
            if (isValidate) {
                loginMessageLabel.setText("user authorized to login");
                 // swith the scene. pass argument 'e'
                switchToSalaryCalcForm(e);
            } else {
                loginMessageLabel.setText("failed to login");
            }
        }
    }
}