Java GUI 登录屏幕

Question

我为我的 Java GUI 程序创建了一个登录屏幕，单击按钮时的登录屏幕会检查文本字段中输入的用户名和密码是否等于文本文件中的行，如果相同，则允许用户移动到下一个屏幕，如果没有，将显示 JOptionPane.showMessageDialog。我还有另一个屏幕，允许用户写入插入新用户名和密码的文件。

是的，我的问题是它只读取最后两行代码，所以我只能使用上次创建的用户名和密码登录。我该如何让它读取每一行来检查用户名和密码？

主登录屏幕

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;

public class login extends JFrame {
  JButton blogin;
  JPanel loginpanel;
  JTextField txuser;
  JTextField pass;
  JButton newUSer;
  JLabel username;
  JLabel password;


  public login(){
    super("Login Autentification");

    blogin = new JButton("Login");
    loginpanel = new JPanel();
    txuser = new JTextField(15);
    pass = new JPasswordField(15);
    newUSer = new JButton("New User?");
    username = new JLabel("User - ");
    password = new JLabel("Pass - ");

    setSize(300,200);
    setLocation(500,280);
    loginpanel.setLayout (null); 


    txuser.setBounds(70,30,150,20);
    pass.setBounds(70,65,150,20);
    blogin.setBounds(110,100,80,20);
    newUSer.setBounds(110,135,80,20);
    username.setBounds(20,28,80,20);
    password.setBounds(20,63,80,20);

    loginpanel.add(blogin);
    loginpanel.add(txuser);
    loginpanel.add(pass);
    loginpanel.add(newUSer);
    loginpanel.add(username);
    loginpanel.add(password);

    getContentPane().add(loginpanel);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);

    Writer writer = null;
    File check = new File("userPass.txt");
    if(check.exists()){

      //Checks if the file exists. will not add anything if the file does exist.
    }else{
      try{
        File texting = new File("userPass.txt");
        writer = new BufferedWriter(new FileWriter(texting));
        writer.write("message");
      }catch(IOException e){
        e.printStackTrace();
      }
    }




    blogin.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        try {
          File file = new File("userPass.txt");
          Scanner scan = new Scanner(file);;
          String line = null;
          FileWriter filewrite = new FileWriter(file, true);

          String usertxt = " ";
          String passtxt = " ";
          String puname = txuser.getText();
          String ppaswd = pass.getText();


          while (scan.hasNext()) {
            usertxt = scan.nextLine();
            passtxt = scan.nextLine();

          }




          if(puname.equals(usertxt) && ppaswd.equals(passtxt)) {
            MainMenu menu =new MainMenu();
            dispose();
          } 
          else if(puname.equals("") && ppaswd.equals("")){
            JOptionPane.showMessageDialog(null,"Please insert Username and Password");
          }
          else {

            JOptionPane.showMessageDialog(null,"Wrong Username / Password");
            txuser.setText("");
            pass.setText("");
            txuser.requestFocus();
          }
        } catch (IOException d) {
          d.printStackTrace();
        }

      }
    });

    newUSer.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent e) {
        NewUser user = new NewUser();
        dispose();

      }
    });
  } 

}

以及新的用户文件

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;

public class NewUser extends JFrame {
  JButton create;
  JPanel newUserPanel;
  JTextField txuserer;
  JTextField passer;


  public NewUser(){
    super("Registration");

    create = new JButton("Create");
    newUserPanel = new JPanel();
    txuserer = new JTextField(15);
    passer = new JPasswordField(15);


    setSize(300,200);
    setLocation(500,280);
    newUserPanel.setLayout (null); 


    txuserer.setBounds(70,30,150,20);
    passer.setBounds(70,65,150,20);
    create.setBounds(110,100,80,20);

    newUserPanel.add(create);
    newUserPanel.add(txuserer);
    newUserPanel.add(passer);

    getContentPane().add(newUserPanel);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);

    Writer writer = null;
    File check = new File("userPass.txt");
    if(check.exists()){

      //Checks if the file exists. will not add anything if the file does exist.
    }else{
      try{
        File texting = new File("userPass.txt");
        writer = new BufferedWriter(new FileWriter(texting));
        writer.write("message");
      }catch(IOException e){
        e.printStackTrace();
      }
    }




    create.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        try {
    File file = new File("userPass.txt");
    Scanner scan = new Scanner(file);;

      FileWriter filewrite = new FileWriter(file, true);

      String usertxter = " ";
      String passtxter = " ";
      String punamer = txuserer.getText();
      String ppaswder = passer.getText();
      while (scan.hasNext()) {
        usertxter = scan.nextLine();
        passtxter = scan.nextLine();
      }

        if(punamer.equals(usertxter) && ppaswder.equals(passtxter)) {
           JOptionPane.showMessageDialog(null,"Username is already in use");
          txuserer.setText("");
          passer.setText("");
          txuserer.requestFocus();

        } 
        else if(punamer.equals("") && ppaswder.equals("")){
        JOptionPane.showMessageDialog(null,"Please insert Username and Password");
        }
        else {
        filewrite.write(punamer+"\r\n" +ppaswder+ "\r\n");
        filewrite.close();
        JOptionPane.showMessageDialog(null,"Account has been created.");
        dispose();
        login log = new login();



        }
        } catch (IOException d) {
      d.printStackTrace();
    }

      }
    });
  } 

}

Answer 1

这个:

if(puname.equals(usertxt) && ppaswd.equals(passtxt)) {
    MainMenu menu =new MainMenu();
    dispose();
} 

需要进入其中:

while (scan.hasNext()) {
    usertxt = scan.nextLine();
    passtxt = scan.nextLine();
}

您正在使用 while 循环遍历文件，但仅在 while 循环结束后测试字符串的相等性。正如您所发现的，这不会起作用。