爲什麼我的用戶GUI登錄不能正確設置警告標籤？

Question

我正在編寫一個簡單的用戶登錄屏幕，通過序列化來存儲用戶。 GUI很好，剩下的就是實現序列化，但是當用戶輸入不正確的密碼或用戶名時，我無法正確顯示文本warningLabel。它將顯示第一條錯誤消息，但如果發生不同的錯誤，則標籤保持不變。我需要標籤來改變每次都有錯誤。我將在下面發佈整個代碼。

UserCreateAccountGUI類：

package userInfoAndSerialization; 

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.GridBagConstraints; 
import java.awt.GridBagLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.util.Arrays; 

import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JPasswordField; 
import javax.swing.JTextField; 
import javax.swing.UIManager; 

public class UserCreateAccount implements ActionListener { 

    public static int numOfUsers; 

    String username; 
    String password; 

    public static void main(String[] args) { 
     try { 
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
     UserCreateAccount ucaGUI = new UserCreateAccount(); 
     ucaGUI.start(); 
    } 

    JFrame frame; 
    JPanel panel; 
    JTextField usernameField; 
    JPasswordField passwordField; 
    JPasswordField confirmPasswordField; 
    JLabel warningLabel; 

    public void start() { 
     frame = new JFrame("Create a new account"); 
     panel = new JPanel(); 

     panel.setLayout(new GridBagLayout()); 

     frame.getContentPane().add(BorderLayout.CENTER, panel); 
     panel.setBackground(Color.ORANGE); 

     JLabel userLabel = new JLabel("Username:"); 
     JLabel passwordLabel = new JLabel("Password:"); 
     JLabel confirmPasswordLabel = new JLabel("Confirm Password:"); 
     usernameField = new JTextField(15); 
     passwordField = new JPasswordField(15); 
     confirmPasswordField = new JPasswordField(15); 

     GridBagConstraints right = new GridBagConstraints(); 
     right.anchor = GridBagConstraints.WEST; 
     GridBagConstraints left = new GridBagConstraints(); 
     left.anchor = GridBagConstraints.EAST; 

     right.weightx = (int) 2; 
     right.fill = GridBagConstraints.REMAINDER; 
     right.gridwidth = GridBagConstraints.REMAINDER; 
     // actual GUI 

     panel.add(userLabel, left); 
     panel.add(usernameField, right); 
     panel.add(passwordLabel, left); 
     panel.add(passwordField, right); 
     panel.add(confirmPasswordLabel, left); 
     panel.add(confirmPasswordField, right); 

     frame.setSize(300, 250); 
     frame.setVisible(true); 

     JButton createAccount = new JButton("Create this account"); 
     frame.getContentPane().add(BorderLayout.SOUTH, createAccount); 
     createAccount.addActionListener(this); 

     warningLabel = new JLabel(); 
     frame.getContentPane().add(BorderLayout.NORTH, warningLabel); 
    } 

    // this is where the problem is. 
    public void actionPerformed(ActionEvent event) { 
     if (!(passwordField.getPassword().toString().equals(confirmPasswordField.getPassword().toString()))) { 
      warningLabel.setText("Your passwords do not match! Please try again!"); 
     } else if (passwordField.getPassword().toString().length() < 1) { 
      warningLabel.setText("Your password is not long enough! Please try again!"); 
     } else if (usernameField.getText().length() < 1) { 
      warningLabel.setText("Your username is not long enough! Please try again!"); 
     } else { 
      warningLabel.setText("Account created successfully."); 
     } 
    } 
} 

Answer 1

這不會飛：

passwordField.getPassword().toString(). 
     equals(confirmPasswordField.getPassword().toString()) 

你最好打印出一個字符數組上調用.toString()的結果看正是我的意思。

舉例來說，當我運行：

String fooString = "Foo"; 
char[] fooArray = fooString.toCharArray(); 
System.out.println(fooArray.toString()); 

你似乎在期待它不返回「富」，而是典型的和預期的字符數組的toString()表示：[C@19821f。請注意，如果你運行這個，你的hashcode號碼將與我的不同（如果我再次運行這個，也是一樣！）。

最好使用數組類equals(...)來讓你比較兩個char數組。即，

char[] pw1 = passwordField.getPassword(); 
char[] pw2 = confirmPasswordField.getPassword(); 
if (Arrays.equals(pw1, pw2)) { 
    //... 
} 

注：一個壞的解決方案是將字符數組轉換成使用new String(myCharArray)一個「真實」的字符串，但我強烈反對這樣做，因爲它使你的密碼很虛弱，容易折斷。