擺動顯示錯誤與擺動

Question

我想這個應用程序拋出一個錯誤，並顯示文本，但它只是繼續顯示空。該錯誤需要顯示該人是否試圖提取超過帳戶中的金額。這是我的。當餘額不夠高時，如何讓文本顯示出來？提前致謝！

林甚至不知道，如果需要處理，並在賬戶類，他們現在還是WithdrawListener顯示的錯誤...

MainFrame類

package appgui; 

import java.awt.Color; 
import java.awt.Font; 
import java.awt.event.ActionListener; 

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


public class MainFrame extends JFrame implements AccountDisplay { 
    private BankAccount account; 
    private JLabel label; 
    private JLabel errorLabel; 
    private JTextField amountField; 

    private static final int FRAME_HEIGHT = 600; 
    private static final int FRAME_WIDTH = 400; 

    public MainFrame(String t, BankAccount anAccount) { 
     super(t); 

     account = anAccount; 

     // Label that displays the result 
     label = new JLabel("Balance: " + account.getBalance()); 
     label.setFont(new Font("Arial", Font.BOLD, 22)); 
     label.setForeground(Color.RED); 

     errorLabel = new JLabel("Error: " + account.getErrors()); 

     // Create the label, text field, and button for entering amount 
     JLabel amountLabel = new JLabel("Amount: "); 
     amountField = new JTextField(7); 

     // Create the Control Panel that holds all components 
     JPanel controlPanel = new JPanel(); 
     controlPanel.add(amountLabel); 
     controlPanel.add(amountField); 
     controlPanel.add(createWithdrawButton()); 
     controlPanel.add(createDepositeButton()); 
     controlPanel.add(label); 
     controlPanel.add(errorLabel); 

     add(controlPanel); 
     setSize(FRAME_HEIGHT, FRAME_WIDTH); 
     //setLayout(new GridBagLayout()); 
    } 

    private JButton createDepositeButton() { 
     JButton depositButton = new JButton("Deposit"); 

     ActionListener depositLstener = new DepositListener(this); 
     depositButton.addActionListener(depositLstener); 
     return depositButton; 
    } 

    private JButton createWithdrawButton() { 
     JButton withdrawButton = new JButton("Withdraw"); 

     ActionListener withdrawListener = new WithdrawListener(this); 
     withdrawButton.addActionListener(withdrawListener); 
     return withdrawButton; 
    } 

    public String getAmount() { 
     return this.amountField.getText(); 
    } 

    public BankAccount getAccount() { 
     return this.account; 
    } 

    public JLabel getLabel() { 
     return this.label; 
    } 
} 

和賬戶類，我有檢查賬戶餘額

package appgui; 

public class BankAccount { 
    private double balance; 
    private String error; 

    public BankAccount(int b) { 
     balance = b; 
    } 

    public void deposit(double amount) { 
     balance = balance + amount; 
    } 

    public void withdraw(double amount) { 
     if(balance - amount < 0) { 
      balance = balance; 
      setErrors("Can't withdraw that amount, account balance is too low."); 
     } else { 
      balance = balance - amount; 
     } 
    } 

    public double getBalance() { 
     return this.balance; 
    } 

    public String setErrors(String err) { 
     this.error = err; 
     return err; 
    } 

    public String getErrors() { 
     return this.error; 
    } 
} 

Answer 1

我可以看到你設置錯誤消息，但我看不到你去哪裏抓住它，這樣你就可以做的是：

public void withdraw(double amount) { 
    if(balance - amount < 0) { 
     JOptionPane.showMessageDialog(null, "Can't withdraw that amount, account balance is too low.", "Error", JOptionPane.ERROR_MESSAGE); 
    } else { 
     balance = balance - amount; 
    } 
} 

如果餘額低於您剛纔發出的錯誤味精... 量，你不需要做平衡=平衡，其同樣是說1 = 1,1已經是1 ..

希望它有幫助:)