java: validating that all text fields in GUI are c

问题:

I am trying to create a GUI that allows someone to set up an account. I would like to validate that all the text fields are complete when the create account button is pressed. What is the best way to do this? I am attaching my code but my validation that the text fields are complete is not working.

see code below:

public class GUIaccounts extends JFrame{

private JLabel name;
private JLabel initDeposit;
private JLabel chooseAccount;
private JLabel empty;
private JTextField nameTextField;
private JTextField initDepositTextField;
private JPanel dataPanel;
private JPanel accountTypePanel;
private JRadioButton savingsAccount;
private JRadioButton premiereChecking;
private ButtonGroup radioButtonGroup;
private JButton createAccountButton;
private JPanel createAccountPanel;
private Bank myBank;



public GUIaccounts(){
    setTitle("Create an Account");
    setSize(1000,1000);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    buildPanels();
    setVisible(true);
    pack();
    setLocationRelativeTo(null);
     myBank=new Bank();

}

private void buildPanels(){
    //create the panels
    dataPanel= new JPanel();
    dataPanel.setLayout(new GridLayout(2,2));
    accountTypePanel=new JPanel();
    accountTypePanel.setLayout(new GridLayout(3,1));
    createAccountPanel=new JPanel();
    createAccountPanel.setLayout(new FlowLayout());
    //create labels
    name=new JLabel("Enter Name:");
    Border border = LineBorder.createBlackLineBorder();
    name.setBorder(border);
    initDeposit=new JLabel("Enter Initial Deposit:");
    initDeposit.setBorder(border);
    chooseAccount=new JLabel("Choose Account:");
    empty=new JLabel(" ");
    //create text fields
    nameTextField=new JTextField();
    initDepositTextField=new JTextField();
    //create buttons
    savingsAccount = new JRadioButton("Savings Account");
    premiereChecking =new JRadioButton ("Premiere Checking Account");
    createAccountButton=new JButton("Create Account");
    //add labels and field to the panel
    dataPanel.add(name);
    dataPanel.add(nameTextField);
    dataPanel.add(initDeposit);
    dataPanel.add(initDepositTextField);
    //add button to the panel
    accountTypePanel.add(chooseAccount);
    accountTypePanel.add(empty);
    accountTypePanel.add(savingsAccount);
    accountTypePanel.add(premiereChecking);
    createAccountPanel.add(createAccountButton);

    //add actionListeners to the buttons
    savingsAccount.addActionListener(new RadioButtonListener());
    premiereChecking.addActionListener(new RadioButtonListener());
    createAccountButton.addActionListener(new createAccountListener());
    //add focus to the text field
    nameTextField.addFocusListener(new nameFieldListener());
    initDepositTextField.addFocusListener(new initDepositFieldListener());
    //add panels to the contentPane
    add(dataPanel, BorderLayout.NORTH);
    add(accountTypePanel, BorderLayout.CENTER);
    add(createAccountPanel, BorderLayout.SOUTH);
    //group radio buttons
    radioButtonGroup= new ButtonGroup();
    radioButtonGroup.add(savingsAccount);
    radioButtonGroup.add(premiereChecking);
}
    private class createAccountListener implements ActionListener{
        public void actionPerformed(ActionEvent e){
            String name=null;
            Double amount=null;
            if (savingsAccount.isSelected()){
                name=nameTextField.getText();
                amount=Double.valueOf(initDepositTextField.getText());
                if(name!=null && amount !=null){
                try{

                    SavingsAccount account=new SavingsAccount(name,AccountIDs.getNextID(), amount);
                    myBank.addAccount(account);
                    JOptionPane.showMessageDialog(null,"Account setup was successful" + myBank.toString());
                }



                catch(Exception e1){
                    JOptionPane.showMessageDialog(null,"Unable to set up account. " +e1.getMessage());
                }
            }
                else{
                    JOptionPane.showMessageDialog(null, "All fields must be completed in order to set up account");
                }
            }

            else if(premiereChecking.isSelected()){
                name=nameTextField.getText();
                amount=Double.valueOf(initDepositTextField.getText());
                if(name!=null && amount!=null){
                try{
                    PremiereCheckingAccount account=new PremiereCheckingAccount(name, AccountIDs.getNextID(),amount);
                    myBank.addAccount(account);
                    JOptionPane.showMessageDialog(null,"Account setup was successful" +myBank.toString());
                }
                catch(Exception e1){
                    JOptionPane.showMessageDialog(null,"Unable to set up account. " + e1.getMessage());
                }
                }
                else{
                    JOptionPane.showMessageDialog(null, "All fields must be completed in order to set up account");
                }

            }
            else{
                JOptionPane.showMessageDialog(null,"Please select the type of account you want to create.");
            }
        }
    }
    private class RadioButtonListener implements ActionListener{
        public void actionPerformed(ActionEvent e){


        }
    }

    private class nameFieldListener implements FocusListener{
        public void focusGained(FocusEvent e){

            nameTextField.selectAll();//highlight contents
        }

        public void focusLost(FocusEvent e){
    }



}
    private class initDepositFieldListener implements FocusListener{
        public void focusGained(FocusEvent e){
            initDepositTextField.selectAll();
        }

        public void focusLost(FocusEvent e) {


        }
    }



    public static void main(String[]args){
    GUIaccounts myAccount=new GUIaccounts();
    }   

}

回答1:

The getText() method will not return null. It will return the empty String ("").

Your test should be something like:

if ( textField.getText().trim().length() == 0 )
  // error

回答2:

Old question, but it's generally a good idea to create a "validation" helper method that does all the validation first, then if it checks out you can load all the values into whatever you're doing (variables, class attributes to instantiate something, etc).

eg:

private class createAccountListener implements ActionListener
{
  public void actionPerformed(ActionEvent ae)
  {
    // first we validate all fields... if they pass, we do
    // the rest of the code, otherwise we let the failed validation
    // code tell user what happened, and skip the rest of the code
    if ( validateFields() )
    {
      String fname = fieldFirstName.getText();
      String lname = fieldFirstName.getText();
      int    age   = fieldAge.getText();
    }
  }
}

// test all text fields for input 
public boolean validateFields()
{
  if (! validateField( fieldFirstName, "Please enter a first name")
    return false;
  else
  if (! validateField( fieldLastName, "Please enter a last name")
    return false;
  else
  if (! validateInteger( fieldAge, "Please enter an age greater then 0")
    return false;
  else
    return true;
}

// test if field is empty
public boolean validateField( JTextField f, String errormsg )
{
  if ( f.getText().equals("") )
    return failedMessage( f, errormsg );
  else
    return true; // validation successful
}

public boolean validateInteger( JTextField f, String errormsg )
{
  try
  {  // try to convert input to integer
    int i = Integer.parseInt(f.getText());

    // input must be greater then 0
    // if it is, success
    if ( i > 0 )
      return true; // success, validation succeeded
   }
   catch(Exception e)
   {
      // if conversion failed, or input was <= 0,
      // fall-through and do final return below
   }
   return failedMessage( f, errormsg );
}

public boolean failedMessage(JTextField f, String errormsg)
{
  JOptionPane.showMessageDialog(null, errormsg); // give user feedback
  f.requestFocus(); // set focus on field, so user can change
  return false; // return false, as validation has failed
}