JLabel 更改时 GridBagLayout 更改

Question

I want to make an input form and do a validation for the input field when focus is lost. If the validation fails, I want to display an error message next to the InputField.

My problem: The input field and it's underline will resize when I change the text of the error JLabel next to it.

Steps to reproduce:

1. Run main method
2. Enter more than 10 characters in the input field

--> Current result: Textfield and Seperator resize, Error-JLabel is displayed far right

--> Wanted result: Textfield and Seperator remain unchanged, Error JLabel is displayed same place like the test message

I've been struggling with a small issue for days. Please help!

package View;

import javafx.scene.input.KeyCode;

import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
import java.awt.*;
import java.awt.event.*;

public class PersonDataInput extends JPanel {

    private JLabel emailLabel;
    private JLabel mobileLabel;
    private JLabel nameLabel;
    private JLabel phoneLabel;
    private JLabel surnameLabel;

    private JLabel emailErrorLabel;
    private JLabel mobileErrorLabel;
    private JLabel nameErrorLabel;
    private JLabel phoneErrorLabel;
    private JLabel surnameErrorLabel;

    private JTextField mobileInputField;
    private JTextField nameInputField;
    private JTextField phoneInputField;
    private JTextField surnameInputField;
    private JTextField emailInputField;

    public static void main(String[] args) {

        JFrame frame = new JFrame("Test");
        frame.setContentPane(new PersonDataInput());
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }

    public PersonDataInput() {
        Border redline = BorderFactory.createLineBorder(Color.red);
        setBorder(redline);
        //setMaximumSize(new Dimension(200,300));
        initComponents();
    }

    private void initComponents() {


        // <editor-fold defaultstate="collapsed" desc="Components">
        emailLabel = new JLabel("Email");
        mobileLabel = new JLabel("Mobile");
        nameLabel = new JLabel("Name");
        phoneLabel = new JLabel("Phone");
        surnameLabel = new JLabel("Surname");

        emailErrorLabel = new JLabel();
        mobileErrorLabel = new JLabel();
        nameErrorLabel = new JLabel();
        phoneErrorLabel = new JLabel();
        surnameErrorLabel = new JLabel();

        mobileInputField = new JTextField();
        nameInputField = new JTextField();
        phoneInputField = new JTextField();
        surnameInputField = new JTextField();
        emailInputField = new JTextField();

        mobileInputField.setDocument(new JTextFieldLimit(10));
        nameInputField.setDocument(new JTextFieldLimit(10));
        phoneInputField.setDocument(new JTextFieldLimit(10));
        surnameInputField.setDocument(new JTextFieldLimit(10));
        emailInputField.setDocument(new JTextFieldLimit(10));

        mobileInputField.setName("mobileInputField");
        nameInputField.setName("nameInputField");
        phoneInputField.setName("phoneInputField");
        surnameInputField.setName("surnameInputField");
        emailInputField.setName("emailInputField");

        JSeparator seperator1 = new JSeparator();
        JSeparator seperator2 = new JSeparator();
        JSeparator seperator3 = new JSeparator();
        JSeparator seperator4 = new JSeparator();
        JSeparator seperator5 = new JSeparator();
        // </editor-fold>

        // <editor-fold defaultstate="collapsed" desc="EventListeners">

        //...
        //...
        KeyListener keyListener = new KeyAdapter() {
            @Override
            public void keyTyped(KeyEvent keyEvent) {
                //...
            }

            @Override
            public void keyPressed(KeyEvent keyEvent) {
                keyPressedMethod(keyEvent);
            }

            @Override
            public void keyReleased(KeyEvent keyEvent) {
                //...
            }
        };

        //...
        FocusListener focusListener = new FocusAdapter() {
            @Override
            public void focusGained(FocusEvent focusEvent) {
                focusGainedMethod(focusEvent);
            }

            @Override
            public void focusLost(FocusEvent focusEvent) {
                focusLostMethod(focusEvent);
            }
        };

        mobileInputField.addFocusListener(focusListener);
        mobileInputField.addKeyListener(keyListener);

        nameInputField.addFocusListener(focusListener);
        nameInputField.addKeyListener(keyListener);

        phoneInputField.addFocusListener(focusListener);
        phoneInputField.addKeyListener(keyListener);

        surnameInputField.addFocusListener(focusListener);
        surnameInputField.addKeyListener(keyListener);

        emailInputField.addFocusListener(focusListener);
        emailInputField.addKeyListener(keyListener);
        // </editor-fold>s

        // <editor-fold defaultstate="collapsed" desc="Styles">
        mobileInputField.setBorder(null);
        nameInputField.setBorder(null);
        phoneInputField.setBorder(null);
        surnameInputField.setBorder(null);
        emailInputField.setBorder(null);
        setBackground(new java.awt.Color(255, 255, 255));
        //</editor-fold>

        // <editor-fold defaultstate="collapsed" desc="Layout">
        GridBagLayout gridBagLayout = new GridBagLayout();
        setLayout(gridBagLayout);


        // this component is needed to anchor all components within the JPanel to the upper right corner
        GridBagConstraints horizontalFill = new GridBagConstraints();
        horizontalFill.anchor = GridBagConstraints.NORTHWEST;
        horizontalFill.fill = GridBagConstraints.HORIZONTAL;
        horizontalFill.gridwidth=4;
        horizontalFill.weightx = 1;
        add(Box.createHorizontalGlue(), horizontalFill);

        add(nameLabel,
                new GBC(0, 0)
                        .setSpan(1,1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(nameInputField,
                new GBC(0, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        nameErrorLabel.setText("Test: The error message shall be displayed here.");
        add(nameErrorLabel,
                new GBC(1, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(200,0)
                        .setAnchor(GBC.NORTHWEST)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(seperator1,
                new GBC(0, 2)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0.0, 1.0));
/*
        add(surnameLabel,
                new GBC(0, 3)
                        .setSpan(1,1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(surnameInputField,
                new GBC(0, 4)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(seperator2,
                new GBC(0, 5)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(emailLabel,
                new GBC(0, 6)
                        .setSpan(1,1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(emailInputField,
                new GBC(0, 7)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(seperator3,
                new GBC(0, 8)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(phoneLabel,
                new GBC(0, 9)
                        .setSpan(1,1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(phoneInputField,
                new GBC(0, 10)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(seperator4,
                new GBC(0, 11)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(mobileLabel,
                new GBC(0, 12)
                        .setSpan(1,1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(mobileInputField,
                new GBC(0, 13)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setIpad(100,0)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

        add(seperator5,
                new GBC(0, 14)
                        .setSpan(2, 1)
                        .setFill(GBC.HORIZONTAL)
                        .setInsets(5,10,0,0)
                        .setWeight(0, 1.0));

 */




    }// </editor-fold>
        //</editor-fold>



    private void keyPressedMethod(KeyEvent keyEvent) {
        String component = keyEvent.getComponent().getName();

        if (keyEvent.getKeyCode() == KeyEvent.VK_ENTER) {
            switch (component) {
                case "nameInputField":
                    surnameInputField.requestFocus();
                    break;
                case "surnameInputField":
                    emailInputField.requestFocus();
                    break;
                case "emailInputField":
                    phoneInputField.requestFocus();
                    break;
                case "phoneInputField":
                    mobileInputField.requestFocus();
                    break;
                case "mobileInputField":
                    this.requestFocus();
                default:
                    break;
            }

        }

        // todo: field validation anpassen, Email Validation,
        else {
            switch (component) {
                case "nameInputField":
                    if (nameInputField.getText().length() == 10) {
                        nameErrorLabel.setText("Max. 10 characters.");
                    }
                    break;
                case "surnameInputField":
                    if (surnameInputField.getText().length() == 10) {
                        surnameErrorLabel.setText("Max. 10 characters.");
                    }
                    break;
                case "emailInputField":
                    if (emailInputField.getText().length() == 10) {
                        emailErrorLabel.setText("Max. 10 characters.");
                    }
                    break;
                case "phoneInputField":
                    if (phoneInputField.getText().length() == 10) {
                        phoneErrorLabel.setText("Max. 10 characters.");
                    }
                    break;
                case "mobileInputField":
                    if (mobileInputField.getText().length() == 10) {
                        mobileErrorLabel.setText("Max. 10 characters.");
                    }
                default:
                    break;
            }

        }
    }

    private void focusLostMethod(FocusEvent focusEvent) {
        String component = focusEvent.getComponent().getName();
        switch (component) {
            case "nameInputField":
                nameLabel.setForeground(Color.black);
                nameErrorLabel.setText("");
                break;
            case "surnameInputField":
                surnameLabel.setForeground(Color.black);
                break;
            case "emailInputField":
                emailLabel.setForeground(Color.black);
                break;
            case "phoneInputField":
                phoneLabel.setForeground(Color.black);
                break;
            case "mobileInputField":
                mobileLabel.setForeground(Color.black);
            default:
                break;
        }
    }

    private void focusGainedMethod(FocusEvent focusEvent) {
        String component = focusEvent.getComponent().getName();
        switch (component) {
            case "nameInputField":
                nameLabel.setForeground(new Color(51, 102, 255));
                break;
            case "surnameInputField":
                surnameLabel.setForeground(new Color(51, 102, 255));
                break;
            case "emailInputField":
                emailLabel.setForeground(new Color(51, 102, 255));
                break;
            case "phoneInputField":
                phoneLabel.setForeground(new Color(51, 102, 255));
                break;
            case "mobileInputField":
                mobileLabel.setForeground(new Color(51, 102, 255));
            default:
                break;
        }
    }


    //Class to set limits for JTextFields
    class JTextFieldLimit extends PlainDocument {
        private int limit;

        JTextFieldLimit(int limit) {
            super();
            this.limit = limit;
        }

        JTextFieldLimit(int limit, boolean upper) {
            super();
            this.limit = limit;
        }

        public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
            if (str == null)
                return;

            if ((getLength() + str.length()) <= limit) {
                super.insertString(offset, str, attr);
            }
        }
    }

}

Answer 1

GridBagLayout will only take into consideration visible components. If the JLabel has no text, then it's size will be 0x0 and the GridBagLayout will respond accordingly. "IF" the error message is static, you could simply set it's text color to be the same as the background color of the container and just "fake" it. Also - KeyListeners are probably not what you want to use – MadProgrammer 9 hours ago

Thanks this helped!