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¿Error de repintado de GUI de Java?

Question

Este es difícil: tengo un JFrame que genera JTextFields. Cuando paso de generar 2 JTextFields a 12 JTextfields (por ejemplo), veo algún error donde hay un JTextField de tamaño diferente al final. Parece ser un error de repintado.

Código main.java:

import java.awt.*;
import javax.swing.*;

public class Main {
    public static Display display = new Display();

    public static void main(String[] args) {
        display.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        display.setVisible(true);
    }
}

Código Display.java:

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class Display extends JFrame {
    final int FRAME_WIDTH = 820;
    final int FRAME_HEIGHT = 700;
    final int X_OFFSET = 40;
    final int Y_OFFSET = 40;

    final int GRAPH_OFFSETX = 35;
    final int GRAPH_OFFSETY = 60;
    final int GRAPH_WIDTH = 500;
    final int GRAPH_HEIGHT = 500;
    final int GRAPH_INTERVAL = 20;

    JButton submit;
    JTextField top;
    JTextField bottom;
    JTextField numPoint;
    JPanel bpanel;
    JPanel points;

    int maxPoints;

    public Display() {
        init();
    }

    public void init() {
        setBackground(Color.WHITE);
        setLocation(X_OFFSET, Y_OFFSET);
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
        setTitle("Geometric Transformations");
        getContentPane().setLayout(null);
        setDefaultLookAndFeelDecorated(true);

        top = new JTextField();    // parameter is size of input characters
        top.setText("1 2 3");
        top.setBounds(590, 150, 120, 25);

        bottom = new JTextField();    // parameter is size of input characters
        bottom.setText("5 6 7");
        bottom.setBounds(590, 200, 120, 25);

        numPoint = new JTextField();
        numPoint.setText("Number of Points?");
        numPoint.setBounds(550,200,200,25);
        this.add(numPoint);

        SubmitButton submit = new SubmitButton("Submit");
        submit.setBounds(570, 250, 170, 25);

        bpanel = new JPanel(new GridLayout(2,3));
        bpanel.add(top);
        bpanel.add(bottom);
        bpanel.add(submit);

        points = new JPanel(new GridLayout(2,2));
        points.setBounds(540,250,265,60);
        this.add(points);

        bpanel.setBounds(550,100,200,70);
        this.add(bpanel, BorderLayout.LINE_START);

        Component[] a = points.getComponents();
        System.out.println(a.length);
        repaint();
    }

    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.WHITE);
        g.fillRect(100, 100, 20, 30);
        g.setColor(Color.BLACK);
        genGraph(g, GRAPH_OFFSETX, GRAPH_OFFSETY, GRAPH_WIDTH, GRAPH_HEIGHT, GRAPH_INTERVAL);
    }

    public void genGraph (Graphics g, int x, int y, int width, int height, int interval) {
        // draw background
        int border = 5;
        g.setColor(Color.BLACK);
        width = width - (width % interval);
        height = height - (height % interval);
        for (int col=x; col <= x+width; col+=interval) {
            g.drawLine(col, y, col, y+height);
        }
        for (int row=y; row <= y+height; row+=interval) {
            g.drawLine(x, row, x+width, row);
        }
    }
    class SubmitButton extends JButton implements ActionListener {

        public SubmitButton(String title){
            super(title);
            addActionListener(this);
            this.setVisible(true);
        }
        public void actionPerformed(ActionEvent e) {
            maxPoints = Integer.parseInt(numPoint.getText()) * 2;

            points.removeAll();

            for (int i=0; i<maxPoints; i++) {
                JTextField textField = new JTextField();
                points.add(textField);
            }
            points.validate();        // necessary when adding components to a JPanel
            // http://stackoverflow.com/questions/369823/java-gui-repaint-problem-solved
            // What to Check:
            // Things between commas are either spaces (which will be stripped later)
            // or numbers!

            // Pairs must match up!
        }
    }
}

Answer 1

Los nuevos componentes se vuelven a dibujar sobre los anteriores. points.repaint(); después de points.validate(); y el problema desapareció

Answer 2

Nota: También me molestó el tema del repintado de la cuadrícula (coloque la ventana al frente y luego hacia atrás, verá).
A partir de una búsqueda rápida, parece mejor evitar pintar directamente en el JFrame, pero delegarlo en un subcomponente. Si estoy equivocado, alguien me diga. Aquí está mi solución (imperfecta, te dejo la tarea de mejorarla ... :-P

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class SODisplay extends JFrame {
    final int FRAME_WIDTH = 820;
    final int FRAME_HEIGHT = 700;
    final int X_OFFSET = 40;
    final int Y_OFFSET = 40;

    JButton submit;
    JTextField top;
    JTextField bottom;
    JTextField numPoint;
    JPanel bpanel;
    JPanel points;
    GridPanel grid;

    int maxPoints;

    public SODisplay() {
        init();
    }

    public void init() {
        setBackground(Color.WHITE);
        setLocation(X_OFFSET, Y_OFFSET);
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
        setTitle("Geometric Transformations");
        getContentPane().setLayout(null);
        setDefaultLookAndFeelDecorated(true);

        grid = new GridPanel();
        grid.setBounds(0,0,530,FRAME_HEIGHT);
        this.add(grid);

        top = new JTextField();    // parameter is size of input characters
        top.setText("1 2 3");
        top.setBounds(590, 150, 120, 25);

        bottom = new JTextField();    // parameter is size of input characters
        bottom.setText("5 6 7");
        bottom.setBounds(590, 200, 120, 25);

        numPoint = new JTextField();
        numPoint.setText("Number of Points?");
        numPoint.setBounds(550,200,200,25);
        this.add(numPoint);

        SubmitButton submit = new SubmitButton("Submit");
        submit.setBounds(570, 250, 170, 25);

        bpanel = new JPanel(new GridLayout(2,3));
        bpanel.add(top);
        bpanel.add(bottom);
        bpanel.add(submit);

        points = new JPanel(new GridLayout(2,2));
        points.setBounds(540,250,265,60);
        this.add(points);

        bpanel.setBounds(550,100,200,70);
        this.add(bpanel, BorderLayout.LINE_START);

        Component[] a = points.getComponents();
        System.out.println(a.length);
        repaint();
    }

    class SubmitButton extends JButton implements ActionListener {

        public SubmitButton(String title){
            super(title);
            addActionListener(this);
            this.setVisible(true);
        }
        public void actionPerformed(ActionEvent e) {
            maxPoints = Integer.parseInt(numPoint.getText()) * 2;

            points.removeAll();

            for (int i=0; i<maxPoints; i++) {
                JTextField textField = new JTextField();
                points.add(textField);
            }
            points.validate();        // necessary when adding components to a JPanel
            points.repaint();
            // http://.com/questions/369823/java-gui-repaint-problem-solved
            // What to Check:
            // Things between commas are either spaces (which will be stripped later)
            // or numbers!

            // Pairs must match up!
        }
    }

    public static void main(String[] args) {
        // Schedule a job for the event-dispatching thread:
        // creating and showing this application''s GUI.
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                SODisplay display = new SODisplay();
                display.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                display.setVisible(true);
            }
        });
    }

    class GridPanel extends JPanel {
        // Or drop the offset and adjust the placement of the component
        final int GRAPH_OFFSETX = 35;
        final int GRAPH_OFFSETY = 60;
        final int GRAPH_WIDTH = 500;
        final int GRAPH_HEIGHT = 500;
        final int GRAPH_INTERVAL = 20;

        public GridPanel() {
        }

        public void paint(Graphics g) {
            super.paint(g);
            g.setColor(Color.WHITE);
            g.fillRect(100, 100, 20, 30);
            g.setColor(Color.BLACK);
            genGraph(g, GRAPH_OFFSETX, GRAPH_OFFSETY, GRAPH_WIDTH, GRAPH_HEIGHT, GRAPH_INTERVAL);
        }

        public void genGraph (Graphics g, int x, int y, int width, int height, int interval) {
            // draw background
            int border = 5;
            g.setColor(Color.BLACK);
            width = width - (width % interval);
            height = height - (height % interval);
            for (int col=x; col <= x+width; col+=interval) {
                g.drawLine(col, y, col, y+height);
            }
            for (int row=y; row <= y+height; row+=interval) {
                g.drawLine(x, row, x+width, row);
            }
        }
    }
}

Ese es solo mi código de prueba en un archivo para simplificar, por lo que es posible que desee diseccionarlo de manera diferente.