Why JTextField.setText("String") doesn't work in a DocumentListener?

Question

I have to build a GUI that takes 4 colorable shapes (MyShape class) that are going to be grey in the beginning. Later, writing the RGB values on the three JTextField on the bottom of the GUI i'll be able to set the new color that will paint every picture that I'll click later.

Everything works great except the fact that in the DocumentListener i can't use the setText method or I'll get an IllegalStateException. I'd like to call that method in order to correct a wrong value of an RGB component: for instance, if the user writes 500, the text will automatically set the JTextField to 255.

Here is the code of the full project, so that you can run it (in the code I commented the line right before the method with the problem (I know it's kinda long to read, thank you if you'll help me anyway! :) ):

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import java.util.Arrays;
import java.util.List;

public class ShapesGUI extends JFrame {
private ShapesPlayGround shapesPlayGround;
private ColorPreview colorPreview;
private RGB rgb;
private List<MyShape> shapeList;

public ShapesGUI() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    setLayout(new BorderLayout());
    Container cnt = getContentPane();

    shapesPlayGround = new ShapesPlayGround();
    colorPreview = new ColorPreview();
    rgb = new RGB();

    cnt.add(shapesPlayGround, BorderLayout.CENTER);
    cnt.add(colorPreview, BorderLayout.WEST);
    cnt.add(rgb, BorderLayout.SOUTH);

    pack();
    setVisible(true);

}

public void setShapeList(List<MyShape> shapeList) {this.shapeList = shapeList;}

class ShapesPlayGround extends JPanel {
    MyShape[] shapes;

    public ShapesPlayGround() {
        setPreferredSize(new Dimension(800, 450));
        setBorder(new TitledBorder("Shapes"));

        shapes = new MyShape[4];

        shapes[0] = new MyShape(new Rectangle2D.Double(50, 250, 40, 180));      // Rettangolo, basso sinistra
        shapes[1] = new MyShape(new Rectangle2D.Double(500, 100, 250, 250));    // Quadrato, estrema destra
        shapes[2] = new MyShape(new Ellipse2D.Double(75, 50, 250, 120));        // Ellisse, alto sinistra
        shapes[3] = new MyShape(new Ellipse2D.Double(310, 200, 230, 230));      // Cerchio, destra

        setShapeList(Arrays.asList(shapes));
        addMouseListener(new MyMouseListener());

    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;

        for (MyShape shape : shapes) {
            g2.setPaint(shape.getColor());
            g2.fill(shape.getShape());

            g2.setPaint(Color.black);
            g2.draw(shape.getShape());

        }
    }

    class MyMouseListener extends MouseAdapter {
        @Override
        public void mouseClicked(MouseEvent e) {
            Point p = new Point(e.getX(), e.getY());

            if (shapeList != null) {

                for (MyShape shape : shapes) {
                    if (shape.getShape().contains(p)) {
                        shape.setColor(rgb.getColor());

                    }
                    repaint();

                }
            }
        }
    }
}

class ColorPreview extends JPanel {
    int[] rgbValue = new int[3];
    JPanel panel;
    Shape preview;

    public ColorPreview() {
        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        add(new JLabel("      Preview      "));

        panel = new JPanel();
        panel.setBorder(new TitledBorder("Color"));

        add(panel);

    }

    public void setColor(int[] rgbValue) {this.rgbValue = rgbValue;}
    public int[] getColor() {return rgbValue;}

    public void paintColor() {
        Graphics2D g2 = (Graphics2D)getGraphics();

        preview = new Rectangle2D.Double(panel.getX() + 5, panel.getY() + 20, panel.getWidth() - 10, panel.getWidth() - 10);

        g2.setPaint(rgb.getColor());
        g2.fill(preview);

    }
}

class RGB extends JPanel {
    private JPanel[] rgbPanel = new JPanel[3];
    private String[] panelTitles = {"Red", "Green", "Blue"};
    private JTextField[] rgbText = new JTextField[3];
    private JTextField[] partialColor = new JTextField[3];
    private Shape[] rgbShape;
    private int[] rgbValue = new int[3];
    private Color color;

    public RGB() {
        setLayout(new BoxLayout(this, BoxLayout.X_AXIS));

        for (int i = 0; i < 3; i++) {
            rgbPanel[i] = new JPanel();
            rgbPanel[i].setLayout(new GridLayout(1, 2));
            rgbPanel[i].setBorder(new TitledBorder(panelTitles[i]));

            rgbText[i] = new JTextField();
            partialColor[i] = new JTextField();

            rgbValue[i] = 0;
            rgbText[i].setText("0");

            rgbText[i].getDocument().addDocumentListener(new TextChanged(i));

            partialColor[i].setBackground(Color.black);
            partialColor[i].setEditable(false);

            rgbPanel[i].add(rgbText[i]);
            rgbPanel[i].add(partialColor[i]);
            add(rgbPanel[i]);

        }

        color = new Color(rgbValue[0], rgbValue[1], rgbValue[2]);

    }

    public int[] getRgbValue() {return rgbValue;}
    public Color getColor() {return color;}

    public void setRgbValue(int[] rgbValue) {this.rgbValue = rgbValue;}
    public void setColor(Color color) {this.color = color;}

    class TextChanged implements DocumentListener {
        private int i;

        public TextChanged(int i) {this.i = i;}

        @Override
        public void insertUpdate(DocumentEvent e) {listen(i);}

        @Override
        public void removeUpdate(DocumentEvent e) {listen(i);}

        @Override
        public void changedUpdate(DocumentEvent e) {listen(i);}

        private int fixValue(int value) {return value < 0 ? 0 : (value > 255 ? 255 : value);}
        // HERE'S THE PROBLEM!!!
        private void listen(int i) {
            try {
                rgbValue[i] = fixValue(Integer.parseInt(rgbText[i].getText()));

            } catch (NumberFormatException e) {
                rgbValue[i] = 0;

            }

            color = new Color(rgbValue[0], rgbValue[1], rgbValue[2]);
            rgb.setColor(color);
            colorPreview.paintColor();

            try {
                rgbText[i].setText("" + rgbValue[i]);

            } catch (IllegalStateException e) {
                System.out.println("~Shit, Exception");

            }

            if (i == 0) partialColor[0].setBackground(new Color(rgbValue[0], 0, 0));
            else if (i == 1) partialColor[1].setBackground(new Color(0, rgbValue[1], 0));
            else if (i == 2) partialColor[2].setBackground(new Color(0, 0, rgbValue[2]));

        }
    }
}

public static void main(String args[]) {
    new ShapesGUI();

}

}

Answer 1

One possible solution is to wrap your change to the text in a Runnable and queue it on the event thread using SwingUtilitiles.invokeLater(yourRunnable), but better perhaps ..... you're trying to correct the input before it is fully registered in the text component. In this situation, don't use a DocumentListener, but rather use a DocumentFilter.

Better still -- use a JSlider or a JSpinner

e.g.,

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.util.EnumMap;
import java.util.Map;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class SpinnerEg extends JPanel {
   private Map<RGB, JSlider> sliderMap = new EnumMap<>(RGB.class);
   private JPanel displayPanel = new JPanel();
   private Color displayPanelColor = new Color(0, 0, 0);

   public SpinnerEg() {
      displayPanel.setBackground(displayPanelColor);
      JPanel sliderPanel = new JPanel(new GridLayout(1, 0));
      for (RGB rgb : RGB.values()) {
         createRgbSlider(sliderPanel, rgb);
      }

      displayPanel.setPreferredSize(new Dimension(400, 400));

      setLayout(new BorderLayout());
      add(displayPanel);
      add(sliderPanel, BorderLayout.PAGE_END);
   }

   private void createRgbSlider(JPanel sliderPanel, final RGB rgb) {
      final  JSlider slider = new JSlider(0, 255, 0);
      slider.setMajorTickSpacing(50);
      slider.setPaintLabels(true);
      slider.setPaintTicks(true);
      sliderMap.put(rgb, slider);

      slider.addChangeListener(new ChangeListener() {

         @Override
         public void stateChanged(ChangeEvent e) {
            int red = sliderMap.get(RGB.RED).getValue();
            int green = sliderMap.get(RGB.GREEN).getValue();
            int blue = sliderMap.get(RGB.BLUE).getValue();
            displayPanelColor = new Color(red, green, blue);
            displayPanel.setBackground(displayPanelColor);
         }
      });

      JPanel rgbPanel = new JPanel(new BorderLayout());
      rgbPanel.setBorder(BorderFactory.createTitledBorder(rgb.getName()));
      rgbPanel.add(slider);

      sliderPanel.add(rgbPanel);
   }

   private static void createAndShowGui() {
      SpinnerEg mainPanel = new SpinnerEg();

      JFrame frame = new JFrame("SpinnerEg");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

enum RGB {
   RED("Red", Color.red), GREEN("Green", Color.green), BLUE("Blue", Color.blue);
   private String name;
   private Color color;

   private RGB(String name, Color color) {
      this.name = name;
      this.color = color;
   }

   public String getName() {
      return name;
   }

   public Color getColor() {
      return color;
   }

}