Search code examples
javaswingjpanellayout-managerpreferredsize

Writing a custom JPanel that will follow LayoutManager specifications

I am trying to code a custom JPanel that follows the layoutmanager of the containing JPanel (I am using gridbag). My custom JPanel is getting a little too long to paste here, but a checklist of all methods to overwrite to have for this to work.

Here is an excerpt from my custom JPanel:

        public class GridPanel extends JPanel implements MouseMotionListener, MouseListener{
            private Rectangle offdutyRect, sbRect, driveRect, onRect;
            private int delta = 60;
            private int[][] gridArray;
            int draggedStartX = -1;
            int draggedStartY = -1;
            private int dutyStatusSpacing = 60;
            private int totalSpacing = 100;

            public GridPanel(){
            this.setSize(new Dimension(800, 100));
            this.addMouseMotionListener((MouseMotionListener) this);
            this.addMouseListener(this);
            int gridArrayColumns = 24*60/delta;
            gridArray = new int[4][gridArrayColumns];

            int r = 0;
            int rHeight = this.getHeight()/4;
            offdutyRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, this.getWidth() - totalSpacing, rHeight);
            r++;
            sbRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, this.getWidth() - totalSpacing, rHeight);
            r++;
            driveRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, this.getWidth() - totalSpacing, rHeight);
            r++;
            onRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, this.getWidth() - totalSpacing, rHeight);

            Rectangle rect = null;
            for(r = 0; r < gridArray.length; r++){
                if(r == 0){
                rect = offdutyRect;
                }else if(r == 1){
                rect = sbRect;
                }else if(r == 2){
                rect = driveRect;
                }else if(r == 3){
                rect = onRect;
                }

                //I haven't actually derived any of these things, just my best guesses.
                int len = gridArray[r].length;
                int width = (int) (rect.getWidth()/len);
                rect.setSize((int)(width*len), (int) rect.getHeight());
            }
        }

    public void paintComponent(Graphics g){
        g.clearRect(this.getX(), this.getY(), this.getWidth(), this.getHeight());
        //the center black bar for duty status "placeholders"
        g.setColor(Color.black);
        g.drawRect(getX(), getY(), getWidth() - 1, getHeight() - 1);
        g.drawRect((int)offdutyRect.getX(), (int)offdutyRect.getY() + (int)offdutyRect.getHeight()/2, (int)offdutyRect.getWidth(), 1);
        g.drawRect((int)sbRect.getX(), (int)sbRect.getY() + (int)sbRect.getHeight()/2, (int)sbRect.getWidth(), 1);
        g.drawRect((int)driveRect.getX(), (int)driveRect.getY() + (int)driveRect.getHeight()/2, (int)driveRect.getWidth(), 1);
        g.drawRect((int)onRect.getX(), (int)onRect.getY() + (int)onRect.getHeight()/2, (int)onRect.getWidth(), 1);
        g.setColor(Color.pink);
        g.drawRect((int)offdutyRect.getX(), (int)offdutyRect.getY(), (int)offdutyRect.getWidth(), (int)offdutyRect.getHeight());
        g.drawRect((int)sbRect.getX(), (int)sbRect.getY(), (int)sbRect.getWidth(), (int)sbRect.getHeight());
        g.drawRect((int)driveRect.getX(), (int)driveRect.getY(), (int)driveRect.getWidth(), (int)driveRect.getHeight());
        g.drawRect((int)onRect.getX(), (int)onRect.getY(), (int)onRect.getWidth(), (int)onRect.getHeight());

        //draw the array
        g.setColor(Color.green);
        Rectangle rect = null;
        for(int r = 0; r < gridArray.length; r++){
            if(r == 0){
            rect = offdutyRect;
            }else if(r == 1){
            rect = sbRect;
            }else if(r == 2){
            rect = driveRect;
            }else if(r == 3){
            rect = onRect;
            }

            //I haven't actually derived any of these things, just my best guesses.
            int len = gridArray[r].length;
            int width = (int) (rect.getWidth()/len);

            int height = (int) rect.getHeight() - 2;
            for(int c = 0; c < gridArray[r].length; c++){
            if(gridArray[r][c] == 1){
                    int x = (int) (rect.getX() + width*c);
                    int y = (int) rect.getY() + 2;
                    g.fillRect(x, y, width, height);
            }
            }
        }
        }
    //implement setSize
    public void setSize(Dimension d){

    if(gridArray == null){

        int gridArrayColumns = 24*60/delta;
        gridArray = new int[4][gridArrayColumns];
    }
    int r = 0;
    int rHeight = this.getHeight()/4;
    offdutyRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, (int)d.getWidth() - totalSpacing, rHeight);
    r++;
    sbRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, (int)d.getWidth() - totalSpacing, rHeight);
    r++;
    driveRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, (int)d.getWidth() - totalSpacing, rHeight);
    r++;
    onRect = new Rectangle(this.getX() + dutyStatusSpacing, this.getY() + r*rHeight, (int)d.getWidth() - totalSpacing, rHeight);

    Rectangle rect = null;
    for(r = 0; r < gridArray.length; r++){
        if(r == 0){
        rect = offdutyRect;
        }else if(r == 1){
        rect = sbRect;
        }else if(r == 2){
        rect = driveRect;
        }else if(r == 3){
        rect = onRect;
        }

        //I haven't actually derived any of these things, just my best guesses.
        int len = gridArray[r].length;
        int width = (int) (rect.getWidth()/len);
        rect.setSize((int)(width*len), (int) rect.getHeight());
    }
    }

}

And here is the relatively short custom container that multiple instances of my custom class will be added:

public class GridContainer extends JPanel implements ActionListener{
    List<GridPanel> panels = new ArrayList<GridPanel>();

    public GridContainer(){
    GridBagLayout gb = new GridBagLayout();
    this.setLayout(gb);
    GridBagConstraints c = new GridBagConstraints();

    c.gridx = 0;
    c.gridy = 0;
    c.weightx = .5;
    c.weighty = .5;
    c.fill = GridBagConstraints.HORIZONTAL;
    BufferedImage img = null;
    try {
        img = ImageIO.read(this.getClass().getResource("/res/add.png"));
    } catch (IOException e) { }
    JButton addButton = new JButton();
    addButton.setIcon(new ImageIcon(img));
    addButton.addActionListener(this);
    this.add(addButton, c);
    }

    public void actionPerformed(ActionEvent e) {
    System.out.println("action performed"  +  panels.size());
    this.setLayout(new GridBagLayout());
    removeAll();
    repaint();
    panels.add(new GridPanel());
    int r = 0;
    GridBagConstraints c = new GridBagConstraints();
    for(int i = 0; i < panels.size(); i++){
            JLabel label = new JLabel("day " + i);
            c = new GridBagConstraints();
            c.gridx = 0;
            c.gridy = r;
            c.weightx = 1;
            c.weighty = 1;
            this.add(label, c);
            r++;

            c = new GridBagConstraints();
            c.gridx = 0;
            c.gridy = r;
            c.weightx = 1;
            c.weighty = 1;
            c.fill = GridBagConstraints.HORIZONTAL;
            this.add(panels.get(i), c);
            r++;
    }

    c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = r;
    c.weightx = 1;
    c.weighty = 1;
    c.fill = GridBagConstraints.HORIZONTAL;
    BufferedImage img = null;
    try {
        img = ImageIO.read(this.getClass().getResource("/res/add.png"));
    } catch (IOException ex) { }
    JButton addButton = new JButton();
    addButton.setIcon(new ImageIcon(img));
    addButton.addActionListener(this);
    this.add(addButton, c);
    repaint();

    }
}

Don't feel obligated to debug this wall of code, just some context to where I'm at.

Solution
    • A component should provide, at the very least, a preferredSize for the parent layout manager to determine how best it should be laid out. You should not be making calculations about your size expect to meet these requirements...
    • When painting, your component's graphics context has already begin translated to the x/y position of your component. This means that the top/left corner of your component is actually 0x0
    • You should be calling super.paintComponent. This is very important as it prepares the graphics context for painting, this doubly important when dealing with transparent components

    enter image description here

    public class GridPanel extends JPanel implements MouseMotionListener, MouseListener {

    private Rectangle offdutyRect, sbRect, driveRect, onRect;
    private int delta = 60;
    private int[][] gridArray;
    int draggedStartX = -1;
    int draggedStartY = -1;
    private int dutyStatusSpacing = 60;
    private int totalSpacing = 100;

    public GridPanel() {
        setBackground(Color.WHITE);
        //this.setSize(new Dimension(800, 100));
        this.addMouseMotionListener((MouseMotionListener) this);
        this.addMouseListener(this);
        int gridArrayColumns = 24 * 60 / delta;
        gridArray = new int[4][gridArrayColumns];

        int r = 0;
        int rHeight = this.getHeight() / 4;
        offdutyRect = new Rectangle(dutyStatusSpacing, r * rHeight, this.getWidth() - totalSpacing, rHeight);
        r++;
        sbRect = new Rectangle(dutyStatusSpacing, r * rHeight, this.getWidth() - totalSpacing, rHeight);
        r++;
        driveRect = new Rectangle(dutyStatusSpacing, r * rHeight, this.getWidth() - totalSpacing, rHeight);
        r++;
        onRect = new Rectangle(dutyStatusSpacing, r * rHeight, this.getWidth() - totalSpacing, rHeight);

        Rectangle rect = null;
        for (r = 0; r < gridArray.length; r++) {
            if (r == 0) {
                rect = offdutyRect;
            } else if (r == 1) {
                rect = sbRect;
            } else if (r == 2) {
                rect = driveRect;
            } else if (r == 3) {
                rect = onRect;
            }

            //I haven't actually derived any of these things, just my best guesses.
            int len = gridArray[r].length;
            int width = (int) (rect.getWidth() / len);
            rect.setSize((int) (width * len), (int) rect.getHeight());
        }
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        //the center black bar for duty status "placeholders"
        g.setColor(Color.black);
        g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
        g.drawRect((int) offdutyRect.getX(), (int) offdutyRect.getY() + (int) offdutyRect.getHeight() / 2, (int) offdutyRect.getWidth(), 1);
        g.drawRect((int) sbRect.getX(), (int) sbRect.getY() + (int) sbRect.getHeight() / 2, (int) sbRect.getWidth(), 1);
        g.drawRect((int) driveRect.getX(), (int) driveRect.getY() + (int) driveRect.getHeight() / 2, (int) driveRect.getWidth(), 1);
        g.drawRect((int) onRect.getX(), (int) onRect.getY() + (int) onRect.getHeight() / 2, (int) onRect.getWidth(), 1);
        g.setColor(Color.pink);
        g.drawRect((int) offdutyRect.getX(), (int) offdutyRect.getY(), (int) offdutyRect.getWidth(), (int) offdutyRect.getHeight());
        g.drawRect((int) sbRect.getX(), (int) sbRect.getY(), (int) sbRect.getWidth(), (int) sbRect.getHeight());
        g.drawRect((int) driveRect.getX(), (int) driveRect.getY(), (int) driveRect.getWidth(), (int) driveRect.getHeight());
        g.drawRect((int) onRect.getX(), (int) onRect.getY(), (int) onRect.getWidth(), (int) onRect.getHeight());

        //draw the array
        g.setColor(Color.green);
        Rectangle rect = null;
        for (int r = 0; r < gridArray.length; r++) {
            if (r == 0) {
                rect = offdutyRect;
            } else if (r == 1) {
                rect = sbRect;
            } else if (r == 2) {
                rect = driveRect;
            } else if (r == 3) {
                rect = onRect;
            }

            //I haven't actually derived any of these things, just my best guesses.
            int len = gridArray[r].length;
            int width = (int) (rect.getWidth() / len);

            int height = (int) rect.getHeight() - 2;
            for (int c = 0; c < gridArray[r].length; c++) {
                if (gridArray[r][c] == 1) {
                    int x = (int) (rect.getX() + width * c);
                    int y = (int) rect.getY() + 2;
                    g.fillRect(x, y, width, height);
                }
            }
        }
    }

    //implement setSize
    //        public void setSize(Dimension d) {
    @Override
    public void doLayout() {

        if (gridArray == null) {

            int gridArrayColumns = 24 * 60 / delta;
            gridArray = new int[4][gridArrayColumns];
        }
        int r = 0;
        int rHeight = this.getHeight() / 4;
        offdutyRect = new Rectangle(dutyStatusSpacing, r * rHeight, (int) getWidth() - totalSpacing, rHeight);
        r++;
        sbRect = new Rectangle(dutyStatusSpacing, r * rHeight, (int) getWidth() - totalSpacing, rHeight);
        r++;
        driveRect = new Rectangle(dutyStatusSpacing, r * rHeight, (int) getWidth() - totalSpacing, rHeight);
        r++;
        onRect = new Rectangle(dutyStatusSpacing, r * rHeight, (int) getWidth() - totalSpacing, rHeight);

        Rectangle rect = null;
        for (r = 0; r < gridArray.length; r++) {
            if (r == 0) {
                rect = offdutyRect;
            } else if (r == 1) {
                rect = sbRect;
            } else if (r == 2) {
                rect = driveRect;
            } else if (r == 3) {
                rect = onRect;
            }

            //I haven't actually derived any of these things, just my best guesses.
            int len = gridArray[r].length;
            int width = (int) (rect.getWidth() / len);
            rect.setSize((int) (width * len), (int) rect.getHeight());
        }
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(200, 200);
    }

    @Override
    public void mouseDragged(MouseEvent e) {
    }

    @Override
    public void mouseMoved(MouseEvent e) {
    }

    @Override
    public void mouseClicked(MouseEvent e) {
    }

    @Override
    public void mousePressed(MouseEvent e) {
    }

    @Override
    public void mouseReleased(MouseEvent e) {
    }

    @Override
    public void mouseEntered(MouseEvent e) {
    }

    @Override
    public void mouseExited(MouseEvent e) {
    }
}

    I highly recommend that you take a look at Performing Custom Painting