How to clear a line of ImageIcons like in tetris?

Question

If I have a JPanel with different ImageIcons in it like tetris and if the line is filled it will be removed. Does anyone know how i can redraw the area occupied by the ImageIcons? should I redraw the entire panel "down " to overlap it? Thanks

Answer 1

Load your images with ImageIO.read(url_file_inputStream) to get BufferedImages.
There are two general approaches to something like this. One is using components: JLabels
set in a layout manager that forms a grid (eg, GridLayout or GridBagLayout). You set the
images in the labels with setIcon(new ImageIcon(image)). To get the image to disappear use
setIcon(null).
The other approach is a graphic approach in which you draw everything. Here is an example
of how you could put this together with this second approach:
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class DrawingControl extends JPanel {
    BufferedImage[] images;
    boolean[] showRows;
    int size = 5;
    final int PAD = 25;
    public DrawingControl() {
        initImages();
        showRows = new boolean[size];
        for(int j = 0; j < showRows.length; j += 2)
            showRows[j] = true;
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        // Draw a centered grid.
        double xInc = (double)(w - 2*PAD)/size;
        double yInc = (double)(h - 2*PAD)/size;
        g2.setPaint(Color.red);
        for(int j = 0; j <= size; j++) {
            double y = PAD + j*yInc;
            for(int k = 0; k <= size; k++) {
                g2.draw(new Line2D.Double(PAD, y, w-PAD, y));
        for(int j = 0; j <= size; j++) {
            double x = PAD + j*xInc;
            for(int k = 0; k <= size; k++) {
                g2.draw(new Line2D.Double(x, PAD, x, h-PAD));
        // Draw images in visible rows.
        int iw = images[0].getWidth();
        int ih = images[0].getHeight();
        for(int j = 0; j < size; j++) {
            if(!showRows[j])
                continue;
            for(int k = 0; k < size; k++) {
                int n = (j*size + k) % images.length;
                int x = (int)(PAD + k*xInc + (xInc-iw)/2);
                int y = (int)(PAD + j*yInc + (yInc-ih)/2);
                g2.drawImage(images[n], x, y, this);
    private void initImages() {
        int s = 40, type = BufferedImage.TYPE_INT_RGB;
        images = new BufferedImage[4];
        double theta = 0;
        AffineTransform at = new AffineTransform();
        for(int j = 0; j < images.length; j++) {
            images[j] = new BufferedImage(s, s, type);
            Graphics2D g2 = images[j].createGraphics();
            g2.setBackground(Color.orange);
            g2.clearRect(0,0,s-1,s-1);
            g2.setPaint(Color.blue);
            g2.drawRect(0,0,s-1,s-1);
            g2.setStroke(new BasicStroke(4f));
            at.setToRotation(theta, s/2, s/2);
            g2.setTransform(at);
            g2.setPaint(Color.green.darker());
            g2.drawLine(10,s/2,s/2,s-10);
            g2.drawLine(s/2,s-10,s-10,s/2);
            g2.dispose();
            theta += Math.PI/2;
    public static void main(String[] args) {
        DrawingControl test = new DrawingControl();
        test.addMouseListener(test.rowToggle);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    private MouseListener rowToggle = new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            Point p = e.getPoint();
            int w = getWidth();
            double h = getHeight();
            if(p.x > PAD && p.x < w-PAD && p.y > PAD && p.y < h-PAD) {
                double yInc = (h - 2*PAD)/size;
                int row = (int)((p.y - PAD)/yInc);
                showRows[row] = !showRows[row];
                repaint();
}