How to rotate an image gradually in Swing?

Question

I have an image I am rotating when the user clicks on a button. But it is not working.

I would like to see the image rotating gradually to 90 degrees till it stops but it doesn't. The image must rotate 90 degrees gradually when the button is clicked.

I have created an SSCCE to demonstrate the problem. Please replace the image in the CrossingPanelSSCE class with any image of your choice. Just put the image in your images folder and name it images/railCrossing.JPG.

RotateButtonSSCE

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JPanel;

public class RotateButtonSSCE extends JPanel implements ActionListener{
      private JButton rotate = new JButton("Rotate");
      private VisualizationPanelSSCE vis = new VisualizationPanelSSCE();

    public RotateButtonSSCE() {
        this.setBorder(BorderFactory.createTitledBorder("Rotate Button "));
        this.rotate.addActionListener(this);
        this.add(rotate);
    }

    public void actionPerformed(ActionEvent ev) {
        vis.rotatetheCrossing();
    }

}

CrossingPanelSSCE

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;

import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.border.TitledBorder;

public class CrossingPanelSSCE  extends JPanel{

    private static final long serialVersionUID = 1L;

    // private data members
     private Image crossingImage;
     private int currentRotationAngle;
     private int imageWidth;
     private int imageHeight;
     private AffineTransform affineTransform;
     private boolean clockwise; 
     private static int ROTATE_ANGLE_OFFSET = 2;

     private int xCoordinate;
     private int yCoordinate;

     private static javax.swing.Timer timer;

     private void initialize(){
         this.crossingImage = Toolkit.getDefaultToolkit().getImage("images/railCrossing.JPG");
         this.imageWidth = this.getCrossingImage().getWidth(this);
         this.imageHeight = this.getCrossingImage().getHeight(this);
         this.affineTransform = new AffineTransform();
         currentRotationAngle = 90;
         timer = new javax.swing.Timer(20, new MoveListener());
     } 

    public CrossingPanelSSCE(int x, int y) {
        this.setxCoordinate(x);
        this.setyCoordinate(y);
        this.setPreferredSize(new Dimension(50, 50));
        this.setBackground(Color.red);
        TitledBorder border = BorderFactory.createTitledBorder("image");
        this.setLayout(new FlowLayout());
        this.initialize();

    }


    public void paintComponent(Graphics grp){ 

        Rectangle rect = this.getBounds();
        Graphics2D g2d = (Graphics2D)grp;
        g2d.setColor(Color.BLACK);
        this.getAffineTransform().setToTranslation(this.getxCoordinate(), this.getyCoordinate());

          //rotate with the rotation point as the mid of the image
        this.getAffineTransform().rotate(Math.toRadians(this.getCurrentRotationAngle()), this.getCrossingImage().getWidth(this) /2, 
                                         this.getCrossingImage().getHeight(this)/2);

        //draw the image using the AffineTransform
        g2d.drawImage(this.getCrossingImage(), this.getAffineTransform(), this);
    }


    public  void rotateCrossing(){
        System.out.println("CurrentRotationAngle: " + currentRotationAngle);
        this.currentRotationAngle += ROTATE_ANGLE_OFFSET;
        //int test = currentRotationAngle % 90;
        if(currentRotationAngle % 90 == 0){
         setCurrentRotationAngle(currentRotationAngle);
         timer.stop();           
        }

         //repaint the image panel
         repaint(); 
    }


    void start() {
        if (timer != null) {
            timer.start();
        }
    }


     private class MoveListener implements ActionListener {

            public void actionPerformed(ActionEvent e) {
               rotateCrossing();
        }

     }

    public Image getCrossingImage() {
        return crossingImage;
    }
    public void setCrossingImage(Image crossingImage) {
        this.crossingImage = crossingImage;
    }

    public int getCurrentRotationAngle() {
        return currentRotationAngle;
    }
    public void setCurrentRotationAngle(int currentRotationAngle) {
        this.currentRotationAngle = currentRotationAngle;
    }

    public int getImageWidth() {
        return imageWidth;
    }
    public void setImageWidth(int imageWidth) {
        this.imageWidth = imageWidth;
    }

    public int getImageHeight() {
        return imageHeight;
    }
    public void setImageHeight(int imageHeight) {
        this.imageHeight = imageHeight;
    }

    public AffineTransform getAffineTransform() {
        return affineTransform;
    }
    public void setAffineTransform(AffineTransform affineTransform) {
        this.affineTransform = affineTransform;
    }

    public boolean isClockwise() {
        return clockwise;
    }
    public void setClockwise(boolean clockwise) {
        this.clockwise = clockwise;
    }

    public int getxCoordinate() {
        return xCoordinate;
    }
    public void setxCoordinate(int xCoordinate) {
        this.xCoordinate = xCoordinate;
    }

    public int getyCoordinate() {
        return yCoordinate;
    }
    public void setyCoordinate(int yCoordinate) {
        this.yCoordinate = yCoordinate;
    }

    public javax.swing.Timer getTimer() {
        return timer;
    }
    public void setTimer(javax.swing.Timer timer) {
        this.timer = timer;
    }



}

VisualizationPanelSSCE

import gui.CrossingPanel;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.GeneralPath;

import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.TitledBorder;

import application.Robot2;

public class VisualizationPanelSSCE extends JPanel{


        //private data members
        private GeneralPath path;
        private Shape horizontalRail;
        private Shape verticalRail;
        private static int LENGTH = 350;
        private CrossingPanelSSCE crossingP;



         private void initializeComponents(){
             this.path = new GeneralPath();
             this.horizontalRail = this.createHorizontalRail();
             this.verticalRail = this.createVerticalRail();
             this.crossingP = new CrossingPanelSSCE(328,334);
         }

        public VisualizationPanelSSCE(){ 
            this.initializeComponents();
            this.setPreferredSize(new Dimension(400,400));
             TitledBorder border = BorderFactory.createTitledBorder("Rotation");
             this.setBorder(border);

        }

        public GeneralPath getPath() {
            return path;
        }
        public void setPath(GeneralPath path) {
            this.path = path;
        }


        private Shape createHorizontalRail(){
            this.getPath().moveTo(5, LENGTH);
            this.getPath().lineTo(330, 350);
            this.getPath().closePath();
            return this.getPath();
        }

        private Shape createVerticalRail(){
            this.getPath().moveTo(350, 330);
            this.getPath().lineTo(350,10);
            this.getPath().closePath();
            return this.getPath();
        }


        public void paintComponent(Graphics comp){
             super.paintComponent(comp); 
            Graphics2D comp2D = (Graphics2D)comp;
            BasicStroke pen = new BasicStroke(15.0F, BasicStroke.CAP_BUTT,BasicStroke.JOIN_ROUND);

            comp2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                    RenderingHints.VALUE_ANTIALIAS_ON);
            comp2D.setPaint(Color.black);
            comp2D.setBackground(Color.WHITE);
            comp2D.draw(this.horizontalRail);
            this.crossingP.paintComponent(comp2D);
        }


        public CrossingPanelSSCE getCrossingP() {
            return crossingP;
        }
        public void setCrossingP(CrossingPanelSSCE crossingP) {
            this.crossingP = crossingP;
        }

        public void rotatetheCrossing(){

             Runnable rotateCrossing1 = new Runnable(){  
                public void run() {
                  crossingP.start();
              }
          };
            SwingUtilities.invokeLater(rotateCrossing1);
        }


    }

TestGUISSCE it contains the main method.

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Random;

import javax.swing.*;

public class TestGUISSCE{
    private RotateButtonSSCE rotate = new RotateButtonSSCE();
    private VisualizationPanelSSCE vision = new VisualizationPanelSSCE();

    public void createGui(){

         JFrame frame = new JFrame("Example");
         frame.setSize(new Dimension(500, 500));


         JPanel pane = new JPanel();
         pane.add(this.vision);
         pane.add(rotate);  
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.add(pane);
         frame.setVisible(true);

    }

    public static void main(String[] args) {
        new TestGUISSCE().createGui();
    }
}

Answer 1

this.crossingP.paintComponent(comp2D);

Never do this! Your CrossingPane is not added to any component, so repaint() doesn't have any effect. You can check it by adding prints in the paintComponent() method. SO you need to add CrossingPane to the VisualizationPane:

setLayout(new BorderLayout());
add(crossingP, BorderLayout.CENTER);

There are some issues with centering the image, but this shouldn't be hard to fix.

PS. Read again about layouts and painting.

Answer 2

In addition to @tulskiy's helpful observations, I would add two points:

1. Always construct you GUI on the event dispatch thread, as shown below.

2. An sscce should be a Short, Self Contained, Correct (Compilable), Example. As a convenience, don't require others to recreate multiple public classes; use top-level (package-private) or nested classes. As this is a graphics problem, use a public or synthetic image that reflects your problem.

In the example below, paintComponent() alters the graphics context's transform to effect the rotation. Note that the operations are performed in the (apparent) reverse of the declaration order: First, the image's center is translated to the origin; second, the image is rotated; third, the image's center is translated to the center of the panel. You can see the effect by resizing the panel.

package overflow;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.*;

/**
 * @see http://stackoverflow.com/questions/3371227
 * @see http://stackoverflow.com/questions/3405799
 */
public class RotateApp {

    private static final int N = 3;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setLayout(new GridLayout(N, N, N, N));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                for (int i = 0; i < N * N; i++) {
                    frame.add(new RotatePanel());
                }
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}

class RotatePanel extends JPanel implements ActionListener {

    private static final int SIZE = 256;
    private static double DELTA_THETA = Math.PI / 90;
    private final Timer timer = new Timer(25, this);
    private Image image = RotatableImage.getImage(SIZE);
    private double dt = DELTA_THETA;
    private double theta;

    public RotatePanel() {
        this.setBackground(Color.lightGray);
        this.setPreferredSize(new Dimension(
            image.getWidth(this), image.getHeight(this)));
        this.addMouseListener(new MouseAdapter() {

            @Override
            public void mousePressed(MouseEvent e) {
                image = RotatableImage.getImage(SIZE);
                dt = -dt;
            }
        });
        timer.start();
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.translate(this.getWidth() / 2, this.getHeight() / 2);
        g2d.rotate(theta);
        g2d.translate(-image.getWidth(null) / 2, -image.getHeight(null) / 2);
        g2d.drawImage(image, 0, 0, null);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        theta += dt;
        repaint();
    }
}

class RotatableImage {

    private static final Random r = new Random();

    static public Image getImage(int size) {
        BufferedImage bi = new BufferedImage(
            size, size, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = bi.createGraphics();
        g2d.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setPaint(new Color(r.nextInt()));
        g2d.setStroke(new BasicStroke(size / 8));
        g2d.drawLine(0, size / 2, size, size / 2);
        g2d.drawLine(size / 2, 0, size / 2, size);
        g2d.dispose();
        return bi;
    }
}