Code example: Simple animation, smart use of clipping

Question

The code posted below creates a set of eyes that will track the mouse around, and blink periodically.
In particular, notice the way I use clipping to only paint part of the eyelid oval.
There are two dependencies in the code. One is MathUtils.angle(). Comment this out and replace with the correct call to Math.atan2. The other place is WindowUtilities.visualize(). Remove this and put the Eyes class is a window and you should be good to go
tjacobs.ui.Eyes
package tjacobs.ui;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Timer;
import java.util.TimerTask;
import javax.swing.JComponent;
import javax.swing.SwingUtilities;
import tjacobs.MathUtils;
public class Eyes extends JComponent implements MouseMotionListener {
     private int mEyeGap = 0;
     private double mEyeDir1 = Double.NaN, mEyeDir2;
     private double mEyeRatio = .6;
     private int mBatEyesState = 0;
     private Timer mEyeBatter;
     private long mTimeBetweenBats;
     private long mBatAnimationSpeed = 100;
     public Eyes() {
          //setBackground(Color.BLACK);
          setBackground(Color.PINK);
          setForeground(Color.BLUE);
          addMouseMotionListener(this);
     public void setBatAnimationSpeed(long speed) {
          mBatAnimationSpeed = speed;
     public long getBatAnimationSpeed() {
          return mBatAnimationSpeed;
     public void mouseMoved(MouseEvent me) {
          Point p = SwingUtilities.convertPoint(me.getComponent(), me.getPoint(), this);
          int height = getHeight();
          mEyeDir1 = MathUtils.angle(height / 2, height / 2, p.x, p.y);
          mEyeDir2 = MathUtils.angle((3 * height) / 2 + mEyeGap, height / 2, p.x, p.y);
          repaint();
     public void mouseDragged(MouseEvent me) {
          mouseMoved(me);
     public int getEyeGap() {
          return mEyeGap;
     public void setEyeGap(int gap) {
          mEyeGap = gap;
     public void setBatEyes(long timeBetweenBats) {
          mTimeBetweenBats = timeBetweenBats;
          if (mEyeBatter != null) {
               mEyeBatter.cancel();
               mEyeBatter = null;
          if (timeBetweenBats < mBatAnimationSpeed * 8) {
               return;
          else {
               mEyeBatter = new Timer(true); //allow it to be a daemon thread
               mEyeBatter.scheduleAtFixedRate(new BatEyesTask(), mTimeBetweenBats, mTimeBetweenBats);
               //Thread t = new Thread(mEyeBatter);
               //t.start();
     private class BatEyesTask extends TimerTask {
          public void run() {
               try {
                    //System.out.println("bat");
                    Thread t = Thread.currentThread();
                    mBatEyesState = 1;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 2;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 3;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 4;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 3;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 2;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 1;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 0;
                    repaint();
               catch (InterruptedException ex) {
                    if (mBatEyesState != 0) {
                         mBatEyesState = 0;
                         repaint();
     public void paintComponent(Graphics g) {
          int height = getHeight();
          int r = height / 2;
          g.setColor(Color.WHITE);
          g.fillOval(0, 0, height, height);
          g.fillOval(height + mEyeGap + 0, 0, height, height);
          g.setColor(Color.BLACK);
          g.drawOval(0, 0, height, height);
          g.drawOval(height + mEyeGap + 0, 0, height, height);
          g.setColor(getForeground());
          int irisR = (int) (r * mEyeRatio);
          if (Double.isNaN(mEyeDir1)) {
               int x1 = (r - irisR);
               int y1 = x1;
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
               x1 += height + mEyeGap;
               g.fillOval(x1, y1, irisR * 2 , irisR * 2);
//               int x1 = r - r/4;
//               int y1 = r - r/4;
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
//               x1 += height + mEyeGap;
//               g.fillOval(x1, y1, (int) (r * mEyeRatio) , (int)(r * mEyeRatio));
          } else {
               int x1 = (r - irisR);
               int y1 = x1;
               x1 -= Math.cos(mEyeDir1) * (r - irisR);
               y1 -= Math.sin(mEyeDir1) * (r - irisR);
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
               x1 = (r - irisR) + height + mEyeGap;
               y1 = r - irisR;
               x1 -= Math.cos(mEyeDir2) * (r - irisR);
               y1 -= Math.sin(mEyeDir2) * (r - irisR);
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
//               int x1 = (int) (r - Math.cos(mEyeDir1) * r);
//               int y1 = (int) (r - Math.sin(mEyeDir1) * r);
//               System.out.println("height" + height + " x1 = " + x1 + " y1 = " + y1);
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
//               x1 = height + mEyeGap + (int) (r - Math.cos(mEyeDir2) * r);
//               y1 = (int) (r - Math.sin(mEyeDir2) * r);
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
               //Eye Batting
          //System.out.println("painting");
          if (mBatEyesState != 0) {
               Rectangle rect = new Rectangle(0,0,getWidth(), getHeight() * mBatEyesState / 4);
               g.setClip(rect);
               g.setColor(getBackground());
               g.fillOval(0, 0, height, height);
               g.fillOval(height + mEyeGap + 0, 0, height, height);
      * @param args
     public static void main(String[] args) {
          // TODO Auto-generated method stub
          Eyes eyes = new Eyes();
          eyes.setBatEyes(10000);
          eyes.setPreferredSize(new Dimension(60,25));
          eyes.setEyeGap(5);
          WindowUtilities.visualize(eyes);
}

Answer 1

The code posted below creates a set of eyes that will track the mouse around, and blink periodically.
In particular, notice the way I use clipping to only paint part of the eyelid oval.
There are two dependencies in the code. One is MathUtils.angle(). Comment this out and replace with the correct call to Math.atan2. The other place is WindowUtilities.visualize(). Remove this and put the Eyes class is a window and you should be good to go
tjacobs.ui.Eyes
package tjacobs.ui;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Timer;
import java.util.TimerTask;
import javax.swing.JComponent;
import javax.swing.SwingUtilities;
import tjacobs.MathUtils;
public class Eyes extends JComponent implements MouseMotionListener {
     private int mEyeGap = 0;
     private double mEyeDir1 = Double.NaN, mEyeDir2;
     private double mEyeRatio = .6;
     private int mBatEyesState = 0;
     private Timer mEyeBatter;
     private long mTimeBetweenBats;
     private long mBatAnimationSpeed = 100;
     public Eyes() {
          //setBackground(Color.BLACK);
          setBackground(Color.PINK);
          setForeground(Color.BLUE);
          addMouseMotionListener(this);
     public void setBatAnimationSpeed(long speed) {
          mBatAnimationSpeed = speed;
     public long getBatAnimationSpeed() {
          return mBatAnimationSpeed;
     public void mouseMoved(MouseEvent me) {
          Point p = SwingUtilities.convertPoint(me.getComponent(), me.getPoint(), this);
          int height = getHeight();
          mEyeDir1 = MathUtils.angle(height / 2, height / 2, p.x, p.y);
          mEyeDir2 = MathUtils.angle((3 * height) / 2 + mEyeGap, height / 2, p.x, p.y);
          repaint();
     public void mouseDragged(MouseEvent me) {
          mouseMoved(me);
     public int getEyeGap() {
          return mEyeGap;
     public void setEyeGap(int gap) {
          mEyeGap = gap;
     public void setBatEyes(long timeBetweenBats) {
          mTimeBetweenBats = timeBetweenBats;
          if (mEyeBatter != null) {
               mEyeBatter.cancel();
               mEyeBatter = null;
          if (timeBetweenBats < mBatAnimationSpeed * 8) {
               return;
          else {
               mEyeBatter = new Timer(true); //allow it to be a daemon thread
               mEyeBatter.scheduleAtFixedRate(new BatEyesTask(), mTimeBetweenBats, mTimeBetweenBats);
               //Thread t = new Thread(mEyeBatter);
               //t.start();
     private class BatEyesTask extends TimerTask {
          public void run() {
               try {
                    //System.out.println("bat");
                    Thread t = Thread.currentThread();
                    mBatEyesState = 1;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 2;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 3;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 4;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 3;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 2;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 1;
                    repaint();
                    t.sleep(mBatAnimationSpeed);
                    mBatEyesState = 0;
                    repaint();
               catch (InterruptedException ex) {
                    if (mBatEyesState != 0) {
                         mBatEyesState = 0;
                         repaint();
     public void paintComponent(Graphics g) {
          int height = getHeight();
          int r = height / 2;
          g.setColor(Color.WHITE);
          g.fillOval(0, 0, height, height);
          g.fillOval(height + mEyeGap + 0, 0, height, height);
          g.setColor(Color.BLACK);
          g.drawOval(0, 0, height, height);
          g.drawOval(height + mEyeGap + 0, 0, height, height);
          g.setColor(getForeground());
          int irisR = (int) (r * mEyeRatio);
          if (Double.isNaN(mEyeDir1)) {
               int x1 = (r - irisR);
               int y1 = x1;
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
               x1 += height + mEyeGap;
               g.fillOval(x1, y1, irisR * 2 , irisR * 2);
//               int x1 = r - r/4;
//               int y1 = r - r/4;
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
//               x1 += height + mEyeGap;
//               g.fillOval(x1, y1, (int) (r * mEyeRatio) , (int)(r * mEyeRatio));
          } else {
               int x1 = (r - irisR);
               int y1 = x1;
               x1 -= Math.cos(mEyeDir1) * (r - irisR);
               y1 -= Math.sin(mEyeDir1) * (r - irisR);
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
               x1 = (r - irisR) + height + mEyeGap;
               y1 = r - irisR;
               x1 -= Math.cos(mEyeDir2) * (r - irisR);
               y1 -= Math.sin(mEyeDir2) * (r - irisR);
               g.fillOval(x1, y1, irisR * 2, irisR * 2);
//               int x1 = (int) (r - Math.cos(mEyeDir1) * r);
//               int y1 = (int) (r - Math.sin(mEyeDir1) * r);
//               System.out.println("height" + height + " x1 = " + x1 + " y1 = " + y1);
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
//               x1 = height + mEyeGap + (int) (r - Math.cos(mEyeDir2) * r);
//               y1 = (int) (r - Math.sin(mEyeDir2) * r);
//               g.fillOval(x1, y1, (int) (r * mEyeRatio), (int) (r * mEyeRatio));
               //Eye Batting
          //System.out.println("painting");
          if (mBatEyesState != 0) {
               Rectangle rect = new Rectangle(0,0,getWidth(), getHeight() * mBatEyesState / 4);
               g.setClip(rect);
               g.setColor(getBackground());
               g.fillOval(0, 0, height, height);
               g.fillOval(height + mEyeGap + 0, 0, height, height);
      * @param args
     public static void main(String[] args) {
          // TODO Auto-generated method stub
          Eyes eyes = new Eyes();
          eyes.setBatEyes(10000);
          eyes.setPreferredSize(new Dimension(60,25));
          eyes.setEyeGap(5);
          WindowUtilities.visualize(eyes);
}