Simple class to enable kinetic scrolling through dragging to any JScrollPane

TouchScreenScrollPane.java

import java.awt.AWTEvent;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Point;
import java.awt.Toolkit;
import java.awt.event.AWTEventListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.HashMap;
import javax.swing.JComponent;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JViewport;
 
/**
 * Simple class to 'touchify' JScrollPanes by enabling kinetic scrolling through dragging
 * Usage: just create the JScrollPane as you normally would, but call TouchScreenScrollPane.install(JScrollPane) on it after
 * all initialisation is done.
 * @author martenjacobs
 */
public class TouchScreenScrollPane {
    private TouchScreenScrollPane(){}
    
    private static final HashMap<JScrollPane, MouseEventListener> listeners = new HashMap();
    
    public static void install(JScrollPane p){
        
        AWTEventListener awtevtlis = createAWTWindowListener();
        Toolkit.getDefaultToolkit().addAWTEventListener(awtevtlis, AWTEvent.MOUSE_EVENT_MASK);
        Toolkit.getDefaultToolkit().addAWTEventListener(awtevtlis, AWTEvent.MOUSE_MOTION_EVENT_MASK);
        listeners.put(p, new MouseEventListener(p));
        Component c = p.getViewport().getView();
        if(c instanceof JTable){
            JTable itm = (JTable) c;
            itm.setRowHeight(36);
        }
        if(c instanceof JList){
            JList itm = (JList) c;
            itm.setFixedCellHeight(36);
        }
        if(c instanceof JComponent){
            JComponent itm = (JComponent) c;
            itm.setAutoscrolls(false);
            Font f = itm.getFont();
            Font nf = new Font(f.getFontName(), f.getStyle(), 16);
            itm.setFont(nf);
        }
    }
    
    
    private static void doDispatchEvent(MouseEvent awte, JScrollPane comp) {
        MouseEventListener listener;
        synchronized(listeners){
            if(!listeners.containsKey(comp)) return;
            listener = listeners.get(comp);
        }
        if (MouseEvent.MOUSE_CLICKED == awte.getID()) {
            listener.mouseClicked(awte);
        } else if (MouseEvent.MOUSE_PRESSED == awte.getID()) {
            listener.mousePressed(awte);
        } else if (MouseEvent.MOUSE_RELEASED == awte.getID()) {
            listener.mouseReleased(awte);
        } else if (MouseEvent.MOUSE_ENTERED == awte.getID()) {
            listener.mouseEntered(awte);
        } else if (MouseEvent.MOUSE_EXITED == awte.getID()) {
            listener.mouseExited(awte);
        } else if (MouseEvent.MOUSE_DRAGGED == awte.getID()) {
            listener.mouseDragged(awte);
        } else if (MouseEvent.MOUSE_MOVED == awte.getID()) {
            listener.mouseMoved(awte);
        }
    }
 
    private static AWTEventListener createAWTWindowListener() {
        return new AWTEventListener() {
            @Override
            public void eventDispatched(AWTEvent awte) {
                MouseEvent event = (MouseEvent) awte;
                JScrollPane comp = checkForScrollPanel(event.getComponent());
                if (comp!=null) {
                    doDispatchEvent(event, comp);
                }
            }
        };
    }
 
    private static JScrollPane checkForScrollPanel(Component comp) {
        if (comp instanceof JScrollPane) {
            synchronized(listeners){
                return (listeners.containsKey((JScrollPane) comp))?(JScrollPane) comp:null;
            }
        } else {
            comp = comp.getParent();
            if (comp != null) {
                return checkForScrollPanel(comp);
            }
        }
        return null;
    }
 
    private static class MouseEventListener implements MouseListener, MouseMotionListener {
 
        private Point lastPos = null;
        private Point relPos = null;
        private ArrayList<MouseEvent> lastEvents = new ArrayList();
        private Thread kinetic = new Thread();
        private final JScrollPane pane;
        
        public MouseEventListener(JScrollPane pane){
            this.pane=pane;
        }
        
        @Override
        public void mouseDragged(MouseEvent me) {
            JViewport vp = pane.getViewport();
            if(lastPos==null) lastPos=me.getLocationOnScreen();
            
            moveBy(lastPos.x-me.getXOnScreen(), lastPos.y-me.getYOnScreen(), vp);
            
            synchronized(lastEvents){
                if(lastEvents.size()>5){
                    lastEvents.remove(0);
                }
                lastEvents.add(me);
            }
 
        }
 
        @Override
        public synchronized void mouseMoved(MouseEvent me) {
        }
 
        @Override
        public synchronized void mouseClicked(MouseEvent me) {
        }
        
        @Override
        public synchronized void mousePressed(MouseEvent me) {
            JViewport vp = pane.getViewport();
            
            lastPos=me.getLocationOnScreen();
            relPos=vp.getViewPosition();
            
            synchronized(lastEvents){
                lastEvents.clear();
            }
            kinetic.interrupt();
        }
 
        @Override
        public synchronized void mouseReleased(MouseEvent me) {
            JViewport vp = pane.getViewport();
            
            MouseEvent last;
            MouseEvent first;
            if(lastEvents.size()<2) return;
            synchronized(lastEvents){
                last = lastEvents.get(lastEvents.size()-1);
                first = lastEvents.get(0);
                lastEvents.clear();
            }
            Dimension vector = new Dimension(
                    first.getXOnScreen()-last.getXOnScreen(),
                    first.getYOnScreen()-last.getYOnScreen());
            long time = last.getWhen()-first.getWhen();
            
            Point2D p = new Point2D.Float(
                    ((float) vector.width)/((float) time), 
                    ((float) vector.height)/((float) time));
            
            kinetic.interrupt();
            kinetic=new MoveThread(p, vp);
            kinetic.start();
        }
 
        @Override
        public synchronized void mouseEntered(MouseEvent me) {
        }
 
        @Override
        public synchronized void mouseExited(MouseEvent me) {
        }
        
        public void moveBy(int x,int y,JViewport vp){
            Point vis = relPos.getLocation();
            vis.translate(x, y);
            
            
            if(vis.x<0)vis.x=0;
            if(vis.y<0)vis.y=0;
            if(vis.x+vp.getWidth()>vp.getViewSize().width){
                vis.x=vp.getViewSize().width-vp.getWidth();
            }
            if(vis.y+vp.getHeight()>vp.getViewSize().height){
                vis.y=vp.getViewSize().height-vp.getHeight();
            }
 
            vp.setViewPosition(vis);
        }
        
        private class MoveThread extends Thread{
            private Point2D speed;
            private final JViewport vp;
            public MoveThread(Point2D initialspeed, JViewport vp){
                this.speed=initialspeed;
                this.vp=vp;
            }
            
            private int ms = 1000/50;
            private double modx = 0;
            private double mody = 0;
            
            @Override
            public void run(){
                try{
                    while(true){
                        double mx = speed.getX()*ms + modx;
                        double my = speed.getY()*ms + mody;
                        
                        if(mx<=0.005 && my<=0.005
                                && speed.getX()>=-0.005 && speed.getY()>=-0.005){
                            return;
                        }
                        relPos=vp.getViewPosition();
                        
                        modx = mx % 1d;
                        mody = my % 1d;
                        
                        moveBy((int) mx, (int) my, vp);
                        speed.setLocation(
                                speed.getX()/(Math.exp((double) ms/150d)), 
                                speed.getY()/(Math.exp((double) ms/150d)));
                        Thread.sleep(ms);
                    }
                }catch(Exception e){
                    
                }
            }
        }
    }
}

ToDo:

• disable passing through of press events when a user starts dragging
• adding comments