The Java Boutique: Java Tutorial: Java by Example: Input Devices

import java.awt.*; import java.applet.*; public class Project34 extends Applet { Image Buffer; Graphics gBuffer; int x, y; boolean mouseInside, collide; Rectangle r1, r2; public void init() { Buffer=createImage(size().width,size().height); gBuffer=Buffer.getGraphics(); //create 2 rectangle objects r1=new Rectangle(110,115,60,50); //we don't know the coordinates yet, so we create it //with a different constructor, passing only the size r2=new Rectangle(40,40); } public void drawStuff() { gBuffer.setColor(Color.white); gBuffer.fillRect(0,0,size().width,size().height); gBuffer.setColor(Color.red); gBuffer.fillRect(r1.x, r1.y, r1.width, r1.height); gBuffer.setColor(Color.blue); gBuffer.setFont(new Font("Helvetica",Font.BOLD,16)); if(mouseInside) gBuffer.fillRect(r2.x, r2.y, r2.width, r2.height); else gBuffer.drawString("Move the mouse around!", 10, 20); gBuffer.setColor(Color.black); if(collide) gBuffer.drawString("Collision!", 10, 20); } public boolean mouseEnter(Event evt,int x,int y) { mouseInside=true; repaint(); return true; } public boolean mouseExit(Event evt,int x,int y) { mouseInside=false ; repaint(); return true; } public boolean mouseMove(Event evt,int x,int y) { //submit the mouse coordinates to our instance variables this.x=x; this.y=y; //move the blue square according to mouse position //we use the Rectangle method "move" here r2.move(x-r2.width/2, y-r2.height/2); //check for collision here, use the "intersects" method //of the Rectangle class collide=r1.intersects(r2); drawStuff(); repaint(); return true; } public void update(Graphics g) { paint(g); } public void paint(Graphics g) { drawStuff(); g.drawImage (Buffer,0,0, this); } }