Jim Priest, Peter Lundgren, Russell Bennett

Background info  A sequence of fames  You have some experience already  Used for some GUI’s and Games

Example /** * Draws the World and its Balls. * g the Graphics object onto which to draw. public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D graphics = (Graphics2D) g; this.drawWorld(graphics); this.drawBalls(graphics); } /** * Repeatedly repaints this panel. */ public void run() { while (true) { try { Thread.sleep(this.timeToSleep); this.repaint(); } catch (InterruptedException exception) { // If you can't sleep, no problem -- just continue. }

Important Concepts  Using threads to control animation behavior  Controlling the speed and smoothness using.sleep() Have a frame rate field. Pass 1000/frameRate to.sleep() Can’t have different frame rates for different animation objects on screen at same time After sleep, calls repaint.

Important Concepts  Using the run method Contains the animation thread Can be used to draw on the Frame  Using the paintComponent method Can be used to draw on the frame Still needs a thread to handle updating the frame

Important Concepts  “Flashing”  Overriding the update() method  Off-screen images “Double buffering”

Example class OptimizedDoubleBufferedCanvas extends Canvas { public void update(Graphics g) { Graphics offgc; Image offscreen = null; Rectangle box = g.getClipRect(); // create the offscreen buffer and associated Graphics offscreen = createImage(box.width, box.height); offgc = offscreen.getGraphics(); // clear the exposed area offgc.setColor(getBackground()); offgc.fillRect(0, 0, box.width, box.height); offgc.setColor(getForeground()); // do normal redraw offgc.translate(-box.x, -box.y); paint(offgc); // transfer offscreen to window g.drawImage(offscreen, box.x, box.y, this); }

Questions? Next, Demo