Animation in java

1. Jim Priest, Peter Lundgren, Russell Bennett Animation in java

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

3. Example /** *DrawstheWorldanditsBalls. * *@paramgtheGraphicsobjectontowhichtodraw. */ @Override publicvoid paintComponent(Graphics g) { super.paintComponent(g); Graphics2D graphics = (Graphics2D) g; this.drawWorld(graphics); this.drawBalls(graphics); } /** *Repeatedlyrepaintsthispanel. */ publicvoid run() { while (true) { try { Thread.sleep(this.timeToSleep); this.repaint(); } catch (InterruptedException exception) { // If you can't sleep, no problem -- just continue. } } }

4. 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.

5. 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

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

7. Example classOptimizedDoubleBufferedCanvasextends Canvas { publicvoid 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); } }

8. Questions? Next, Demo