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Java: Animation

Java: Animation. Chris North cs3724: HCI. Animation?. Changing graphics over time Examples: cartoons Clippy, agents/assistants Hour glass Save dohicky Progress bar Copy file Amit’s pulsating plot. Purvi. Algorithm Animation. Java Graphics Review. Extend JPanel

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Java: Animation

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  1. Java:Animation Chris North cs3724: HCI

  2. Animation? • Changing graphics over time • Examples: • cartoons • Clippy, agents/assistants • Hour glass • Save dohicky • Progress bar • Copy file • Amit’s pulsating plot

  3. Purvi • Algorithm Animation

  4. Java Graphics Review • Extend JPanel • Override paintComponent( ) method public class MyPanel extends JPanel { public void paintComponent(Graphics g){ super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; // my graphics here: g2.drawString("Hello World", 10, 10); } }

  5. Ticker

  6. Animating the ticker text • Keep repainting graphics using different x public class MyPanel extends JPanel { int x; public void paintComponent(Graphics g){ super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; // my graphics here: g2.drawString("Hello World", x, 10); } }

  7. Animation Loop • Update x location (member variable) • Repaint While(true){ //infinite loop x = x – 1; repaint(); //calls paintComponent() Thread.sleep(10); //slow down animation } • Problem?

  8. Multi-Threading • Loop prevents other parts of code from executing • User events pile up • Multiple threads let multiple methods execute simultaneously (multi-tasking) • Threads = lightweight processes, shared memory Main thread User interaction Anim thread Update graphics

  9. Java Threads • implement Runnable interface • Override run( ) method • Put animation loop here • new Thread(runnable) • Thread.start( ) • Calls runnable.run( )in new thread My Panel Runnable run( ) Thread start( )

  10. Simplifying • MyPanel implements Runnable My Panel Runnable run( ) My Panel Runnable run( ) Thread start( ) Thread start( )

  11. Threaded Ticker public class MyPanel extends JPanel implements Runnable { int x = 100; Thread mythread; public MyPanel(){ // constructor mythread = new Thread(this); mythread.start(); } public void run(){ while(true){ // animation loop x = x – 5; repaint(); Thread.sleep(100); } } public void paintComponent(Graphics g){ super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; g2.drawString("Hello World", x, 10); // my graphics } } or in button code that starts animation

  12. Stopping a Thread • Stop animation loop with a flag • mythread = null; will cleanup thread object Boolean runMyAnimation; While(runMyAnimation){ //flag stops loop x = x – 5; repaint(); //calls paintComponent() Thread.sleep(100); //slow down animation }

  13. Controlling Animation Speed While(true){ x = x – 5; //animation step size repaint(); Thread.sleep(100); //delay between steps } Milliseconds 1000 = 1 second

  14. Animation Summary • In a secondary thread: • Make changes to global state • Repaint • Sleep delay • Repeat • Use double buffering as needed

  15. JBuilder Example

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