As a beginner at this, I still need some explanations of how to use Threads and Graphics at the same time. What I want to do is very basic : only make two balls move simultaneously in a frame. Here is what I tried :
public class Main extends JFrame { private static final long serialVersionUID = 1L; private static final int _HEIGHT = 320, _WIDTH = 480; private MyPanel panel; public Main() { super("Test"); panel = new MyPanel(); this.setContentPane(panel); this.setBounds(350,100,_HEIGHT,_WIDTH); this.setDefaultCloseOperation(EXIT_ON_CLOSE); this.setVisible(true); } public static void main(String[] args) { new Main(); } } public class MyPanel extends JPanel { private static final long serialVersionUID = 1L; ArrayList<Ball> listBalls; public MyPanel() { this.setBackground(Color.WHITE); listBalls = new ArrayList<Ball>(); listBalls.add(new Ball(30,30)); } @Override public void paint(Graphics gr) { Graphics2D g = (Graphics2D) gr; g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g.setStroke(new BasicStroke(3f)); super.paint(g); synchronized (listBalls) { for(Ball b : listBalls) { b.drawItself(g); } } } } public class Ball extends JPanel implements Runnable { private static final long serialVersionUID = 1L; private int x, y; private Thread thread; public Ball(int x, int y) { this.x = x; this.y = y; } public void drawItself(Graphics2D g) { g.setColor(Color.BLACK); g.fillOval(x, y, 13, 13); } public void run() { Thread currentThread = Thread.currentThread(); while (thread == currentThread) { x+=2; y+=2; repaint(); try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); } } } } But this won't work (the balls don't appear), and I've no idea of what to do.. please help!
