Java threads with Swing

Question

I would like to illustrate a project about railroads.

I decided to use Swing. I have a background map in a JPanel and I draw little circles that moves on the railroads. It works perfectly if I have only one train, but I would like to add more trains.

Here is what I started to do (and works) :

public static void main(String[] args) {

  // JFrame and background panel construction
  JFrame frame = new JFrame();
  JLayeredPane lpane = new JLayeredPane();
  ImagePanel panelBg = new ImagePanel(new ImageIcon("map.jpg").getImage());;

  frame.setPreferredSize(new Dimension(1791, 695));
  frame.setLayout(new BorderLayout());
  frame.add(lpane,BorderLayout.CENTER);
  lpane.setBounds(0,0,panelBg.getImg().getWidth(null),panelBg.getImg().getHeight(null));

  panelBg.setBounds(0,0,panelBg.getImg().getWidth(null),panelBg.getImg().getHeight(null));
  panelBg.setOpaque(true);

  lpane.add(panelBg, new Integer(0), 0);

  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.pack();
  frame.setVisible(true);
  go(lpane,panelBg);  
  }

private static void go(JLayeredPane pan,ImagePanel panBg) {

  Parcours panelP = new Parcours();
  panelP.setBounds(0,0,panBg.getImg().getWidth(null),panBg.getImg().getHeight(null));
  panelP.setOpaque(false);
  pan.add(panelP, new Integer(1), 0);

  for(int i=0; i<panelP.getTable().size(); i++){
    panelP.setPosX(panelP.getTable().get(i).getX()-6);
    panelP.setPosY(panelP.getTable().get(i).getY()-6);
    panelP.repaint();
    try{
      Thread.sleep(100);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}

"go" reads an ArrayList containing coordinates where my circle should go.

I really don't know how to create several trains. Should I create several JPanels or only one with all my circles ?

If I remember well, I should use Threads but I tried to implement them and I can't start.

Thank you for your help

Swing is not thread safe. You could start reading the [Swing concurrency tutorial](http://docs.oracle.com/javase/tutorial/uiswing/concurrency/) which would already learn you that you should never call `Thread.sleep` on the Swing thread. Instead, use a `javax.swing.Timer` if you want animations — Robin, Jun 27 '13 at 12:49
See also [`FleetPanel`](http://stackoverflow.com/a/14887457/230513). — trashgod, Jun 27 '13 at 17:23

score 1 · Answer 1 · answered Jun 27 '13 at 13:40

You could use a central data object that stores the trains.In every cycle the trains get drawn inside swing. On the other side the trains get updated from your threads.

Another approach contains train objects that get drawn and run a thread inside them to update them self.

score 0 · Answer 2 · answered Jun 28 '13 at 17:20

0

Thank you Robin (see comments of my first post), Swing Timers seem to be the best solution so far. I removed my awful Thread.sleep and set timers instead, it works, thanks again.

Thank you Templar too

answered Jun 28 '13 at 17:20

T. Dex

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Java threads with Swing

2 Answers2