see

http://forum.processing.org/topic/update-screen-from-recursive-function

For exemple:

In a Class SimpleThread

 // We must implement run, this gets triggered by start()
  void run ()
  {
    while(true)
    {

      println("Run()");
      grafo.draw();

      // Ok, let's wait for however long we should wait
      try
      {
        sleep((long)(wait));
      }
      catch (Exception e)
      {
      }
    }
  }

A Method Draw in Class Graph

void draw()
  {
    delay(100);
    Iterator<Vertice> it = vertices.iterator();
    while(it.hasNext()){
      Vertice v = it.next();
      v.drawAresta();
    }
   
    it = vertices.iterator();
    while(it.hasNext())
    {
      Vertice v = it.next();
      if(v.pertence())
      {
         fill(0,255,0);
      }
      if(v.visitado == 1)
      {
        println("pinto diferente");
        fill(50,100,150);
      }
      v.draw();
    }
  }

THE METHOD RECURSIVE, While this method is running the progam does not draw more
Boolean temCiclo(Vertice u, Vertice pai)
  {
     u.visitado = 1;
     boolean resp = false;    
    
     delay(2000);
    
     ArrayList<Aresta> adjacencias = u.arestas;
     Iterator ia = adjacencias.iterator();
     while ( ia.hasNext() )
     {
       Aresta a = (Aresta) ia.next();
       Vertice w = (Vertice) a.destino;
           
       if(w != pai)
       {
         println("U: " + u.valor + " = visitado? " + u.visitado);
         println("W: " + w.valor + " = visitado? " + w.visitado);
         if (w.visitado == 1)
         {
           println("======================");
           println("TEM CICLO");
           println("======================");
           resp = true;
         }
         else
         {
           resp = temCiclo(w, u);
         } 
       }//fim if w dif pai
       if (resp == true)
          break;
     }//fim while tem aresta
    
     if (resp == true)
     {
        return true;
     }
     else
       return false;
  }// fim temCiclo

yes, I understand.

It's because the draw() updates the screen only once at it's end (but this in theory 60 times per second but this doesn't matter here).

A recursion works before the end of draw().

Only when the recursion is finished, the program returns to draw() and at its end, it updates the screen.

Thus during the recursion nothing is drawn.

rbrauer, in the topic pointed at, uses redraw() in the thread, I guess it is the key to updating the drawing surface.

I see......

Good Luck!