Stepping through an algorithm - can't do it in java?

Question

I'm trying to solve a tiling problem displayed in a GUI. The problem is, I need the algorithm to solve the problem step by step. But whenever I click start, it just solves it. Here's my code.
if (e.getSource() == start) { //push the start button
     while (!isSolved(boxes)) { //until the puzzle is solved
          if (condition) {
               right.doClick(); //click on the rightButton
          else {
               left.doClick(); //click on the leftButton
          try { /sleep for 1000 seconds so i can see the move
               Thread.sleep(1000);
          } catch (InterruptedException e1) {
               // TODO Auto-generated catch block
               e1.printStackTrace();
}What's wrong? I make it sleep after every iteration of the while loop but instead it doesnt show the intermediate steps. It does wait the 1 second after every iteration, but none of the steps are shown on the gui - the buttons don't appear to get pushed every second. It should show the steps every second, right??
Please help
Thanks in advance.
jboolean23

Answer 1

I'm not sure how to do it on another thread. Could
you please explain?Swing runs a special Thread called the dispatcher thread, which does all the GUI management stuff, redraws and so on.
When it calls back to your actionPerformed method or whatever the callback is on that thread. The important thing is that nothing in the way of screen updates can happen untill that call returns. So your actionPerformed should return withing a fraction of a second (the only common exception is when it calls a model dialog).
In a case like this what it needs to to is to build and start a new thread to do the long-running process, and then return, leaving the child thread doing its stuff.
To start a thread create a class which implements Runnable. Usually an anonymous class will to the job. Then you pass an object of this class to the constructor of a new Thread. Call start() and the Thread is up and running.
However, when such a thread requires changes to be made in what's on display the updates need to be done back on the dispatcher thread. What it does is to create another Runnable class and put it on the dispatcher thread's TODO list.
Learn to use small, often anonymous classes for these purposes. And that goes for ActionListener classes too - don't make your JFrame or whatever the ActionListner.
In a case like this you should probably also disable the control that starts the model while the model is running.
Starting a thread using an anonymous class would look something like this:
modelThread = new Thread(new Runnable() {  // anonymous class syntax
     public void run() {  // this is the code that's run as the thread's body
              doThreadStuff(); // a private method of the outer class
        },   // end of anonymous class definition
      "Model Thread");  // give the thread a name - it helps with debugging
modelThread.start();To do screen updates from a background thread like this use EventQueue.invokeLater()