Rendering Loop Problem (Java)

Question

I'm not new to programming, but I am relatively new to game programming. I am trying to create a version of Breakout, as a good basic game to get myself introduced to 2d game programming.

I currently have a class structure as the following:

The BreakoutRunner class is the basic initialization stuff for a JFrame. It holds a BreakoutView, which is a JPanel that contains the update logic, and the renderer.

First off, is this a correct structure?

Secondly, I am having problems getting this to work correctly. In BreakoutView, I have the following constructor:

public BreakoutView()
{
    setPreferredSize(new Dimension(WIDTH, HEIGHT));
    setBackground(Color.black);

    state = GameState.PLAYING;

    gameBlocks = new Block[NUM_ROWS][BLOCK_ROWS];        
    gameBall = new Ball(WIDTH / 2, HEIGHT /2);
    player = new Player(WIDTH / 2);

    initializeGrid();

    //start();
}

I have the method start() which is commented because it is causing the problems. With the line commented, the game looks like so:

But the problem arises when I take away the comment, and add the start() method.

The start method:

private void start()
{
    while(state == GameState.PLAYING)
    {
        update();
        repaint();

        try
        {
            Thread.sleep(50);
        }
        catch(InterruptedException e)
        {
            assert(e == null);
        }          
    }
}

Which includes calls to update:

private void update()
{    
    checkBlocks();
    moveBall();
}

and repaint, which I believe calls the paintComponent method:

public void paintComponent(Graphics g)
{
    super.paintComponent(g);

    drawWalls(g);
    drawBlocks(g);
    drawPlayer(g);
    drawBall(g);
}

When the code is run with start() uncommented, it gets thrown into an infinite loop, while the frame and the panel get turned into something that looks like this:

What is going on here? Any idea why I'm just sent into an infinite loop?

Thanks Everyone!

DISCLAIMER: I know the update loop is not completely correct. I am more worried about getting it to work period, rather than at an even frame rate... (IE. sleep == bad).

Answer 1

You're not supposed to call your start() method inside the class's constructor, is your problem.

You need to create a separate Thread object that handles your main logic/rendering loop.
That you can start in your constructor, but it would be safer to start in your main(String[] args) method, just in case.

By not allowing control to drop back into Swing, you're preventing it from actually pack()ing the JFrame and preparing it for rendering.