Updating a game x times per second in Java

Question

I'm a bit new to game programming and I've decided to do a little experiment in Java. I'm using the Swing/AWT api to implement a game by drawing on a JPanel. However, I'm unsure as to how to implement "passing time" in the game. Does anyone have any ideas on this?

Thanks!

laobeylu · Answer 1 · 2012-08-07T15:29:04.617

1

Maybe you should look at threads in Java: http://www.javaworld.com/jw-04-1996/jw-04-threads.html Create a new thread dedicated to repainting and handling the game loop (see the other answer).

EDIT: This tutorial may be useful: http://zetcode.com/tutorials/javagamestutorial/

edited Aug 07 '12 at 15:29

answered Aug 07 '12 at 15:12

laobeylu

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With regards to the edit, can you please refer to a specific tutorial – Blunderchips Nov 22 '17 at 12:43

Lanaru · Accepted Answer · 2012-08-07T15:29:43.573

1

What you're looking for is called a game loop. There's a lot of documentation available concerning this. Here's a simple one:

private boolean isRunning;

public void gameLoop()
{
    while(isRunning) //the loop
    {
        doGameUpdates();
        render();
        Thread.sleep(1000); //the timing mechanism
    }
}

The idea is that the code inside a while loop is executed over and over, and will sleep for 1 second between execution. This is a way of implementing the "passing of time". For example, if you have an object with a X position, and in the while loop you put object.X += 1, the object's X position will advance by 1 for every iteration of the loop, that is 1 per second.

This is a very basic game loop and it has some problems, but it will do if you're a beginner. Once you become a bit more experienced, look up variable and fixed timestep game loops.

However, you'll have to run this code in a separate thread so that the display will actually get updated.

edited Aug 07 '12 at 15:29

answered Aug 07 '12 at 15:13

Lanaru

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I think that the sleep time is in `milliseconds` so you must introduce `1000` instead of `1`. – anonymous Aug 07 '12 at 15:15
if you use swing the idea ain't good at all, `Thread.sleep` uses milliseconds not seconds as well. – bestsss Aug 07 '12 at 15:15
6

And if you do this on the Event Dispatch Thread, nothing gets repainted and your whole UI freezes – Robin Aug 07 '12 at 15:15
@Robin Thanks, added a note to reflect your comment – Lanaru Aug 07 '12 at 15:48
Could this be accomplished with the use of java.swingx.Timer that repeats? – MadProgrammer Aug 07 '12 at 20:24

Updating a game x times per second in Java

2 Answers2