您如何在Java中更新此自定义绘画？

Question

I have a GUI based game that is real time and uses a JPanel and JFrame. I currently have a overridden paintComponent which paints based on certain conditions in my code. For example:

protected void paintComponent(Graphics gfx)
{
    super.paintComponent(gfx);
    gfx.setFont(new Font("default", Font.BOLD, 18));

    if (one)
    {
        //do something
    }

    else
    {
        // do something else
    }
}

This works once depending on the condition. I have implemented a mouse listener that I'd like to use for the statements so that if someone clicks on a certain part it shows something else. I'd like to go back and run the paintComponent again so that it paints over top of the old one. Does paintComponent() already loop? If not, how can you run the method in a loop?

Answer 1

You can repaint by calling repaint() . You can do this in a loop by creating a timer to repaint it, or just call it when it needs to be updated (probably better if your code is simple enough)

EDIT: About when to use a timer:

The timer is not necessary. I used it in a game once because I was custom painting the entire window and there were dozens of always-changing things to paint, and calling render() every time would not make my CPU happy. For something simple, though, it is better to call repaint() only when something changes, because if nothing changed, you are wasting that much time repainting it.