Java中的游戏跳转

Question

So I'm trying to get this rectangle to perform a jumping motion every time I hit the space bar. When I tap the space bar the motion is fine. It goes up and comes back down, but the motion isn't very fluid. It just immediately comes up to the high point and then immediately goes back to the ground. How do I fix this? Here is the code for the jumping motion (Jump is what is called upon pressing the space key and Fall is on the release of the space key) :

class Jump extends AbstractAction 
        {
            public void actionPerformed(ActionEvent e)
            {
                while(time<2.5) 
                {
                    time+=0.1;
                    py-=5-(2*(time));
                    if(py>=300)
                    {
                        py=300;
                        py-=0;
                    }
                    repaint();
                    System.out.println(time);
                }   

            }
        }
        class Fall extends AbstractAction
        {
            public void actionPerformed(ActionEvent e)
            {
                while(time>0)
                {
                    time-=0.1;
                    py+=5-(2*(time));
                    if(py>=300)
                    {
                        py=300;
                        py-=0;
                    }
                    repaint();
                }

            }
        }

Answer 1

I'm guessing that actionPerformed() is getting called by some clock? I think the problem is that, within actionPerformed, you've added your own while loop. So, even though actionPerformed only gets called X times per second, that while loop is going to update your variables (time, py, etc.) and repaint the screen as fast as it can. I can't really give you the correct code without understanding the interface you're using (ie I don't know where "time" and "py" come from), but maybe try something like this:

    class Jump extends AbstractAction 
    {
        public void actionPerformed(ActionEvent e)
        {
            if (time < 2.5)
            {
                time += 0.1;
                py -= 5-(2*(time));
                if (py > 300) py = 300;
                if (py < 0) py = 0;
                repaint();
            }   

        }
    }
    class Fall extends AbstractAction
    {
        public void actionPerformed(ActionEvent e)
        {
            if (time > 0)
            {
                time -= 0.1;
                py += 5-(2*(time));
                if (py > 300) py = 300;
                if (py < 0) py = 0;
                repaint();
            }

        }
    }