Java: Traffic Light - Overclock.net

jrs · 03-23-08

I have an assignment for AP Java to create a switching traffic light app. The Traffic Light is suppose to be drawn then there is a button to change the light. It is a relatively simple program and it is working for the most part. I have one problem....when the light is suppose to be yellow it isn't. I cannot see any problems with my code and have tried different approaches.

Code:

//taken out..noobs in class stealing code....gari

Looking at the control method..it calls repaint when state is 1 which means a light that is yellow should be drawn. I had a different version of control using a for loop which produced the same result. it entered an if statement for yellow evidenced by a println I put in. However, paintComponent was never called because I have a println there. Repaint seems to get called it just doesn't...enter the if statement for drawing the yellow light. I am probably doing a poor job explaining this. Maybe someone can look at my code for me and figure it out because I have looked at it for hours and tried different things.

The rest of this works. I click the button it goes from green to red....click again red to green ect.

Thanks in advance

~jrs

Scriptorum · 03-23-08

I'm thinking that the repaint() does not immediately call paintComponent, but rather puts it in the queue to be called later. I've never messed with Swing, but my googles have indicated that there is danger in using Thread.sleep inside the Event Dispatch Thread; you're not giving Swing a chance to actually process your repaint request because you're starving the EDT. Try creating a new Thread inside Traf that does the actual sleep, state change, and repaint. Do a search on the net for SwingUtilities.invokeLater for examples.

C-bro · 03-24-08

Quote:

Originally Posted by Scriptorum

I'm thinking that the repaint() does not immediately call paintComponent, but rather puts it in the queue to be called later. I've never messed with Swing, but my googles have indicated that there is danger in using Thread.sleep inside the Event Dispatch Thread; you're not giving Swing a chance to actually process your repaint request because you're starving the EDT. Try creating a new Thread inside Traf that does the actual sleep, state change, and repaint. Do a search on the net for SwingUtilities.invokeLater for examples.

I always have 1 underlying frame to keep components encapsulated in the main form. To refresh, I used

mainPanel.paintImmediately(mainPanel.getBounds());

That avoids the whole queue problem that Scriptorum mentioned. I've also included a code of mine that I used to create a player marker for a Monopoly game I did. Basically it just redraws and clears a circle on the screen. You could just use the setColor method and put 3 of these player marks on your panel/form.

Code:

public class PlayerMarker extends javax.swing.JPanel{
    /**
     * Description.
     * @param var    description of variable
     * @return  description of returned value
     */
    private int x=401;
    private int y=411;
    private java.awt.Color col;
    private boolean dispose=false;
    
    public PlayerMarker() {
        super();
    }
    
    public PlayerMarker(java.awt.Color c) {
        super();
        col = c;
    }
    
    public void paint(java.awt.Graphics g){
        java.awt.Graphics Gr = this.getGraphics();
        if(Gr != null)
            Gr.dispose();
        if(dispose)
            g.setClip(0,0,1,1);
        g.setColor(col);
        g.fillOval(x,y,21,21);
        g.setColor(java.awt.Color.BLACK);
        g.drawOval(x,y,20,20);
    }
    
    public void setColor(java.awt.Color c){
        col = c;
    }
    
    public void setCoord(int xloc, int yloc){
        x = xloc;
        y = yloc;
        repaint();
    }
    
    public void dispose(){
        dispose = true;
    }
    
}

jrs · 03-24-08

Thanks guys, I got it working

Scriptorum I know what you mean about the EDT but of course I didnt think of it. My teacher doesn't really teach us much. There are only 8 kids in my high school that take Java

.

C-Bro thanks for the example and the paintImmediately. I switched myPanel to a this reference and replaced all the repaint calls with it. It works well now

Code:

this.paintImmediately(this.getBounds());

Now I can move on to cutting down the size of the control method.

Thanks

~jrs

**Burn** · 03-24-08

Hmm, did you take a look at the GridWorld case study yet? We finished up with that a month back or so

Nice coding

jrs · 03-24-08

Quote:

Originally Posted by Burn

Hmm, did you take a look at the GridWorld case study yet? We finished up with that a month back or so

Nice coding

Noooope. Haha I should really get going on that. We started the year slow and didn't get much done. The past month has been nothing but programing, short answer, MC's and whatnot(lots at home too). Our book is terrible(Java Software Solutions for Computer Science A). All the graphical stuff is spread out, and the text beats around the bush. We are just finishing up recursion now.....so from now until the beginning of may is review time

. Our teacher bought a class set of the Barron's books

, we'll see how that goes.

~jrs

Gari · 04-21-08

what the hell jeff i was using that

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Java: Traffic Light

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