Removing element from array doesn't change graphic

Question

In my application, I made an array to control the flag images in my output. This worked fine but when I remove an element from my array the picture doesn't change at all.

class Flag{

Image FlagImage;
int FlagNum = 0;

public Flag(int FlagNum)  {
    this.FlagNum = FlagNum;
    try{
    FlagImage = ImageIO.read(new File("flag1.png"));
    }catch(Exception e){
    }
}

public void Update() {

}

public void Draw(Graphics g) {
    //Draw Flag
    g.drawImage(FlagImage, ((FlagNum) % 3+1) * 100-100, (int)((FlagNum) / 3) * 100+100, null);
}

}
public class Flags extends JPanel {

/**
 * Creates new form Flags
 */
public Flags(){
    initComponents();
    FlagSet.add(new Flag(1));
    final Timer timer =new Timer(10, new ActionListener(){
        @Override
        public void actionPerformed(final ActionEvent e){
            repaint();
            for (Flag f: FlagSet){
                f.Update();
            }
        }
    });

}

public static ArrayList<Flag> FlagSet = new ArrayList();

@Override
public void paintComponent(Graphics g){

    super.paintComponent(g);

    for (Flag f: FlagSet){
        f.Draw(g);

    }
}

I then try to add flags like so:

flagCounter = 4;
while(flagCounter > -1){
    Flags.FlagSet.add(new Flag(flagCounter));
    flagCounter--;
}

Which works fine but my image doesn't change if I put in a Flgas.FlageSet.remove(//Some flag)later on. Any ideas? Thanks in advance.

I am new to java. How do I use repaint? I think you answered my question. — mtheorylord, Oct 23 '16 at 18:11
Possible duplicate of [How to remove a particular element from an array in JavaScript?](http://stackoverflow.com/questions/5767325/how-to-remove-a-particular-element-from-an-array-in-javascript) — mtheorylord, Oct 24 '16 at 21:35

score 2 · Accepted Answer · answered Oct 23 '16 at 18:18

2

It looks like you're missing a call to repaint().

Repaint is a signal sent to the drawing component to tell it that something has changed, and that it needs to call the paint methods again. In this case, as your addition to your Flags list will change how it is drawn, you should simply call repaint() after you've finished adding your flags.

answered Oct 23 '16 at 18:18

Joe C

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Thank you. How would you add a delay in front of it? – mtheorylord Oct 23 '16 at 18:21
@mtheorylord: Google [Java Swing delay](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=java+swing+delay), and you'll find out about [Swing Timers](https://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html) in the first 3 hits. – Hovercraft Full Of Eels Oct 23 '16 at 18:31
Thank you very much. Both of you. – mtheorylord Oct 23 '16 at 18:32

Removing element from array doesn't change graphic

1 Answers1