Question

I’m writing a program to input a number and draw that number of circles of random color and location on an applet. I’ve been up all night trying to figure out how to add a delay between each of the circles appearing. Right now if I have a for-each statement with a delay in it, and say I input 20 circles and have a delay of 1000, it won’t do anything for 20 seconds, then all the circles will appear at once, because the screen doesn’t get refreshed until the end of the paint() method.

The only other alternative I could think of was to have a for-each statement in the start() method that would add a color and coordinate to an array, and have the paint() method draw all the circles in this array. I could be wrong, but I would imagine that this would use up way too much memory.

Another possibility would be to just add a circle on to the existing frame without clearing it, but I couldn’t find a way to do this.

Answer 1

Use a javax.swing.Timer to add a new Circle object to an expandable list such as an ArrayList. Call repaint() after each addition. In paintComponent(Graphics) draw every Circle in the list.

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Update

Unfortunately I cannot add comments at the moment (see External JS failed to load for the gory details). For that reason, I’m adding this as an edit.

@mKorbel: No I sure have not tried it on 1.6.0_26! If I’d tried it at all, I’d have posted the code. 😉

@Tycho: I did not notice you added the awt tag and presumed you were working with Swing.

Are you really using AWT? (If so.) Why?

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@Tycho: "The only thing I could tell by quickly searching was that Swing is used more for user interfaces, which is not what I’m going for here."

Umm.. both AWT and Swing (using Applet/JApplet or Frame/JFrame) are used for developing Graphical User Interfaces. Or to put that another way, whether using AWT or Swing, or developing an applet or free-floating frame, you are developing a (G)UI.

Either the applet extends java.applet.Applet (AWT) or javax.swing.JApplet (Swing).

If your applet extends Applet, change it to a Swing JApplet. Few GUI developers can even remember AWT well enough to give good advice on it. My advice was all related to JApplet/Swing. It would not work using AWT.