Question

Does anyone know how to animate a radar animation like the image below?
alt text http://img197.imageshack.us/img197/7124/circle0.png

With it growing outwards? I have to draw the circle using Quartz or some other way?

Answer 1

To draw a static circle in a UIView subclass:

- (void)drawRect:(CGRect)rect
{
    CGRect rect = { 0.0f, 0.0f, 100.0f, 100.0f };
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextSetLineWidth(context, 2.0f);
    CGContextAddEllipseInRect(context, rect);
    CGContextStrokePath(context);
}

From there you just need to animate it with a timer, vary the size of the rect, and add more circles.