How to do a radar animation in the iPhone SDK?

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.