Are there any standard way to implement the “blue badge” in iPhone?

Question

A lot of iPhone apps use a blue badge to indicate the number of items in the subviews, such as the Mail client:

iPhoto http://img.skitch.com/20081103-tjr9yupbhgr3sqf

Answer 1

To my knowledge there's no API for this. However, using CoreGraphics (NSBezierPath is not available on iPhone), you can do it pretty easily. It's just two arcs in a CGPath and some text:

CGContextRef        context = UIGraphicsGetCurrentContext();
float               radius = bounds.size.height / 2.0;
NSString            *countString = [NSString stringWithFormat: @"%d", count];

CGContextClearRect(context, bounds);

CGContextSetFillColorWithColor(context, ovalColor);
CGContextBeginPath(context);
CGContextAddArc(context, radius, radius, radius, M_PI / 2 , 3 * M_PI / 2, NO);
CGContextAddArc(context, bounds.size.width - radius, radius, radius, 3 * M_PI / 2, M_PI / 2, NO);
CGContextClosePath(context);
CGContextFillPath(context);

[[UIColor whiteColor] set];

UIFont              *font = [UIFont boldSystemFontOfSize: 14];
CGSize              numberSize = [countString sizeWithFont: font];

bounds.origin.x = (bounds.size.width - numberSize.width) / 2;

[countString drawInRect: bounds withFont: font];