How is a rounded rect view with transparency done on iphone

Question

When doing a time-consuming action, many apps display a transparent view with rounded sides and an activityIndicator.

How is this rounding carried out, and can it be accomplished using only Interface Builder (because I would like to apply something similar in many places)? Or should I employ an imageview with a stretchable or rounded rect? Do I have to create the background from scratch?

Though it lacks rounded corners and the transparency appears to apply to all subviews (I don't want the text and activity indicator to be translucent, even though I set the alphaValue on zero), I have so far been able to create a basic view with transparency that is similar.

Answer 1

view.layer.cornerRadius = radius;

The difficult technique is to develop your own UIView subclass using the drawRect: method, which was necessary in the initial iPhone SDK.

 CGContextRef context = UIGraphicsGetCurrentContext();
 CGContextSetRGBFillColor(context, 0,0,0,0.75);

 CGContextMoveToPoint(context, rect.origin.x, rect.origin.y + radius);
 CGContextAddLineToPoint(context, rect.origin.x, rect.origin.y + rect.size.height - radius);
 CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + rect.size.height - radius, 
                radius, M_PI, M_PI / 2, 1); //STS fixed
 CGContextAddLineToPoint(context, rect.origin.x + rect.size.width - radius, 
                        rect.origin.y + rect.size.height);
 CGContextAddArc(context, rect.origin.x + rect.size.width - radius, 
                rect.origin.y + rect.size.height - radius, radius, M_PI / 2, 0.0f, 1);
 CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, rect.origin.y + radius);
 CGContextAddArc(context, rect.origin.x + rect.size.width - radius, rect.origin.y + radius, 
                radius, 0.0f, -M_PI / 2, 1);
 CGContextAddLineToPoint(context, rect.origin.x + radius, rect.origin.y);
 CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + radius, radius, 
                -M_PI / 2, M_PI, 1);

 CGContextFillPath(context);

Note: The rect in this code should be taken from [self limits] (or wherever you want it to be), since the rect supplied to the drawRect: method will not make sense.