How is a rounded rect view with transparency done on iphone?

cocoa-touch, iphone, rounded-corners

Solution

view.layer.cornerRadius = radius;

The hard way (that used to be required in the first iPhone SDK) is to create your own `UIView` subclass with `drawRect:` method:

 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: `rect` in this code should be taken from `[self bounds]` (or whatever location you want it in), it won't make sense with `rect` passed to `drawRect:` method.

Problem

A lot of apps pop up a transparent view with rounded corners and an activityIndicator when running a time consuming operation. How is this rounding done and is it possible to do it just using Interface Builder (as there are lots of places I'd like to use something like this)? Or, should I use an imageview with a rounded rect or stretchable image? Do I need to draw the background myself? So far, I have managed to get a basic view with similar transparency by setting the alphaValue in Interface Builder however it doesn't have rounded corners, and also the transparency seems to apply to all subviews (I don't want the text and activityindicator to be transparent, however even though I set the alphaValue on those in IB it seems to get ignored).

Original source