Question

In UIView if you do the following:

CAGradientLayer *layer = [CAGradientLayer layer];
layer.colors = [NSArray arrayWithObjects:(id) [UIColor colorWithRed:0 green:0 blue:0.1 alpha:1].CGColor,[UIColor colorWithRed:0.3 green:0.3 blue:0.74 alpha:1].CGColor, nil];
layer.frame=CGRectMake(0, 0, self.frame.size.width,self.frame.size.height);
[self.layer insertSublayer:layer atIndex:0];

Will drawRect then perform custom drawing on top of this gradient? Does drawRect affect the actual background of a view, or is it a different layer entirely? If the background color of the view is clearColor does drawRect still display?

Answer 1

A sublayer obscures the content of its superlayer. If you override drawRect: to draw content, that content will be obscured by the gradient layer.

If you want to draw the gradient behind your (view) content, you should either draw the gradient in your drawRect: instead of using a sublayer, or use a container view that contains both the gradient layer and your drawRect:-using content view, with your content view on top.

Also, if you want the gradient layer to cover your view, it would be better to initialize layer.frame like this:

layer.frame = self.bounds;