Manually drawing a gradient in iPhone apps?

Question

If I have two UIColors, what's the best way to draw an even gradient between them over an arbitrarily-sized area?

I am guessing you would create a UIView subclass and use the CG drawing methods in the drawRect method. I just don't know which ones, or if there are any pitfalls to watch out for, like performance. Has anyone done this?

Answer 1

#import <QuartzCore/QuartzCore.h>    
- (void) setGradient {
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = self.view.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor], (id)[[UIColor blackColor] CGColor], nil];
    [self.view.layer insertSublayer:gradient atIndex:0];     
}

Don't forget to add QuartzCore library to your project.

Answer 2

You'll want to use CGGradient. See the iPhone Dev Center "CGGradient Reference" document.

Answer 3

The Swift way to add Gradient is :

    var view : UIView = UIView(frame: CGRectMake(0, 0, 320, 100))
    var g : CAGradientLayer = CAGradientLayer()
    g.frame = gradientView.bounds
    g.colors = ["000000".UIColor.CGColor , "111111".UIColor.CGColor]
    view.layer.insertSublayer(g, atIndex: 0)

UIColor() is a helper class for Swift to convert hex color to rgb color, highly recommended.