adding gradient to UIView in drawRect - objective-c

Question

I am trying to add a CAGradientLayer in my drawRect, the code is the following:
- (void)drawRect:(CGRect)rect {
CAGradientLayer *gradientOverlay = [CAGradientLayer layer];
CGColorRef grayColor = [UIColor colorWithRed:37/255.f green:37/255.f
blue:37/255.f alpha:1.0].CGColor;
CGColorRef blueColor = [UIColor colorWithRed:23.0/255.0 green:171.0/255.0
blue:219.0/255.0 alpha:1.0].CGColor;
gradientOverlay.colors = [NSArray arrayWithObjects:
(id) grayColor,
(id) grayColor,
(id) blueColor,
nil];
gradientOverlay.locations = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0],
[NSNumber numberWithFloat:0.4],
[NSNumber numberWithFloat:1],
nil];
CGPoint startPoint = CGPointMake(CGRectGetMinX(rect), CGRectGetMidY(rect));
CGPoint endPoint = CGPointMake(CGRectGetMaxX(rect), CGRectGetMidY(rect));
gradientOverlay.startPoint = startPoint;
gradientOverlay.frame = self.bounds;
gradientOverlay.endPoint = endPoint;
self.layer.mask = gradientOverlay;
}
Any idea why this is not working?

Answer 1

How about trying this instead of overriding drawRect?
+ (void) applyGradient:(NSArray *)cgColors toView:(UIView *)view {
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = view.bounds;
gradient.colors = cgColors;
for(CALayer *layer in view.layer.sublayers) {
if([layer isKindOfClass:[CAGradientLayer class]]) return;
}
[view.layer insertSublayer:gradient atIndex:0];
}

Answer 2

Add your CAGradientLayer as a sublayer of your self.layer.
Note: If you're doing it in the drawRect: method make sure you're not adding a new CAGradientLayer every time drawRect: is called.
UPDATE (regarding the comment):
Here's the code for what you're asking:
//Create a layer that holds your background image and add it as sublayer of your self.layer
CALayer *layer = [CALayer layer];
layer.frame = self.layer.frame;
layer.contents = (id)[UIImage imageNamed:#"background.png"].CGImage;
[self.layer addSublayer:layer];
//Create your CAGradientLayer
CAGradientLayer *gradientOverlay = [CAGradientLayer layer];
CGColorRef grayColor = [UIColor colorWithRed:37/255.f green:37/255.f
blue:37/255.f alpha:1.0].CGColor;
CGColorRef blueColor = [UIColor colorWithRed:23.0/255.0 green:171.0/255.0
blue:219.0/255.0 alpha:1.0].CGColor;
gradientOverlay.colors = [NSArray arrayWithObjects:
(id) grayColor,
(id) grayColor,
(id) blueColor,
nil];
gradientOverlay.locations = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0],
[NSNumber numberWithFloat:0.4],
[NSNumber numberWithFloat:1],
nil];
CGPoint startPoint = CGPointMake(CGRectGetMinX(rect), CGRectGetMidY(rect));
CGPoint endPoint = CGPointMake(CGRectGetMaxX(rect), CGRectGetMidY(rect));
gradientOverlay.startPoint = startPoint;
gradientOverlay.frame = self.layer.frame;
gradientOverlay.endPoint = endPoint;
//set its opacity from 0 ~ 1
gradientOverlay.opacity = 0.6f;
//add it as sublayer of self.layer (it will be over the layer with the background image
[self.layer addSublayer:gradientOverlay];
Note: You don't have to do this in drawRect: method. Create your layer hierarchy in the init method for example, if you need to change the geometry of some views/layers override the layoutSubviews method.

Answer 3

Generally, you should only override drawRect: when you will be drawing your view using CoreGraphics.
A better place to put your code would be in init if you're creating this view in code, or awakeFromNib if you're placing this view in a .xib