Replace a CALayer with a CAGradientLayer doesn't work - ios

Question

I'm developing an iOS app with latest SDK.
I want to change a background layer dynamically:
#import <QuartzCore/QuartzCore.h>
#interface MyClass : UIView
{
#private
CALayer* _gradientBackground;
}
And some methods:
- (CALayer*)createLayerWithColor:(UIColor*)color
{
CALayer* layer = [CALayer layer];
layer.frame = CGRectMake(NSLayerX, NSLayerY,
NSLayerWidth, NSLayerHeight);
layer.backgroundColor = [color CGColor];
layer.cornerRadius = NSCornerRadius;
return layer;
}
- (CAGradientLayer*)createLayerWithGradient:(UIColor*)startColor
endColor:(UIColor*)endColor
{
CAGradientLayer* gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = CGRectMake(NSLayerX, NSLayerY,
NSLayerWidth, NSLayerHeight);
gradientLayer.colors =
[NSArray arrayWithObjects:(id)[startColor CGColor],
(id)[endColor CGColor], nil];
gradientLayer.cornerRadius = NSCornerRadius;
return gradientLayer;
}
- (void)changeBackgroundWithLayer:(CALayer*)newLayer
{
if (_gradientBackground != nil)
[_gradientBackground removeFromSuperlayer];
_gradientBackground = newLayer;
[self.layer insertSublayer:newLayer atIndex:0];
}
And I do this to change background layer:
[self changeBackgroundWithLayer:[self createLayerWithGradient:startColor endColor:endColor]];
And sometimes with this:
[self changeBackgroundWithLayer:[self createLayerWithColor:newColor]];
The way I do is:
First solid layer, next gradient layer and finally solid layer.
I have also tried with this code with no result:
- (void)changeBackgroundWithLayer:(CALayer*)newLayer
{
if (_gradientBackground != nil)
[self.layer replaceSublayer:_gradientBackground with:newLayer];
else
[self.layer insertSublayer:newLayer atIndex:0];
_gradientBackground = newLayer;
}
But it doesn't work.
Any advice?

Answer 1

Try this
- (void)changeBackgroundWithLayer:(CALayer*)newLayer
{
[_gradientBackground removeFromSuperlayer], _gradientBackground = nil;
[self.layer insertSublayer:newLayer atIndex:0];
_gradientBackground = newLayer;
}
This will remove the _gradientBackground and set it to nil in every case, which is perfectly acceptable in Objective-C. The newLayer is added to the layer hierarchy and the gradientBackground layer is updated.