CALayer, subLayer alpha overriding - ios

Question

I have a CALayer ( superlayer ) with 0.3 opacity property. The superlayer contains another CALayer(sublayer). Although sublayer does not have a opacity property superLayer's opacity affects sublayer's appearance. Is there a method that I can override superLayer'a opacity property.
SuperLayer
#implementation SuperView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setOpaque:NO];
[self.layer setOpaque:NO];
}
return self;
}
-(void)drawRect:(CGRect)rect
{
CALayer* superLaer=self.layer;
superLaer.backgroundColor = [UIColor blackColor].CGColor;
superLaer.shadowOffset = CGSizeMake(0, 3);
superLaer.shadowRadius = 5.0;
superLaer.shadowColor = [UIColor blackColor].CGColor;
superLaer.shadowOpacity = 0.6;
superLaer.frame = CGRectMake(10, 10, 300,300);
superLaer.borderColor = [UIColor blackColor].CGColor;
superLaer.borderWidth = 2.0;
superLaer.cornerRadius = 10.0;
superLaer.cornerRadius = 10.0;
superLaer.masksToBounds=YES;
superLaer.opacity = 0.1;
}
#end
SubLayer
#implementation SubView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setOpaque:NO];
[self.layer setOpaque:NO];
}
return self;
}
-(void)drawRect:(CGRect)rect
{
CALayer* superLaer=self.layer;
superLaer.backgroundColor = [UIColor redColor].CGColor;
superLaer.shadowOffset = CGSizeMake(0, 3);
superLaer.shadowRadius = 5.0;
superLaer.shadowColor = [UIColor blackColor].CGColor;
superLaer.shadowOpacity = 0.6;
superLaer.frame = CGRectMake(100, 100, 100,100);
superLaer.borderColor = [UIColor blackColor].CGColor;
superLaer.borderWidth = 2.0;
superLaer.cornerRadius = 10.0;
superLaer.cornerRadius = 10.0;
superLaer.masksToBounds=YES;
}
#end
I have added the subView to the superView in Viewcontroller.

Answer 1

Based on your question, The super layer's opacity controls the sublayers' opacity,
you could subclass CALayer and override some of its properties in init method like
#implementation SomeSuperCALayer
-(id)init
{
self = [super init];
if (self) {
[self setup];
}
return self;
}
#define W_H 100.0
#define X_Y 50.0f
-(void)setup
{
self.frame = CGRectMake(X_Y, X_Y, W_H, W_H);
self.backgroundColor = [UIColor blueColor].CGColor;
self.opacity = 1.0f; // big opacity
}
#implementation SomeSubCALayer
-(id)init
{
self = [super init];
if (self) {
[self setup];
}
return self;
}
#define W_H 100.0
#define X_Y 150.0f
-(void)setup
{
self.frame = CGRectMake(X_Y, X_Y, W_H, W_H);
self.backgroundColor = [UIColor blueColor].CGColor;
self.opacity = .5f; // small opacity
}
# implementation MyViewController
//
-(void)viewDidLoad
{
SomeSuperCALayer *superLayer = [[SomeSuperCALayer alloc] init]; SomeSubCALayer *subLayer = [[SomeSubCALayer alloc] init];
//add sub layer to super layer
[superLayer addSubLayer:subLayer];
// add super layer to main View
[self.view.layer addSubLayer:superLayer];
//
//...
}
Also don't use drawRect for calling layer's properties, drawRect is mean't for drawing like the Apple's documentation dictates:
/ Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.