CALayer，子图层Alpha覆盖

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.