iOS：动态更改UIView

Question

I have an app that every time a user draws a freehand circle, the program does alloc/init to a circle class(uiview) which draws CAShapelayer circle instead the one was drawn by the user. now i want that when the user will press a button on the superview, the alpha of the drawn circle will change. this is the relevant code:

blueCircleView =[[ASFBlueCircle alloc]initWithFrame:CGRectMake(startPoint.x-10, startPoint.y-20, 60, 60)];

[self addSubview:blueCircleView];

and the init code from the class:

-(id)initWithFrame:(CGRect)frame{
self = [super initWithFrame:frame];
if (self) {
    // Initialization code

    self.backgroundColor=[UIColor clearColor];
     UIBezierPath *circle = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 75, 75)];
   blueCircleLayer = [CAShapeLayer layer];
    blueCircleLayer.path = circle.CGPath;
    blueCircleLayer.strokeColor = [UIColor blueColor].CGColor;
    blueCircleLayer.fillColor = [UIColor clearColor].CGColor;
    blueCircleLayer.shadowColor =[UIColor blackColor].CGColor;
    blueCircleLayer.shadowOffset = CGSizeMake(0.0f, 5.0f);
    blueCircleLayer.shadowOpacity = 0.7f;
    blueCircleLayer.lineWidth = 7.0;

    [self.layer addSublayer:blueCircleLayer];

Answer 1

In ASFBlueCircle.h add property @property CAShapeLayer *blueCircleLayer;

In init, after addsublayer write a following line self.blueCircleLayer = blueCircleLayer;

And in the method called when button is pressed self.blueCircleLayer.color = [UIColor colorWithRed:red green:green blue:blue alpha:alpha].CGColor;

with the red, green, blue, alpha values you want.