CAShapeLayer used in UIView subclass doesn't work

Question

i tried a few hours to get a dotted border around my UIView with CAShapeLayer but i don't get it displayed.
ScaleOverlay.h

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

@interface ScaleOverlay : UIView <UIGestureRecognizerDelegate> {
    CAShapeLayer *shapeLayer_;
}
@end

ScaleOverlay.m

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
    self.backgroundColor = [UIColor redColor];
    self.alpha = 0;
    //Round corners
    [[self layer] setCornerRadius:8.f];
    [[self layer] setMasksToBounds:YES];
    //Border
    shapeLayer_ = [[CAShapeLayer layer] retain];

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, frame);
    shapeLayer_.path = path;
    CGPathRelease(path);
    shapeLayer_.backgroundColor = [[UIColor clearColor] CGColor];
    shapeLayer_.frame = frame;
    shapeLayer_.position = self.center;

    [shapeLayer_ setValue:[NSNumber numberWithBool:NO] forKey:@"isCircle"];
    shapeLayer_.fillColor = [[UIColor blueColor] CGColor];
    shapeLayer_.strokeColor = [[UIColor blackColor] CGColor];
    shapeLayer_.lineWidth = 4.;
    shapeLayer_.lineDashPattern = [NSArray arrayWithObjects:[NSNumber numberWithInt:8], [NSNumber numberWithInt:8], nil];
    shapeLayer_.lineCap = kCALineCapRound;
}
return self;
}

I got a red rect drawn in my Superview but not the border. Copied this from a source example in the hope it would work, but it doesn't.

Brad Larson Brad Larson · Accepted Answer · 2011-03-25T15:24:40

You never add shapeLayer as a sublayer of your UIView's layer, so it's never displayed onscreen. Try adding

[self.layer addSublayer:shapeLayer_];

after you set up your CAShapeLayer in your -initWithFrame: method.

Even better, you could try making your UIView's backing layer a CAShapeLayer by overriding the following class method:

+ (Class) layerClass 
{
    return [CAShapeLayer class];
}

You could then deal with the view's layer directly, and eliminate the additional CAShapeLayer instance variable.

CAShapeLayer used in UIView subclass doesn't work

1 Answers