Objective C - CAGradientLayer covers the text in UILabel?

问题

I am trying to add a gradient layet to my UILabel for some reasons the CAGradientLayer covers my text. Am I doing anything wrong

- (void)viewDidLoad {
   [super viewDidLoad];

   CAGradientLayer *gradient = [CAGradientLayer layer];
   gradient.frame = CGRectMake(0, 0, myLabel.frame.size.width, myLabel.frame.size.height);
   gradient.colors = myColors;
   [myLabel.layer insertSublayer:gradient atIndex:0];
}

回答1:

The CAGradientLayer is covering the text of your label because the text is drawn by the content of the super layer that you explicitly covered by adding a sublayer.

Your easiest solution is to use two views. A UIView subclass where you override +[UIView layerClass] and return a [CAGradientLayer]. Add a good init method to setup your gradient.

Next pup add the UILabel as a subview of your custom gradient view.

回答2:

I had the same problem. I made this method to get a reference for the shape layer and or generate it if it wasn't there. This method makes sure to throw that layer in the back so that it doesn't cover the label text layer. Just use this and you should be all good, no extra subclasses required.

- (CAShapeLayer*) getShapeLayerForObject: (UIView*) object{
    CAShapeLayer *maskLayer;
    int loc = -1;
    for(int x = 0; x < object.layer.sublayers.count; x++){
        if([[object.layer.sublayers objectAtIndex:x] isKindOfClass:[CAShapeLayer class]]){
            loc = x;
            break;
        }
    }
    if(loc > -1){
        maskLayer = (CAShapeLayer*) [object.layer.sublayers objectAtIndex:loc];
    }else{
        maskLayer = [[CAShapeLayer alloc] init];
        [object.layer insertSublayer:maskLayer atIndex:0];

    }
    return maskLayer;
}

回答3:

If you for example need to subclass your UILabel, then add some CALayer which covers the text, it is recommended to add CATextLayer to your CALayer, here is an swift example:

@IBDesignable class BWRoundedLabel: UILabel {

    override var text: String? {
        didSet {
            updateView()
        }
    }

    @IBInspectable override var shadowColor: UIColor? {

        didSet {
            updateView()
        }
    }

    private func updateView() {

        let width = bounds.size.width - 1
        let height = bounds.size.height - 1

        let shadowLayer = CAShapeLayer()
        shadowLayer.path = UIBezierPath(roundedRect: CGRectMake(0, 0, width, height), cornerRadius: width/2).CGPath
        shadowLayer.fillColor = UIColor.yellowOrange().CGColor
        shadowLayer.shadowColor = shadowColor?.CGColor
        shadowLayer.shadowPath = shadowLayer.path
        shadowLayer.shadowOffset = CGSize(width: 0, height: 1.0)
        shadowLayer.shadowOpacity = 1
        shadowLayer.shadowRadius = 0

        let textLayer = CATextLayer()
        textLayer.foregroundColor = UIColor.whiteColor().CGColor
        textLayer.string = text
        textLayer.fontSize = font.pointSize
        textLayer.font = "Calibri-Bold"
        textLayer.alignmentMode = kCAAlignmentCenter
        textLayer.frame = CGRectMake(0, (height - 16)/2, width, 16)

        if let sublayers = layer.sublayers {
            for sublayer in sublayers {
                sublayer.removeFromSuperlayer()
            }
        }

        layer.insertSublayer(shadowLayer, atIndex: 0)
        layer.insertSublayer(textLayer, atIndex: 1)
    }
}

来源：https://stackoverflow.com/questions/7209407/objective-c-cagradientlayer-covers-the-text-in-uilabel

标签

objective-c

uiview

calayer

cagradientlayer