Adding a CGGradient as sublayer to UILabel hides the text of label

问题

I want to add the gradient as a background to label. I used the following code to acheive that. but the problem is that though the gradient color appears on the label, but the text is not visible. please help

lblPatientDetail.text=PatientsDetails;

lblPatientDetail.textColor=[UIColor blackColor];  

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = lblPatientDetail.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:1.0] CGColor],nil];  

[lblPatientDetail.layer addSublayer:gradient];

lblPatientDetail.backgroundColor=[UIColor clearColor];

回答1:

Inserting a sublayer to a UILabel hides the text, so the best way to get what you want is to add the label and gradient layer to a UIView.

UIView *gradientLabelView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 30)];

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = gradientLabelView.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:1.0] CGColor],nil];

[gradientLabelView.layer addSublayer:gradient];

lblPatientDetail.frame = gradientLabelView.bounds;
lblPatientDetail.backgroundColor = [UIColor clearColor];
[gradientLabelView addSubview:lblPatientDetail];

[self addSubview:gradientLabelView];

回答2:

The suggested answer with the UILabel inside a UIView works. Apparently UILabels cannot have text within them after giving the background a gradient color background... don't know why....

But heres the full code for the solution.... hope this helps someone :)

UIView *EnvironmentalsLabelView = [[UIView alloc] initWithFrame:CGRectMake(0, 300, 320, 20)];
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = EnvironmentalsLabelView.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor darkGrayColor]CGColor], (id)[[UIColor blackColor]CGColor], nil];
[EnvironmentalsLabelView.layer insertSublayer:gradient atIndex:0];
[scroller addSubview:EnvironmentalsLabelView];

UILabel *EnviornmentalsLabelText = [[UILabel alloc] initWithFrame:EnvironmentalsLabelView.bounds];
[EnviornmentalsLabelText setFont:[UIFont fontWithName:@"Arial-BoldMT" size:12.0f]];
EnviornmentalsLabelText.textAlignment = NSTextAlignmentCenter;
EnviornmentalsLabelText.backgroundColor = [UIColor clearColor];
EnviornmentalsLabelText.text = @"Environmental Benefits";
[EnvironmentalsLabelView addSubview:EnviornmentalsLabelText];

Happy coding!!!!

回答3:

One more additional think to correct answer. If you are use autolayouts for place your custom view you can get this problem - http://prntscr.com/5tj7bx

So your view has a different size then subView - UILabel and subLayer - gradient layer.

I solve this problem by add one method

class wResultView: UIView {
var label = UILabel()
var gradientLayer = CAGradientLayer()

override func layoutSubviews() {
    gradientLayer.frame = self.bounds
    label.frame = self.bounds
}
......

回答4:

I think you can create a gradient color by adjusting the alpha value in the above code.

gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:0.1] CGColor],nil];

I was able to get a gradient effect by doing so.

来源：https://stackoverflow.com/questions/4850149/adding-a-cggradient-as-sublayer-to-uilabel-hides-the-text-of-label

标签

iphone

uilabel