iphone swift add - How do I draw a shadow under a UIView?



7 Answers

A by far easier approach is to set some layer attributes of the view on initialization:

self.layer.masksToBounds = NO;
self.layer.shadowOffset = CGSizeMake(-15, 20);
self.layer.shadowRadius = 5;
self.layer.shadowOpacity = 0.5;

You need to import QuartzCore.

#import <QuartzCore/QuartzCore.h>
to and rounded

I'm trying to draw a shadow under the bottom edge of a UIView in Cocoa Touch. I understand that I should use CGContextSetShadow() to draw the shadow, but the Quartz 2D programming guide is a little vague:

  1. Save the graphics state.
  2. Call the function CGContextSetShadow, passing the appropriate values.
  3. Perform all the drawing to which you want to apply shadows.
  4. Restore the graphics state

I've tried the following in a UIView subclass:

- (void)drawRect:(CGRect)rect {
    CGContextRef currentContext = UIGraphicsGetCurrentContext();
    CGContextSaveGState(currentContext);
    CGContextSetShadow(currentContext, CGSizeMake(-15, 20), 5);
    CGContextRestoreGState(currentContext);
    [super drawRect: rect];
}

..but this doesn't work for me and I'm a bit stuck about (a) where to go next and (b) if there's anything I need to do to my UIView to make this work?




Same solution, but just to remind you: You can define the shadow directly in the storyboard.

Ex:




Simple and clean solution using Interface Builder

Add a file named UIView.swift in your project (or just paste this in any file) :

import UIKit

@IBDesignable extension UIView {

    /* The color of the shadow. Defaults to opaque black. Colors created
    * from patterns are currently NOT supported. Animatable. */
    @IBInspectable var shadowColor: UIColor? {
        set {
            layer.shadowColor = newValue!.CGColor
        }
        get {
            if let color = layer.shadowColor {
                return UIColor(CGColor:color)
            }
            else {
                return nil
            }
        }
    }

    /* The opacity of the shadow. Defaults to 0. Specifying a value outside the
    * [0,1] range will give undefined results. Animatable. */
    @IBInspectable var shadowOpacity: Float {
        set {
            layer.shadowOpacity = newValue
        }
        get {
            return layer.shadowOpacity
        }
    }

    /* The shadow offset. Defaults to (0, -3). Animatable. */
    @IBInspectable var shadowOffset: CGPoint {
        set {
            layer.shadowOffset = CGSize(width: newValue.x, height: newValue.y)
        }
        get {
            return CGPoint(x: layer.shadowOffset.width, y:layer.shadowOffset.height)
        }
    }

    /* The blur radius used to create the shadow. Defaults to 3. Animatable. */
    @IBInspectable var shadowRadius: CGFloat {
        set {
            layer.shadowRadius = newValue
        }
        get {
            return layer.shadowRadius
        }
    }
}

Then this will be available in Interface Builder for every view in the Utilities Panel > Attributes Inspector :

You can easily set the shadow now.

Notes:
- The shadow won't appear in IB, only at runtime.
- As Mazen Kasser said

To those who failed in getting this to work [...] make sure Clip Subviews (clipsToBounds) is not enabled




Swift 3

extension UIView {
    func installShadow() {
        layer.cornerRadius = 2
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOffset = CGSize(width: 0, height: 1)
        layer.shadowOpacity = 0.45
        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
        layer.shadowRadius = 1.0
    }
}



If you would like to use StoryBoard and wouldnt like to keep typing in runtime attributes, you can easily create an extension to views and make them usable in storyboard.

Step 1. create extension

extension UIView {

@IBInspectable var shadowRadius: CGFloat {
    get {
        return layer.shadowRadius
    }
    set {
        layer.shadowRadius = newValue
    }
}

@IBInspectable var shadowOpacity: Float {
    get {
        return layer.shadowOpacity
    }
    set {
        layer.shadowOpacity = newValue
    }
}

@IBInspectable var shadowOffset: CGSize {
    get {
        return layer.shadowOffset
    }
    set {
        layer.shadowOffset = newValue
    }
}

@IBInspectable var maskToBound: Bool {
    get {
        return layer.masksToBounds
    }
    set {
        layer.masksToBounds = newValue
    }
}
}

step 2. you can now use these attributes in storyboard




All Answer all well but I want to add one more point

If you encounter a problem when you have table cells, Deque a new cell there is a mismatch in shadow so in this case, you need to place your shadow code in a layoutSubviews method so that it will behave nicely in all conditions.

-(void)layoutSubviews{
    [super layoutSubviews];

    [self.contentView setNeedsLayout];
    [self.contentView layoutIfNeeded];
    [VPShadow applyShadowView:self];
}

or in ViewControllers for specific view place shadow code inside the following method so that it's work well

-(void)viewDidLayoutSubviews{
    [super viewDidLayoutSubviews];

    [self.viewShadow layoutIfNeeded];
    [VPShadow applyShadowView:self.viewShadow];
}

I have modified my shadow implementation for new devs for more generalized form ex:

/*!
 @brief Add shadow to a view.

 @param layer CALayer of the view.

 */
+(void)applyShadowOnView:(CALayer *)layer OffsetX:(CGFloat)x OffsetY:(CGFloat)y blur:(CGFloat)radius opacity:(CGFloat)alpha RoundingCorners:(CGFloat)cornerRadius{
    UIBezierPath *shadowPath = [UIBezierPath bezierPathWithRoundedRect:layer.bounds cornerRadius:cornerRadius];
    layer.masksToBounds = NO;
    layer.shadowColor = [UIColor blackColor].CGColor;
    layer.shadowOffset = CGSizeMake(x,y);// shadow x and y
    layer.shadowOpacity = alpha;
    layer.shadowRadius = radius;// blur effect
    layer.shadowPath = shadowPath.CGPath;
}



For fellow Xamarians, the Xamarin.iOS/C# version of the answer would look like the following:

public override void DrawRect(CGRect area, UIViewPrintFormatter formatter)
{
    CGContext currentContext = UIGraphics.GetCurrentContext();
    currentContext.SaveState();
    currentContext.SetShadow(new CGSize(-15, 20), 5);
    base.DrawRect(area, formatter);
    currentContext.RestoreState();                
}

The main difference is that you acquire an instance of CGContext on which you directly call the appropriate methods.




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