I am relatively new to Swift. I'm just messing around trying to design a taxi app.
I discovered CGGradientLayer and thought it would add a nice effect to the top bar on the app.
I've added it and for some reason, it's not fully stretching to the views width.
This is my subclass:
import UIKit
class GradientView: UIView {
let gradient = CAGradientLayer()
override func awakeFromNib() {
setupGradientView()
}
func setupGradientView() {
gradient.frame = self.frame
gradient.colors = [UIColor.white.cgColor, UIColor.init(white: 1.0, alpha: 0.0).cgColor]
gradient.startPoint = CGPoint.zero
gradient.endPoint = CGPoint(x: 0, y: 1)
gradient.locations = [0.9, 1.0]
self.layer.addSublayer(gradient)
}
}
And this is the result.
The green background is actually the width of the UIView which the sub class is applied too.
You are setting the frame of the gradient too early. You should set it up in an override of layoutSubviews:
override func layoutSubviews() {
super.layoutSubviews()
gradient.frame = self.bounds
}
Notes:
You should be setting the gradient frame to self.bounds. That is the coordinate system used inside of the view. The gradient is placed relative to the GradientView and doesn't change if the GradientView is placed in another location on the screen (because the bounds do not change in that case, but the frame does).
At the time your view is first created, Auto Layout has not established the size of your view for your current device (or orientation). By setting the frame in layoutSubviews you always get the latest value for the size of the view.
Related
What I am trying to do is to get the position of my label (timerLabel) in order to pass those coordinates to UIBezierPath (so that the center of the shape and the center of the label coincide).
Here's my code so far, inside the viewDidLoad method, using Xcode 13.2.1:
// getting the center of the label
let center = CGPoint.init(x: timerLabel.frame.midX , y: timerLabel.frame.midY)
// drawing the shape
let trackLayer = CAShapeLayer()
let circularPath = UIBezierPath(arcCenter: center, radius: 100, startAngle: -CGFloat.pi / 2, endAngle: 2 * CGFloat.pi, clockwise: true)
trackLayer.path = circularPath.cgPath
trackLayer.strokeColor = UIColor.lightGray.cgColor
trackLayer.lineWidth = 10
trackLayer.fillColor = UIColor.clear.cgColor
and this is what I have when I run my app:
link
What I don't understand is why I get (0,0) as coordinates even though I access the label's property (timerLabel.frame.midX).
The coordinates of your label may vary depending on current layout. You need to track all changes and reposition your circle when changes occur. In view controller that uses constraints you would override
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
// recreate your circle here
}
this alone does not explain why your circle is so far out. First of all, looking at your image you do not get (0, 0) but some other value which may be relative position of your label within the blue bubble. The frame is always relative to its superview so you need to convert that into your own coordinate system:
let targetView = self.view!
let sourceView = timerLabel!
let centerOfSourceViewInTargetView: CGPoint = targetView.convert(CGPoint(x: sourceView.bounds.midX, y: sourceView.bounds.midY), to: targetView)
// Use centerOfSourceViewInTargetView as center
but I suggest using neither of the two. If you are using constraints (which you should) then rather create more views than adding layers to your existing views.
For instance you could try something like this:
#IBDesignable class CircleView: UIView {
#IBInspectable var lineWidth: CGFloat = 10 { didSet { refresh() } }
#IBInspectable var strokeColor: UIColor = .lightGray { didSet { refresh() } }
override var frame: CGRect { didSet { refresh() } }
override func layoutSubviews() {
super.layoutSubviews()
refresh()
}
override func draw(_ rect: CGRect) {
super.draw(rect)
let fillRadius: CGFloat = min(bounds.width, bounds.height)*0.5
let strokeRadius: CGFloat = fillRadius - lineWidth*0.5
let path = UIBezierPath(ovalIn: .init(x: bounds.midX-strokeRadius, y: bounds.midY-strokeRadius, width: strokeRadius*2.0, height: strokeRadius*2.0))
path.lineWidth = lineWidth
strokeColor.setStroke()
UIColor.clear.setFill() // Probably not needed
path.stroke()
}
private func refresh() {
setNeedsDisplay() // This is to force redraw
}
}
this view should draw your circle within itself by overriding draw rect method. You can easily use it in your storyboard (first time it might not draw in storyboard because Xcode. Simply close your project and reopen it and you should see the circle even in storyboard).
Also in storyboard you can directly modify both line width and stroke color which is very convenient.
About the code:
Using #IBDesignable to see drawing in storyboard
Using #IBInspectable to be able to set values in storyboard
Refreshing on any value change to force redraw (sometimes needed)
When frame changes forcing a redraw (Needed when setting frame from code)
A method layoutSubviews is called when resized from constraints. Again redrawing.
Path is computed so that it fits within the size of view.
I'm using this approach to cut out a rounded rect "window" from a background view:
override func draw(_ rect: CGRect) {
guard let rectsArray = rectsArray else {
return
}
for holeRect in rectsArray {
let holeRectIntersection = rect.intersection(holeRect)
if let context = UIGraphicsGetCurrentContext() {
let roundedWindow = UIBezierPath(roundedRect: holeRect, cornerRadius: 15.0)
if holeRectIntersection.intersects(rect) {
context.addPath(roundedWindow.cgPath)
context.clip()
context.clear(holeRectIntersection)
context.setFillColor(UIColor.clear.cgColor)
context.fill(holeRectIntersection)
}
}
}
}
In layoutSubviews() I update the background colour add my "window frame" rect:
override func layoutSubviews() {
super.layoutSubviews()
backgroundColor = self.baseMoodColour
isOpaque = false
self.rectsArray?.removeAll()
self.rectsArray = [dragAreaView.frame]
}
I'm adding the rect here because layoutSubviews() updates the size of the "window frame" (i.e., the rect changes after layoutSubviews() runs).
The basic mechanism works as expected, however, if I change the background colour, the cutout window fills with black. So I'm wondering how I can animate a background colour change with this kind of setup? That is, I want to animate the colour of the area outside the cutout window (the window remains clear).
I've tried updating backgroundColor directly, and also using didSet in the accessor of a custom colour variable in my UIView subclass, but both cause the same filling-in of the "window".
var baseMoodColour: UIColor {
didSet {
self.backgroundColor = baseMoodColour
self.setNeedsDisplay()
}
}
Try to use UIView.animate, you can check it here
UIView.animate(withDuration: 1.0, delay: 0.0, options: [.curveEaseOut], animations: {
self.backgroundColor = someNewColour
//Generally
//myView.backgroundColor = someNewColor
}, nil)
The problem in the short run is that that is simply what clear does if the background color is opaque. Just give your background color some transparency — even a tiny bit of transparency, so tiny that the human eye cannot perceive it — and now clear will cut a hole in the view.
For example, your code works fine if you set the view's background color to UIColor.green.withAlphaComponent(0.99).
By the way, you should delete the lines about UIColor.clear; that's a red herring. You should also cut the lines about the backgroundColor; you should not be repainting the background color into your context. They are two different things.
The problem in the long run is that what you're doing is not how to punch a hole in a view. You should be using a mask instead. That's the only way you're going to get the animation while maintaining the hole.
Answering my own question, based on #matt's suggestion (and linked example), I did it with a CAShapeLayer. There was an extra "hitch" in my requirements, since I have a couple of views on top of the one I needed to mask out. So, I did the masking like this:
func cutOutWindow() {
// maskedBackgroundView is an additional view, inserted ONLY for the mask
let r = self.maskedBackgroundView.bounds
// Adjust frame for dragAreaView's border
var dragSize = self.dragAreaView.frame.size
var dragPosition = self.dragAreaView.frame.origin
dragSize.width -= 6.0
dragSize.height -= 6.0
dragPosition.x += 3.0
dragPosition.y += 3.0
let r2 = CGRect(x: dragPosition.x, y: dragPosition.y, width: dragSize.width, height: dragSize.height)
let roundedWindow = UIBezierPath(roundedRect: r2, cornerRadius: 15.0)
let mask = CAShapeLayer()
let path = CGMutablePath()
path.addPath(roundedWindow.cgPath)
path.addRect(r)
mask.path = path
mask.fillRule = kCAFillRuleEvenOdd
self.maskedBackgroundView.layer.mask = mask
}
Then I had to apply the colour change to maskedBackgroundView.layer.backgroundColor (i.e., to the layer, not the view). With that in place, I get the cutout I need, with animatable colour changes. Thanks #matt for pointing me in the right direction.
I am trying to add a Gradient in IOS like I did in Android. So I can see my label on top of the UIImageView and its not hidden.
In android I did this in a drawable `
<gradient
android:angle="90"
android:endColor="#00ffffff"
android:startColor="#aa000000"
android:centerColor="#00ffffff" />
<corners android:radius="0dp" />
`
I am trying to do this in IOS Swift 4.2 and I get the following :
let gradient: CAGradientLayer = CAGradientLayer()
gradient.colors = [UIColor.blue.cgColor, UIColor.red.cgColor]
gradient.locations = [0.0 , 1.0]
gradient.startPoint = CGPoint(x: 0.0, y: 1.0)
gradient.endPoint = CGPoint(x: 0.5, y: 0.5)
gradient.frame = CGRect(x: 0.0, y: 0.0, width: showImageView.frame.size.width, height: showImageView.frame.size.height)
showImageView.layer.addSublayer(gradient)
How do I get the Gradient to start black from the bottom and go up in 90 degrees?How do I change the opacity?Any idea?
A few thoughts:
Choose colors with alpha less than 1. Perhaps:
gradient.colors = [
UIColor.black.withAlphaComponent(0.8).cgColor,
UIColor.black.withAlphaComponent(0).cgColor
]
To have this gradient go vertically, choose start and end points that have the same x value. E.g. to cover bottom half, perhaps:
gradient.startPoint = CGPoint(x: 0.5, y: 1)
gradient.endPoint = CGPoint(x: 0.5, y: 0.5)
Be very careful about using frame. You want the layer to reference the bounds of the image view (using the image view’s coordinate system), not the frame (which specifies where the image view is in its superview’s coordinate system). If your image view happens to be at 0, 0, you might not see a difference, but if you move the image view around at all, these will start to deviate. So, assuming you’re adding this gradient to the image view, itself, you’d use the image view’s bounds:
gradient.frame = showImageView.bounds
Be aware that the frame/bounds of the image view can sometimes change. So, we will implement layoutSubviews in our UIImageView or UITableViewCell subclass, and update the gradient’s frame there, e.g.
override func layoutSubviews() {
super.layoutSubviews()
gradient.frame = bounds
}
That way it will update the gradient’s frame when the view’s layout changes.
The other solution is to define a UIView subclass, say GradientView, that renders the CAGradientLayer and define the base layerClass of that view to be a CAGradientLayer. Then add this view in between the image view and the label, define its constraints, and then you’ll have a gradient that changes dynamically as the GradientView size changes. (This layerClass approach has the advantage that it yields better animation/transitions than you’d get by just updating the frame programmatically.)
Thus, something like:
class GradientView: UIView {
override class var layerClass: AnyClass { return CAGradientLayer.self }
var gradientLayer: CAGradientLayer { return layer as! CAGradientLayer }
var firstColor: UIColor = UIColor.black.withAlphaComponent(0.8) {
didSet { updateColors() }
}
var secondColor: UIColor = UIColor.black.withAlphaComponent(0) {
didSet { updateColors() }
}
override init(frame: CGRect = .zero) {
super.init(frame: frame)
configure()
}
required init?(coder: NSCoder) {
super.init(coder: coder)
configure()
}
}
private extension GradientView {
func configure() {
updateColors()
gradientLayer.startPoint = CGPoint(x: 0.5, y: 1)
gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.5)
}
func updateColors() {
gradientLayer.colors = [firstColor, secondColor].map { $0.cgColor }
}
}
If you really want your white text to pop, in addition to adding gradient over the image, you might also add a black glow/shadow to the text. It’s subtle, but really makes the text pop. Just make its shadow color the same color as the gradient.
So you can see the effect, here are four renditions of a cell, with (a) no gradient; (b) with gradient; (c) with gradient and nice gaussian blur around text; and (d) with simple shadow around text:
The nice, gaussian blur around the text is rendered with:
customLabel.layer.shadowColor = UIColor.black.cgColor
customLabel.layer.shadowRadius = 3
customLabel.layer.shadowOpacity = 1
customLabel.layer.masksToBounds = false
customLabel.layer.shouldRasterize = true
I think that third rendition (with gradient over the image, with glow around the text) is best. It’s subtle, but the text really pops. But gaussian blurs are computationally expensive, so if you find this adversely affects your performance too much, you can use the fourth option, with the simple, non-blurred shadow:
customLabel.shadowColor = .black
// perhaps also
// customLabel.shadowOffset = CGSize(width: -1, height: -1)
First I set constraints to a button in storyboard. Then, I edited it in code to make it look good.
When I apply my gradient function to a button it becomes bigger than before. How do you fix that?
extension UIView {
func applyGradient(colours: [UIColor]) -> Void {
self.applyGradient(colours, locations: nil)
}
func applyGradient(colours: [UIColor], locations: [NSNumber]?) -> Void {
let gradient: CAGradientLayer = CAGradientLayer()
gradient.frame = self.bounds
gradient.colors = colours.map { $0.CGColor }
gradient.locations = locations
self.layer.insertSublayer(gradient, atIndex: 0)
}
}
I just applied it on one button and..
Here is the pic...
Now after that it looks like this...The gradient bound did nothing It goes way outside frame PLZPLZPLZ try to help me :) I appreciate ur help so far
Add self.layer.masksToBounds = true to the function. This will mean that the sublayer you added won't draw outside of the original frame of the button
EDIT:
If you want the shadow as well you'll need to set self.layer.masksToBounds to false, since it will clip the shadow too.
Try gradient.frame = self.layer.bounds instead maybe?
I have a blue view with a white dashed border. As you can see from the image below, once the app is rotated the view changes its dimensions and the border doesn't adjust to the view's new width and height.
I need to find a way to
Know when the view controller changes its size - perhaps using viewWillTransitionToSize.
Delete the previously drawn border, if any.
Add a new border to the view - in the view's drawRect method.
How can I delete the border previously drawn on the view?
#IBOutlet weak var myView: UIView!
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
coordinator.animateAlongsideTransition(nil, completion: {
_ in
self.myView.setNeedsDisplay()
})
}
class RenderView: UIView {
override func drawRect(rect: CGRect) {
self.addDashedBorder()
}
}
extension UIView {
func addDashedBorder() {
let color = UIColor.whiteColor().CGColor
let shapeLayer:CAShapeLayer = CAShapeLayer()
let frameSize = self.frame.size
let shapeRect = CGRect(x: 0, y: 0, width: frameSize.width, height: frameSize.height)
shapeLayer.bounds = shapeRect
shapeLayer.position = CGPoint(x: frameSize.width/2, y: frameSize.height/2)
shapeLayer.fillColor = UIColor.clearColor().CGColor
shapeLayer.strokeColor = color
shapeLayer.lineWidth = 6
shapeLayer.lineJoin = kCALineJoinRound
shapeLayer.lineDashPattern = [6,3]
shapeLayer.path = UIBezierPath(roundedRect: shapeRect, cornerRadius: 5).CGPath
self.layer.addSublayer(shapeLayer)
}
}
Download sample project here.
This is not the right way to do things. Each time your RenderView is redrawn, its drawRect method will be called, and addDashedBorder will add a new layer to your view.
drawRect is for drawing inside of your view using CoreGraphics or UIKit, not CoreAnimation. Inside that method, you should just draw, nothing else. If you want to use it a layer, layoutSubviews is a better place to add it, and to update it to match the view.
Here are two ways to solve your problem. Both update the border correctly, and animate the border smoothly when the device is rotated.
Alternative 1: Just draw the border in drawRect, rather than using a separate shape layer. Also, set your view's contentMode so it automatically redraws when its size changes.
class ViewController: UIViewController {
#IBOutlet weak var myView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
self.myView.contentMode = .Redraw
}
}
class RenderView: UIView {
override func drawRect(rect: CGRect) {
let path = UIBezierPath(roundedRect: self.bounds, cornerRadius: 5)
path.lineWidth = 6
let pattern: [CGFloat] = [6.0, 3.0]
path.setLineDash(pattern, count: 2, phase: 0)
UIColor.whiteColor().setStroke()
path.stroke()
}
}
Alternative 2: Continue to use CAShapeLayer, but only create a single one, by using a lazy stored property. Update the layer in an override of layoutSubviews, and if necessary, animate it alongside any changes in the view's bounds.
class ViewController: UIViewController {
#IBOutlet weak var myView: UIView!
}
class RenderView: UIView {
// Create the borderLayer, and add it to our view's layer, on demand, only once.
lazy var borderLayer: CAShapeLayer = {
let shapeLayer = CAShapeLayer()
shapeLayer.fillColor = nil
shapeLayer.strokeColor = UIColor.whiteColor().CGColor
shapeLayer.lineWidth = 6
shapeLayer.lineDashPattern = [6,3]
self.layer.addSublayer(shapeLayer)
return shapeLayer
}()
override func layoutSubviews() {
super.layoutSubviews()
// We will update the borderLayer's path to match the view's current bounds.
let newPath = UIBezierPath(roundedRect: self.bounds, cornerRadius: 5).CGPath
// We may be animating from the old bounds to the new bounds.
// If so, we want the borderLayer to animate alongside that.
// (UIView does not do this automatically, since it does not know
// anything about our borderLayer; it's at the the CoreAnimation level,
// below UIKit.)
//
// We want an animation that uses the same properties as the existing
// animation, but applies to a different value: the borderLayer's path.
// We'll find the existing animation on the view's bounds.size,
// and if it exists, add our own animation based on it that will
// apply the path change.
if let viewBoundsAnimation = self.layer.animationForKey("bounds.size") {
let pathAnimation = CABasicAnimation()
pathAnimation.beginTime = viewBoundsAnimation.beginTime
pathAnimation.duration = viewBoundsAnimation.duration
pathAnimation.speed = viewBoundsAnimation.speed
pathAnimation.timeOffset = viewBoundsAnimation.timeOffset
pathAnimation.timingFunction = viewBoundsAnimation.timingFunction
pathAnimation.keyPath = "path"
pathAnimation.fromValue = borderLayer.path
pathAnimation.toValue = newPath
borderLayer.addAnimation(pathAnimation, forKey: "path")
}
// Finally, whether we are animating or not, make the border layer show the new path.
// If we are animating, this will appear when the animation is finished.
// If we are not animating, this will appear immediately.
self.borderLayer.path = newPath
}
}
Note that neither of these alternatives require overriding viewWillTransitionToSize or traitCollectionDidChange. Those are higher-level UIViewController concepts, that may get called during device rotation, but won't happen if some other code changes your view's size. It's better to use the simple UIView-level drawRect or layoutSubviews methods, because they will always work.
Call set needs display when the view transitions.You can detect it by using this function.It works perfectly to detect orientation change
override func traitCollectionDidChange(previousTraitCollection: UITraitCollection?) {
self.myView.setNeedsDisplay()
}