While working on a project you will have to deal with customized UI components, sometimes the customization is a bit complicated and it will add complexity to your project. In my case, I had to create a customized button with specific padding for the title, and a loading indicator when the state is loading. So I had to start from somewhere, and I decided to create my own loading indicator like what we going to see later in this article For this project, I have created two types of loading indicators, I named them HueSpinnerView & SpinnerView. For SpinnerView we're going to use CABasicAnimation to achieve the circular animation. While in HueSpinnerView we will be using CAKeyframeAnimation in order to have a circular animation with custom timing & animated stroke hue.

Let us begin with creating a simple class of UIView for SpinnerView

we make sure that in the layoutSubviews layer will be rounded by setting its cornerRadius equal to frame.width / 2. If you are wondering what is a layer? The layer is the object that manages image-based content and allows you to perform animations on that content. To draw the circle we need to create a customCAShapeLayer . The CAShapeLayer is a layer that draws a cubic Bezier spline in its coordinate space. The shape is comprised between the layer's contents and its first sublayer.

We are going to use the SpinnerShapeLayer to draw the circular shape, but let us see the properties declared within SpinnerShapeLayer  strokeColor The color of the path

• lineWidth determines the width of the path

• fillColor background-color of the path layer

• lineCap specifies the shape of the endpoints of an open path when stroked. In our case we wanted it .round

Now you can see a new private property of SpinnerShapeLayer type and

that the initializer has strokeColor & lineWidth with frame = .zero to help us initialize the SpinnerShapeLayer . A new function configureShapePath() called in func layoutSubviews() to create the path of theshapeLayer , the path is an animatable property and may be animated using any of the concrete subclasses of CAPropertyAnimation

class CAPropertyAnimation : CAAnimation

The property to animate is specified using a key path that is relative to the layer using the animation. You do not create instances of CAPropertyAnimation to animate the properties of a Core Animation layer, create instance of the concrete subclasses CABasicAnimation or CAKeyframeAnimation

Apple Developer Documentation

Stroke Animation Now after that said, it is time for CABasicAnimation class . We are going to create a new class StrokeAnimation as follows:

An enum State to specify the stroke animation type, start & end signify the edge of the path, and the animationKey the name says it all.

An initializer that takes state, beginTime, fromValue, toValue and duration as arguments. Based on the state we're going to define the stoke animation by assigning it to the keyPath.

the timingFunction of type CAMediaTimingFunction represents one segment of a function that defines the pacing of animation as a timing curve, in simple words, it will make our animation start and end slowly.

Full tutorial exist on MEDIUM