Kyrie

Kyrie is a superset of Android's VectorDrawable and AnimatedVectorDrawable classes: it can do everything they can do and more.

Motivation

VectorDrawables are great because they provide density independence—they can be scaled arbitrarily on any device without loss of quality. AnimatedVectorDrawables make them even more awesome, allowing us to animate specific properties of a VectorDrawable in a variety of ways.

However, these two classes have three main limitations:

1. They can't be paused, resumed, or seeked.
2. They can't be dynamically created at runtime (they must be inflated from a drawable resource).
3. They only support a small subset of features that SVGs provide on the web.

Kyrie was created in order to address these problems.

Getting started

To create an animation using Kyrie, you first need to build a KyrieDrawable. There are two ways to do this:

Option #1: from an existing VD/AVD resource

With Kyrie, you can convert an existing VectorDrawable or AnimatedVectorDrawable resource into a KyrieDrawable with a single line:

val drawable = KyrieDrawable.create(context, R.drawable.my_vd_or_avd);

Option #2: programatically using a KyrieDrawable.Builder

You can also build KyrieDrawables at runtime using the builder pattern. KyrieDrawables are similar to SVGs and VectorDrawables in that they are tree-like structures built of Nodes. As you build the tree, you can optionally assign Animations to the properties of each Node to create an animatable KyrieDrawable.

Here is a snippet of code from the sample app that builds a material design circular progress indicator:

val drawable =
    kyrieDrawable {
        viewport = size(48f, 48f)
        tint = Color.RED
        group {
            translateX(24f)
            translateY(24f)
            rotation(
                Animation.ofFloat(0f, 720f)
                    .duration(4444)
                    .repeatCount(Animation.INFINITE)
            )
            path {
                strokeColor(Color.WHITE)
                strokeWidth(4f)
                trimPathStart(
                    Animation.ofFloat(0f, 0.75f)
                        .duration(1333)
                        .repeatCount(Animation.INFINITE)
                        .interpolator("M 0 0 h .5 C .7 0 .6 1 1 1".asPathInterpolator())
                )
                trimPathEnd(
                    Animation.ofFloat(0.03f, 0.78f)
                        .duration(1333)
                        .repeatCount(Animation.INFINITE)
                        .interpolator("M 0 0 c .2 0 .1 1 .5 1 C 1 1 1 1 1 1".asPathInterpolator())
                )
                trimPathOffset(
                    Animation.ofFloat(0f, 0.25f)
                        .duration(1333)
                        .repeatCount(Animation.INFINITE)
                )
                strokeLineCap(StrokeLineCap.SQUARE)
                pathData("M 0 -18 a 18 18 0 1 1 0 36 18 18 0 1 1 0 -36")
            }
        }
    }

Features

Kyrie supports 100% of the features that VectorDrawables and AnimatedVectorDrawables provide. It also extends the functionality of VectorDrawables and AnimatedVectorDrawables in a number of ways, making it possible to create even more powerful and elaborate scalable assets and animations.

VectorDrawable features

In addition to the features supported by VectorDrawable, Kyrie provides the following:

<path> features

• CircleNode. Equivalent to the <circle> node in SVG.
• EllipseNode. Equivalent to the <ellipse> node in SVG.
• LineNode. Equivalent to the <line> node in SVG.
• RectangleNode. Equivalent to the <rect> node in SVG.
• strokeDashArray (FloatArray). Equivalent to the stroke-dasharray attribute in SVG.
• strokeDashOffset (Float). Equivalent to the stroke-dashoffset attribute in SVG.
• isScalingStroke (Boolean). Equivalent to vector-effect="non-scaling-stroke" in SVG. Defines whether a path's stroke width will be affected by scaling transformations.
• The strokeMiterLimit attribute is animatable.

<clip-path> features

• FillType (either NON_ZERO or EVEN_ODD). Equivalent to the clip-rule attribute in SVG.
• ClipType (either INTERSECT or DIFFERENCE). Defines whether the clipping region is additive or subtractive.

<group> features

• Transformations (pivot, scale, rotation, and translation) can be set on any Node, not just GroupNodes.

AnimatedVectorDrawable features

In addition to the features supported by AnimatedVectorDrawable, Kyrie provides the following:

• setCurrentPlayTime(long).
  • Allows you to manually scrub the animation.
• pause() and resume().
  • Allows you to pause and resume the animation.
• addListener(KyrieDrawable.Listener).
  • Allows you to listen for the following animation events: start, update, pause, resume, cancel, and end.

Further reading

• Check out this blog post for more on the motivation behind the library.
• Check out the sample app for example usages in both Java and Kotlin.
• Check out the documentation for a complete listing of all supported Animations and Nodes that can be used when constructing KyrieDrawables programatically.

Dependency

Add this to your root build.gradle file (not your module's build.gradle file):

allprojects {
    repositories {
        // ...
        jcenter()
    }
}

Then add the library to your module's build.gradle file:

dependencies {
    // ...
    implementation 'com.github.alexjlockwood:kyrie:0.2.1'
}

Compatibility

• Minimum Android SDK: Kyrie requires a minimum API level of 14.
• Compile Android SDK: Kyrie requires you to compile against API 28 or later.