Crafting Inclusive Android Animations with Kotlin: An Expert Guide

As Android developers, we have an incredible opportunity to create app experiences that delight and empower all of our users, regardless of their abilities. While animations can be a great way to make our apps more engaging and intuitive, they can actually make our apps less accessible if we don‘t implement them thoughtfully.

According to the World Health Organization, over 1 billion people (15% of the world‘s population) have some form of disability. Many disabilities can affect the way people perceive and interact with animations on mobile devices:

• Visual impairments can make it difficult to see and understand animations
• Cognitive and learning disabilities can cause confusion with complex animations
• Vestibular disorders can cause dizziness and nausea from certain types of motion
• Motor impairments can make it difficult to interact with animated UI controls

When we don‘t consider these diverse needs in our animation design and implementation, we risk creating apps that exclude a significant portion of our potential users and customers.

Fortunately, Android provides us with both the APIs and the guidelines we need to create animations that are accessible and inclusive. By combining Kotlin‘s expressive power with Android‘s animation and accessibility frameworks, we can craft animated experiences that are both delightful and usable for everyone.

Understanding Android‘s Accessibility APIs

At the heart of accessible app development on Android is a suite of powerful APIs that allow us to express accessible properties and relationships in our UI.

Some of the key accessibility APIs relevant to animations include:

• ContentDescription – Allows us to provide text alternatives for visual elements in our UI, including animated drawables and transitions. These descriptions are read aloud by screen readers like TalkBack.

• ImportantForAccessibility – Allows us to control whether a view is visible to accessibility services and how it is traversed in the accessibility focus order. This is useful for hiding decorative animations and ensuring users can logically navigate animated content.

• AccessibilityEvent – Allows us to programmatically notify accessibility services of important changes in our UI, such as when an animation starts or ends. This can help orientate users and keep them informed of what‘s happening on the screen.

• AccessibilityNodeInfo – Allows us to customize the properties and actions exposed to accessibility services for a given view or animated element. We can use this to provide more granular control over animated content.

To dive deeper into these APIs and how they work, check out Google‘s excellent Accessibility Overview in the Android docs.

Applying Accessibility Best Practices to Animations

Now that we have a general understanding of Android‘s accessibility features, let‘s look at how we can apply them specifically to animations in our apps.

Google‘s Material Design system provides a comprehensive set of guidelines for motion that take accessibility into account. Some key principles include:

• Use animations to support and reinforce user actions, not just for decoration
• Prefer simple, subtle animations over complex, flashy ones
• Make sure animated content can also be consumed as static, non-animated content
• Allow users to disable or reduce animations in your app‘s settings

In terms of implementation, here are some best practices to follow for accessible Android animations in Kotlin:

1. Always Provide a ContentDescription

Any time you use an animated drawable or transition in your UI, make sure to provide a brief, meaningful ContentDescription that conveys the essential information about that animation to screen reader users.

val rotateDrawable = AnimatedVectorDrawableCompat.create(context, R.drawable.rotate_animation)
rotateDrawable?.contentDescription = getString(R.string.rotate_animation_description)

val scaleTransition = TransitionInflater.from(context).inflateTransition(R.transition.scale_transition)
scaleTransition.addListener(object: TransitionListener {
    override fun onTransitionStart() { 
        view.contentDescription = getString(R.string.scale_animation_description)
    }
})

2. Respect ImportantForAccessibility

Make sure to test your animations with a screen reader and verify the focus order matches the logical reading order. For decorative animations that don‘t convey meaningful information, you can set their ImportantForAccessibility to "noHideDescendants" so they are hidden from accessibility services entirely.

<ImageView
    android:id="@+id/decorative_animation"
    android:importantForAccessibility="noHideDescendants"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

3. Use AccessibilityEvent to Provide Feedback

When an important animation starts or ends, notify accessibility services by sending a custom AccessibilityEvent. This can help provide additional context and keep users orientated as your UI changes.

val successDrawable = AnimatedVectorDrawableCompat.create(context, R.drawable.success_animation)
successDrawable?.registerAnimationCallback(object: Animatable2Compat.AnimationCallback() {
    override fun onAnimationStart() {
        sendAccessibilityEvent(AccessibilityEvent.TYPE_ANNOUNCEMENT, getString(R.string.success_animation_start))
    }
    override fun onAnimationEnd() {
        sendAccessibilityEvent(AccessibilityEvent.TYPE_ANNOUNCEMENT, getString(R.string.success_animation_end))
    }
})

4. Use Animation Durations and Interpolators Thoughtfully

Avoid animations that are too fast or too slow, as they can be disorienting and confusing. Material Design recommends animation durations between 200-500ms for most transitions. Use interpolators like FastOutSlowIn to create natural easing and avoid abrupt changes in velocity.

val translateAnim = ValueAnimator.ofFloat(0f, 100f).apply {
    interpolator = FastOutSlowInInterpolator()
    duration = 300L
    addUpdateListener {
        view.translationX = it.animatedValue as Float
    }
}
translateAnim.start()

5. Provide an Option to Reduce or Disable Animations

For users with vestibular disorders or motion sensitivities, even subtle animations can cause discomfort. Always provide an option in your app settings to reduce animation durations or disable them entirely. You can use the system Animator Duration Scale to determine if animations are enabled at a global level.

val animationsEnabled = Settings.Global.getFloat(context.contentResolver, Settings.Global.ANIMATOR_DURATION_SCALE, 1f) > 0f
if (animationsEnabled) {
    // Start animation
} else {
    // Skip animation
}

By following these guidelines and leveraging Kotlin‘s extension functions and lambdas for more expressive animation code, we can create Android animations that are both accessible and delightful.

Testing and Validating Animation Accessibility

Of course, our work isn‘t done once we‘ve implemented our accessible animations – we need to rigorously test and validate them to make sure they actually meet the needs of our users.

Some key steps for accessibility testing include:

1. Manual testing with TalkBack and other accessibility services enabled – Walk through your key animations with TalkBack on and make sure the content descriptions, focus order, and announcements are all accurate and informative.

2. Automated accessibility scanning with Accessibility Scanner – This free tool from Google can help catch common accessibility issues in your app, including missing content descriptions on animated elements.

3. Usability testing with people with disabilities – Whenever possible, recruit users with a diverse range of disabilities to test your app and give feedback on the animation experience. There are many great accessibility testing services that can help with this.

4. Ongoing accessibility reviews and regression testing – Make sure to include accessibility in your regular QA and code review processes to catch any regressions and ensure new features meet your accessibility standards.

By combining manual, automated, and usability testing techniques, we can make sure our animations are truly inclusive and meet the needs of all our users.

Measuring the Impact of Accessible Animations

Implementing accessible animations takes effort and intentionality, but the impact is well worth it. When we create inclusive experiences, we can reach and empower more users while also driving positive business outcomes.

Consider these statistics:

• The global market of people with disabilities is over 1 billion people with a spending power of more than $6 trillion
• 71% of people with disabilities leave a website that is not accessible
• Mobile apps with accessible features have been shown to increase downloads by up to 200%

By making our animations accessible, we‘re not only doing the right thing ethically, but we‘re also expanding our market reach and user engagement.

We can measure the impact of our accessibility efforts by tracking metrics like:

• % of users with accessibility services enabled who complete key flows
• App store rating and review sentiment from users with disabilities
• Social media mentions and PR related to our app‘s accessibility features
• NPS and user satisfaction scores segmented by users with disabilities

Tracking these metrics over time can help us quantify the ROI of our accessibility work and make the case for continued investment and prioritization.

Conclusion and Resources

Animations are a powerful tool for creating engaging and intuitive mobile experiences, but with great power comes great responsibility. When we don‘t consider the diverse needs of our users, we risk creating animations that exclude and frustrate people with disabilities.

By following best practices for accessible animations, leveraging Android‘s accessibility APIs, and testing our work with real users, we can create animated experiences that are truly inclusive and empowering for everyone.

Here are some additional resources to dive even deeper into Android animation accessibility:

• Animation and Inclusiveness in the Material Design docs
• Accessibility Testing Checklist for Android from the Android Developers site
• How to write an Accessibility Statement from the W3C Web Accessibility Initiative
• Android Accessibility Tutorial on RayWenderlich.com
• 8 Ways to Make Your Animations More Accessible on uxdesign.cc

Let‘s all commit to making accessibility a core part of our animation practice – together we can create mobile experiences that empower and delight ALL of our users!