In this Notes article, I roughly jotted down notes in English from the content of the English session video/podcast. This article is intended to be read as a reference while watching the video. I hope this article helps you even a little when you watch the actual video. (Please feel free to contact me if there are any errors or typos! m(__)m)

This article is based on Get Animated (Android Dev Summit ‘18).

Android Animation APIs

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• View Animations

• Value Animator

• Object Animator

• View Property Animator

• Transitions

• Animated Vector Drawable

• Physics

• MotionLayout

android.view.animation

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is now consider deprecated

• Measure => Layout => Draw

  • android.view.animation is only applied in Draw process

• WindowAnimation only accepts android.view.animation so it should be used only here, but otherwise consider it as deprecated

• You may use it in FragmentTransaction

  • API also accepts Android animator so prefer animator

When to use which Animator

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• ObjectAnimator - general purpose, property animator

• ValueAnimator - custom animation

• ViewPropertyAnimator

  • Multiple properties on the same View

  • Fire and forget

• PropertyValuesHolder - multiple properties on the same object

• AnimatorSet - choreograph a set of animations

AnimatedVectorDrawable

#

When to use

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• Icon animation

• Fire & forget animations

• Performance critical

Physics

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Physics-based Animation

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• Interruptible

• Continuity

• Realistic Look

Transitions

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• Shared element activity transitions

• Window content enter/exit

• Modularize animations

• Simple changes

Motion / Animation

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Helper

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In ConstraintLayout 2.0, all the helpers are exposed for achieving encapsulated behaviors

• ConstraintLayout utility

• Apply it to a set of widgets

• Supported in Android Studio

• Use Animation APIs in helpers to promote reuse

E.g. Circular Reveal:

@Override
public void updatePostLayout(ConstraintLayout container) {
  super.updatePostLayout(container);
  if (mContainer != container) {
    int rad = (int) Math.hypot(mComputedMaxY - mComputedMinY, mComputedMaxX - mComputedMinX);
    Animator anim = ViewAnimationUtils.createCircularReveal(this, (int) mComputedCenterX - getLeft(), (int) mComputedCenterY - getTop(), 0, rad);
    anim.setDuration(2000);
    anim.start();
  }
  mContainer = container;
}

<com.example.CircularRevealHelper
    android:id="@+id/helper"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/lake"
    app:constraint_referenced_ids="imageView" />

MotionLayout

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• Only two states: Start to End

• Where it shines

  • Declarative motion

  • Bespoke motion

  • Touch-driven motion

MotionLayout: Library

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• Part of ConstraintLayout 2.0

• Released at Google IO'18

• Built upon ConstraintLayout 1.1

• Alpha 2

📝

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• android.view.animation is currently necessary for window animations, but it seems better to use other APIs for other animations.
• MotionLayout will allow for amazing animations, but it should be used in the right place alongside existing APIs.
• I was very surprised to see Sumitomo-san’s Twitter account featured in the MotionLayout explanation.