public final void setValue(@Nullable T value) {
    this.value = value;
    if (animation != null) {
      animation.notifyListeners();
    }
  }
Override this if you haven't set a static value in the constructor or with setValue.
<p>
Return null to resort to the default value.

Refer to the javadoc for this class for a special case that requires manual invalidation
each time you want to return something different from this method.
lottie/src/main/java/com/airbnb/lottie/value/LottieValueCallback.java