애니메이션과 전환

애니메이션이 중요한 이유

ViewPropertyAnimator — 빠른 애니메이션

// Fade a view out:
binding.tvMessage
    .animate()
    .alpha(0f)
    .setDuration(300)
    .withEndAction { binding.tvMessage.visibility = View.GONE }
    .start()

// Slide in from bottom:
binding.cardView.translationY = 200f
binding.cardView.alpha = 0f
binding.cardView
    .animate()
    .translationY(0f)
    .alpha(1f)
    .setDuration(250)
    .setInterpolator(DecelerateInterpolator())
    .start()

ObjectAnimator

// Rotate an image:
val rotateAnimator = ObjectAnimator.ofFloat(
    binding.ivLogo,
    "rotation",
    0f, 360f
).apply {
    duration = 600
    repeatCount = ObjectAnimator.INFINITE
    interpolator = LinearInterpolator()
    start()
}

// Stop it:
rotateAnimator.cancel()

AnimatorSet — 순차 및 병렬 실행

val fadeIn  = ObjectAnimator.ofFloat(binding.card, "alpha", 0f, 1f).setDuration(300)
val scaleX  = ObjectAnimator.ofFloat(binding.card, "scaleX", 0.8f, 1f).setDuration(300)
val scaleY  = ObjectAnimator.ofFloat(binding.card, "scaleY", 0.8f, 1f).setDuration(300)
val slideUp = ObjectAnimator.ofFloat(binding.card, "translationY", 100f, 0f).setDuration(300)

AnimatorSet().apply {
    // Run fadeIn + scaleX + scaleY together, then slideUp
    play(fadeIn).with(scaleX).with(scaleY)
    play(slideUp).after(fadeIn)
    interpolator = DecelerateInterpolator()
    start()
}

보간기

TransitionManager — 레이아웃 변경

binding.btnToggle.setOnClickListener {
    // Tell the framework to animate the next layout change
    TransitionManager.beginDelayedTransition(
        binding.root,
        ChangeBounds().apply { duration = 300 }
    )

    // Now change visibility/size — Android animates the difference automatically
    binding.expandedSection.visibility =
        if (binding.expandedSection.isVisible) View.GONE else View.VISIBLE
}

Fragment 전환

supportFragmentManager.beginTransaction()
    .setCustomAnimations(
        R.anim.slide_in_right,   // enterAnim
        R.anim.slide_out_left,   // exitAnim
        R.anim.slide_in_left,    // popEnterAnim
        R.anim.slide_out_right   // popExitAnim
    )
    .replace(R.id.container, DetailFragment())
    .addToBackStack(null)
    .commit()

// Or use MaterialSharedAxis for a modern, Material Motion feel:
val forward = MaterialSharedAxis(MaterialSharedAxis.X, true)
exitTransition = forward
enterTransition = MaterialSharedAxis(MaterialSharedAxis.X, true)

공유 요소 전환

// In ListFragment:
binding.ivThumbnail.transitionName = "hero_image_${item.id}"

val extras = FragmentNavigatorExtras(
    binding.ivThumbnail to "hero_image_${item.id}"
)
findNavController().navigate(R.id.action_list_to_detail, null, null, extras)

// In DetailFragment:
sharedElementEnterTransition = TransitionInflater
    .from(requireContext())
    .inflateTransition(android.R.transition.move)

// ImageView in detail layout must have the same transitionName

스프링 애니메이션

implementation 'androidx.dynamicanimation:dynamicanimation:1.0.0'

// Spring animation on a button press:
val spring = SpringAnimation(binding.fabAdd, DynamicAnimation.SCALE_X, 1f).apply {
    spring = SpringForce(1f).apply {
        stiffness = SpringForce.STIFFNESS_MEDIUM
        dampingRatio = SpringForce.DAMPING_RATIO_LOW_BOUNCY
    }
}

binding.fabAdd.setOnClickListener {
    binding.fabAdd.scaleX = 0.8f
    spring.start()
}

Lottie — 복잡한 애니메이션

// app/build.gradle:
// implementation 'com.airbnb.android:lottie:6.4.0'

<!-- In layout XML -->
<com.airbnb.lottie.LottieAnimationView
    android:id="@+id/lottieView"
    android:layout_width="200dp"
    android:layout_height="200dp"
    app:lottie_rawRes="@raw/loading_animation"
    app:lottie_autoPlay="true"
    app:lottie_loop="true" />

// Control in code:
binding.lottieView.playAnimation()
binding.lottieView.pauseAnimation()

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