Add better UX while loading sustainer data and when a load failure happens.

app/src/main/java/org/thoughtcrime/securesms/subscription/Subscription.kt

@@ -1,8 +1,14 @@
 package org.thoughtcrime.securesms.subscription
 
+import android.animation.Animator
+import android.animation.AnimatorSet
+import android.animation.ObjectAnimator
 import android.view.View
 import android.widget.ImageView
 import android.widget.TextView
+import androidx.core.animation.doOnEnd
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.LifecycleOwner
 import org.signal.core.util.money.FiatMoney
 import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.badges.BadgeImageView
@@ -30,6 +36,46 @@ data class Subscription(
   companion object {
     fun register(adapter: MappingAdapter) {
       adapter.registerFactory(Model::class.java, MappingAdapter.LayoutFactory({ ViewHolder(it) }, R.layout.subscription_preference))
+      adapter.registerFactory(LoaderModel::class.java, MappingAdapter.LayoutFactory({ LoaderViewHolder(it) }, R.layout.subscription_preference_loader))
+    }
+  }
+
+  class LoaderModel : PreferenceModel<LoaderModel>() {
+    override fun areItemsTheSame(newItem: LoaderModel): Boolean = true
+  }
+
+  class LoaderViewHolder(itemView: View) : MappingViewHolder<LoaderModel>(itemView), DefaultLifecycleObserver {
+
+    private val animator: Animator = AnimatorSet().apply {
+      val fadeTo25Animator = ObjectAnimator.ofFloat(itemView, "alpha", 0.8f, 0.25f).apply {
+        duration = 1000L
+      }
+
+      val fadeTo80Animator = ObjectAnimator.ofFloat(itemView, "alpha", 0.25f, 0.8f).apply {
+        duration = 300L
+      }
+
+      playSequentially(fadeTo25Animator, fadeTo80Animator)
+      doOnEnd { start() }
+    }
+
+    init {
+      lifecycle.addObserver(this)
+    }
+
+    override fun bind(model: LoaderModel) {
+    }
+
+    override fun onResume(owner: LifecycleOwner) {
+      if (animator.isStarted) {
+        animator.resume()
+      } else {
+        animator.start()
+      }
+    }
+
+    override fun onDestroy(owner: LifecycleOwner) {
+      animator.pause()
     }
   }