Fix wacky layout while scrolling in thread.

app/src/main/java/org/thoughtcrime/securesms/components/RecyclerViewParentTransitionController.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.components
+
+import android.animation.LayoutTransition
+import android.view.View
+import android.view.View.OnAttachStateChangeListener
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+
+/**
+ * Helps manage layout transition state inside a RecyclerView.
+ *
+ * Because of how RecyclerViews scroll, we need to be very careful about LayoutTransition
+ * usage inside of them. This class helps wrap up the pattern of finding and listening to
+ * the scroll events of a parent recycler view, so that we don't need to manually wire
+ * the scroll state in everywhere.
+ */
+class RecyclerViewParentTransitionController(
+  private val child: ViewGroup,
+  private val transition: LayoutTransition = LayoutTransition()
+) : RecyclerView.OnScrollListener(), OnAttachStateChangeListener {
+
+  private var recyclerViewParent: RecyclerView? = null
+
+  override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
+    if (newState == RecyclerView.SCROLL_STATE_IDLE) {
+      child.layoutTransition = transition
+    } else {
+      child.layoutTransition = null
+    }
+  }
+
+  override fun onViewAttachedToWindow(v: View) {
+    val parent = findRecyclerParent()
+
+    if (parent != null) {
+      onScrollStateChanged(parent, parent.scrollState)
+    }
+
+    parent?.addOnScrollListener(this)
+    recyclerViewParent = parent
+  }
+
+  override fun onViewDetachedFromWindow(v: View) {
+    recyclerViewParent?.removeOnScrollListener(this)
+    child.layoutTransition = null
+  }
+
+  private fun findRecyclerParent(): RecyclerView? {
+    var target: ViewGroup? = child.parent as? ViewGroup
+    while (target != null) {
+      if (target is RecyclerView) {
+        return target
+      }
+
+      target = target.parent as? ViewGroup
+    }
+
+    return null
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/components/transfercontrols/TransferControlView.kt

@@ -4,7 +4,6 @@
  */
 package org.thoughtcrime.securesms.components.transfercontrols
 
-import android.animation.LayoutTransition
 import android.annotation.SuppressLint
 import android.content.Context
 import android.os.Build
@@ -23,6 +22,7 @@ import org.greenrobot.eventbus.ThreadMode
 import org.signal.core.util.logging.Log
 import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.attachments.Attachment
+import org.thoughtcrime.securesms.components.RecyclerViewParentTransitionController
 import org.thoughtcrime.securesms.database.AttachmentTable
 import org.thoughtcrime.securesms.databinding.TransferControlsViewBinding
 import org.thoughtcrime.securesms.events.PartProgressEvent
@@ -45,10 +45,11 @@ class TransferControlView @JvmOverloads constructor(context: Context, attrs: Att
     binding = TransferControlsViewBinding.inflate(LayoutInflater.from(context), this)
     visibility = GONE
     isLongClickable = false
-    layoutTransition = LayoutTransition()
     disposables += store.stateFlowable.distinctUntilChanged().observeOn(AndroidSchedulers.mainThread()).subscribe {
       applyState(it)
     }
+
+    addOnAttachStateChangeListener(RecyclerViewParentTransitionController(child = this))
   }
 
   override fun onAttachedToWindow() {