New UI: Select a tab and then, while holding down, start dragging

app/src/main/java/org/mozilla/fenix/tabstray/browser/AbstractBrowserTabViewHolder.kt

@@ -4,6 +4,8 @@
 
 package org.mozilla.fenix.tabstray.browser
 
+import android.annotation.SuppressLint
+import android.view.MotionEvent
 import android.view.View
 import android.widget.ImageButton
 import android.widget.ImageView
@@ -31,6 +33,7 @@ import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.ext.increaseTapArea
 import org.mozilla.fenix.ext.removeAndDisable
 import org.mozilla.fenix.ext.removeTouchDelegate
+import org.mozilla.fenix.ext.settings
 import org.mozilla.fenix.ext.showAndEnable
 import org.mozilla.fenix.ext.toShortUrl
 import org.mozilla.fenix.selection.SelectionHolder
@@ -201,6 +204,7 @@ abstract class AbstractBrowserTabViewHolder(
         imageLoader.loadIntoView(thumbnailView, ImageLoadRequest(id, thumbnailSize))
     }
 
+    @SuppressLint("ClickableViewAccessibility")
     private fun setSelectionInteractor(
         item: TabSessionState,
         holder: SelectionHolder<TabSessionState>,
@@ -222,22 +226,36 @@ abstract class AbstractBrowserTabViewHolder(
                 metrics.track(Event.CollectionTabLongPressed)
                 interactor.select(item)
                 true
-            } else if (holder.selectedItems.contains(item)) {
-                val parent = itemView.parent as? AbstractBrowserTrayList
-                if (parent?.context?.settings()?.searchTermTabGroupsAreEnabled == false) {
-                    val shadow = View.DragShadowBuilder(itemView)
-                    @Suppress("DEPRECATION")
-                    itemView.startDrag(null, shadow, item, 0)
-                    // startDragAndDrop is the non-deprecated version, but requires API 24
-                    true
-                } else false
             } else {
                 false
             }
         }
+        // Since I immediately pass the event to onTouchEvent if it's not a move
+        // The ClickableViewAccessibility warning isn't useful
+        itemView.setOnTouchListener { view, motionEvent ->
+            when (motionEvent.actionMasked) {
+                MotionEvent.ACTION_MOVE -> if (holder.selectedItems.contains(item)) {
+                    val parent = itemView.parent as? AbstractBrowserTrayList
+                    if (parent?.context?.settings()?.searchTermTabGroupsAreEnabled == false) {
+                        for (tabSelected in holder.selectedItems) {
+                            // Exit selection mode by deselecting everything
+                            interactor.deselect(tabSelected)
+                        }
+                        val shadow = View.DragShadowBuilder(itemView)
+                        // startDragAndDrop is the non-deprecated version, but requires API 24
+                        @Suppress("DEPRECATION")
+                        itemView.startDrag(null, shadow, item, 0)
+                        view.alpha = DRAG_TRANSPARENCY // Make the dragged tab mostly invisible
+                    }
+                }
+                else -> view.onTouchEvent(motionEvent)
+            }
+            true
+        }
     }
 
     companion object {
+        internal const val DRAG_TRANSPARENCY = 0.2f
         internal const val PLAY_PAUSE_BUTTON_EXTRA_DPS = 24
         internal const val GRID_ITEM_CLOSE_BUTTON_EXTRA_DPS = 24
     }

app/src/main/java/org/mozilla/fenix/tabstray/browser/AbstractBrowserTrayList.kt

@@ -8,6 +8,7 @@ import android.content.Context
 import android.graphics.Rect
 import android.util.AttributeSet
 import android.view.DragEvent
+import android.view.View
 import androidx.recyclerview.widget.RecyclerView
 import mozilla.components.browser.state.state.TabSessionState
 import mozilla.components.browser.tabstray.TabViewHolder
@@ -76,8 +77,6 @@ abstract class AbstractBrowserTrayList @JvmOverloads constructor(
     // Find the closest item to the x/y position of the drop.
     private fun getDropPosition(x: Float, y: Float): String? {
         if (childCount < 2) return null // If there's 0 or 1 tabs visible, can't reorder
-        if (layoutManager == null) return null
-        val lm = layoutManager!!
         var bestDist = Float.MAX_VALUE
         var bestId: String? = null
         for (i in 0 until childCount) {
@@ -85,7 +84,7 @@ abstract class AbstractBrowserTrayList @JvmOverloads constructor(
             val targetHolder = findContainingViewHolder(proposedTarget)
             if (targetHolder is TabViewHolder) {
                 var rect = Rect() // Use layoutManager to get post-animation positioning
-                lm.getDecoratedBoundsWithMargins(proposedTarget, rect)
+                getDecoratedBoundsWithMargins(proposedTarget, rect)
                 val targetX = (rect.left + rect.right) / 2
                 val targetY = (rect.top + rect.bottom) / 2
                 val xDiff = x - targetX
@@ -99,6 +98,16 @@ abstract class AbstractBrowserTrayList @JvmOverloads constructor(
         }
         return bestId
     }
+    private fun findSourceView(id: String): View? {
+        for (i in 0 until childCount) {
+            val proposed = getChildAt(i)
+            val targetHolder = findContainingViewHolder(proposed)
+            if (targetHolder is TabViewHolder && targetHolder.tab?.id == id) {
+                return proposed
+            }
+        }
+        return null
+    }
     private val dragListen = OnDragListener { _, event ->
         when (event.action) {
             DragEvent.ACTION_DRAG_STARTED -> {
@@ -127,6 +136,12 @@ abstract class AbstractBrowserTrayList @JvmOverloads constructor(
                 true
             }
             DragEvent.ACTION_DRAG_ENDED -> {
+                // Revert the invisibility
+                val id = (event.localState as TabSessionState).id
+                val sourceView = findSourceView(id)
+                if (sourceView != null) {
+                    sourceView.alpha = 1.0f
+                }
                 true
             }
             else -> { // Unknown action