[fenix] For https://github.com/mozilla-mobile/fenix/issues/12856: Add save to collections button to Tabs Tray

Using the ConcatAdapter, we're now able to insert multiple data sources
of information into one RecyclerView and preserve layout/scrolling in
addition to adding the 'Save to Collection' button.

app/src/main/java/org/mozilla/fenix/migration/MigrationStatusAdapter.kt

@@ -96,7 +96,7 @@ internal class MigrationStatusItemDecoration(
         parent: RecyclerView,
         state: RecyclerView.State
     ) {
-        val position = parent.getChildViewHolder(view).adapterPosition
+        val position = parent.getChildViewHolder(view).bindingAdapterPosition
         val itemCount = state.itemCount
 
         outRect.left = spacing

app/src/main/java/org/mozilla/fenix/tabtray/SaveToCollectionsButtonAdapter.kt

@@ -0,0 +1,67 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.tabtray
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import org.mozilla.fenix.R
+import org.mozilla.fenix.tabtray.SaveToCollectionsButtonAdapter.Item
+import org.mozilla.fenix.tabtray.SaveToCollectionsButtonAdapter.ViewHolder
+
+/**
+ * An adapter to display a single 'Save to Collections' button that can be used to display between
+ * multiple [RecyclerView.Adapter] in one [RecyclerView].
+ */
+class SaveToCollectionsButtonAdapter(
+    private val interactor: TabTrayInteractor
+) : ListAdapter<Item, ViewHolder>(DiffCallback) {
+
+    init {
+        submitList(listOf(Item))
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        val itemView = LayoutInflater.from(parent.context).inflate(viewType, parent, false)
+        return ViewHolder(itemView, interactor)
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) = Unit
+
+    override fun getItemViewType(position: Int): Int {
+        return ViewHolder.LAYOUT_ID
+    }
+
+    private object DiffCallback : DiffUtil.ItemCallback<Item>() {
+        override fun areItemsTheSame(oldItem: Item, newItem: Item) = true
+
+        override fun areContentsTheSame(oldItem: Item, newItem: Item) = true
+    }
+
+    /**
+     * An object to identify the data type.
+     */
+    object Item
+
+    class ViewHolder(
+        itemView: View,
+        private val interactor: TabTrayInteractor
+    ) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
+        init {
+            itemView.setOnClickListener(this)
+        }
+
+        override fun onClick(v: View?) {
+            interactor.onEnterMultiselect()
+        }
+
+        companion object {
+            const val LAYOUT_ID = R.layout.tabs_tray_save_to_collections_item
+        }
+    }
+}

app/src/main/java/org/mozilla/fenix/tabtray/TabTrayView.kt

@@ -17,6 +17,7 @@ import androidx.core.content.ContextCompat
 import androidx.core.view.isVisible
 import androidx.core.view.updateLayoutParams
 import androidx.lifecycle.LifecycleCoroutineScope
+import androidx.recyclerview.widget.ConcatAdapter
 import androidx.recyclerview.widget.LinearLayoutManager
 import com.google.android.material.bottomsheet.BottomSheetBehavior
 import com.google.android.material.tabs.TabLayout
@@ -34,6 +35,7 @@ import mozilla.components.browser.state.selector.getNormalOrPrivateTabs
 import mozilla.components.browser.state.selector.normalTabs
 import mozilla.components.browser.state.selector.privateTabs
 import mozilla.components.browser.state.state.BrowserState
+import mozilla.components.browser.tabstray.TabViewHolder
 import mozilla.components.support.ktx.android.util.dpToPx
 import org.mozilla.fenix.R
 import org.mozilla.fenix.components.metrics.Event
@@ -69,6 +71,7 @@ class TabTrayView(
     private var menu: BrowserMenu? = null
 
     private var tabsTouchHelper: TabsTouchHelper
+    private val collectionsButtonAdapter = SaveToCollectionsButtonAdapter(interactor)
 
     private var hasLoaded = false
 
@@ -131,9 +134,13 @@ class TabTrayView(
                 reverseLayout = true
                 stackFromEnd = true
             }
-            adapter = tabsAdapter
+            adapter = ConcatAdapter(collectionsButtonAdapter, tabsAdapter)
+
+            tabsTouchHelper = TabsTouchHelper(
+                observable = tabsAdapter,
+                onViewHolderTouched = { it is TabViewHolder }
+            )
 
-            tabsTouchHelper = TabsTouchHelper(tabsAdapter)
             tabsTouchHelper.attachToRecyclerView(this)
 
             tabsAdapter.tabTrayInteractor = interactor
@@ -468,7 +475,11 @@ class TabTrayView(
             val selectedBrowserTabIndex = tabs
                 .indexOfFirst { it.id == sessionId }
 
-            layoutManager?.scrollToPosition(selectedBrowserTabIndex)
+            // We offset the tab index by the number of items in the other adapters.
+            // We add the offset, because the layoutManager is initialized with `reverseLayout`.
+            val recyclerViewIndex = selectedBrowserTabIndex + collectionsButtonAdapter.itemCount
+
+            layoutManager?.scrollToPosition(recyclerViewIndex)
         }
     }
 

app/src/main/java/org/mozilla/fenix/tabtray/TabsTouchHelper.kt

@@ -8,6 +8,7 @@ import android.graphics.Canvas
 import android.graphics.drawable.Drawable
 import androidx.appcompat.content.res.AppCompatResources
 import androidx.recyclerview.widget.ItemTouchHelper
+import androidx.recyclerview.widget.ItemTouchHelper.ACTION_STATE_IDLE
 import androidx.recyclerview.widget.RecyclerView
 import mozilla.components.browser.tabstray.TabTouchCallback
 import mozilla.components.concept.tabstray.TabsTray
@@ -18,8 +19,44 @@ import mozilla.components.support.ktx.android.util.dpToPx
 import org.mozilla.fenix.R
 import org.mozilla.fenix.home.sessioncontrol.SwipeToDeleteCallback
 
-class TabsTouchHelper(observable: Observable<TabsTray.Observer>) :
+/**
-    ItemTouchHelper(object : TabTouchCallback(observable) {
+ * A callback for consumers to know when a [RecyclerView.ViewHolder] is about to be touched.
+ * Return false if the default behaviour should be ignored.
+ */
+typealias OnViewHolderTouched = (RecyclerView.ViewHolder) -> Boolean
+
+/**
+ * An [ItemTouchHelper] for handling tab swiping to delete.
+ *
+ * @param onViewHolderTouched See [OnViewHolderTouched].
+ */
+class TabsTouchHelper(
+    observable: Observable<TabsTray.Observer>,
+    onViewHolderTouched: OnViewHolderTouched = { true },
+    delegate: Callback = TouchCallback(observable, onViewHolderTouched)
+) : ItemTouchHelper(delegate)
+
+/**
+ * An [ItemTouchHelper.Callback] for drawing custom layouts on [RecyclerView.ViewHolder] interactions.
+ *
+ * @param onViewHolderTouched invoked when a tab is about to be swiped. See [OnViewHolderTouched].
+ */
+class TouchCallback(
+    observable: Observable<TabsTray.Observer>,
+    private val onViewHolderTouched: OnViewHolderTouched
+) : TabTouchCallback(observable) {
+
+    override fun getMovementFlags(
+        recyclerView: RecyclerView,
+        viewHolder: RecyclerView.ViewHolder
+    ): Int {
+        if (!onViewHolderTouched.invoke(viewHolder)) {
+            return ItemTouchHelper.Callback.makeFlag(ACTION_STATE_IDLE, 0)
+        }
+
+        return super.getMovementFlags(recyclerView, viewHolder)
+    }
+
     override fun onChildDraw(
         c: Canvas,
         recyclerView: RecyclerView,
@@ -30,6 +67,7 @@ class TabsTouchHelper(observable: Observable<TabsTray.Observer>) :
         isCurrentlyActive: Boolean
     ) {
         super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
+
         val icon = recyclerView.context.getDrawableWithTint(
             R.drawable.ic_delete,
             recyclerView.context.getColorFromAttr(R.attr.destructive)
@@ -86,4 +124,4 @@ class TabsTouchHelper(observable: Observable<TabsTray.Observer>) :
         background.draw(c)
         icon.draw(c)
     }
-    })
+}

app/src/main/res/layout/tabs_tray_save_to_collections_item.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<com.google.android.material.button.MaterialButton
+        xmlns:android="http://schemas.android.com/apk/res/android"
+        xmlns:app="http://schemas.android.com/apk/res-auto"
+        style="@style/NeutralButton"
+        android:layout_margin="8dp"
+        android:text="@string/save_to_collection"
+        app:icon="@drawable/ic_tab_collection" />

app/src/test/java/org/mozilla/fenix/tabtray/SaveToCollectionsButtonAdapterTest.kt

@@ -0,0 +1,53 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.tabtray
+
+import android.widget.FrameLayout
+import io.mockk.mockk
+import io.mockk.verify
+import mozilla.components.support.test.robolectric.testContext
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mozilla.fenix.helpers.FenixRobolectricTestRunner
+import org.mozilla.fenix.tabtray.SaveToCollectionsButtonAdapter.Item
+import org.mozilla.fenix.tabtray.SaveToCollectionsButtonAdapter.ViewHolder
+import kotlin.random.Random
+
+@RunWith(FenixRobolectricTestRunner::class)
+class SaveToCollectionsButtonAdapterTest {
+
+    private lateinit var adapter: SaveToCollectionsButtonAdapter
+    private lateinit var interactor: TabTrayInteractor
+
+    @Before
+    fun setup() {
+        interactor = mockk(relaxed = true)
+        adapter = SaveToCollectionsButtonAdapter(interactor)
+    }
+
+    @Test
+    fun `create adapter only has one item in it`() {
+        assertEquals(1, adapter.itemCount)
+        assertTrue(adapter.currentList.first() is Item)
+    }
+
+    @Test
+    fun `viewholder click invokes interactor`() {
+        val itemView = FrameLayout(testContext)
+        val viewHolder = ViewHolder(itemView, interactor)
+
+        viewHolder.onClick(itemView)
+
+        verify { interactor.onEnterMultiselect() }
+    }
+
+    @Test
+    fun `always use the same layout`() {
+        assertEquals(ViewHolder.LAYOUT_ID, adapter.getItemViewType(Random.nextInt()))
+    }
+}

app/src/test/java/org/mozilla/fenix/tabtray/TabsTouchHelperTest.kt

@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.tabtray
+
+import android.widget.FrameLayout
+import androidx.recyclerview.widget.ItemTouchHelper
+import androidx.recyclerview.widget.ItemTouchHelper.ACTION_STATE_IDLE
+import androidx.recyclerview.widget.ItemTouchHelper.Callback.makeMovementFlags
+import androidx.recyclerview.widget.RecyclerView
+import io.mockk.mockk
+import mozilla.components.support.test.robolectric.testContext
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mozilla.fenix.helpers.FenixRobolectricTestRunner
+
+@RunWith(FenixRobolectricTestRunner::class)
+class TabsTouchHelperTest {
+
+    @Test
+    fun `movement flags remain unchanged if onSwipeToDelete is true`() {
+        val recyclerView = RecyclerView(testContext)
+        val layout = FrameLayout(testContext)
+        val interactor: TabTrayInteractor = mockk(relaxed = true)
+        val viewHolder = SaveToCollectionsButtonAdapter.ViewHolder(layout, interactor)
+        val callback = TouchCallback(mockk()) { true }
+
+        assertEquals(0, callback.getDragDirs(recyclerView, viewHolder))
+        assertEquals(ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT, callback.getSwipeDirs(recyclerView, viewHolder))
+
+        val actual = callback.getMovementFlags(recyclerView, viewHolder)
+        val expected = makeMovementFlags(0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT)
+
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun `movement flags remain unchanged if onSwipeToDelete is false`() {
+        val recyclerView = RecyclerView(testContext)
+        val layout = FrameLayout(testContext)
+        val interactor: TabTrayInteractor = mockk(relaxed = true)
+        val viewHolder = SaveToCollectionsButtonAdapter.ViewHolder(layout, interactor)
+        val callback = TouchCallback(mockk()) { false }
+
+        assertEquals(0, callback.getDragDirs(recyclerView, viewHolder))
+        assertEquals(ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT, callback.getSwipeDirs(recyclerView, viewHolder))
+
+        val actual = callback.getMovementFlags(recyclerView, viewHolder)
+        val expected = ItemTouchHelper.Callback.makeFlag(ACTION_STATE_IDLE, 0)
+
+        assertEquals(expected, actual)
+    }
+}

buildSrc/src/main/java/Dependencies.kt

@@ -23,7 +23,7 @@ object Versions {
     const val androidx_lifecycle = "2.2.0"
     const val androidx_fragment = "1.2.5"
     const val androidx_navigation = "2.3.0"
-    const val androidx_recyclerview = "1.1.0"
+    const val androidx_recyclerview = "1.2.0-alpha05"
     const val androidx_core = "1.2.0"
     const val androidx_paging = "2.1.0"
     const val androidx_transition = "1.3.0"