Fix crash while scrolling during call to updateBricks (#256)

* Fix crash while scrolling during call to updateBricks

BrickKit/bricks/src/androidTest/java/com/wayfair/brickkit/SafeAdapterListUpdateCallbackTest.kt

@@ -0,0 +1,53 @@
+package com.wayfair.brickkit
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Before
+import org.junit.runner.RunWith
+import com.nhaarman.mockitokotlin2.mock
+import com.nhaarman.mockitokotlin2.verify
+import org.junit.Test
+
+@RunWith(AndroidJUnit4::class)
+class SafeAdapterListUpdateCallbackTest {
+
+    private val brickRecyclerAdapter: BrickRecyclerAdapter = mock()
+    private lateinit var adapter: SafeAdapterListUpdateCallback
+
+    @Before
+    fun setup() {
+        adapter = SafeAdapterListUpdateCallback(brickRecyclerAdapter)
+    }
+
+    @Test
+    fun testOnInserted() {
+        val position = 3
+        val count = 1
+        adapter.onInserted(position, count)
+        verify(brickRecyclerAdapter).safeNotifyItemRangeInserted(position, count)
+    }
+
+    @Test
+    fun testOnRemoved() {
+        val position = 4
+        val count = 1
+        adapter.onRemoved(position, count)
+        verify(brickRecyclerAdapter).safeNotifyItemRangeRemoved(position, count)
+    }
+
+    @Test
+    fun testOnMoved() {
+        val position = 5
+        val count = 9
+        adapter.onMoved(position, count)
+        verify(brickRecyclerAdapter).safeNotifyItemMoved(position, count)
+    }
+
+    @Test
+    fun testOnChanged() {
+        val position = 2
+        val count = 6
+        val any: Any = mock()
+        adapter.onChanged(position, count, any)
+        verify(brickRecyclerAdapter).safeNotifyItemRangeChanged(position, count, any)
+    }
+}

BrickKit/bricks/src/main/java/com/wayfair/brickkit/BrickDataManager.kt

@@ -122,7 +122,11 @@ open class BrickDataManager : Serializable {
         currentItems.addAll(bricks)
 
         dataHasChanged()
-        brickRecyclerAdapter?.let { DiffUtil.calculateDiff(diffUtilCallback).dispatchUpdatesTo(it) }
+        brickRecyclerAdapter?.let {
+            DiffUtil.calculateDiff(diffUtilCallback).dispatchUpdatesTo(
+                SafeAdapterListUpdateCallback(it)
+            )
+        }
     }
 
     /**

BrickKit/bricks/src/main/java/com/wayfair/brickkit/SafeAdapterListUpdateCallback.kt

@@ -0,0 +1,29 @@
+package com.wayfair.brickkit
+
+import androidx.recyclerview.widget.ListUpdateCallback
+
+/**
+ * A safe implementation of [androidx.recyclerview.widget.ListUpdateCallback],
+ * which allows updates to the adapter during scrolling by mapping the calls
+ * to safe versions.
+ */
+internal class SafeAdapterListUpdateCallback(
+    private val adapter: BrickRecyclerAdapter
+) : ListUpdateCallback {
+
+    override fun onInserted(position: Int, count: Int) {
+        adapter.safeNotifyItemRangeInserted(position, count)
+    }
+
+    override fun onRemoved(position: Int, count: Int) {
+        adapter.safeNotifyItemRangeRemoved(position, count)
+    }
+
+    override fun onMoved(fromPosition: Int, toPosition: Int) {
+        adapter.safeNotifyItemMoved(fromPosition, toPosition)
+    }
+
+    override fun onChanged(position: Int, count: Int, payload: Any?) {
+        adapter.safeNotifyItemRangeChanged(position, count, payload)
+    }
+}