fixed erratic behavior when performing diffing against new list. Rele…

…ased 2.1.5. Improved demo app with shuffle addition.

README.md

@@ -33,7 +33,7 @@ In this way every item of the recycler view has its own set of files, resulting
 ## <a name="setup"></a>Setup
 In your gradle dependencies add:
 ```groovy
-implementation 'net.gotev:recycleradapter:2.1.1'
+implementation 'net.gotev:recycleradapter:2.1.5'
 ```
 
 ## <a name="basicTutorial"></a>Basic usage tutorial

app/demo/src/main/java/net/gotev/recycleradapterdemo/SyncActivity.kt

@@ -8,9 +8,14 @@ import androidx.appcompat.app.AppCompatActivity
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import kotlinx.android.synthetic.main.activity_sync.*
+import net.gotev.recycleradapter.AdapterItem
 import net.gotev.recycleradapter.RecyclerAdapter
 import net.gotev.recycleradapterdemo.adapteritems.LabelItem
 import net.gotev.recycleradapterdemo.adapteritems.SyncItem
+import java.util.concurrent.ScheduledFuture
+import java.util.concurrent.ScheduledThreadPoolExecutor
+import java.util.concurrent.TimeUnit
+import kotlin.random.Random
 
 
 class SyncActivity : AppCompatActivity() {
@@ -22,26 +27,26 @@ class SyncActivity : AppCompatActivity() {
     }
 
     private lateinit var recyclerAdapter: RecyclerAdapter
+    private var executor = ScheduledThreadPoolExecutor(1)
+    private var scheduledOperation: ScheduledFuture<*>? = null
+
+    private var listB = arrayListOf(
+            SyncItem(this, 1, "listB"),
+            SyncItem(this, 3, "listB"),
+            SyncItem(this, 4, "listB"),
+            SyncItem(this, 5, "listB")
+    )
+
+    private fun listB(): ArrayList<SyncItem> {
+        listB.add(SyncItem(this, listB.last().id + 1, "listB${listB.last().id + 1}"))
+        listB.add(SyncItem(this, listB.last().id + 1, "listB${listB.last().id + 1}"))
+        return listB
+    }
 
     private fun listA() =
             arrayListOf(
-                    SyncItem(this, 2, "listA"),
-                    SyncItem(this, 3, "listA"),
-                    SyncItem(this, 6, "listA")
-            )
-
-    private fun listB() =
-            arrayListOf(
-                    SyncItem(this, 1, "listB"),
-                    SyncItem(this, 2, "listB"),
-                    SyncItem(this, 3, "listB"),
-                    SyncItem(this, 4, "listB"),
-                    SyncItem(this, 5, "listB")
-            )
-
-    private fun listC() =
-            arrayListOf(
-                    SyncItem(this, 3, "listC")
+                    SyncItem(this, 1, "listA"),
+                    SyncItem(this, 2, "listA")
             )
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -55,11 +60,23 @@ class SyncActivity : AppCompatActivity() {
             setDisplayHomeAsUpEnabled(true)
         }
 
+        val linearLayoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL, false)
+
         recyclerAdapter = RecyclerAdapter()
         recyclerAdapter.setEmptyItem(LabelItem(getString(R.string.empty_list)))
 
+        // prevent recyclerview from scrolling when adding many items
+        // https://github.com/airbnb/epoxy/issues/224#issuecomment-305991898
+        recyclerAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
+            override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+                if (positionStart == 0) {
+                    linearLayoutManager.scrollToPosition(0)
+                }
+            }
+        })
+
         recycler_view.apply {
-            layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)
+            layoutManager = linearLayoutManager
             adapter = recyclerAdapter
         }
 
@@ -71,10 +88,30 @@ class SyncActivity : AppCompatActivity() {
             recyclerAdapter.syncWithItems(listB())
         }
 
-        syncC.setOnClickListener {
-            recyclerAdapter.syncWithItems(listC())
+        shuffle.setOnClickListener {
+            scheduledOperation = if (scheduledOperation == null) {
+                executor.scheduleAtFixedRate({
+                    runOnUiThread {
+                        recyclerAdapter.syncWithItems(ArrayList(createItems()))
+                    }
+                }, 1, 100, TimeUnit.MILLISECONDS)
+            } else {
+                scheduledOperation?.cancel(true)
+                null
+            }
         }
+    }
 
+    override fun onPause() {
+        super.onPause()
+        scheduledOperation?.cancel(true)
+        scheduledOperation = null
+    }
+
+    fun createItems(): List<AdapterItem<*>> {
+        return (0..Random.nextInt(1, 10)).flatMap {
+            listOf(LabelItem("$it"), SyncItem(this, it, "ListC"))
+        }
     }
 
     override fun onCreateOptionsMenu(menu: Menu): Boolean {

app/demo/src/main/java/net/gotev/recycleradapterdemo/adapteritems/SyncItem.kt

@@ -4,7 +4,7 @@ import android.content.Context
 
 import net.gotev.recycleradapter.AdapterItem
 
-class SyncItem(context: Context, private val id: Int, private val suffix: String) : ExampleItem(context, "item $id $suffix") {
+class SyncItem(context: Context, val id: Int, private val suffix: String) : ExampleItem(context, "item $id $suffix") {
 
     override fun equals(other: Any?): Boolean {
         if (other == null || javaClass != other.javaClass) {
@@ -15,9 +15,7 @@ class SyncItem(context: Context, private val id: Int, private val suffix: String
     }
 
     override fun hashCode(): Int {
-        var result = id
-        result = 31 * result + suffix.hashCode()
-        return result
+        return id.hashCode()
     }
 
     override fun compareTo(other: AdapterItem<*>): Int {

app/demo/src/main/res/layout/activity_sync.xml

@@ -35,13 +35,13 @@
         android:layout_alignParentLeft="true"
         android:layout_alignParentStart="true"
         android:layout_alignParentTop="true"
-        android:layout_above="@+id/syncC" />
+        android:layout_above="@+id/shuffle" />
 
     <Button
-        android:text="Sync C"
+        android:text="Shuffle"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:id="@+id/syncC"
+        android:id="@+id/shuffle"
         android:layout_alignParentBottom="true"
         android:layout_alignParentRight="true"
         android:layout_alignParentEnd="true" />

manifest.gradle

@@ -9,7 +9,7 @@ ext {
     library_licenses = ["Apache-2.0"]
     library_licenses_url = 'http://www.apache.org/licenses/LICENSE-2.0.txt'
     library_project_group = 'net.gotev'
-    library_version = '2.1.1'
+    library_version = '2.1.5'
     version_code = 5
     min_sdk = 18
     target_sdk = 28

recycleradapter/src/main/java/net/gotev/recycleradapter/RecyclerAdapter.kt

@@ -241,8 +241,22 @@ class RecyclerAdapter : RecyclerView.Adapter<RecyclerAdapterViewHolder>(), Recyc
      */
     fun add(item: AdapterItem<*>, position: Int? = null): RecyclerAdapter {
         val insertPosition = if (position != null) {
-            items.add(position, item.castAsIn())
-            position
+            when {
+                position >= items.size -> {
+                    items.add(item.castAsIn())
+                    items.lastIndex
+                }
+
+                position < 0 -> {
+                    items.add(0, item.castAsIn())
+                    0
+                }
+
+                else -> {
+                    items.add(position, item.castAsIn())
+                    position
+                }
+            }
         } else {
             items.add(item.castAsIn())
             items.lastIndex
@@ -364,6 +378,8 @@ class RecyclerAdapter : RecyclerView.Adapter<RecyclerAdapterViewHolder>(), Recyc
             return this
         }
 
+        items.ensureCapacity(newItems.size)
+
         newItems.forEachIndexed { newItemsIndex, newItem ->
             val internalItemIndex = items.indexOf(newItem)
 
@@ -373,13 +389,12 @@ class RecyclerAdapter : RecyclerView.Adapter<RecyclerAdapterViewHolder>(), Recyc
                 val internalItem = items[internalItemIndex]
 
                 if (internalItem.hasToBeReplacedBy(newItem)) {
-                    removeItem(internalItem)
+                    removeItemAtPosition(internalItemIndex)
                     add(newItem, newItemsIndex)
                 } else {
                     if (internalItemIndex != newItemsIndex) {
-                        items.removeAt(internalItemIndex)
-                        items.add(newItemsIndex, internalItem)
-                        notifyItemMoved(internalItemIndex, newItemsIndex)
+                        removeItemAtPosition(internalItemIndex)
+                        add(internalItem, newItemsIndex)
                     }
                 }
             }