Diff update performance improvement (#38)

* Apply performance improvement even when we now hashes can't be used as unique identifiers. This will reduce the number of collisions and the refresh rate will not be perfect but good enough for the implementation we've decided to use without any interface asking for the item id

* Prepare release

* Check if the type is the same before checking the item hash. This will improve performance

* Update documentation and ask also for the object memory reference in order to know if two items are the same

README.md

@@ -201,7 +201,7 @@ If the ``RecyclerView`` performance is crucial in your application remember you
 adapter.diffUpdate(newList)
 ```
 
-This method provides a ready to use diff update for our adapter based on the implementation of the standard ``equals`` method from ``Object`` class.
+This method provides a ready to use diff update for our adapter based on the implementation of the standard ``equals`` and ``hashCode`` methods from ``Object`` class.
 
 Usage
 -----
@@ -214,7 +214,7 @@ Or declare it into your pom.xml
 <dependency>
     <groupId>com.github.pedrovgs</groupId>
     <artifactId>renderers</artifactId>
-    <version>3.3.0</version>
+    <version>3.3.1</version>
     <type>aar</type>
 </dependency>
 ```
@@ -223,7 +223,7 @@ Or declare it into your pom.xml
 Or into your build.gradle
 ```groovy
 dependencies{
-    compile 'com.github.pedrovgs:renderers:3.3.0'
+    compile 'com.github.pedrovgs:renderers:3.3.1'
 }
 ```
 

gradle.properties

@@ -2,7 +2,7 @@ POM_NAME=Renderers
 POM_ARTIFACT_ID=renderers
 POM_PACKAGING=aar
 
-VERSION_NAME=3.3.1-SNAPSHOT
+VERSION_NAME=3.3.1
 VERSION_CODE=030301
 GROUP=com.github.pedrovgs
 

renderers/src/main/java/com/pedrogomez/renderers/DiffCallbacks.java → renderers/src/main/java/com/pedrogomez/renderers/DiffCallback.java

@@ -19,16 +19,12 @@
 
 import java.util.List;
 
-class DiffCallbacks<T> extends DiffUtil.Callback {
+class DiffCallback<T> extends DiffUtil.Callback {
 
   private final AdapteeCollection<T> oldList;
   private final List<T> newList;
 
-  private int oldItemPosition;
-
-  private boolean deep;
-
-  DiffCallbacks(AdapteeCollection<T> oldList, List<T> newList) {
+  DiffCallback(AdapteeCollection<T> oldList, List<T> newList) {
     this.oldList = oldList;
     this.newList = newList;
   }
@@ -42,27 +38,15 @@ class DiffCallbacks<T> extends DiffUtil.Callback {
   }
 
   @Override public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
-    this.deep = false;
-    this.oldItemPosition = oldItemPosition;
-    return equals(newList.get(newItemPosition));
+    T oldItem = oldList.get(oldItemPosition);
+    T newItem = newList.get(newItemPosition);
+    boolean areTheSameInstance = oldItem == newItem;
+    boolean hasTheSameType = oldItem.getClass().equals(newItem);
+    boolean hasTheSameHash = oldItem.hashCode() == newItem.hashCode();
+    return areTheSameInstance && hasTheSameType && hasTheSameHash;
   }
 
   @Override public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
-    this.deep = true;
-    this.oldItemPosition = oldItemPosition;
-    return equals(newList.get(newItemPosition));
-  }
-
-  @Override public boolean equals(Object newItem) {
-    Object current = oldList.get(oldItemPosition);
-    if (deep) {
-      return newItem.equals(current);
-    } else {
-      return newItem.getClass().equals(current.getClass());
-    }
-  }
-
-  @Override public int hashCode() {
-    return super.hashCode();
+    return oldList.get(oldItemPosition).equals(newList.get(newItemPosition));
   }
 }

renderers/src/main/java/com/pedrogomez/renderers/RVRendererAdapter.java

@@ -203,8 +203,8 @@ public void diffUpdate(List<T> newList) {
       addAll(newList);
       notifyDataSetChanged();
     } else {
-      DiffCallbacks diffCallbacks = new DiffCallbacks(collection, newList);
-      DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallbacks);
+      DiffCallback diffCallback = new DiffCallback(collection, newList);
+      DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallback);
       clear();
       addAll(newList);
       diffResult.dispatchUpdatesTo(this);