Properly add and remove views based on the notify call instead of just recreating everything every time.

Author: Jawnnypoo

adapterlayout/src/main/java/com/commit451/adapterlayout/AdapterLayoutDelegate.java

@@ -16,19 +16,20 @@ public class AdapterLayoutDelegate {
     private ViewGroup mViewGroup;
 
     /**
-     * Checks for if the data changes
+     * Checks for if the data changes and changes the views accordingly 
      */
     private RecyclerView.AdapterDataObserver mObserver = new RecyclerView.AdapterDataObserver() {
         @Override
         public void onChanged() {
             super.onChanged();
+            //too general, we just have to completely recreate
             recreateViews();
         }
 
         @Override
         public void onItemRangeChanged(int positionStart, int itemCount) {
             super.onItemRangeChanged(positionStart, itemCount);
-            recreateViews();
+            updateViews(positionStart, itemCount, null);
         }
 
         @Override
@@ -40,13 +41,13 @@ public void onItemRangeChanged(int positionStart, int itemCount, Object payload)
         @Override
         public void onItemRangeInserted(int positionStart, int itemCount) {
             super.onItemRangeInserted(positionStart, itemCount);
-            recreateViews();
+            addViews(positionStart, itemCount);
         }
 
         @Override
         public void onItemRangeRemoved(int positionStart, int itemCount) {
             super.onItemRangeRemoved(positionStart, itemCount);
-            recreateViews();
+            removeViews(positionStart, itemCount);
         }
 
         @Override
@@ -83,6 +84,10 @@ public void setAdapter(RecyclerView.Adapter adapter) {
         recreateViews();
     }
 
+    /**
+     * Returns the adapter which was passed via {@link #setAdapter(RecyclerView.Adapter)}
+     * @return the adapter
+     */
     public @Nullable RecyclerView.Adapter getAdapter() {
         return mAdapter;
     }
@@ -101,7 +106,8 @@ public void setAdapter(RecyclerView.Adapter adapter) {
     }
 
     private void addViews(int positionStart, int itemCount) {
-        for (int i=positionStart; i<itemCount; i++) {
+        final int end = positionStart + itemCount;
+        for (int i=positionStart; i<end; i++) {
             addViewAt(i);
         }
     }
@@ -120,7 +126,8 @@ private void addViewAt(int viewType, int index) {
 
     private void updateViews(int positionStart, int itemCount, Object payload) {
         //TODO do something with the payload?
-        for (int i=positionStart; i<itemCount; i++) {
+        final int end = positionStart + itemCount;
+        for (int i=positionStart; i<end; i++) {
             RecyclerView.ViewHolder viewHolder = getViewHolderAt(i);
             if (payload != null) {
                 mAdapter.onBindViewHolder(viewHolder, i);

app/src/main/java/com/commit451/adapterlayout/sample/CheeseAdapter.java

@@ -55,6 +55,23 @@ public void changeMiddle() {
         }
     }
 
+    public void changeAll() {
+        if (!mValues.isEmpty()) {
+            for (Cheese cheese : mValues) {
+                cheese.setName("Swiss");
+            }
+            notifyItemRangeChanged(0, mValues.size());
+        }
+    }
+
+    public void clear() {
+        if (!mValues.isEmpty()) {
+            int size = mValues.size();
+            mValues.clear();
+            notifyItemRangeRemoved(0, size);
+        }
+    }
+
     @Override
     public CheeseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         CheeseViewHolder holder = CheeseViewHolder.inflate(parent);

app/src/main/java/com/commit451/adapterlayout/sample/CustomAdapterLayoutActivity.java

@@ -28,11 +28,6 @@ void onRemoveCheeseClicked() {
         mAdapter.removeLast();
     }
 
-    @OnClick(R.id.change_middle)
-    void onRemoveMiddleClicked() {
-        mAdapter.changeMiddle();
-    }
-
     @OnClick(R.id.new_adapter)
     void onNewAdapterClicked() {
         mAdapterLayout.setAdapter(null);

app/src/main/java/com/commit451/adapterlayout/sample/MainActivity.java

@@ -39,6 +39,16 @@ void onRemoveMiddleClicked() {
         mAdapter.changeMiddle();
     }
 
+    @OnClick(R.id.clear_all)
+    void onClearAll() {
+        mAdapter.clear();
+    }
+
+    @OnClick(R.id.change_all)
+    void onChangeAll() {
+        mAdapter.changeAll();
+    }
+
     @OnClick(R.id.new_adapter)
     void onNewAdapterClicked() {
         mAdapterLinearLayout.setAdapter(null);

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

@@ -48,6 +48,18 @@
                     android:layout_height="wrap_content"
                     android:text="Change Middle" />
 
+                <Button
+                    android:id="@+id/clear_all"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Clear All" />
+
+                <Button
+                    android:id="@+id/change_all"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Change All" />
+
                 <Button
                     android:id="@+id/new_adapter"
                     android:layout_width="wrap_content"