From 2de36ba0fdb2223dcb51900efd41da952b5cd1cf Mon Sep 17 00:00:00 2001
From: Eli Hart <konakid@gmail.com>
Date: Mon, 21 Jan 2019 22:30:28 -0600
Subject: [PATCH] Enable recycling of views within groups (#657)

* Enable recycling of views within groups

* cleanup

* revert to kotlin 1.2.71

* fix test
---
 .idea/codeStyles/Project.xml                  |   5 +-
 build.gradle                                  |   4 +-
 .../com/airbnb/epoxy/ActivityRecyclerPool.kt  | 106 +++++++
 .../com/airbnb/epoxy/BaseEpoxyAdapter.java    |   2 +-
 .../com/airbnb/epoxy/EpoxyModelGroup.java     | 288 +++---------------
 .../com/airbnb/epoxy/EpoxyRecyclerView.java   | 137 +--------
 .../java/com/airbnb/epoxy/ModelGroupHolder.kt | 250 +++++++++++++++
 .../com/airbnb/epoxy/UnboundedViewPool.kt     |  47 +++
 .../com/airbnb/epoxy/ViewTypeManager.java     |  10 +-
 .../com/airbnb/epoxy/EpoxyModelGroupTest.kt   | 174 +++++++++++
 .../ModelGroupWithAnnotation.java             |   3 +-
 .../EpoxyModelGroupWithAnnotations_.java      |  38 ++-
 12 files changed, 655 insertions(+), 409 deletions(-)
 create mode 100644 epoxy-adapter/src/main/java/com/airbnb/epoxy/ActivityRecyclerPool.kt
 create mode 100644 epoxy-adapter/src/main/java/com/airbnb/epoxy/ModelGroupHolder.kt
 create mode 100644 epoxy-adapter/src/main/java/com/airbnb/epoxy/UnboundedViewPool.kt
 create mode 100644 epoxy-adapter/src/test/java/com/airbnb/epoxy/EpoxyModelGroupTest.kt

diff --git a/.idea/codeStyles/Project.xml b/.idea/codeStyles/Project.xml
index 6adb8c42c1..3104a751ca 100644
--- a/.idea/codeStyles/Project.xml
+++ b/.idea/codeStyles/Project.xml
@@ -48,6 +48,9 @@
       <option name="JD_KEEP_EMPTY_RETURN" value="false" />
     </JavaCodeStyleSettings>
     <JetCodeStyleSettings>
+      <option name="PACKAGES_TO_USE_STAR_IMPORTS">
+        <value />
+      </option>
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT" value="2147483647" />
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT_FOR_MEMBERS" value="2147483647" />
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
@@ -296,4 +299,4 @@
       </indentOptions>
     </codeStyleSettings>
   </code_scheme>
-</component>
+</component>
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 129e2246f3..d25a5e7a03 100755
--- a/build.gradle
+++ b/build.gradle
@@ -9,7 +9,7 @@ buildscript {
     jcenter()
   }
   dependencies {
-    classpath "com.android.tools.build:gradle:3.2.1"
+    classpath "com.android.tools.build:gradle:$ANDROID_PLUGIN_VERSION"
     classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$KOTLIN_VERSION"
     classpath 'com.bmuschko:gradle-nexus-plugin:2.3.1'
   }
@@ -83,6 +83,6 @@ def getRepositoryPassword() {
 }
 
 task wrapper(type: Wrapper) {
-  gradleVersion = '4.9'
+  gradleVersion = '4.10.2'
   distributionUrl = "https://services.gradle.org/distributions/gradle-$gradleVersion-all.zip"
 }
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/ActivityRecyclerPool.kt b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ActivityRecyclerPool.kt
new file mode 100644
index 0000000000..5c4152d6d8
--- /dev/null
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ActivityRecyclerPool.kt
@@ -0,0 +1,106 @@
+package com.airbnb.epoxy
+
+import android.app.Activity
+import android.content.Context
+import android.os.Build
+import androidx.core.view.ViewCompat
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleObserver
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.OnLifecycleEvent
+import androidx.recyclerview.widget.RecyclerView
+import java.lang.ref.WeakReference
+import java.util.ArrayList
+
+internal class ActivityRecyclerPool {
+
+    /**
+     * Store one unique pool per activity. They are cleared out when activities are destroyed, so this
+     * only needs to hold pools for active activities.
+     */
+    private val pools = ArrayList<PoolReference>(5)
+
+    @JvmOverloads
+    fun getPool(
+        context: Context,
+        poolFactory: () -> RecyclerView.RecycledViewPool = { UnboundedViewPool() }
+    ): PoolReference {
+
+        val iterator = pools.iterator()
+        var poolToUse: PoolReference? = null
+
+        while (iterator.hasNext()) {
+            val poolReference = iterator.next()
+            when {
+                poolReference.context === context -> {
+                    if (poolToUse != null) {
+                        throw IllegalStateException("A pool was already found")
+                    }
+                    poolToUse = poolReference
+                    // finish iterating to remove any old contexts
+                }
+                poolReference.context.isActivityDestroyed() -> {
+                    // A pool from a different activity that was destroyed.
+                    // Clear the pool references to allow the activity to be GC'd
+                    poolReference.viewPool.clear()
+                    iterator.remove()
+                }
+            }
+        }
+
+        if (poolToUse == null) {
+            poolToUse = PoolReference(context, poolFactory(), this)
+            (context as? LifecycleOwner)?.lifecycle?.addObserver(poolToUse)
+            pools.add(poolToUse)
+        }
+
+        return poolToUse
+    }
+
+    fun clearIfDestroyed(pool: PoolReference) {
+        if (pool.context.isActivityDestroyed()) {
+            pool.viewPool.clear()
+            pools.remove(pool)
+        }
+    }
+}
+
+internal class PoolReference(
+    context: Context,
+    val viewPool: RecyclerView.RecycledViewPool,
+    private val parent: ActivityRecyclerPool
+) : LifecycleObserver {
+    private val contextReference: WeakReference<Context> = WeakReference(context)
+
+    val context: Context? get() = contextReference.get()
+
+    fun clearIfDestroyed() {
+        parent.clearIfDestroyed(this)
+    }
+
+    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
+    fun onContextDestroyed() {
+        clearIfDestroyed()
+    }
+}
+
+internal fun Context?.isActivityDestroyed(): Boolean {
+    if (this == null) {
+        return true
+    }
+
+    if (this !is Activity) {
+        return false
+    }
+
+    if (isFinishing) {
+        return true
+    }
+
+    return if (Build.VERSION.SDK_INT >= 17) {
+        isDestroyed
+    } else {
+        // Use this as a proxy for being destroyed on older devices
+        !ViewCompat.isAttachedToWindow(window.decorView)
+    }
+}
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/BaseEpoxyAdapter.java b/epoxy-adapter/src/main/java/com/airbnb/epoxy/BaseEpoxyAdapter.java
index b5ec803ec3..fd0ebaada7 100644
--- a/epoxy-adapter/src/main/java/com/airbnb/epoxy/BaseEpoxyAdapter.java
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/BaseEpoxyAdapter.java
@@ -149,7 +149,7 @@ protected BoundViewHolders getBoundViewHolders() {
 
   @Override
   public int getItemViewType(int position) {
-    return viewTypeManager.getViewType(getModelForPosition(position));
+    return viewTypeManager.getViewTypeAndRememberModel(getModelForPosition(position));
   }
 
   @Override
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModelGroup.java b/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModelGroup.java
index c360b42ad6..53325c14ab 100644
--- a/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModelGroup.java
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModelGroup.java
@@ -1,16 +1,12 @@
 package com.airbnb.epoxy;
 
 import android.view.View;
-import android.view.ViewGroup;
-import android.view.ViewGroup.LayoutParams;
 import android.view.ViewStub;
 
-import com.airbnb.epoxy.EpoxyModelGroup.Holder;
-import com.airbnb.viewmodeladapter.R;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import androidx.annotation.CallSuper;
@@ -35,7 +31,7 @@
  * viewgroups, such as a LinearLayout inside of a CardView.
  * <p>
  * 2. Include a {@link ViewStub} for each of the models in the list. There should be at least as
- * many view stubs as models. Extra stubs will be ignored. Each model will be inflated into a view
+ * many view stubs as models. Extra stubs will be ignored. Each model will have its view replace the
  * stub in order of the view stub's position in the view group. That is, the view group's children
  * will be iterated through in order. The first view stub found will be used for the first model in
  * the models list, the second view stub will be used for the second model, and so on. A depth first
@@ -48,12 +44,6 @@
  * view by default. If you want a model to keep the layout params from it's own layout resource you
  * can override {@link #useViewStubLayoutParams(EpoxyModel, int)}
  * <p>
- * If an {@link EpoxyModelWithView} is used then the view created by that model will simply replace
- * its ViewStub instead of inflating the view stub with a resource. If layout params are set on the
- * view created by {@link EpoxyModelWithView#buildView(ViewGroup)} then those will be kept,
- * otherwise any layout params specified on the view stub will be transferred over as with normal
- * models.
- * <p>
  * If you want to override the id used for a model's view you can set {@link
  * ViewStub#setInflatedId(int)} via xml. That id will be transferred over to the view taking that
  * stub's place. This is necessary if you want your model to save view state, since without this the
@@ -62,14 +52,12 @@
  * By default this model inherits the same id as the first model in the list. Call {@link #id(long)}
  * to override that if needed.
  * <p>
- * The same number of models must always be used for a specific layout resource. This is because the
- * view stubs are only inflated once and then the view is recycled between groups with the same
- * layout. If you want to dynamically change what models are shown you can use {@link
- * EpoxyModel#hide()} to have the associated view be set to GONE.
+ * When a model group is recycled, its child views are automatically recycled to a pool that is
+ * shared with all other model groups in the activity. This enables model groups to more efficiently
+ * manage their children. The shared pool is cleaned up when the activity is destroyed.
  */
 @SuppressWarnings("rawtypes")
-public class EpoxyModelGroup extends EpoxyModelWithHolder<Holder>
-    implements GeneratedModel<Holder> {
+public class EpoxyModelGroup extends EpoxyModelWithHolder<ModelGroupHolder> {
 
   protected final List<? extends EpoxyModel<?>> models;
   /** By default we save view state if any of the models need to save state. */
@@ -115,157 +103,103 @@ private EpoxyModelGroup(@LayoutRes int layoutRes, List<? extends EpoxyModel<?>>
     shouldSaveViewState = saveState;
   }
 
-  @Override
-  public void handlePostBind(Holder groupHolder, final int position) {
-    iterateModels(groupHolder, new IterateModelsCallback() {
-      @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        if (model instanceof GeneratedModel) {
-          //noinspection unchecked
-          ((GeneratedModel) model).handlePostBind(boundObject, position);
-        }
-      }
-    });
-  }
-
-  @Override
-  public void handlePreBind(final EpoxyViewHolder holder, Holder groupHolder, final int position) {
-    iterateModels(groupHolder, new IterateModelsCallback() {
-      @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        if (model instanceof GeneratedModel) {
-          //noinspection unchecked
-          ((GeneratedModel) model).handlePreBind(holder, boundObject, position);
-        }
-      }
-    });
-  }
-
   @CallSuper
   @Override
-  public void bind(@NonNull Holder holder) {
+  public void bind(@NonNull ModelGroupHolder holder) {
     iterateModels(holder, new IterateModelsCallback() {
       @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        setViewVisibility(model, view);
-        //noinspection unchecked
-        model.bind(boundObject);
+      public void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex) {
+        setViewVisibility(model, viewHolder);
+        viewHolder.bind(model, null, Collections.emptyList(), modelIndex);
       }
     });
   }
 
   @CallSuper
   @Override
-  public void bind(@NonNull Holder holder, @NonNull final List<Object> payloads) {
+  public void bind(@NonNull ModelGroupHolder holder, @NonNull final List<Object> payloads) {
     iterateModels(holder, new IterateModelsCallback() {
       @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        setViewVisibility(model, view);
-        //noinspection unchecked
-        model.bind(boundObject);
+      public void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex) {
+        setViewVisibility(model, viewHolder);
+        viewHolder.bind(model, null, Collections.emptyList(), modelIndex);
       }
     });
   }
 
   @Override
-  public void bind(@NonNull Holder holder, @NonNull EpoxyModel<?> previouslyBoundModel) {
+  public void bind(@NonNull ModelGroupHolder holder, @NonNull EpoxyModel<?> previouslyBoundModel) {
     if (!(previouslyBoundModel instanceof EpoxyModelGroup)) {
       bind(holder);
       return;
     }
 
     final EpoxyModelGroup previousGroup = (EpoxyModelGroup) previouslyBoundModel;
-    if (previousGroup.models.size() != models.size()) {
-      throw createInconsistentModelCountException();
-    }
 
     iterateModels(holder, new IterateModelsCallback() {
       @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        setViewVisibility(model, view);
+      public void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex) {
+        setViewVisibility(model, viewHolder);
 
         EpoxyModel<?> previousModel = previousGroup.models.get(modelIndex);
         if (previousModel.id() == model.id()) {
-          //noinspection unchecked
-          model.bind(boundObject, previousModel);
+          viewHolder.bind(model, previousModel, Collections.emptyList(), modelIndex);
         } else {
-          //noinspection unchecked
-          model.bind(boundObject);
+          viewHolder.bind(model, null, Collections.emptyList(), modelIndex);
         }
       }
     });
   }
 
-  private static void setViewVisibility(EpoxyModel model, View view) {
+  private static void setViewVisibility(EpoxyModel model, EpoxyViewHolder viewHolder) {
     if (model.isShown()) {
-      view.setVisibility(View.VISIBLE);
+      viewHolder.itemView.setVisibility(View.VISIBLE);
     } else {
-      view.setVisibility(View.GONE);
+      viewHolder.itemView.setVisibility(View.GONE);
     }
   }
 
   @CallSuper
   @Override
-  public void unbind(@NonNull Holder holder) {
-    iterateModels(holder, new IterateModelsCallback() {
-      @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
-        //noinspection unchecked
-        model.unbind(boundObject);
-      }
-    });
+  public void unbind(@NonNull ModelGroupHolder holder) {
+    holder.unbindGroup();
   }
 
   @CallSuper
   @Override
-  public void onViewAttachedToWindow(Holder holder) {
+  public void onViewAttachedToWindow(ModelGroupHolder holder) {
     iterateModels(holder, new IterateModelsCallback() {
       @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
+      public void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex) {
         //noinspection unchecked
-        model.onViewAttachedToWindow(boundObject);
+        model.onViewAttachedToWindow(viewHolder.objectToBind());
       }
     });
   }
 
   @CallSuper
   @Override
-  public void onViewDetachedFromWindow(Holder holder) {
+  public void onViewDetachedFromWindow(ModelGroupHolder holder) {
     iterateModels(holder, new IterateModelsCallback() {
       @Override
-      public void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex) {
+      public void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex) {
         //noinspection unchecked
-        model.onViewDetachedFromWindow(boundObject);
+        model.onViewDetachedFromWindow(viewHolder.objectToBind());
       }
     });
   }
 
-  private void iterateModels(Holder holder, IterateModelsCallback callback) {
+  private void iterateModels(ModelGroupHolder holder, IterateModelsCallback callback) {
+    holder.bindGroupIfNeeded(this);
     int modelCount = models.size();
-    if (modelCount != holder.views.size()) {
-      throw createInconsistentModelCountException();
-    }
 
     for (int i = 0; i < modelCount; i++) {
-      EpoxyModel model = models.get(i);
-      View view = holder.views.get(i);
-      EpoxyHolder epoxyHolder = holder.holders.get(i);
-      Object objectToBind = (model instanceof EpoxyModelWithHolder) ? epoxyHolder : view;
-
-      callback.onModel(model, objectToBind, view, i);
+      callback.onModel(models.get(i), holder.getViewHolders().get(i), i);
     }
   }
 
-  private RuntimeException createInconsistentModelCountException() {
-    return new IllegalStateException(
-        "The number of models used in this group has changed. The model count must remain "
-            + "constant if the same layout resource is used. If you need to change which models"
-            + " are shown you can call EpoxyMode#hide() to have a model's view hidden, or use a"
-            + " different layout resource for the group.");
-  }
-
   private interface IterateModelsCallback {
-    void onModel(EpoxyModel model, Object boundObject, View view, int modelIndex);
+    void onModel(EpoxyModel model, EpoxyViewHolder viewHolder, int modelIndex);
   }
 
   @Override
@@ -301,158 +235,8 @@ protected boolean useViewStubLayoutParams(EpoxyModel<?> model, int modelPosition
   }
 
   @Override
-  protected final Holder createNewHolder() {
-    return new Holder(this);
-  }
-
-  public static class Holder extends EpoxyHolder {
-    // We use the model group that was used to create the view holder for initializing the view.
-    // We release the reference after the viewholder is initialized.
-    private EpoxyModelGroup initializingModelGroup;
-    private List<View> views;
-    private List<EpoxyHolder> holders;
-    private ViewGroup rootView;
-
-    public Holder(@NonNull EpoxyModelGroup initializingModelGroup) {
-      this.initializingModelGroup = initializingModelGroup;
-    }
-
-    /**
-     * Get the root view group (aka
-     * {@link androidx.recyclerview.widget.RecyclerView.ViewHolder#itemView}.
-     * You can override {@link EpoxyModelGroup#bind(Holder)} and use this method to make custom
-     * changes to the root view.
-     */
-    public ViewGroup getRootView() {
-      return rootView;
-    }
-
-    @Override
-    protected void bindView(@NonNull View itemView) {
-      if (!(itemView instanceof ViewGroup)) {
-        throw new IllegalStateException(
-            "The layout provided to EpoxyModelGroup must be a ViewGroup");
-      }
-      rootView = (ViewGroup) itemView;
-      ViewGroup childContainer = findChildContainer(rootView);
-
-      List<? extends EpoxyModel<?>> models = initializingModelGroup.models;
-      int modelCount = models.size();
-
-      views = new ArrayList<>(modelCount);
-      holders = new ArrayList<>(modelCount);
-
-      boolean useViewStubs = childContainer.getChildCount() != 0;
-      for (int i = 0; i < models.size(); i++) {
-        EpoxyModel model = models.get(i);
-        View view;
-        if (useViewStubs) {
-          view = replaceNextViewStub(childContainer, model,
-              initializingModelGroup.useViewStubLayoutParams(model, i));
-        } else {
-          view = createAndAddView(childContainer, model);
-        }
-
-        if (model instanceof EpoxyModelWithHolder) {
-          EpoxyHolder holder = ((EpoxyModelWithHolder) model).createNewHolder();
-          holder.bindView(view);
-          holders.add(holder);
-        } else {
-          holders.add(null);
-        }
-
-        views.add(view);
-      }
-
-      initializingModelGroup = null;
-    }
-
-    /**
-     * By default the outermost viewgroup is used as the container that views are added to. However,
-     * users can specify a different, nested view group to use as the child container by marking it
-     * with a special id.
-     */
-    private ViewGroup findChildContainer(ViewGroup outermostRoot) {
-      View customRoot = outermostRoot.findViewById(R.id.epoxy_model_group_child_container);
-
-      if (customRoot instanceof ViewGroup) {
-        return (ViewGroup) customRoot;
-      }
-
-      return outermostRoot;
-    }
-
-    private View createAndAddView(ViewGroup groupView, EpoxyModel<?> model) {
-      View modelView = model.buildView(groupView);
-      LayoutParams modelLayoutParams = modelView.getLayoutParams();
-      if (modelLayoutParams != null) {
-        groupView.addView(modelView, modelLayoutParams);
-      } else {
-        groupView.addView(modelView);
-      }
-      return modelView;
-    }
-
-    private View replaceNextViewStub(ViewGroup groupView, EpoxyModel<?> model,
-        boolean useStubLayoutParams) {
-      ViewStubData stubData = getNextViewStubPosition(groupView);
-      if (stubData == null) {
-        throw new IllegalStateException(
-            "Your layout should provide a ViewStub for each model to be inflated into.");
-      }
-
-      stubData.viewGroup.removeView(stubData.viewStub);
-      View modelView = model.buildView(stubData.viewGroup);
-
-      // Carry over the stub id manually since we aren't inflating via the stub
-      int inflatedId = stubData.viewStub.getInflatedId();
-      if (inflatedId != View.NO_ID) {
-        modelView.setId(inflatedId);
-      }
-
-      LayoutParams modelLayoutParams = modelView.getLayoutParams();
-      if (useStubLayoutParams) {
-        stubData.viewGroup
-            .addView(modelView, stubData.position, stubData.viewStub.getLayoutParams());
-      } else if (modelLayoutParams != null) {
-        stubData.viewGroup.addView(modelView, stubData.position, modelLayoutParams);
-      } else {
-        stubData.viewGroup.addView(modelView, stubData.position);
-      }
-
-      return modelView;
-    }
-
-    private ViewStubData getNextViewStubPosition(ViewGroup viewGroup) {
-      int childCount = viewGroup.getChildCount();
-      for (int i = 0; i < childCount; i++) {
-        View child = viewGroup.getChildAt(i);
-
-        if (child instanceof ViewGroup) {
-          ViewStubData nestedResult = getNextViewStubPosition((ViewGroup) child);
-          if (nestedResult != null) {
-            return nestedResult;
-          }
-        } else if (child instanceof ViewStub) {
-          return new ViewStubData(viewGroup, (ViewStub) child, i);
-        }
-      }
-
-      return null;
-    }
-  }
-
-  private static class ViewStubData {
-
-    private final ViewGroup viewGroup;
-    private final ViewStub viewStub;
-    private final int position;
-
-    private ViewStubData(ViewGroup viewGroup, ViewStub viewStub, int position) {
-      this.viewGroup = viewGroup;
-      this.viewStub = viewStub;
-      this.position = position;
-    }
+  protected final ModelGroupHolder createNewHolder() {
+    return new ModelGroupHolder();
   }
 
   @Override
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyRecyclerView.java b/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyRecyclerView.java
index 61cf96ef59..c84f654f79 100644
--- a/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyRecyclerView.java
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyRecyclerView.java
@@ -1,22 +1,14 @@
 package com.airbnb.epoxy;
 
-import android.app.Activity;
 import android.content.Context;
 import android.content.res.TypedArray;
-import android.os.Build.VERSION;
 import android.util.AttributeSet;
-import android.util.SparseArray;
 import android.util.TypedValue;
 import android.view.ViewGroup;
 
 import com.airbnb.viewmodeladapter.R;
 
-import java.lang.ref.WeakReference;
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
-import java.util.Queue;
 
 import androidx.annotation.CallSuper;
 import androidx.annotation.DimenRes;
@@ -24,10 +16,12 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.Px;
-import androidx.core.view.ViewCompat;
 import androidx.recyclerview.widget.GridLayoutManager;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
+import kotlin.jvm.functions.Function0;
+
+import static com.airbnb.epoxy.ActivityRecyclerPoolKt.isActivityDestroyed;
 
 /**
  * <i>This feature is in Beta - please report bugs, feature requests, or other feedback at
@@ -72,7 +66,7 @@ public class EpoxyRecyclerView extends RecyclerView {
    * Store one unique pool per activity. They are cleared out when activities are destroyed, so this
    * only needs to hold pools for active activities.
    */
-  private static final List<PoolReference> RECYCLER_POOLS = new ArrayList<>(5);
+  private static final ActivityRecyclerPool ACTIVITY_RECYCLER_POOL = new ActivityRecyclerPool();
 
   protected final EpoxyItemSpacingDecorator spacingDecorator = new EpoxyItemSpacingDecorator();
 
@@ -190,35 +184,13 @@ private void initViewPool() {
       return;
     }
 
-    Context context = getContext();
-    Iterator<PoolReference> iterator = RECYCLER_POOLS.iterator();
-    PoolReference poolToUse = null;
-
-    while (iterator.hasNext()) {
-      PoolReference poolReference = iterator.next();
-      if (poolReference.context() == null) {
-        // Clean up entries from old activities so the list doesn't grow large
-        iterator.remove();
-      } else if (poolReference.context() == context) {
-        if (poolToUse != null) {
-          throw new IllegalStateException("A pool was already found");
-        }
-        poolToUse = poolReference;
-        // finish iterating to remove any old contexts
-      } else {
-        // A pool from a different activity, it may be removed soon once the activity reference
-        // is GC'd, but until then we can at least clear the pool references, which may
-        // be keeping the activity from getting GC'd
-        poolReference.clearIfActivityIsDestroyed();
-      }
-    }
-
-    if (poolToUse == null) {
-      poolToUse = new PoolReference(context, createViewPool());
-      RECYCLER_POOLS.add(poolToUse);
-    }
-
-    setRecycledViewPool(poolToUse.viewPool);
+    setRecycledViewPool(ACTIVITY_RECYCLER_POOL.getPool(getContext(),
+        new Function0<RecycledViewPool>() {
+          @Override
+          public RecycledViewPool invoke() {
+            return createViewPool();
+          }
+        }).getViewPool());
   }
 
   /**
@@ -566,91 +538,4 @@ private void clearPoolIfActivityIsDestroyed() {
       getRecycledViewPool().clear();
     }
   }
-
-  private static class PoolReference {
-    private final WeakReference<Context> contextReference;
-    private final RecycledViewPool viewPool;
-
-    private PoolReference(Context context,
-        RecycledViewPool viewPool) {
-      this.contextReference = new WeakReference<>(context);
-      this.viewPool = viewPool;
-    }
-
-    @Nullable
-    private Context context() {
-      return contextReference.get();
-    }
-
-    void clearIfActivityIsDestroyed() {
-      if (isActivityDestroyed(context())) {
-        viewPool.clear();
-      }
-    }
-  }
-
-  private static boolean isActivityDestroyed(@Nullable Context context) {
-    if (context == null) {
-      return true;
-    }
-
-    if (!(context instanceof Activity)) {
-      return false;
-    }
-
-    Activity activity = (Activity) context;
-    if (activity.isFinishing()) {
-      return true;
-    }
-
-    if (VERSION.SDK_INT >= 17) {
-      return activity.isDestroyed();
-    } else {
-      // Use this as a proxy for being destroyed on older devices
-      return !ViewCompat.isAttachedToWindow(activity.getWindow().getDecorView());
-    }
-  }
-
-  /**
-   * Like its parent, UnboundedViewPool lets you share Views between multiple RecyclerViews. However
-   * there is no maximum number of recycled views that it will store. This usually ends up being
-   * optimal, barring any hard memory constraints, as RecyclerViews do not recycle more Views than
-   * they need.
-   */
-  private static class UnboundedViewPool extends RecycledViewPool {
-
-    private final SparseArray<Queue<ViewHolder>> scrapHeaps = new SparseArray<>();
-
-    @Override
-    public void clear() {
-      scrapHeaps.clear();
-    }
-
-    @Override
-    public void setMaxRecycledViews(int viewType, int max) {
-      throw new UnsupportedOperationException(
-          "UnboundedViewPool does not support setting a maximum number of recycled views");
-    }
-
-    @Override
-    @Nullable
-    public ViewHolder getRecycledView(int viewType) {
-      final Queue<ViewHolder> scrapHeap = scrapHeaps.get(viewType);
-      return scrapHeap != null ? scrapHeap.poll() : null;
-    }
-
-    @Override
-    public void putRecycledView(ViewHolder viewHolder) {
-      getScrapHeapForType(viewHolder.getItemViewType()).add(viewHolder);
-    }
-
-    private Queue<ViewHolder> getScrapHeapForType(int viewType) {
-      Queue<ViewHolder> scrapHeap = scrapHeaps.get(viewType);
-      if (scrapHeap == null) {
-        scrapHeap = new LinkedList<>();
-        scrapHeaps.put(viewType, scrapHeap);
-      }
-      return scrapHeap;
-    }
-  }
 }
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/ModelGroupHolder.kt b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ModelGroupHolder.kt
new file mode 100644
index 0000000000..b2b32e1ef8
--- /dev/null
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ModelGroupHolder.kt
@@ -0,0 +1,250 @@
+package com.airbnb.epoxy
+
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewStub
+import androidx.recyclerview.widget.RecyclerView
+
+import com.airbnb.viewmodeladapter.R
+
+import java.util.ArrayList
+
+class ModelGroupHolder : EpoxyHolder() {
+    val viewHolders = ArrayList<EpoxyViewHolder>(4)
+    private lateinit var poolReference: PoolReference
+
+    /**
+     * Get the root view group (aka
+     * [androidx.recyclerview.widget.RecyclerView.ViewHolder.itemView].
+     * You can override [EpoxyModelGroup.bind] and use this method to make custom
+     * changes to the root view.
+     */
+    lateinit var rootView: ViewGroup
+        private set
+
+    private lateinit var childContainer: ViewGroup
+    private lateinit var stubs: List<ViewStubData>
+    private var boundGroup: EpoxyModelGroup? = null
+
+    private fun usingStubs(): Boolean = stubs.isNotEmpty()
+
+    override fun bindView(itemView: View) {
+        if (itemView !is ViewGroup) {
+            throw IllegalStateException(
+                "The layout provided to EpoxyModelGroup must be a ViewGroup"
+            )
+        }
+
+        rootView = itemView
+        childContainer = findChildContainer(rootView)
+        poolReference = ACTIVITY_RECYCLER_POOL.getPool(itemView.context)
+
+        stubs = if (childContainer.childCount != 0) {
+            createViewStubData(childContainer)
+        } else {
+            emptyList()
+        }
+    }
+
+    /**
+     * By default the outermost viewgroup is used as the container that views are added to. However,
+     * users can specify a different, nested view group to use as the child container by marking it
+     * with a special id.
+     */
+    private fun findChildContainer(outermostRoot: ViewGroup): ViewGroup {
+        val customRoot = outermostRoot.findViewById<View>(R.id.epoxy_model_group_child_container)
+
+        return customRoot as? ViewGroup ?: outermostRoot
+    }
+
+    private fun createViewStubData(viewGroup: ViewGroup): List<ViewStubData> {
+        val stubs = ArrayList<ViewStubData>(4)
+
+        while (true) {
+            val stubData = getNextViewStub(viewGroup)
+            if (stubData != null) {
+                stubs.add(stubData)
+                stubData.removeView()
+            } else {
+                break
+            }
+        }
+
+        if (stubs.isEmpty()) {
+            throw IllegalStateException(
+                "No view stubs found. If viewgroup is not empty it must contain ViewStubs."
+            )
+        }
+
+        return stubs
+    }
+
+    private fun getNextViewStub(viewGroup: ViewGroup): ViewStubData? {
+        val childCount = viewGroup.childCount
+        for (i in 0 until childCount) {
+            val child = viewGroup.getChildAt(i)
+
+            if (child is ViewGroup) {
+                getNextViewStub(child)?.let { return it }
+            } else if (child is ViewStub) {
+                return ViewStubData(viewGroup, child, i)
+            }
+        }
+
+        return null
+    }
+
+    fun bindGroupIfNeeded(group: EpoxyModelGroup) {
+        val previouslyBoundGroup = this.boundGroup
+
+        if (previouslyBoundGroup === group) {
+            return
+        } else if (previouslyBoundGroup != null) {
+            // A different group is being bound; this can happen when an onscreen model is changed.
+            // The models or their layouts could have changed, so views may need to be updated
+
+            if (previouslyBoundGroup.models.size > group.models.size) {
+                for (i in previouslyBoundGroup.models.size - 1 downTo group.models.size) {
+                    removeAndRecycleView(i)
+                }
+            }
+        }
+
+        this.boundGroup = group
+        val models = group.models
+        val modelCount = models.size
+
+        if (usingStubs() && stubs.size < modelCount) {
+            throw IllegalStateException(
+                "Insufficient view stubs for EpoxyModelGroup. " + modelCount +
+                        " models were provided but only " + stubs.size + " view stubs exist."
+            )
+        }
+        viewHolders.ensureCapacity(modelCount)
+
+        for (i in 0 until modelCount) {
+            val model = models[i]
+            val previouslyBoundModel = previouslyBoundGroup?.models?.getOrNull(i)
+            val stubData = stubs.getOrNull(i)
+            val parent = stubData?.viewGroup ?: childContainer
+
+            if (previouslyBoundModel != null) {
+                if (areSameViewType(previouslyBoundModel, model)) {
+                    continue
+                }
+
+                removeAndRecycleView(i)
+            }
+
+            val holder = getViewHolder(parent, model)
+
+            if (stubData == null) {
+                childContainer.addView(holder.itemView, i)
+            } else {
+                stubData.setView(holder.itemView, group.useViewStubLayoutParams(model, i))
+            }
+
+            viewHolders.add(i, holder)
+        }
+    }
+
+    private fun areSameViewType(model1: EpoxyModel<*>, model2: EpoxyModel<*>?): Boolean {
+        return ViewTypeManager.getViewType(model1) == ViewTypeManager.getViewType(model2)
+    }
+
+    private fun getViewHolder(parent: ViewGroup, model: EpoxyModel<*>): EpoxyViewHolder {
+        val viewType = ViewTypeManager.getViewType(model)
+        val recycledView = poolReference.viewPool.getRecycledView(viewType)
+
+        return recycledView as? EpoxyViewHolder
+            ?: HELPER_ADAPTER.createViewHolder(
+                model,
+                parent,
+                viewType
+            )
+    }
+
+    fun unbindGroup() {
+        if (boundGroup == null) {
+            throw IllegalStateException("Group is not bound")
+        }
+
+        repeat(viewHolders.size) {
+            // Remove from the end for more efficient list actions
+            removeAndRecycleView(viewHolders.size - 1)
+        }
+
+        poolReference.clearIfDestroyed()
+        boundGroup = null
+    }
+
+    private fun removeAndRecycleView(modelPosition: Int) {
+        if (usingStubs()) {
+            stubs[modelPosition].removeView()
+        } else {
+            childContainer.removeViewAt(modelPosition)
+        }
+
+        val viewHolder = viewHolders.removeAt(modelPosition)
+        viewHolder.unbind()
+        poolReference.viewPool.putRecycledView(viewHolder)
+    }
+
+    companion object {
+
+        private val HELPER_ADAPTER = HelperAdapter()
+        private val ACTIVITY_RECYCLER_POOL = ActivityRecyclerPool()
+    }
+}
+
+private class ViewStubData(
+    val viewGroup: ViewGroup,
+    val viewStub: ViewStub,
+    val position: Int
+) {
+
+    fun setView(view: View, useStubLayoutParams: Boolean) {
+        // Carry over the stub id manually since we aren't inflating via the stub
+        val inflatedId = viewStub.inflatedId
+        if (inflatedId != View.NO_ID) {
+            view.id = inflatedId
+        }
+
+        if (useStubLayoutParams) {
+            viewGroup.addView(view, position, viewStub.layoutParams)
+        } else {
+            viewGroup.addView(view, position)
+        }
+    }
+
+    fun removeView() {
+        val view = viewGroup.getChildAt(position)
+            ?: throw IllegalStateException("No view exists at position $position")
+        viewGroup.removeView(view)
+    }
+}
+
+/**
+ * A viewholder's viewtype can only be set internally in an adapter when the viewholder
+ * is created. To work around that we do the creation in an adapter.
+ */
+private class HelperAdapter : RecyclerView.Adapter<EpoxyViewHolder>() {
+
+    private var model: EpoxyModel<*>? = null
+
+    fun createViewHolder(model: EpoxyModel<*>, parent: ViewGroup, viewType: Int): EpoxyViewHolder {
+        this.model = model
+        val viewHolder = createViewHolder(parent, viewType)
+        this.model = null
+        return viewHolder
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): EpoxyViewHolder {
+        return EpoxyViewHolder(model!!.buildView(parent), model!!.shouldSaveViewState())
+    }
+
+    override fun onBindViewHolder(holder: EpoxyViewHolder, position: Int) {
+    }
+
+    override fun getItemCount() = 1
+}
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/UnboundedViewPool.kt b/epoxy-adapter/src/main/java/com/airbnb/epoxy/UnboundedViewPool.kt
new file mode 100644
index 0000000000..f05f9adb5d
--- /dev/null
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/UnboundedViewPool.kt
@@ -0,0 +1,47 @@
+package com.airbnb.epoxy
+
+import android.util.SparseArray
+
+import java.util.LinkedList
+import java.util.Queue
+import androidx.recyclerview.widget.RecyclerView.RecycledViewPool
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+
+/**
+ * Like its parent, UnboundedViewPool lets you share Views between multiple RecyclerViews. However
+ * there is no maximum number of recycled views that it will store. This usually ends up being
+ * optimal, barring any hard memory constraints, as RecyclerViews do not recycle more Views than
+ * they need.
+ */
+internal class UnboundedViewPool : RecycledViewPool() {
+
+    private val scrapHeaps = SparseArray<Queue<ViewHolder>>()
+
+    override fun clear() {
+        scrapHeaps.clear()
+    }
+
+    override fun setMaxRecycledViews(viewType: Int, max: Int) {
+        throw UnsupportedOperationException(
+            "UnboundedViewPool does not support setting a maximum number of recycled views"
+        )
+    }
+
+    override fun getRecycledView(viewType: Int): ViewHolder? {
+        val scrapHeap = scrapHeaps.get(viewType)
+        return scrapHeap?.poll()
+    }
+
+    override fun putRecycledView(viewHolder: ViewHolder) {
+        getScrapHeapForType(viewHolder.itemViewType).add(viewHolder)
+    }
+
+    private fun getScrapHeapForType(viewType: Int): Queue<ViewHolder> {
+        var scrapHeap: Queue<ViewHolder>? = scrapHeaps.get(viewType)
+        if (scrapHeap == null) {
+            scrapHeap = LinkedList()
+            scrapHeaps.put(viewType, scrapHeap)
+        }
+        return scrapHeap
+    }
+}
diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/ViewTypeManager.java b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ViewTypeManager.java
index ff15684f81..6c2490434e 100644
--- a/epoxy-adapter/src/main/java/com/airbnb/epoxy/ViewTypeManager.java
+++ b/epoxy-adapter/src/main/java/com/airbnb/epoxy/ViewTypeManager.java
@@ -24,12 +24,12 @@ void resetMapForTesting() {
     VIEW_TYPE_MAP.clear();
   }
 
-  int getViewType(EpoxyModel<?> model) {
+  int getViewTypeAndRememberModel(EpoxyModel<?> model) {
     lastModelForViewTypeLookup = model;
-    return getViewTypeInternal(model);
+    return getViewType(model);
   }
 
-  private static int getViewTypeInternal(EpoxyModel<?> model) {
+  static int getViewType(EpoxyModel<?> model) {
     int defaultViewType = model.getViewType();
     if (defaultViewType != 0) {
       return defaultViewType;
@@ -66,7 +66,7 @@ private static int getViewTypeInternal(EpoxyModel<?> model) {
    */
   EpoxyModel<?> getModelForViewType(BaseEpoxyAdapter adapter, int viewType) {
     if (lastModelForViewTypeLookup != null
-        && getViewTypeInternal(lastModelForViewTypeLookup) == viewType) {
+        && getViewType(lastModelForViewTypeLookup) == viewType) {
       // We expect this to be a hit 100% of the time
       return lastModelForViewTypeLookup;
     }
@@ -76,7 +76,7 @@ && getViewTypeInternal(lastModelForViewTypeLookup) == viewType) {
 
     // To be extra safe in case RecyclerView implementation details change...
     for (EpoxyModel<?> model : adapter.getCurrentModels()) {
-      if (getViewTypeInternal(model) == viewType) {
+      if (getViewType(model) == viewType) {
         return model;
       }
     }
diff --git a/epoxy-adapter/src/test/java/com/airbnb/epoxy/EpoxyModelGroupTest.kt b/epoxy-adapter/src/test/java/com/airbnb/epoxy/EpoxyModelGroupTest.kt
new file mode 100644
index 0000000000..a91a00cafe
--- /dev/null
+++ b/epoxy-adapter/src/test/java/com/airbnb/epoxy/EpoxyModelGroupTest.kt
@@ -0,0 +1,174 @@
+package com.airbnb.epoxy
+
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewStub
+import android.widget.FrameLayout
+import android.widget.LinearLayout
+import android.widget.Space
+import androidx.recyclerview.widget.RecyclerView
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.ParameterizedRobolectricTestRunner
+import org.robolectric.RuntimeEnvironment
+import org.robolectric.annotation.Config
+
+@Config(sdk = [21], manifest = TestRunner.MANIFEST_PATH)
+@RunWith(ParameterizedRobolectricTestRunner::class)
+class EpoxyModelGroupTest(val useViewStubs: Boolean) {
+
+    private lateinit var recyclerView: RecyclerView
+    private var topLevelHolder: EpoxyViewHolder? = null
+
+    private val modelGroupHolder get() = topLevelHolder!!.objectToBind() as ModelGroupHolder
+
+    @Before
+    fun init() {
+        recyclerView = RecyclerView(RuntimeEnvironment.application)
+        topLevelHolder?.unbind()
+        topLevelHolder = null
+    }
+
+    @After
+    fun unbind() {
+        topLevelHolder!!.unbind()
+        assertEquals(0, modelGroupHolder.viewHolders.size)
+    }
+
+    private fun bind(modelGroup: EpoxyModelGroup) {
+        if (topLevelHolder == null) {
+            topLevelHolder = EpoxyViewHolder(modelGroup.buildView(recyclerView), false)
+        }
+        topLevelHolder!!.bind(modelGroup, null, emptyList(), 0)
+    }
+
+    private fun assertModelsBound(modelGroup: EpoxyModelGroup) {
+        assertEquals(modelGroupHolder.viewHolders.size, modelGroup.models.size)
+        modelGroupHolder.viewHolders.forEachIndexed { index, viewHolder ->
+            assertEquals("Model at index $index", viewHolder.model, modelGroup.models[index])
+        }
+    }
+
+    @Test
+    fun bindLinearLayout() {
+        createFrameLayoutGroup(3).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun bind_Unbind_Rebind_LinearLayoutWithLessModels() {
+        bind(createFrameLayoutGroup(3))
+        unbind()
+        createSpaceGroup(2).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun bind_Unbind_Rebind_LinearLayoutWithMoreModels() {
+        bind(createFrameLayoutGroup(3))
+        unbind()
+        createSpaceGroup(4).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun rebind_LinearLayoutWithSameViewTypes() {
+        bind(createFrameLayoutGroup(3))
+        createFrameLayoutGroup(4).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun rebind_LinearLayoutWithMoreModels() {
+        bind(createFrameLayoutGroup(3))
+        createSpaceGroup(4).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun rebind_LinearLayoutWithLessModels() {
+        bind(createFrameLayoutGroup(3))
+        createSpaceGroup(2).let {
+            bind(it)
+            assertModelsBound(it)
+        }
+    }
+
+    @Test
+    fun viewholdersAreRecycled() {
+        bind(createFrameLayoutGroup(3))
+        val firstHolders = modelGroupHolder.viewHolders.toSet()
+
+        unbind()
+
+        bind(createFrameLayoutGroup(3))
+        val secondHolders = modelGroupHolder.viewHolders.toSet()
+
+        assertEquals(firstHolders, secondHolders)
+    }
+
+    private fun createFrameLayoutGroup(modelCount: Int): EpoxyModelGroup {
+        val models = (0 until modelCount).map { NestedModelFrameLayout().id(it) }
+        return if (useViewStubs) ViewStubsGroupModel(models) else LinerLayoutGroupModel(models)
+    }
+
+    private fun createSpaceGroup(modelCount: Int): EpoxyModelGroup {
+        val models = (0 until modelCount).map { NestedModelSpace().id(it) }
+        return if (useViewStubs) ViewStubsGroupModel(models) else LinerLayoutGroupModel(models)
+    }
+
+    companion object {
+        @JvmStatic
+        @ParameterizedRobolectricTestRunner.Parameters(name = "Use viewstubs: {0}")
+        fun useViewStubsParameters() = listOf(
+            arrayOf(true),
+            arrayOf(false)
+        )
+    }
+}
+
+private class LinerLayoutGroupModel(models: List<EpoxyModel<*>>) : EpoxyModelGroup(0, models) {
+    public override fun buildView(parent: ViewGroup): View {
+        return LinearLayout(parent.context)
+    }
+}
+
+private class ViewStubsGroupModel(models: List<EpoxyModel<*>>) : EpoxyModelGroup(0, models) {
+    public override fun buildView(parent: ViewGroup): View {
+        fun LinearLayout.addStubLayer(): LinearLayout {
+            addView(ViewStub(parent.context))
+
+            LinearLayout(parent.context).let {
+                addView(it)
+                return it
+            }
+        }
+
+        return (0 until models.size).fold(LinearLayout(parent.context)) { linearLayout, _ -> linearLayout.addStubLayer() }
+    }
+}
+
+private class NestedModelFrameLayout : EpoxyModelWithView<FrameLayout>() {
+    override fun buildView(parent: ViewGroup): FrameLayout {
+        return FrameLayout(parent.context)
+    }
+}
+
+private class NestedModelSpace : EpoxyModelWithView<Space>() {
+    override fun buildView(parent: ViewGroup): Space {
+        return Space(parent.context)
+    }
+}
\ No newline at end of file
diff --git a/epoxy-integrationtest/src/main/java/com/airbnb/epoxy/integrationtest/ModelGroupWithAnnotation.java b/epoxy-integrationtest/src/main/java/com/airbnb/epoxy/integrationtest/ModelGroupWithAnnotation.java
index 44d7039d9c..9f6b4d5352 100644
--- a/epoxy-integrationtest/src/main/java/com/airbnb/epoxy/integrationtest/ModelGroupWithAnnotation.java
+++ b/epoxy-integrationtest/src/main/java/com/airbnb/epoxy/integrationtest/ModelGroupWithAnnotation.java
@@ -4,6 +4,7 @@
 import com.airbnb.epoxy.EpoxyModel;
 import com.airbnb.epoxy.EpoxyModelClass;
 import com.airbnb.epoxy.EpoxyModelGroup;
+import com.airbnb.epoxy.ModelGroupHolder;
 
 import java.util.List;
 
@@ -18,7 +19,7 @@ public ModelGroupWithAnnotation(List<? extends EpoxyModel<?>> models) {
   }
 
   @Override
-  public void bind(@NonNull Holder holder) {
+  public void bind(@NonNull ModelGroupHolder holder) {
     super.bind(holder);
     holder.getRootView().setBackgroundColor(backgroundColor);
   }
diff --git a/epoxy-processortest/src/test/resources/EpoxyModelGroupWithAnnotations_.java b/epoxy-processortest/src/test/resources/EpoxyModelGroupWithAnnotations_.java
index 4abc4f2db3..8532283bf8 100644
--- a/epoxy-processortest/src/test/resources/EpoxyModelGroupWithAnnotations_.java
+++ b/epoxy-processortest/src/test/resources/EpoxyModelGroupWithAnnotations_.java
@@ -11,14 +11,14 @@
 
 /**
  * Generated file. Do not modify! */
-public class EpoxyModelGroupWithAnnotations_ extends EpoxyModelGroupWithAnnotations implements GeneratedModel<EpoxyModelGroup.Holder>, EpoxyModelGroupWithAnnotationsBuilder {
-  private OnModelBoundListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> onModelBoundListener_epoxyGeneratedModel;
+public class EpoxyModelGroupWithAnnotations_ extends EpoxyModelGroupWithAnnotations implements GeneratedModel<ModelGroupHolder>, EpoxyModelGroupWithAnnotationsBuilder {
+  private OnModelBoundListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> onModelBoundListener_epoxyGeneratedModel;
 
-  private OnModelUnboundListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> onModelUnboundListener_epoxyGeneratedModel;
+  private OnModelUnboundListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> onModelUnboundListener_epoxyGeneratedModel;
 
-  private OnModelVisibilityStateChangedListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> onModelVisibilityStateChangedListener_epoxyGeneratedModel;
+  private OnModelVisibilityStateChangedListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> onModelVisibilityStateChangedListener_epoxyGeneratedModel;
 
-  private OnModelVisibilityChangedListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> onModelVisibilityChangedListener_epoxyGeneratedModel;
+  private OnModelVisibilityChangedListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> onModelVisibilityChangedListener_epoxyGeneratedModel;
 
   public EpoxyModelGroupWithAnnotations_(int layoutRes,
       Collection<? extends EpoxyModel<?>> models) {
@@ -32,15 +32,13 @@ public void addTo(EpoxyController controller) {
   }
 
   @Override
-  public void handlePreBind(final EpoxyViewHolder holder, final EpoxyModelGroup.Holder object,
+  public void handlePreBind(final EpoxyViewHolder holder, final ModelGroupHolder object,
       final int position) {
-    super.handlePreBind(holder, object, position);
     validateStateHasNotChangedSinceAdded("The model was changed between being added to the controller and being bound.", position);
   }
 
   @Override
-  public void handlePostBind(final EpoxyModelGroup.Holder object, int position) {
-    super.handlePostBind(object, position);
+  public void handlePostBind(final ModelGroupHolder object, int position) {
     if (onModelBoundListener_epoxyGeneratedModel != null) {
       onModelBoundListener_epoxyGeneratedModel.onModelBound(this, object, position);
     }
@@ -55,14 +53,14 @@ public void handlePostBind(final EpoxyModelGroup.Holder object, int position) {
    * <p>
    * You may clear the listener by setting a null value, or by calling {@link #reset()} */
   public EpoxyModelGroupWithAnnotations_ onBind(
-      OnModelBoundListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> listener) {
+      OnModelBoundListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> listener) {
     onMutation();
     this.onModelBoundListener_epoxyGeneratedModel = listener;
     return this;
   }
 
   @Override
-  public void unbind(EpoxyModelGroup.Holder object) {
+  public void unbind(ModelGroupHolder object) {
     super.unbind(object);
     if (onModelUnboundListener_epoxyGeneratedModel != null) {
       onModelUnboundListener_epoxyGeneratedModel.onModelUnbound(this, object);
@@ -77,14 +75,14 @@ public void unbind(EpoxyModelGroup.Holder object) {
    * <p>
    * You may clear the listener by setting a null value, or by calling {@link #reset()} */
   public EpoxyModelGroupWithAnnotations_ onUnbind(
-      OnModelUnboundListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> listener) {
+      OnModelUnboundListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> listener) {
     onMutation();
     this.onModelUnboundListener_epoxyGeneratedModel = listener;
     return this;
   }
 
   @Override
-  public void onVisibilityStateChanged(int visibilityState, final EpoxyModelGroup.Holder object) {
+  public void onVisibilityStateChanged(int visibilityState, final ModelGroupHolder object) {
     if (onModelVisibilityStateChangedListener_epoxyGeneratedModel != null) {
       onModelVisibilityStateChangedListener_epoxyGeneratedModel.onVisibilityStateChanged(this, object, visibilityState);
     }
@@ -96,10 +94,9 @@ public void onVisibilityStateChanged(int visibilityState, final EpoxyModelGroup.
    * <p>
    * The listener will contribute to this model's hashCode state per the {@link
    * com.airbnb.epoxy.EpoxyAttribute.Option#DoNotHash} rules.
-   * <p>
-   * You may clear the listener by setting a null value, or by calling {@link #reset()} */
+   */
   public EpoxyModelGroupWithAnnotations_ onVisibilityStateChanged(
-      OnModelVisibilityStateChangedListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> listener) {
+      OnModelVisibilityStateChangedListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> listener) {
     onMutation();
     this.onModelVisibilityStateChangedListener_epoxyGeneratedModel = listener;
     return this;
@@ -107,7 +104,7 @@ public EpoxyModelGroupWithAnnotations_ onVisibilityStateChanged(
 
   @Override
   public void onVisibilityChanged(float percentVisibleHeight, float percentVisibleWidth,
-      int visibleHeight, int visibleWidth, final EpoxyModelGroup.Holder object) {
+      int visibleHeight, int visibleWidth, final ModelGroupHolder object) {
     if (onModelVisibilityChangedListener_epoxyGeneratedModel != null) {
       onModelVisibilityChangedListener_epoxyGeneratedModel.onVisibilityChanged(this, object, percentVisibleHeight, percentVisibleWidth, visibleHeight, visibleWidth);
     }
@@ -119,10 +116,9 @@ public void onVisibilityChanged(float percentVisibleHeight, float percentVisible
    * <p>
    * The listener will contribute to this model's hashCode state per the {@link
    * com.airbnb.epoxy.EpoxyAttribute.Option#DoNotHash} rules.
-   * <p>
-   * You may clear the listener by setting a null value, or by calling {@link #reset()} */
+   */
   public EpoxyModelGroupWithAnnotations_ onVisibilityChanged(
-      OnModelVisibilityChangedListener<EpoxyModelGroupWithAnnotations_, EpoxyModelGroup.Holder> listener) {
+      OnModelVisibilityChangedListener<EpoxyModelGroupWithAnnotations_, ModelGroupHolder> listener) {
     onMutation();
     this.onModelVisibilityChangedListener_epoxyGeneratedModel = listener;
     return this;
@@ -264,4 +260,4 @@ public String toString() {
         "value=" + value +
         "}" + super.toString();
   }
-}
+}
\ No newline at end of file