Introduce SimpleRecyclerViewAdapter

This patch adds a basic adapter for RecyclerView that follows chrome's
MVC pattern. The API it exposes is intended to be as similar as
possible to the existing ModelListAdapter.

Bug: 909779
Change-Id: Ibda434edadf365c185433614f4a0d1da9e4b9862
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1650522
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682823}

ui/android/BUILD.gn

@@ -283,6 +283,7 @@ android_library("ui_full_java") {
     "java/src/org/chromium/ui/modelutil/ListModelChangeProcessor.java",
     "java/src/org/chromium/ui/modelutil/ListObservable.java",
     "java/src/org/chromium/ui/modelutil/ListObservableImpl.java",
+    "java/src/org/chromium/ui/modelutil/MVCListAdapter.java",
     "java/src/org/chromium/ui/modelutil/ModelListAdapter.java",
     "java/src/org/chromium/ui/modelutil/PropertyKey.java",
     "java/src/org/chromium/ui/modelutil/PropertyListModel.java",
@@ -291,6 +292,7 @@ android_library("ui_full_java") {
     "java/src/org/chromium/ui/modelutil/PropertyObservable.java",
     "java/src/org/chromium/ui/modelutil/RecyclerViewAdapter.java",
     "java/src/org/chromium/ui/modelutil/SimpleList.java",
+    "java/src/org/chromium/ui/modelutil/SimpleRecyclerViewAdapter.java",
     "java/src/org/chromium/ui/modelutil/SimpleRecyclerViewMcp.java",
     "java/src/org/chromium/ui/modelutil/SimpleRecyclerViewMcpBase.java",
     "java/src/org/chromium/ui/resources/HandleViewResources.java",

ui/android/java/src/org/chromium/ui/modelutil/MVCListAdapter.java

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.ui.modelutil;
+
+import android.view.View;
+
+import org.chromium.ui.modelutil.PropertyModelChangeProcessor.ViewBinder;
+
+/**
+ * An interface that defined a simple API for list adapters in MVC. This class also contains a small
+ * number of common utilities shared between implementations. In general, the only means of
+ * interaction with these kinds of list adapters post-initialization should be to register the
+ * different types of views that can be shown by the list, i.e.:
+ * {@link #registerType(int, ViewBuilder, ViewBinder)}.
+ */
+public interface MVCListAdapter {
+    /** A basic container for {@link PropertyModel}s with a type. */
+    class ListItem {
+        /** The type of view that the {@code model} is associated with. */
+        public final int type;
+        /** The model to be managed by a list. */
+        public final PropertyModel model;
+
+        /**
+         * Build a new item to managed by a {@link ModelListAdapter}.
+         * @param type The view type the model will bind to.
+         * @param model The model that will be bound to a view.
+         */
+        public ListItem(int type, PropertyModel model) {
+            this.type = type;
+            this.model = model;
+        }
+    }
+
+    /** A basic observable list for this adapter to use. This more or less acts as a typedef. */
+    class ModelList extends ListModelBase<ListItem, Void> {}
+
+    /**
+     * An interface to provide a means to build specific view types.
+     * @param <T> The type of view that the implementor will build.
+     */
+    interface ViewBuilder<T extends View> {
+        /**
+         * @return A new view to show in the list.
+         */
+        T buildView();
+    }
+
+    /**
+     * Register a new view type that this adapter knows how to show.
+     * @param typeId The ID of the view type. This should not match any other view type registered
+     *               in this adapter.
+     * @param builder A mechanism for building new views of the specified type.
+     * @param binder A means of binding a model to the provided view.
+     */
+    <T extends View> void registerType(
+            int typeId, ViewBuilder<T> builder, ViewBinder<PropertyModel, T, PropertyKey> binder);
+}

ui/android/java/src/org/chromium/ui/modelutil/SimpleRecyclerViewAdapter.java

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.ui.modelutil;
+
+import android.support.annotation.Nullable;
+import android.support.v7.widget.RecyclerView;
+import android.util.Pair;
+import android.util.SparseArray;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.chromium.ui.modelutil.ListObservable.ListObserver;
+import org.chromium.ui.modelutil.PropertyModelChangeProcessor.ViewBinder;
+
+/**
+ * A simple adapter for {@link RecyclerView}. This is the RecyclerView version of the
+ * {@link ModelListAdapter} with the API surfaces being identical in terms of managing items in the
+ * view. In summary, use {@link #registerType(int, ViewBuilder, ViewBinder)} to tell the list
+ * adapter how to display a particular item. Updates to the {@link ListObservable} list provided in
+ * the constructor will immediately be reflected in the list.
+ */
+public class SimpleRecyclerViewAdapter
+        extends RecyclerView.Adapter<SimpleRecyclerViewAdapter.ViewHolder>
+        implements MVCListAdapter {
+    /**
+     * A simple {@link ViewHolder} that keeps a view, view binder, and an MCP that relate the two.
+     */
+    public class ViewHolder extends RecyclerView.ViewHolder {
+        /** The model change processor currently associated with this view and model. */
+        private PropertyModelChangeProcessor<PropertyModel, View, PropertyKey> mCurrentMcp;
+
+        /** The view binder that knows how to apply a model to the view this holder owns. */
+        private ViewBinder<PropertyModel, View, PropertyKey> mBinder;
+
+        /** A handle to the model currently held by this view holder. */
+        public PropertyModel model;
+
+        /**
+         * @param itemView The view to manage.
+         * @param binder The binder that knows how to apply a model to the view.
+         */
+        public ViewHolder(View itemView, ViewBinder<PropertyModel, View, PropertyKey> binder) {
+            super(itemView);
+            mBinder = binder;
+        }
+
+        /**
+         * Set the model for this view holder to manage.
+         * @param model The model that should be bound to the view.
+         */
+        void setModel(PropertyModel model) {
+            if (mCurrentMcp != null) mCurrentMcp.destroy();
+            this.model = model;
+            if (this.model == null) return;
+            mCurrentMcp = PropertyModelChangeProcessor.create(model, itemView, mBinder);
+        }
+    }
+
+    /** The data that is shown in the list. */
+    private final ModelList mListData;
+
+    /** The observer that watches the data for changes. */
+    private final ListObserver<Void> mListObserver;
+
+    /** A map of view types to view binders. */
+    private final SparseArray<Pair<ViewBuilder, ViewBinder>> mViewBuilderMap = new SparseArray<>();
+
+    public SimpleRecyclerViewAdapter(ModelList data) {
+        mListData = data;
+        mListObserver = new ListObserver<Void>() {
+            @Override
+            public void onItemRangeInserted(ListObservable source, int index, int count) {
+                notifyItemInserted(index);
+            }
+
+            @Override
+            public void onItemRangeRemoved(ListObservable source, int index, int count) {
+                notifyItemRangeRemoved(index, count);
+            }
+
+            @Override
+            public void onItemRangeChanged(
+                    ListObservable<Void> source, int index, int count, @Nullable Void payload) {
+                notifyItemChanged(index);
+            }
+
+            @Override
+            public void onItemMoved(ListObservable source, int curIndex, int newIndex) {
+                notifyItemMoved(curIndex, newIndex);
+            }
+        };
+        mListData.addObserver(mListObserver);
+    }
+
+    /** Clean up any state that needs to be. */
+    public void destroy() {
+        mListData.removeObserver(mListObserver);
+    }
+
+    @Override
+    public int getItemCount() {
+        return mListData.size();
+    }
+
+    @Override
+    public <T extends View> void registerType(
+            int typeId, ViewBuilder<T> builder, ViewBinder<PropertyModel, T, PropertyKey> binder) {
+        assert mViewBuilderMap.get(typeId) == null;
+        mViewBuilderMap.put(typeId, new Pair<>(builder, binder));
+    }
+
+    @Override
+    public int getItemViewType(int position) {
+        return mListData.get(position).type;
+    }
+
+    @Override
+    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        return new ViewHolder(mViewBuilderMap.get(viewType).first.buildView(),
+                mViewBuilderMap.get(viewType).second);
+    }
+
+    @Override
+    public void onBindViewHolder(ViewHolder viewHolder, int position) {
+        viewHolder.setModel(mListData.get(position).model);
+    }
+
+    @Override
+    public void onViewRecycled(ViewHolder holder) {
+        holder.setModel(null);
+    }
+}