Separate EmptyViewCoordinator from the top model.

- Decouple the EmptyViewCoordinator from the underlying model.
- Add back the concept of loading to the View.

Change-Id: I568fcdc32af7aaf42908c56981538c02cc4f61ed
Reviewed-on: https://chromium-review.googlesource.com/1150840
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579522}

chrome/android/java/res/layout/downloads_empty_view.xml

@@ -9,12 +9,18 @@
     android:layout_height="match_parent" >
 
     <TextView
-        android:id="@+id/empty_view"
+        android:id="@+id/empty"
         android:layout_marginTop="100dp"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:gravity="center"
+        android:layout_gravity="center"
         android:drawablePadding="3dp"
         android:textAppearance="@style/BlackDisabledText1"/>
 
+    <org.chromium.chrome.browser.widget.LoadingView
+        android:id="@+id/loading"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center" />
+
 </FrameLayout>

chrome/android/java/src/org/chromium/chrome/browser/download/home/OfflineItemSource.java

@@ -32,6 +32,9 @@ public class OfflineItemSource implements OfflineItemFilterSource, OfflineConten
     private final Map<ContentId, OfflineItem> mItems = new HashMap<>();
     private final ObserverList<OfflineItemFilterObserver> mObservers = new ObserverList<>();
 
+    /** Used to track whether or not the items have been loaded from {@code mProvider} or not. */
+    private boolean mItemsAvailable;
+
     /**
      * Used to track whether or not this is destroyed so we know whether or not to do additional
      * work when outstanding callbacks return.
@@ -48,7 +51,11 @@ public class OfflineItemSource implements OfflineItemFilterSource, OfflineConten
         mProvider.addObserver(this);
 
         mProvider.getAllItems(items -> {
-            if (!mDestroyed) onItemsAdded(items);
+            if (mDestroyed) return;
+
+            mItemsAvailable = true;
+            for (OfflineItemFilterObserver observer : mObservers) observer.onItemsAvailable();
+            onItemsAdded(items);
         });
     }
 
@@ -69,6 +76,11 @@ public class OfflineItemSource implements OfflineItemFilterSource, OfflineConten
         return mItems.values();
     }
 
+    @Override
+    public boolean areItemsAvailable() {
+        return mItemsAvailable;
+    }
+
     @Override
     public void addObserver(OfflineItemFilterObserver observer) {
         mObservers.addObserver(observer);

chrome/android/java/src/org/chromium/chrome/browser/download/home/PrefetchStatusProvider.java

+// Copyright 2018 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.chrome.browser.download.home;
+
+/** Helper class to expose the status of the offline prefetch feature. */
+public class PrefetchStatusProvider {
+    /** @return Whether or not the offline prefetch feature is enabled. */
+    public boolean enabled() {
+        return true;
+    }
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/download/home/empty/EmptyCoordinator.java

+// Copyright 2018 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.chrome.browser.download.home.empty;
+
+import android.content.Context;
+import android.support.annotation.DrawableRes;
+import android.support.annotation.StringRes;
+import android.view.View;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.download.home.PrefetchStatusProvider;
+import org.chromium.chrome.browser.download.home.empty.EmptyProperties.State;
+import org.chromium.chrome.browser.download.home.filter.FilterCoordinator;
+import org.chromium.chrome.browser.download.home.filter.Filters.FilterType;
+import org.chromium.chrome.browser.download.home.filter.OfflineItemFilterObserver;
+import org.chromium.chrome.browser.download.home.filter.OfflineItemFilterSource;
+import org.chromium.chrome.browser.modelutil.PropertyModel;
+import org.chromium.chrome.browser.modelutil.PropertyModelChangeProcessor;
+import org.chromium.components.offline_items_collection.OfflineItem;
+
+import java.util.Collection;
+
+/** A class that determines whether an empty view should be shown and inserts into the model. */
+public class EmptyCoordinator implements OfflineItemFilterObserver, FilterCoordinator.Observer {
+    private final PrefetchStatusProvider mPrefetchStatusProvider;
+    private final OfflineItemFilterSource mSource;
+
+    private final PropertyModel mModel;
+    private final EmptyView mView;
+
+    private boolean mShowingPrefetch = false;
+
+    /** Creates a {@link EmptyCoordinator} instance that monitors {@code source}. */
+    public EmptyCoordinator(Context context, PrefetchStatusProvider prefetchStatusProvider,
+            OfflineItemFilterSource source) {
+        mPrefetchStatusProvider = prefetchStatusProvider;
+        mSource = source;
+
+        mSource.addObserver(this);
+
+        mModel = new PropertyModel(EmptyProperties.ALL_KEYS);
+        mView = new EmptyView(context);
+        mModel.addObserver(
+                new PropertyModelChangeProcessor<>(mModel, mView, new EmptyViewBinder()));
+
+        calculateState();
+    }
+
+    /** @return The {@link View} that represents the empty screen. */
+    public View getView() {
+        return mView.getView();
+    }
+
+    // OfflineItemFilterObserver implementation.
+    @Override
+    public void onItemsAdded(Collection<OfflineItem> items) {
+        calculateState();
+    }
+
+    @Override
+    public void onItemsRemoved(Collection<OfflineItem> items) {
+        calculateState();
+    }
+
+    @Override
+    public void onItemUpdated(OfflineItem oldItem, OfflineItem item) {}
+
+    @Override
+    public void onItemsAvailable() {
+        calculateState();
+    }
+
+    // FilterCoordinator.Observer implementation.
+    @Override
+    public void onFilterChanged(@FilterType int selectedTab) {
+        mShowingPrefetch = selectedTab == FilterType.PREFETCHED;
+        calculateState();
+    }
+
+    private void calculateState() {
+        @State
+        int state;
+        if (!mSource.areItemsAvailable()) {
+            state = State.LOADING;
+        } else if (mSource.getItems().isEmpty()) {
+            state = State.EMPTY;
+
+            @StringRes
+            int textId;
+            @DrawableRes
+            int iconId;
+            if (mShowingPrefetch) {
+                iconId = R.drawable.ic_library_news_feed;
+
+                if (mPrefetchStatusProvider.enabled()) {
+                    textId = R.string.download_manager_prefetch_tab_empty;
+                } else {
+                    textId = R.string.download_manager_enable_prefetch_message;
+                }
+            } else {
+                iconId = R.drawable.downloads_big;
+                textId = R.string.download_manager_ui_empty;
+            }
+
+            mModel.setValue(EmptyProperties.EMPTY_TEXT_RES_ID, textId);
+            mModel.setValue(EmptyProperties.EMPTY_ICON_RES_ID, iconId);
+        } else {
+            state = State.GONE;
+        }
+
+        mModel.setValue(EmptyProperties.STATE, state);
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/download/home/empty/EmptyProperties.java

+// Copyright 2018 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.chrome.browser.download.home.empty;
+
+import android.support.annotation.IntDef;
+
+import org.chromium.chrome.browser.modelutil.PropertyKey;
+import org.chromium.chrome.browser.modelutil.PropertyModel.IntPropertyKey;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** The properties required to build a {@link EmptyView}. */
+interface EmptyProperties {
+    @IntDef({State.LOADING, State.EMPTY, State.GONE})
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface State {
+        int LOADING = 0;
+        int EMPTY = 1;
+        int GONE = 2;
+    }
+
+    /** The current state of the empty view. */
+    public static final IntPropertyKey STATE = new IntPropertyKey();
+
+    /** The current text resource to use for the empty view. */
+    public static final IntPropertyKey EMPTY_TEXT_RES_ID = new IntPropertyKey();
+
+    /** The current icon resource to use for the empty view. */
+    public static final IntPropertyKey EMPTY_ICON_RES_ID = new IntPropertyKey();
+
+    public static final PropertyKey[] ALL_KEYS =
+            new PropertyKey[] {STATE, EMPTY_TEXT_RES_ID, EMPTY_ICON_RES_ID};
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/download/home/empty/EmptyView.java

+// Copyright 2018 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.chrome.browser.download.home.empty;
+
+import android.content.Context;
+import android.graphics.drawable.Drawable;
+import android.support.annotation.DrawableRes;
+import android.support.annotation.StringRes;
+import android.support.graphics.drawable.VectorDrawableCompat;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.download.home.empty.EmptyProperties.State;
+import org.chromium.chrome.browser.widget.LoadingView;
+
+/** A view that represents the visuals required for the empty state of the download home list. */
+class EmptyView {
+    private final ViewGroup mView;
+    private final TextView mEmptyView;
+    private final LoadingView mLoadingView;
+
+    /** Creates a new {@link EmptyView} instance from {@code context}. */
+    public EmptyView(Context context) {
+        mView = (ViewGroup) LayoutInflater.from(context).inflate(
+                R.layout.downloads_empty_view, null);
+        mEmptyView = (TextView) mView.findViewById(R.id.empty);
+        mLoadingView = (LoadingView) mView.findViewById(R.id.loading);
+    }
+
+    /** The Android {@link View} representing the empty view. */
+    public View getView() {
+        return mView;
+    }
+
+    /** Sets the internal UI based on {@code state}. */
+    public void setState(@State int state) {
+        mEmptyView.setVisibility(state == State.EMPTY ? View.VISIBLE : View.INVISIBLE);
+
+        if (state == State.LOADING) {
+            mLoadingView.showLoadingUI();
+        } else {
+            mLoadingView.hideLoadingUI();
+        }
+    }
+
+    /** Sets the text resource to use for the empty view. */
+    public void setEmptyText(@StringRes int textId) {
+        mEmptyView.setText(textId);
+    }
+
+    /** Sets the icon resource to use for the empty view. */
+    public void setEmptyIcon(@DrawableRes int iconId) {
+        Drawable drawable = VectorDrawableCompat.create(
+                mView.getResources(), iconId, mView.getContext().getTheme());
+        mEmptyView.setCompoundDrawablesWithIntrinsicBounds(null, drawable, null, null);
+    }
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/download/home/empty/EmptyViewBinder.java

+// Copyright 2018 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.chrome.browser.download.home.empty;
+
+import org.chromium.chrome.browser.modelutil.PropertyKey;
+import org.chromium.chrome.browser.modelutil.PropertyModel;
+import org.chromium.chrome.browser.modelutil.PropertyModelChangeProcessor.ViewBinder;
+
+/**
+ * A helper {@link ViewBinder} responsible for gluing {@link EmptyProperties} to
+ * {@link EmptyView}.
+ */
+class EmptyViewBinder implements ViewBinder<PropertyModel, EmptyView, PropertyKey> {
+    @Override
+    public void bind(PropertyModel model, EmptyView view, PropertyKey propertyKey) {
+        if (propertyKey == EmptyProperties.STATE) {
+            view.setState(model.getValue(EmptyProperties.STATE));
+        } else if (propertyKey == EmptyProperties.EMPTY_TEXT_RES_ID) {
+            view.setEmptyText(model.getValue(EmptyProperties.EMPTY_TEXT_RES_ID));
+        } else if (propertyKey == EmptyProperties.EMPTY_ICON_RES_ID) {
+            view.setEmptyIcon(model.getValue(EmptyProperties.EMPTY_ICON_RES_ID));
+        }
+    }
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/download/home/filter/FilterCoordinator.java

@@ -9,9 +9,9 @@ import android.support.annotation.IntDef;
 import android.view.View;
 
 import org.chromium.base.ObserverList;
+import org.chromium.chrome.browser.download.home.PrefetchStatusProvider;
 import org.chromium.chrome.browser.download.home.filter.Filters.FilterType;
 import org.chromium.chrome.browser.download.home.filter.chips.ChipsCoordinator;
-import org.chromium.chrome.browser.modelutil.PropertyKey;
 import org.chromium.chrome.browser.modelutil.PropertyModel;
 import org.chromium.chrome.browser.modelutil.PropertyModelChangeProcessor;
 
@@ -33,6 +33,7 @@ public class FilterCoordinator {
         void onFilterChanged(@FilterType int selectedTab);
     }
 
+    private final PrefetchStatusProvider mPrefetchStatusProvider;
     private final ObserverList<Observer> mObserverList = new ObserverList<>();
     private final PropertyModel mModel;
     private final FilterViewBinder mViewBinder;
@@ -45,22 +46,22 @@ public class FilterCoordinator {
      * Builds a new FilterCoordinator.
      * @param context The context to build the views and pull parameters from.
      */
-    public FilterCoordinator(Context context, OfflineItemFilterSource chipFilterSource) {
+    public FilterCoordinator(Context context, PrefetchStatusProvider prefetchStatusProvider,
+            OfflineItemFilterSource chipFilterSource) {
+        mPrefetchStatusProvider = prefetchStatusProvider;
         mChipsProvider = new FilterChipsProvider(type -> handleChipSelected(), chipFilterSource);
         mChipsCoordinator = new ChipsCoordinator(context, mChipsProvider);
 
         mModel = new PropertyModel(FilterProperties.ALL_KEYS);
         mViewBinder = new FilterViewBinder();
         mView = new FilterView(context);
-        mModel.addObserver(new PropertyModelChangeProcessor<PropertyModel, FilterView, PropertyKey>(
-                mModel, mView, mViewBinder));
+        mModel.addObserver(new PropertyModelChangeProcessor<>(mModel, mView, mViewBinder));
 
         mModel.setValue(
                 FilterProperties.CHANGE_LISTENER, selectedTab -> handleTabSelected(selectedTab));
         selectTab(TabType.FILES);
 
-        // TODO(shaktisahu): Check if prefetch UI is enabled.
-        mModel.setValue(FilterProperties.SHOW_TABS, true);
+        mModel.setValue(FilterProperties.SHOW_TABS, mPrefetchStatusProvider.enabled());
     }
 
     /** @return The {@link View} representing this widget. */

chrome/android/java/src/org/chromium/chrome/browser/download/home/filter/OfflineItemFilter.java

@@ -70,12 +70,17 @@ public abstract class OfflineItemFilter
         addItems(mSource.getItems());
     }
 
-    // OfflineItemSource implementation.
+    // OfflineItemFilterSource implementation.
     @Override
     public Set<OfflineItem> getItems() {
         return mItems;
     }
 
+    @Override
+    public boolean areItemsAvailable() {
+        return mSource.areItemsAvailable();
+    }
+
     @Override
     public void addObserver(OfflineItemFilterObserver observer) {
         mObservers.addObserver(observer);
@@ -112,6 +117,11 @@ public abstract class OfflineItemFilter
         for (OfflineItemFilterObserver obs : mObservers) obs.onItemUpdated(oldItem, item);
     }
 
+    @Override
+    public void onItemsAvailable() {
+        for (OfflineItemFilterObserver obs : mObservers) obs.onItemsAvailable();
+    }
+
     // Helper method to help incorporate a collection of items into this filtered version.
     private void addItems(Collection<OfflineItem> items) {
         Set<OfflineItem> added = new HashSet<>();

chrome/android/java/src/org/chromium/chrome/browser/download/home/filter/OfflineItemFilterObserver.java

@@ -32,4 +32,11 @@ public interface OfflineItemFilterObserver {
      * @param item    The new {@link OfflineItem} after the update.
      */
     void onItemUpdated(OfflineItem oldItem, OfflineItem item);
+
+    /**
+     * Called when the underlying {@link OfflineItem}s are available.  This is meant to help detect
+     * a difference between an empty set and a set that is not loaded yet.
+     */
+    default void
+        onItemsAvailable() {}
 }
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/download/home/filter/OfflineItemFilterSource.java

@@ -19,6 +19,12 @@ public interface OfflineItemFilterSource {
      */
     Collection<OfflineItem> getItems();
 
+    /**
+     * @return Whether or not the items are available, which is meant to help determine the
+     * difference between an empty set and a set that hasn't loaded yet.
+     */
+    boolean areItemsAvailable();
+
     /**
      * Registers {@code observer} to be notified of changes to the item collection managed by this
      * source.

chrome/android/java/src/org/chromium/chrome/browser/download/home/list/DateOrderedListCoordinator.java

@@ -8,6 +8,8 @@ import android.content.Context;
 import android.view.View;
 
 import org.chromium.base.Callback;
+import org.chromium.chrome.browser.download.home.PrefetchStatusProvider;
+import org.chromium.chrome.browser.download.home.empty.EmptyCoordinator;
 import org.chromium.chrome.browser.download.home.filter.FilterCoordinator;
 import org.chromium.chrome.browser.download.home.filter.Filters.FilterType;
 import org.chromium.chrome.browser.download.home.list.ListItem.ViewListItem;
@@ -43,7 +45,7 @@ public class DateOrderedListCoordinator {
     }
 
     private final FilterCoordinator mFilterCoordinator;
-    private final EmptyViewCoordinator mEmptyViewCoordinator;
+    private final EmptyCoordinator mEmptyCoordinator;
     private final DateOrderedListMediator mMediator;
     private final DateOrderedListView mView;
 
@@ -61,20 +63,24 @@ public class DateOrderedListCoordinator {
             OfflineContentProvider provider, DeleteController deleteController,
             SelectionDelegate<ListItem> selectionDelegate,
             FilterCoordinator.Observer filterObserver) {
+        // TODO(shaktisahu): Use a real provider/have this provider query the real data source.
+        PrefetchStatusProvider prefetchProvider = new PrefetchStatusProvider();
+
         ListItemModel model = new ListItemModel();
         DecoratedListItemModel decoratedModel = new DecoratedListItemModel(model);
         mView = new DateOrderedListView(context, decoratedModel);
         mMediator = new DateOrderedListMediator(
                 offTheRecord, provider, deleteController, selectionDelegate, model);
 
-        // Hook up the FilterCoordinator with our mediator.
-        mFilterCoordinator = new FilterCoordinator(context, mMediator.getFilterSource());
+        mEmptyCoordinator =
+                new EmptyCoordinator(context, prefetchProvider, mMediator.getEmptySource());
+
+        mFilterCoordinator =
+                new FilterCoordinator(context, prefetchProvider, mMediator.getFilterSource());
         mFilterCoordinator.addObserver(mMediator::onFilterTypeSelected);
         mFilterCoordinator.addObserver(filterObserver);
+        mFilterCoordinator.addObserver(mEmptyCoordinator);
 
-        mEmptyViewCoordinator =
-                new EmptyViewCoordinator(context, decoratedModel, mMediator.getFilterSource());
-        mFilterCoordinator.addObserver(mEmptyViewCoordinator::onFilterTypeSelected);
         decoratedModel.setHeader(new ViewListItem(Long.MAX_VALUE, mFilterCoordinator.getView()));
     }
 

chrome/android/java/src/org/chromium/chrome/browser/download/home/list/DateOrderedListMediator.java

@@ -138,6 +138,14 @@ class DateOrderedListMediator {
         return mDeleteUndoFilter;
     }
 
+    /**
+     * @return The {@link OfflineItemFilterSource} that should be used to determine whether there
+     * are no items and empty view should be shown.
+     */
+    public OfflineItemFilterSource getEmptySource() {
+        return mTypeFilter;
+    }
+
     private void onDeleteItem(OfflineItem item) {
         onDeleteItems(CollectionUtil.newArrayList(item));
     }

chrome/android/java/src/org/chromium/chrome/browser/download/home/list/EmptyViewCoordinator.java

-// Copyright 2018 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.chrome.browser.download.home.list;
-
-import android.content.Context;
-import android.graphics.drawable.Drawable;
-import android.os.Handler;
-import android.support.graphics.drawable.VectorDrawableCompat;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.widget.TextView;
-
-import org.chromium.chrome.R;
-import org.chromium.chrome.browser.download.home.filter.Filters;
-import org.chromium.chrome.browser.download.home.filter.OfflineItemFilterObserver;
-import org.chromium.chrome.browser.download.home.filter.OfflineItemFilterSource;
-import org.chromium.chrome.browser.download.home.list.ListItem.ViewListItem;
-import org.chromium.components.offline_items_collection.OfflineItem;
-
-import java.util.Collection;
-
-/**
- * A class that determines whether an empty view should be shown and inserts into the model.
- */
-class EmptyViewCoordinator implements OfflineItemFilterObserver {
-    private final Context mContext;
-    private final DecoratedListItemModel mDecoratedModel;
-    private final OfflineItemFilterSource mSource;
-    private final Handler mHandler = new Handler();
-
-    private ViewListItem mEmptyViewItem;
-
-    private @Filters.FilterType int mCurrentFilter;
-
-    /** Creates a {@link EmptyViewCoordinator} instance that wraos {@code model}. */
-    public EmptyViewCoordinator(Context context, DecoratedListItemModel decoratedModel,
-            OfflineItemFilterSource source) {
-        mContext = context;
-        mDecoratedModel = decoratedModel;
-        mSource = source;
-        mSource.addObserver(this);
-        mHandler.post(() -> onFilterTypeSelected(mCurrentFilter));
-    }
-
-    public void onFilterTypeSelected(@Filters.FilterType int filter) {
-        boolean hasEmptyView = mEmptyViewItem != null;
-        if (filter == mCurrentFilter && hasEmptyView == isEmpty()) return;
-
-        mCurrentFilter = filter;
-        updateForEmptyView();
-    }
-
-    private boolean isEmpty() {
-        boolean showingPrefetch = mCurrentFilter == Filters.FilterType.PREFETCHED;
-        for (OfflineItem item : mSource.getItems()) {
-            if (showingPrefetch && item.isSuggested) return false;
-            if (!showingPrefetch && !item.isSuggested) return false;
-        }
-
-        return true;
-    }
-
-    private void updateForEmptyView() {
-        mEmptyViewItem = isEmpty() ? createEmptyView() : null;
-        mDecoratedModel.setEmptyView(mEmptyViewItem);
-    }
-
-    private ViewListItem createEmptyView() {
-        boolean showingPrefetch = mCurrentFilter == Filters.FilterType.PREFETCHED;
-        // TODO(shaktisahu): Supply correct value for prefetch settings.
-        boolean prefetchEnabled = true;
-        View emptyView = LayoutInflater.from(mContext).inflate(R.layout.downloads_empty_view, null);
-
-        Drawable emptyDrawable = VectorDrawableCompat.create(mContext.getResources(),
-                showingPrefetch ? R.drawable.ic_library_news_feed : R.drawable.downloads_big,
-                mContext.getTheme());
-
-        TextView emptyTextView = emptyView.findViewById(R.id.empty_view);
-        emptyTextView.setText(showingPrefetch
-                        ? (prefetchEnabled ? R.string.download_manager_prefetch_tab_empty
-                                           : R.string.download_manager_enable_prefetch_message)
-                        : R.string.download_manager_ui_empty);
-        emptyTextView.setCompoundDrawablesWithIntrinsicBounds(null, emptyDrawable, null, null);
-
-        return new ViewListItem(Long.MAX_VALUE - 1, emptyView);
-    }
-
-    // OfflineItemFilterObserver implementation.
-    @Override
-    public void onItemsAdded(Collection<OfflineItem> items) {
-        mHandler.post(() -> onFilterTypeSelected(mCurrentFilter));
-    }
-
-    @Override
-    public void onItemsRemoved(Collection<OfflineItem> items) {
-        mHandler.post(() -> onFilterTypeSelected(mCurrentFilter));
-    }
-
-    @Override
-    public void onItemUpdated(OfflineItem oldItem, OfflineItem item) {
-        mHandler.post(() -> onFilterTypeSelected(mCurrentFilter));
-    }
-}

chrome/android/java_sources.gni

@@ -444,6 +444,11 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/download/home/DownloadManagerCoordinatorFactory.java",
   "java/src/org/chromium/chrome/browser/download/home/DownloadManagerCoordinatorImpl.java",
   "java/src/org/chromium/chrome/browser/download/home/OfflineItemSource.java",
+  "java/src/org/chromium/chrome/browser/download/home/PrefetchStatusProvider.java",
+  "java/src/org/chromium/chrome/browser/download/home/empty/EmptyCoordinator.java",
+  "java/src/org/chromium/chrome/browser/download/home/empty/EmptyProperties.java",
+  "java/src/org/chromium/chrome/browser/download/home/empty/EmptyView.java",
+  "java/src/org/chromium/chrome/browser/download/home/empty/EmptyViewBinder.java",
   "java/src/org/chromium/chrome/browser/download/home/filter/DeleteUndoOfflineItemFilter.java",
   "java/src/org/chromium/chrome/browser/download/home/filter/Filters.java",
   "java/src/org/chromium/chrome/browser/download/home/filter/FilterChipsProvider.java",
@@ -474,7 +479,6 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/download/home/list/DateOrderedListView.java",
   "java/src/org/chromium/chrome/browser/download/home/list/DateOrderedListViewAdapter.java",
   "java/src/org/chromium/chrome/browser/download/home/list/DecoratedListItemModel.java",
-  "java/src/org/chromium/chrome/browser/download/home/list/EmptyViewCoordinator.java",
   "java/src/org/chromium/chrome/browser/download/home/list/ItemUtils.java",
   "java/src/org/chromium/chrome/browser/download/home/list/ListItem.java",
   "java/src/org/chromium/chrome/browser/download/home/list/ListItemModel.java",

chrome/android/junit/src/org/chromium/chrome/browser/download/home/filter/OfflineItemFilterTest.java

@@ -104,6 +104,23 @@ public class OfflineItemFilterTest {
         Assert.assertEquals(items, filter.getItems());
     }
 
+    @Test
+    public void testItemsAvailable() {
+        when(mSource.areItemsAvailable()).thenReturn(false);
+
+        OfflineItemFilterImpl filter = new OfflineItemFilterImpl(mSource);
+        filter.addObserver(mObserver);
+        verify(mSource, times(1)).addObserver(filter);
+        verify(mSource, times(1)).getItems();
+
+        Assert.assertFalse(filter.areItemsAvailable());
+
+        when(mSource.areItemsAvailable()).thenReturn(true);
+        filter.onItemsAvailable();
+        verify(mObserver, times(1)).onItemsAvailable();
+        Assert.assertTrue(filter.areItemsAvailable());
+    }
+
     @Test
     public void testFiltering() {
         OfflineItem item1 = new OfflineItem();