Android: TabWebContentsUserData

Tab is managing numerous classes used for the active WebContents
it is showing. This CL defines a TabWebContentsUserData that they
can inherit from. New interface initWebContents/cleanupWebContents
are to be defined by child classes.

It is first applied to TabGestureStateListener. The other classes
will follow.

Bug: 884597
Change-Id: I7d31b5a2d4c64aef49697fb0bbe8e3db4e3b2443
Reviewed-on: https://chromium-review.googlesource.com/c/1229734
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596515}

chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java

@@ -1781,7 +1781,7 @@ public class Tab
                     new TabContextMenuPopulator(
                             mDelegateFactory.createContextMenuPopulator(this), this));
 
-            TabGestureStateListener.init(this);
+            TabGestureStateListener.create(this, this::getFullscreenManager);
 
             // The InfoBarContainer needs to be created after the ContentView has been natively
             // initialized.

chrome/android/java/src/org/chromium/chrome/browser/tab/TabGestureStateListener.java

@@ -4,7 +4,7 @@
 
 package org.chromium.chrome.browser.tab;
 
-import org.chromium.base.UserData;
+import org.chromium.base.Supplier;
 import org.chromium.chrome.browser.fullscreen.FullscreenManager;
 import org.chromium.content_public.browser.GestureListenerManager;
 import org.chromium.content_public.browser.GestureStateListener;
@@ -13,91 +13,75 @@ import org.chromium.content_public.browser.WebContents;
 /**
  * {@link GestureStateListener} implementation for a {@link Tab}. Associated with an active
  * {@link WebContents} via its {@link GestureListenerManager}. The listener is managed as
- * UserData and added to (or removed from) the active WebContents.
+ * UserData for the Tab, with WebContents updated as the active one changes over time.
  */
-public final class TabGestureStateListener
-        extends EmptyTabObserver implements GestureStateListener, UserData {
+public final class TabGestureStateListener extends TabWebContentsUserData {
     private static final Class<TabGestureStateListener> USER_DATA_KEY =
             TabGestureStateListener.class;
 
-    private final Tab mTab;
-    private WebContents mWebContents;
+    private GestureStateListener mGestureListener;
+    private Supplier<FullscreenManager> mFullscreenManager;
 
     /**
-     * Initializes (creates if not present) TabGestureStateListener by adding it to
-     * {@link GestureListenerManager} of the active {@link WebContents}.
+     * Creates TabGestureStateListener and lets the WebContentsUserData of the Tab manage it.
      * @param tab Tab instance that the active WebContents instance gets loaded in.
      */
-    public static void init(Tab tab) {
-        TabGestureStateListener listener = tab.getUserDataHost().getUserData(USER_DATA_KEY);
-        if (listener == null) {
-            listener = tab.getUserDataHost().setUserData(
-                    USER_DATA_KEY, new TabGestureStateListener(tab));
-        }
-        listener.init();
+    public static void create(Tab tab, Supplier<FullscreenManager> fullscreen) {
+        tab.getUserDataHost().setUserData(
+                USER_DATA_KEY, new TabGestureStateListener(tab, fullscreen));
     }
 
-    private TabGestureStateListener(Tab tab) {
-        mTab = tab;
-    }
-
-    private void init() {
-        WebContents newWebContents = mTab.getWebContents();
-        if (newWebContents == mWebContents) return;
-        if (mWebContents != null) removeFromManager();
-        if (newWebContents != null) {
-            GestureListenerManager.fromWebContents(newWebContents).addListener(this);
-        }
-        mWebContents = newWebContents;
-    }
-
-    // TabObserver
-
-    @Override
-    public void onWebContentsSwapped(Tab tab, boolean didStartLoad, boolean didFinishLoad) {
-        init();
+    private TabGestureStateListener(Tab tab, Supplier<FullscreenManager> fullscreenManager) {
+        super(tab);
+        mFullscreenManager = fullscreenManager;
     }
 
     @Override
-    public void onDestroyed(Tab tab) {
-        removeFromManager();
-    }
-
-    private void removeFromManager() {
-        GestureListenerManager manager = GestureListenerManager.fromWebContents(mWebContents);
-        if (manager != null) manager.removeListener(this);
+    public void initWebContents(WebContents webContents) {
+        GestureListenerManager manager = GestureListenerManager.fromWebContents(webContents);
+        mGestureListener = new GestureStateListener() {
+            @Override
+            public void onFlingStartGesture(int scrollOffsetY, int scrollExtentY) {
+                onScrollingStateChanged();
+            }
+
+            @Override
+            public void onFlingEndGesture(int scrollOffsetY, int scrollExtentY) {
+                onScrollingStateChanged();
+            }
+
+            @Override
+            public void onScrollStarted(int scrollOffsetY, int scrollExtentY) {
+                onScrollingStateChanged();
+            }
+
+            @Override
+            public void onScrollEnded(int scrollOffsetY, int scrollExtentY) {
+                onScrollingStateChanged();
+            }
+
+            private void onScrollingStateChanged() {
+                FullscreenManager fullscreenManager = mFullscreenManager.get();
+                if (fullscreenManager == null) return;
+                fullscreenManager.onContentViewScrollingStateChanged(isScrollInProgress());
+            }
+
+            private boolean isScrollInProgress() {
+                return manager != null ? manager.isScrollInProgress() : false;
+            }
+        };
+        manager.addListener(mGestureListener);
     }
 
-    // GestureStateListener
-
     @Override
-    public void onFlingStartGesture(int scrollOffsetY, int scrollExtentY) {
-        onScrollingStateChanged();
+    public void cleanupWebContents(WebContents webContents) {
+        GestureListenerManager manager = GestureListenerManager.fromWebContents(webContents);
+        if (manager != null) manager.removeListener(mGestureListener);
+        mGestureListener = null;
     }
 
     @Override
-    public void onFlingEndGesture(int scrollOffsetY, int scrollExtentY) {
-        onScrollingStateChanged();
-    }
-
-    @Override
-    public void onScrollStarted(int scrollOffsetY, int scrollExtentY) {
-        onScrollingStateChanged();
-    }
-
-    @Override
-    public void onScrollEnded(int scrollOffsetY, int scrollExtentY) {
-        onScrollingStateChanged();
-    }
-
-    private void onScrollingStateChanged() {
-        FullscreenManager fullscreenManager = mTab.getFullscreenManager();
-        if (fullscreenManager == null) return;
-        fullscreenManager.onContentViewScrollingStateChanged(isScrollInProgress());
-    }
-
-    private boolean isScrollInProgress() {
-        GestureListenerManager manager = GestureListenerManager.fromWebContents(mWebContents);
-        return manager != null ? manager.isScrollInProgress() : false;
+    public void destroy() {
+        cleanupWebContents(getWebContents());
     }
 }

chrome/android/java/src/org/chromium/chrome/browser/tab/TabWebContentsUserData.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.tab;
+
+import org.chromium.base.UserData;
+import org.chromium.content_public.browser.WebContents;
+
+/**
+ * UserData for a {@link Tab}. Used for a {@link WebContents} while it stays
+ * active for the Tab.
+ */
+public abstract class TabWebContentsUserData implements UserData {
+    private WebContents mWebContents;
+
+    public TabWebContentsUserData(Tab tab) {
+        tab.addObserver(new EmptyTabObserver() {
+            @Override
+            public void onContentChanged(Tab tab) {
+                if (mWebContents == tab.getWebContents()) return;
+                if (mWebContents != null) cleanupWebContents(mWebContents);
+                mWebContents = tab.getWebContents();
+                if (mWebContents != null) initWebContents(mWebContents);
+            }
+
+            @Override
+            public void onDestroyed(Tab tab) {
+                tab.removeObserver(this);
+            }
+        });
+    }
+
+    protected WebContents getWebContents() {
+        return mWebContents;
+    }
+
+    /**
+     * Called when {@link WebContents} becomes active (swapped in) for a {@link Tab}.
+     * @param webContents WebContents object that just became active.
+     */
+    public abstract void initWebContents(WebContents webContents);
+
+    /**
+     * Called when {@link WebContents} gets swapped out.
+     * @param webContents WebContents object that just became inactive.
+     */
+    public abstract void cleanupWebContents(WebContents webContents);
+}

chrome/android/java_sources.gni

@@ -1452,6 +1452,7 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java",
   "java/src/org/chromium/chrome/browser/tab/TabWebContentsDelegateAndroid.java",
   "java/src/org/chromium/chrome/browser/tab/TabWebContentsObserver.java",
+  "java/src/org/chromium/chrome/browser/tab/TabWebContentsUserData.java",
   "java/src/org/chromium/chrome/browser/tabmodel/AsyncTabParams.java",
   "java/src/org/chromium/chrome/browser/tabmodel/AsyncTabParamsManager.java",
   "java/src/org/chromium/chrome/browser/tabmodel/ChromeTabCreator.java",