📰 Ensure NTP Tiles keep tracking recent data

chrome/android/java/src/org/chromium/chrome/browser/suggestions/TileView.java

 // Copyright 2015 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.suggestions;
 
 import android.content.Context;
 import android.util.AttributeSet;
-import android.view.View;
 import android.widget.FrameLayout;
 import android.widget.ImageView;
 import android.widget.TextView;
 
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ntp.TitleUtil;
 
 /**
  * The view for a site suggestion tile. Displays the title of the site beneath a large icon. If a
  * large icon isn't available, displays a rounded rectangle with a single letter in its place.
  */
 public class TileView extends FrameLayout {
-    /**
-     * The tile that holds the data to populate this view.
-     */
-    private Tile mTile;
+    /** The url currently associated to this tile. */
+    private String mUrl;
+
+    private TextView mTitleView;
+    private ImageView mIconView;
+    private ImageView mBadgeView;
 
     /**
      * Constructor for inflating from XML.
      */
     public TileView(Context context, AttributeSet attrs) {
         super(context, attrs);
     }
 
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+
+        mTitleView = (TextView) findViewById(R.id.tile_view_title);
+        mIconView = (ImageView) findViewById(R.id.tile_view_icon);
+        mBadgeView = (ImageView) findViewById(R.id.offline_badge);
+    }
+
     /**
      * Initializes the view using the data held by {@code tile}. This should be called immediately
      * after inflation.
      * @param tile The tile that holds the data to populate this view.
      * @param titleLines The number of text lines to use for the tile title.
      */
     public void initialize(Tile tile, int titleLines) {
-        mTile = tile;
-        TextView titleView = (TextView) findViewById(R.id.tile_view_title);
-        titleView.setLines(titleLines);
-        titleView.setText(TitleUtil.getTitleForDisplay(mTile.getTitle(), mTile.getUrl()));
-        renderIcon();
-        findViewById(R.id.offline_badge)
-                .setVisibility(mTile.isOfflineAvailable() ? View.VISIBLE : View.GONE);
+        mTitleView.setLines(titleLines);
+        mUrl = tile.getUrl();
+        renderTile(tile);
     }
 
-    /**
-     * @return The tile that holds the data to populate this view.
-     */
-    public Tile getTile() {
-        return mTile;
+    /** @return The url associated to this view. */
+    public String getUrl() {
+        return mUrl;
     }
 
     /**
      * Renders the icon held by the {@link Tile} or clears it from the view if the icon is null.
      */
-    public void renderIcon() {
-        ((ImageView) findViewById(R.id.tile_view_icon)).setImageDrawable(mTile.getIcon());
+    public void renderIcon(Tile tile) {
+        mIconView.setImageDrawable(tile.getIcon());
+    }
+
+    /** Updates the view if there have been changes since the last time. */
+    public void updateIfDataChanged(Tile tile) {
+        if (!isUpToDate(tile)) renderTile(tile);
+    }
+
+    private boolean isUpToDate(Tile tile) {
+        assert mUrl.equals(tile.getUrl());
+
+        if (tile.getIcon() != mIconView.getDrawable()) return false;
+        if (tile.isOfflineAvailable() != (mBadgeView.getVisibility() == VISIBLE)) return false;
+        // We don't check the title since it's not likely to change, but that could also be done.
+        return true;
+    }
+
+    private void renderTile(Tile tile) {
+        // A TileView should not be reused across tiles having different urls, as registered
+        // callbacks and handlers use it to look up the data and notify the rest of the system.
+        assert mUrl.equals(tile.getUrl());
+        mTitleView.setText(TitleUtil.getTitleForDisplay(tile.getTitle(), tile.getUrl()));
+        mBadgeView.setVisibility(tile.isOfflineAvailable() ? VISIBLE : GONE);
+        renderIcon(tile);
     }
 }