Fix issue with tap-to-add on recycled WidgetCells

Updates BaseWidgetSheet to check if the last recorded widget cell
to show an add button is still showing an add button before deciding
how to handle the current click.

When a widget is recycled or loses focus, it will reset to the default
state of hiding the add button. However, BaseWidgetSheet still tracks
it. If that cell is clicked again after being reset, we want to show
the add button.

Bug: TODO
Test: manual
Flag: ACONFIG com.android.launcher3.enable_widget_tap_to_add TEAMFOOD
Change-Id: I4614674948a52b8908fabf5c0e5734bf76b9282b

src/com/android/launcher3/widget/BaseWidgetSheet.java

@@ -143,9 +143,17 @@ public abstract class BaseWidgetSheet extends AbstractSlideInView<BaseActivity>
 
         if (enableWidgetTapToAdd()) {
             scrollToWidgetCell(wc);
+
             if (mWidgetCellWithAddButton != null) {
-                // If there is a add button currently showing, hide it.
-                mWidgetCellWithAddButton.hideAddButton(/* animate= */ true);
+                if (mWidgetCellWithAddButton.isShowingAddButton()) {
+                    // If there is a add button currently showing, hide it.
+                    mWidgetCellWithAddButton.hideAddButton(/* animate= */ true);
+                } else {
+                    // The last recorded widget cell to show an add button is no longer showing it,
+                    // likely because the widget cell has been recycled or lost focus. If this is
+                    // the cell that has been clicked, we will show it below.
+                    mWidgetCellWithAddButton = null;
+                }
             }
 
             if (mWidgetCellWithAddButton != wc) {