From eb36f95b9fc2816c6503272f960660982a661b16 Mon Sep 17 00:00:00 2001
From: Annie Chin <afchin@google.com>
Date: Thu, 8 Dec 2016 17:27:19 -0800
Subject: Support accessibility in History.

Fixes: 33429660

Toggle accessibility importance of main Calculator elements based on
the open state of DragLayout. This is necessary due to the fact that
Talkback does not use visibility as a cue for determining accessibility
importance in RelativeLayout, which is the base class of DragLayout.
Without this workaround, it's possible to traverse to main Calculator
elements even when HistoryFragment is open.

Change-Id: Iff3d775ec72aa50fe8972c1def32f4999d90a8f9
---
 res/layout/activity_calculator_main.xml          |  4 +++-
 src/com/android/calculator2/Calculator.java      | 24 ++++++++++++++++++++----
 src/com/android/calculator2/HistoryFragment.java |  2 --
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/res/layout/activity_calculator_main.xml b/res/layout/activity_calculator_main.xml
index 9d19b53..4173d33 100644
--- a/res/layout/activity_calculator_main.xml
+++ b/res/layout/activity_calculator_main.xml
@@ -21,7 +21,9 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-    <include layout="@layout/activity_calculator" />
+    <include
+        android:id="@+id/main_calculator"
+        layout="@layout/activity_calculator" />
 
     <FrameLayout
         android:id="@+id/history_frame"
diff --git a/src/com/android/calculator2/Calculator.java b/src/com/android/calculator2/Calculator.java
index b45597a..44ad0ac 100644
--- a/src/com/android/calculator2/Calculator.java
+++ b/src/com/android/calculator2/Calculator.java
@@ -277,6 +277,7 @@ public class Calculator extends Activity
     private View mDeleteButton;
     private View mClearButton;
     private View mEqualButton;
+    private View mMainCalculator;
 
     private TextView mInverseToggle;
     private TextView mModeToggle;
@@ -390,6 +391,7 @@ public class Calculator extends Activity
             }
         });
 
+        mMainCalculator = findViewById(R.id.main_calculator);
         mDisplayView = (CalculatorDisplay) findViewById(R.id.display);
         mModeView = (TextView) findViewById(R.id.mode);
         mFormulaText = (CalculatorFormula) findViewById(R.id.formula);
@@ -463,6 +465,14 @@ public class Calculator extends Activity
         if (mDisplayView.isToolbarVisible()) {
             showAndMaybeHideToolbar();
         }
+        // If HistoryFragment is showing, hide the main Calculator elements from accessibility.
+        // This is because Talkback does not use visibility as a cue for RelativeLayout elements,
+        // and RelativeLayout is the base class of DragLayout.
+        // If we did not do this, it would be possible to traverse to main Calculator elements from
+        // HistoryFragment.
+        mMainCalculator.setImportantForAccessibility(
+                mDragLayout.isOpen() ? View.IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS
+                        : View.IMPORTANT_FOR_ACCESSIBILITY_AUTO);
     }
 
     @Override
@@ -734,11 +744,13 @@ public class Calculator extends Activity
 
     private void removeHistoryFragment() {
         final FragmentManager manager = getFragmentManager();
-        if (manager == null || manager.isDestroyed()) {
-            return;
+        if (manager != null && !manager.isDestroyed()) {
+            manager.popBackStackImmediate(HistoryFragment.TAG,
+                    FragmentManager.POP_BACK_STACK_INCLUSIVE);
         }
-        manager.popBackStackImmediate(HistoryFragment.TAG,
-                FragmentManager.POP_BACK_STACK_INCLUSIVE);
+
+        // When HistoryFragment is hidden, the main Calculator is important for accessibility again.
+        mMainCalculator.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_AUTO);
     }
 
     /**
@@ -1329,6 +1341,10 @@ public class Calculator extends Activity
                     .addToBackStack(HistoryFragment.TAG)
                     .commit();
             manager.executePendingTransactions();
+
+            // When HistoryFragment is visible, hide all descendants of the main Calculator view.
+            mMainCalculator.setImportantForAccessibility(
+                    View.IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS);
         }
         // TODO: pass current scroll position of result
     }
diff --git a/src/com/android/calculator2/HistoryFragment.java b/src/com/android/calculator2/HistoryFragment.java
index 2401f36..86ab138 100644
--- a/src/com/android/calculator2/HistoryFragment.java
+++ b/src/com/android/calculator2/HistoryFragment.java
@@ -26,7 +26,6 @@ import android.support.v4.content.ContextCompat;
 import android.support.v7.widget.RecyclerView;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
-import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Toolbar;
@@ -130,7 +129,6 @@ public class HistoryFragment extends Fragment {
                 getActivity().onBackPressed();
             }
         });
-
         return view;
     }
 
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