Announce when formula has been completely deleted.

Bug: 23224425
Bug: 23695835

This adds a "cleared" announcement when last token/character is deleted.
Also change the existing "clear" announcements to "cleared".

Improve the comments for desc_clr and desc_del to address prior
misunderstandings.

Improve xml comment formatting consistency.

Change-Id: Ibe5197ceac132b73d72f8ace3982238249f5e82b
(cherry picked from commit db6f99979b713e491ace2f0cd9315e5c1616269b)

2 files changed, 20 insertions, 8 deletions

diff --git a/res/values/strings.xml b/res/values/strings.xml
index 959b979..50bc983 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -118,6 +118,10 @@
     <string name="eq" translatable="false">=</string>
     <!-- Clear button to clear the currently entered expression. [CHAR_LIMIT=4] -->
     <string name="clr">clr</string>
+    <!--
+      Announced when all characters are removed from Formula, e.g. after clear. [CHAR_LIMIT=NONE]
+      -->
+    <string name="cleared">cleared</string>
     <!-- Delete button to remove last entered token. [CHAR_LIMIT=4] -->
     <string name="del">del</string>
     <!-- Toggle button to show/hide inverse functions. [CHAR_LIMIT=4] -->
@@ -197,9 +201,12 @@
 
     <!-- Content description for '=' button. [CHAR_LIMIT=NONE] -->
     <string name="desc_eq">equals</string>
-    <!-- Content description for "clr" button. [CHAR_LIMIT=NONE] -->
+    <!-- Content description for "clr" button. Deletes entire formula. [CHAR_LIMIT=NONE] -->
     <string name="desc_clr">clear</string>
-    <!-- Content description for "del" button. [CHAR_LIMIT=NONE] -->
+    <!--
+      Content description for "del" button. Deletes single character. Should differ
+      from desc_clr. [CHAR_LIMIT=NONE]
+      -->
     <string name="desc_del">delete</string>
     <!-- Content description for "inv" button to show inverse functions. [CHAR_LIMIT=NONE] -->
     <string name="desc_inv_off">show inverse functions</string>
@@ -221,7 +228,7 @@
       be used, e.g. "Division by 0". Exceeding the limit will result in a truncated string.
 
       [CHAR_LIMIT=20]
-    -->
+      -->
     <string name="error_zero_divide">Can\'t divide by 0</string>
 
     <!-- Toast shown when text is copied to the clipboard. [CHAR_LIMIT=40] -->
@@ -239,7 +246,7 @@
       "timing out".
 
       [CHAR_LIMIT=40]
-    -->
+      -->
     <string name="ok_remove_timeout">Use longer timeouts</string>
     <!-- Button label to dismiss informative text message. [CHAR_LIMIT=40] -->
     <string name="dismiss">Dismiss</string>
diff --git a/src/com/android/calculator2/Calculator.java b/src/com/android/calculator2/Calculator.java
index 4eecb50..86953ef 100644
--- a/src/com/android/calculator2/Calculator.java
+++ b/src/com/android/calculator2/Calculator.java
@@ -454,7 +454,7 @@ public class Calculator extends Activity
             if (KeyMaps.isBinary(id) || KeyMaps.isSuffix(id)) {
                 mEvaluator.collapse();
             } else {
-                announceClearForAccessibility();
+                announceClearedForAccessibility();
                 mEvaluator.clear();
             }
             setState(CalculatorState.INPUT);
@@ -653,6 +653,11 @@ public class Calculator extends Activity
         } else {
             mEvaluator.delete();
         }
+        if (mEvaluator.getExpr().isEmpty()
+                && (mUnprocessedChars == null || mUnprocessedChars.isEmpty())) {
+            // Resulting formula won't be announced, since it's empty.
+            announceClearedForAccessibility();
+        }
         redisplayAfterFormulaChange();
     }
 
@@ -710,8 +715,8 @@ public class Calculator extends Activity
         animatorSet.start();
     }
 
-    private void announceClearForAccessibility() {
-        mResultText.announceForAccessibility(getResources().getString(R.string.desc_clr));
+    private void announceClearedForAccessibility() {
+        mResultText.announceForAccessibility(getResources().getString(R.string.cleared));
     }
 
     private void onClear() {
@@ -719,7 +724,7 @@ public class Calculator extends Activity
             return;
         }
         cancelIfEvaluating(true);
-        announceClearForAccessibility();
+        announceClearedForAccessibility();
         reveal(mCurrentButton, R.color.calculator_accent_color, new AnimatorListenerAdapter() {
             @Override
             public void onAnimationEnd(Animator animation) {