Fix animation for RESULT state.

Fixes: 32948596

Introduce isResultState() and pass its value to HistoryAdapter. We
actually can't accurately determine RESULT state from the Evaluator.

Change-Id: Ie50c5743fac8af680073c60a3e9cc9b58ccff167

3 files changed, 21 insertions, 4 deletions

diff --git a/src/com/android/calculator2/Calculator.java b/src/com/android/calculator2/Calculator.java
index 02047af..e22e628 100644
--- a/src/com/android/calculator2/Calculator.java
+++ b/src/com/android/calculator2/Calculator.java
@@ -462,6 +462,10 @@ public class Calculator extends Activity
         }
     }
 
+    public boolean isResultState() {
+        return mCurrentState == CalculatorState.RESULT;
+    }
+
     @Override
     protected void onDestroy() {
         mDragLayout.removeDragCallback(mDragCallback);
diff --git a/src/com/android/calculator2/HistoryAdapter.java b/src/com/android/calculator2/HistoryAdapter.java
index ca5509c..dba887f 100644
--- a/src/com/android/calculator2/HistoryAdapter.java
+++ b/src/com/android/calculator2/HistoryAdapter.java
@@ -39,6 +39,8 @@ public class HistoryAdapter extends RecyclerView.Adapter<HistoryAdapter.ViewHold
 
     private List<HistoryItem> mDataSet;
 
+    private boolean mIsResultState;
+
     public HistoryAdapter(Calculator calculator, ArrayList<HistoryItem> dataSet,
             String currentExpressionDescription) {
         mEvaluator = Evaluator.getInstance(calculator);
@@ -131,6 +133,10 @@ public class HistoryAdapter extends RecyclerView.Adapter<HistoryAdapter.ViewHold
         }
     }
 
+    public void setIsResultState(boolean isResult) {
+        mIsResultState = isResult;
+    }
+
     public static class ViewHolder extends RecyclerView.ViewHolder {
 
         private TextView mDate;
diff --git a/src/com/android/calculator2/HistoryFragment.java b/src/com/android/calculator2/HistoryFragment.java
index dcc7b25..afc8803 100644
--- a/src/com/android/calculator2/HistoryFragment.java
+++ b/src/com/android/calculator2/HistoryFragment.java
@@ -135,7 +135,10 @@ public class HistoryFragment extends Fragment {
         dragLayout.removeDragCallback(mDragCallback);
         dragLayout.addDragCallback(mDragCallback);
 
-        mEvaluator = Evaluator.getInstance((Calculator) getActivity());
+        final Calculator activity = (Calculator) getActivity();
+        final boolean isResultState = activity.isResultState();
+
+        mEvaluator = Evaluator.getInstance(activity);
 
         if (mEvaluator != null) {
             initializeController();
@@ -144,9 +147,12 @@ public class HistoryFragment extends Fragment {
 
             final ArrayList<HistoryItem> newDataSet = new ArrayList<>();
 
-            if (!EvaluatorStateUtils.isDisplayEmpty(mEvaluator)) {
-                // Add the current expression as the first element in the list (the layout is reversed
-                // and we want the current expression to be the last one in the recyclerview).
+            if (!EvaluatorStateUtils.isDisplayEmpty(mEvaluator) && !isResultState) {
+                // Add the current expression as the first element in the list (the layout is
+                // reversed and we want the current expression to be the last one in the
+                // recyclerview).
+                // If we are in the result state, the result will animate to the last history
+                // element in the list and there will be no "Current Expression."
                 newDataSet.add(new HistoryItem(Evaluator.MAIN_INDEX, System.currentTimeMillis(),
                         mEvaluator.getExprAsSpannable(0)));
             }
@@ -158,6 +164,7 @@ public class HistoryFragment extends Fragment {
             }
             mDataSet = newDataSet;
             mAdapter.setDataSet(mDataSet);
+            mAdapter.setIsResultState(isResultState);
         }
 
         mAdapter.notifyDataSetChanged();