イベントリスナー 演算子紐付け
・findViewById
・setOnClickListener
(new onClickListenerForOperation(Operation.演算子));
+
findViewById(R.id.addition).setOnClickListener(new OnClickListenerForOperation(Operation.PLUS));
-
findViewById(R.id.subtraction).setOnClickListener(new OnClickListenerForOperation(Operation.SUBTRACTION));
*
findViewById(R.id.multiplication).setOnClickListener(new OnClickListenerForOperation(Operation.MULTIPLICATION));
/
findViewById(R.id.division).setOnClickListener(new OnClickListenerForOperation(Operation.DIVISION));