Calculator (Input xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:background="@color/black"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/output"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="@dimen/_25sdp"
        android:fontFamily="sans-serif-light"
        android:textColor="@color/white"
        android:background="#000000"
        android:padding="@dimen/_10sdp"
        android:text=""/>


    <TextView
        android:id="@+id/input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="@dimen/_45sdp"
        android:fontFamily="sans-serif-light"
        android:textColor="@color/white"
        android:background="#000000"
        android:padding="@dimen/_10sdp"
        android:text=""/>


</LinearLayout>