Developing Complex UI Part 1

Layouts can be nested inside another layouts...

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
  android:paddingLeft="10dp"
   android:paddingRight="10dp" >
   
    <TextView android:text="Welcome to the Calculator App"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:gravity="left"/>
    <EditText
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="Enter the First Number"
        android:id="@+id/editText1"
        android:paddingTop="20dp"/>
   
    <EditText
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="Enter the Second Number"
        android:id="@+id/editText2"
        android:paddingTop="20dp"/>
   
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:weightSum="60"
        android:id="@+id/l1">
       
    <Button
        android:id="@+id/button1"
        android:text="Add"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="30"
        />   
       
    <Button
        android:id="@+id/button2"
        android:text="Sub"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         android:layout_weight="30"/>   
    </LinearLayout>
   
      <LinearLayout    
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:weightSum="60"
        android:id="@+id/l2"> 
       
        <Button
        android:id="@+id/button3"
        android:text="Mul"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="30"
        />   
       
    <Button
        android:id="@+id/button4"
        android:text="Div"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
         android:layout_weight="30"/>        
       
        </LinearLayout>
          
     
    <TextView
        android:text="Your Result is"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:paddingLeft="80dp"/>
   
   
</LinearLayout>

Following is the UI :