import xml into another xml

You can use

<include  layout="@layout/commonlayout" android:id="@+id/id" />

commonlayout.xml should be defined in res/layout where you can add the repeated parts.

As Labeeb P rightly said, it works. Just want to add that you can also override parameters too:

<include  
        layout="@layout/commonlayout" 
        android:id="@+id/id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_marginLeft="2sp"
        android:layout_marginRight="2sp"
 />

In addition to those great answers, you can also avoid code duplication by using the <merge> tag, like so:

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <Button
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
        android:text="@string/add"/>

    <Button
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
        android:text="@string/delete"/>

</merge>

The <merge> part gets stripped when you include it into other xml. This might help including more than a single Button at a time. See the official documentation.