In most of the android application we have to reuse certain set of layouts. Every time writing same set of code(xml) slows down the user interface performance. To achieve the feature of re-usabilty in our application we have tags include and merge. include and merge tags embedded the reusable layout in our main layout/current layout.

Creating reusable layout:

re_use.xml

    <ImageView
        android:id="@+id/ivImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:src="@drawable/android" />

</LinearLayout>

Use of include tag: Using include tag we will reuse the component/layout re_use.xml in our main layout.

main_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <include layout="@layout/re_use"/>    

    <TextView
        android:id="@+id/tvText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

</LinearLayout>

Another way to include layout: In case of overriding the layout attributes. width and height will be necessary in order to take effect.

<include android:id="@+id/title"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         layout="@layout/re_use"/>

Use of merge tag

To overcome the redundancy in our code tag is most appropriate to eliminate redundant view groups. It will increase the performance as well as reduces the unnecessary code in our UI.

re_use.xml

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

    <TextView
        android:id="@+id/tvText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello India!"/>

</merge>

main_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <include layout="@layout/re_use"/>

    <ImageView
        android:id="@+id/ivImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:src="@drawable/android" />

</LinearLayout>