activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout

 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="com.xiditech.easysplashscreeen.MainActivity">
<include    

android:id="@+id/toolbar"    

layout="@layout/tool_bar"   

 />

    <TextView 

       android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:text="Hello World!"        

android:textSize="40dp"        

android:gravity="center"

        />
</RelativeLayout>

Code for Toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar 
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" 
android:layout_height="wrap_content"
android:background="@color/colorPrimary">

</android.support.v7.widget.Toolbar>