If you are using Linear Layout you have two attributes available to help you align the UI elements.
Gravity Attribute
Use gravity attribute to align the View Content – center, left, right etc.
Layout Gravity Attribute
Use layout_gravity to align the View element itself.
In the following Video I show you how to use these attributes
Source Code : https://github.com/ankur-srivastava/HelloAndroid/blob/master/app/src/main/res/layout/activity_main.xml