android:id. Resource ID. A unique resource name for the element, which you can use to obtain a reference to the View from your application. See more about the value for android:id below.

What is the use of Android ID?

@+id is used for defining a resource where as @id is used for referring the resources which is already defined. android_id=”@+id/unique _key” creates a new entry in R. java. android: layout _below=”@id/unique _key” refer to the entry which is already defined in R.

What is ID and UI in Android?

View is the base class for widgets, which are used to create interactive UI components like buttons, text fields, etc. … The ViewGroup is a subclass of View and provides invisible container that hold other Views or other ViewGroups and define their layout properties.