What do you mean by root view of an activity?

I have a very trivial confusion regarding the what is the root view of an activity. I searched this throughout google and stack overflow. I got some knowledge about it but didn't come to a convincing solution as no one clearly said about that term. The question which seems to be alike my question tell about what a root view of a given layout is but to me they don't seem to specify the root view of an activity is.Though the answer to my question is quite intuitive, I want a definite answer with no confusion.So here is the code structure. I have the following activity class :

package com.example.android.viewpager;

import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;


public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

And the XML code associated with it when I created the activity is (activity_main.xml) :

    <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"
    android:orientation="vertical"
    tools:context="com.example.android.viewpager.MainActivity">
    </LinearLayout>

So according to me is this activity_main.xml the root view of the MainActivity?

Solution

The Root View of Your MainActivity is LinearLayout

The Root View of Your Activity means the Top most parent layout of Your XML Layout

The Root View may be a RelativeLayout, CoordinatorLayout, ConstraintLayout, LinearLayout,FrameLayout

For Example

Your activity_main.xml Contain LinearLayout as parent layout than LinearLayout is your Root View which hold all the child controlls in it like Buttons, Imageview, EditText, TextView, etc....