20.2 The Activity and Fragment Classes

With few exceptions, activities and fragments in an application are created as subclasses of the Android AppCompatActivity class and Fragment classes respectively.

Consider, for example, the AndroidSample project created in “Creating an Example Android App in Android Studio”. Load this project into the Android Studio environment and locate the MainActivity.kt file (located in app -> java -> com.<your domain>.androidsample). Having located the file, double-click on it to load it into the editor where it should read as follows:

package com.example.androidsample

 

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import android.view.View

 

import kotlinx.android.synthetic.main.activity_main.*

 

class MainActivity : AppCompatActivity() {

 

    override fun onCreate(savedInstanceState: Bundle?) {

    &...