In the early days of Android, if you had a non-trivial app, you almost certainly needed to partition your app across multiple activities. That meant you needed the skill to navigate from one activity to another, and back. So, in those days, you might have written something that looked like the code in Listing
10-1.
class FirstActivity extends AppCompatActivity
implements View.OnClickListener {
public void onClick(View v) {
Intent intent = new Intent(this, ...