public class MainActivity extends AppCompatActivity {

    BackStackManager backStackManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...

        BackStack.install(this);
        backStackManager = BackStack.getBackStackManager();
    }

    @Override
    public void onBackPressed() {
        if (!backStackManager.goBack()) {
            super.onBackPressed();
        }
    }
}

public static final String TAG = "TAG";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    BackStack.install(this);
    backStackManager = BackStack.getBackStackManager();

    //This is the container you want to be the root of your back stack
    root = findViewById(R.id.root);

    LinearBackStack linearBackStack = backStackManager.createLinearBackStack("TAG", root, (layoutInflater, container) -> {
        //This is our first view group in the stack
        CustomViewGroup cvg = new CustomViewGroup(layoutInflater.getContext());

        //Make sure that the view is added to container by the end of this block
        container.addView(cvg);

        //Return the view group that was newly inflated
        return cvg;
    });
}

setOnClickListener(v -> {
    //All back stacks can be retrieved anywhere using their tag
    LinearBackStack linearBackStack = (LinearBackStack) BackStack.getStack(MainActivity.TAG);
    linearBackStack.add((layoutInflater, container) -> {
        //if attach to root is true layoutInflater.inflate() returns the container instead
        ViewGroup viewGroup = (ViewGroup) layoutInflater
                .inflate(R.layout.added_view, container, false);
        container.addView(viewGroup);
        return viewGroup;
    });
});