YourConstraintLayout.java

    public ProgressConstraintLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        configureViews();
    }
    
    private void configureViews() {
        // Create a Constraint Set and clone our constraints
        ConstraintSet constraintSet = new ConstraintSet();
        constraintSet.clone(this);
   
        // Create our progress bar…
        ProgressBar progressBar = new ProgressBar(getContext(), null, android.R.attr.progressBarStyleLarge);
        progressBar.setIndeterminate(true);
        progressBar.setId(generateViewId());
        
        // add it to our hierarchy
        addView(progressBar, new ConstraintLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

        // Configure its constraints … basically pin it to every side.
        constraintSet.connect(progressBar.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP);
        constraintSet.connect(progressBar.getId(), ConstraintSet.BOTTOM, ConstraintSet.PARENT_ID, ConstraintSet.BOTTOM);
        constraintSet.connect(progressBar.getId(), ConstraintSet.START, ConstraintSet.PARENT_ID, ConstraintSet.START);
        constraintSet.connect(progressBar.getId(), ConstraintSet.END, ConstraintSet.PARENT_ID, ConstraintSet.END);
   
        // now apply the new constraints (This will not work, by the way) ;)
        constraintSet.applyTo(this);
    }