What functions and methods does FragmentManager provide for managing fragments in an application?

FragmentManager is a class in Android that manages fragments within an Activity or another container. The main functions and methods of FragmentManager include:

• beginTransaction() — starts a new transaction for adding, removing, replacing, or other operations with fragments.
• commit() / commitAllowingStateLoss() — applies the changes made in the transaction.
• add(fragment, tag) — adds a fragment to the container.
• replace(containerViewId, fragment, tag) — replaces the current fragment in the specified container.
• remove(fragment) — removes a fragment.
• findFragmentById(id) and findFragmentByTag(tag) — search for a fragment by its identifier or tag.
• popBackStack() — returns to the previous state in the fragment stack.
• getBackStackEntryCount() — returns the number of entries in the stack.

Example usage:

val fragmentManager = supportFragmentManager
val transaction = fragmentManager.beginTransaction()
transaction.replace(R.id.container, MyFragment(), "myFragmentTag")
transaction.addToBackStack(null) // so you can go back
transaction.commit()