how to setup a back button on a toolbar kotlin

Toolbar toolbar = (Toolbar) findViewById(R.id.my_awesome_toolbar);
setSupportActionBar(toolbar);

mActionBar.setNavigationIcon(getResources().getDrawable(R.drawable.ic_action_back));
mActionBar.setNavigationOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v) {
       //What to do on back clicked
   }
});

getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);