Found the solution:
Instead of:
mActionBarToolbar = (Toolbar) findViewById(R.id.toolbar_actionbar);
mActionBarToolbar.setTitle("My title");
setSupportActionBar(mActionBarToolbar);
I used:
mActionBarToolbar = (Toolbar) findViewById(R.id.toolbar_actionbar);
setSupportActionBar(mActionBarToolbar);
getSupportActionBar().setTitle("My title");
And it works.