getOnBackPressedDispatcher ejemplo

OnBackPressedCallback onBackPressedCallback = new OnBackPressedCallback( true ) {
    boolean doubleBackToExitPressedOnce=false;
    @Override
    public void handleOnBackPressed() {

        if (doubleBackToExitPressedOnce) {
            ActivityCompat.finishAffinity( FirstActivity.this );
            Log.e( "Click", "double back" );
            return;
        }

        this.doubleBackToExitPressedOnce = true;
        Toast.makeText(FirstActivity.this,getStrin(R.string.exitapp),Toast.LENGTH_SHORT).show();

        new Handler().postDelayed( new Runnable() {

            @Override
            public void run() {
                doubleBackToExitPressedOnce=false;
            }
        }, 2000);


    }
};

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_first );
    //getting bottom navigation view and attaching the listener


    getOnBackPressedDispatcher().addCallback( this, onBackPressedCallback );

}