How to use

checkTrigger

method

in

mage.abilities.common.BecomesBlockedTriggeredAbility

@Override
public boolean checkTrigger(GameEvent event, Game game) {
  if (super.checkTrigger(event, game)) {
    UUID defenderId = game.getCombat().getDefendingPlayerId(getSourceId(), game);
    if (defenderId != null) {
      this.getEffects().setTargetPointer(new FixedTarget(defenderId));
      return true;
    }
  }
  return false;
}