3-20 Triggering Special Abilities From Keys

本章要來製作快捷鍵發動技能嘍！首先先讓我們修改一下介面吧，選擇GameObject/UI/Image來新增圖片資源。

將之前提供的圖片檔案Icon Special Ability Power Attack放置上去，如果不知道怎麼指定圖片資源以及排版，可以先參考以前的文章：
3-16 Using Image Fill In UI

https://rpgcorecombat.blogspot.tw/2018/01/3-16-using-image-fill-in-ui.html

接著將剛剛新增好的Image多複製幾份，分別取名為Special Slot (0)、Special Slot (1)、Special Slot (2)。

然後將圖片資源都放進去，排列整齊，如下圖的樣子。

接著，在Game Canvas按右鍵，Create Empty，取名為Keyboard Affordances。

於Keyboard Affordances按右鍵選擇UI/Text，新增文字框。

將文字框移動到技能圖片上面，文字寫1，自己調整Font Size跟Color，Alignment可以如下圖那樣設定，數字就會在技能圖片的右下角。

然後將文字框再複製一份。

將複製的文字框移動到旁邊的技能圖片上，文字改成2。這樣，我們就把UI的部分都設定好了！

主要修改Player.cs，如下圖，我們在Update撰寫方法來實時感應鍵盤的事件，先是撰寫條件式確保Player的血量不為0，以免Player死了以後還能透過快捷鍵發動技能。再來是撰寫ScanForAbilityKeyDown方法，當使用者按下的數字鍵為已存在技能中的其中一項，就呼叫AttemptSpecialAbility發動技能。

以下提供Player.cs完成程式碼：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Assertions;
using UnityEngine.SceneManagement;
using RPG.CameraUI; // TODO consider re-wiring
using RPG.Core;
using RPG.Weapons;

namespace RPG.Character{
 public class Player : MonoBehaviour, IDamageable {

  [SerializeField] float maxHealthPoints = 100f;
  [SerializeField] float baseDamage = 50f;
  [SerializeField] AnimatorOverrideController animatorOverrideController;
  [SerializeField] Weapon weaponInUse;
  [SerializeField] SpecialAbilityConfig[] abilities;
  [SerializeField] AudioClip[] damageSounds;
  [SerializeField] AudioClip[] deathSounds;

  // 定義Trigger的字串常數
  const string DEATH_TRIGGER = "Death";
  const string ATTACK_TRIGGER = "Attack";

  float lastHitTime;
  float currentHealthPoint;
  Enemy currentEnemy;
  CameraRaycaster cameraRaycaster;
  ISpecialAbility[] specialAbility;
  AudioSource audioSource;
  Animator animator;


  public float healthAsPercentage{
   get{ return currentHealthPoint / maxHealthPoints; }
  }

  void Start(){
   audioSource = GetComponent ();

   RegisterForMouseClcik ();
   SetCurrentMaxHealth ();
   PutWeaponInHand ();
   OverrideAnimatorController ();
   AttachSpecialAbility();
  }

  void Update(){
   if (healthAsPercentage > Mathf.Epsilon) {
    ScanForAbilityKeyDown ();
   }
  }

  private void ScanForAbilityKeyDown(){
   for (int keyIndex = 1; keyIndex <= abilities.Length; keyIndex++) {
    if (Input.GetKeyDown (keyIndex.ToString())) {
     AttemptSpecialAbility (keyIndex);
    }
   }
  }

  private void AttachSpecialAbility(){
   specialAbility = new ISpecialAbility[abilities.Length];
   for (int i = 0; i < abilities.Length; i++) {
    // 儲存ISpecialAbility物件
    specialAbility[i] = abilities [i].AddComponent (gameObject);
   }
  }

  private void OverrideAnimatorController(){
   // 取得Animator物件
   animator = GetComponent ();
   // 將人物的Animator取代為我們剛剛新增的Player Animator Override
   animator.runtimeAnimatorController = animatorOverrideController;
   // Player Animator Override中有一預設的DEFAULT ATTACK，將其取代成Weapon物件中的Animation
   // 亦即人物的Animation將會依據不同的Weapon物件，而使用有不同的動畫
   animatorOverrideController ["DEFAULT ATTACK"] = weaponInUse.GetAnimClip ();
  }

  private void PutWeaponInHand(){
   GameObject weaponPrefab = weaponInUse.GetWeaponPrefab ();
   // 生成武器時，將會放置到指定的GameObject之下，此處為WeaponSocket之下
   // 故可將WeaponSocket設置成玩家的右手或左手
   GameObject weaponSocket = RequestDominantHand();
   GameObject weapon = Instantiate (weaponPrefab, weaponSocket.transform);
   // 將武器放置到正確的位置，並有正確的方向
   weapon.transform.localPosition = weaponInUse.gripTransform.localPosition;
   weapon.transform.localRotation = weaponInUse.gripTransform.localRotation;
  }

  private GameObject RequestDominantHand(){
   // 從Children中尋找包含DominantHand的物件
   DominantHand[] dominantHand = GetComponentsInChildren ();
   // 計算取得有DominantHand的物件的數量
   int numberOfDominantHands = dominantHand.Length;
   // 確保該數量不為0
   Assert.AreNotEqual (numberOfDominantHands, 0, "No DominantHand found on player, please add one");
   // 確保該數量不要大於1
   Assert.IsFalse (numberOfDominantHands > 1, "Multiple Dominant script on Player, please remove one");
   // 傳回屬於該DominantHand的GameObject
   return dominantHand [0].gameObject;
  }

  private void SetCurrentMaxHealth(){
   currentHealthPoint = maxHealthPoints;
  }

  private void RegisterForMouseClcik(){
   cameraRaycaster = FindObjectOfType ();
   // 註冊滑鼠碰到敵人的事件
   cameraRaycaster.onMouseOverEnemy += OnMouseOverEnemy;
  }

  void OnMouseOverEnemy(Enemy enemy){
   currentEnemy = enemy;

   if (Input.GetMouseButtonDown (0) && IsTargetInRange (enemy.gameObject)) {
    AttackTarget ();
   }else if (Input.GetMouseButtonDown (1)) {
    // 0為使用第一個技能 
    AttemptSpecialAbility(0);
   }
  }

  private void AttemptSpecialAbility(int abilityIndex){
   Energy energyComponent = GetComponent ();
   // 取得技能需要的能量消耗量
   float energyCost = abilities [abilityIndex].GetEnergyCost ();

   if (energyComponent.IsEnergyAvailable (energyCost)) {
    energyComponent.ConsumeEnergy (energyCost);
    // 發動技能，並傳入Player的baseDamage
    AbilityParams abilityParams = new AbilityParams (currentEnemy, baseDamage);
    specialAbility [abilityIndex].Use(abilityParams);
   }

  }

  private void AttackTarget(){
   // 確認本次攻擊時間離上一次攻擊時間須大於minTimeBetweenHits，相當於技能冷卻時間
   if ( (Time.time - lastHitTime > weaponInUse.GetMinTimeBetweenHits())) {
    // 呼叫Trigger啟動攻擊動畫
    animator.SetTrigger(ATTACK_TRIGGER);
    // 呼叫攻擊Target的方法
    currentEnemy.AdjustHealth(baseDamage);
    // 紀錄目前攻擊的時間
    lastHitTime = Time.time;
   }
  }

  // 確認敵人是否在範圍技的攻擊範圍內
  private bool IsTargetInRange(GameObject target){
   float distanceToTarget = (target.transform.position - transform.position).magnitude;
   return distanceToTarget <= weaponInUse.GetMaxAttackRange();
  }

  public void AdjustHealth(float changePoints){
   // Math.Clamp可以確保數值運算後不會低於最小值或者高於最大值
   currentHealthPoint = Mathf.Clamp (currentHealthPoint - changePoints, 0f, maxHealthPoints);
   // 隨機播放受傷的音效
   audioSource.clip = damageSounds [Random.Range (0, damageSounds.Length)];
   audioSource.Play ();
   bool playerDies = currentHealthPoint <= 0;
   if (playerDies) {
    StartCoroutine (KillPlayer ());
   }
  }

  IEnumerator KillPlayer(){
   // 播放死亡音效
   audioSource.clip = deathSounds [Random.Range (0, deathSounds.Length)];
   audioSource.Play ();
   // 播放死亡動畫
   animator.SetTrigger(DEATH_TRIGGER);
   // 等待一段時間（依音效長度而定）
   yield return new WaitForSecondsRealtime(audioSource.clip.length);
   // 重載關卡
   SceneManager.LoadScene(0);
  }
 }
}

調整一下Player的技能順序，如下圖調整後，按下滑鼠右鍵發動Power Attack L1，按下數字鍵1發動AOE L1，按下數字鍵2發動Self Heal L1。

來執行遊戲看看吧！按下數字鍵1以後，就能夠發動範圍技攻擊敵人了。