Unity 2D遊戲開發教程之遊戲精靈的開火狀態

Unity 2D遊戲開發教程之遊戲精靈的開火狀態

精靈的開火狀態

「開火」就是發射子彈的意思，在戰爭類型的電影或者電視劇中，主角們就愛這麼說！本節打算爲精靈添加發射子彈的能力。由於本遊戲在後面會引入敵人，而精靈最好具有開火的能力，不然會被敵人輕易幹掉！具體的實現方法是：

（1）導入一個表示子彈的圖片到Unity，本示例中選用的子彈圖片，名爲PlayerBullet，如圖2-23所示。

圖2-23  導入到遊戲項目的表示子彈的圖片

（2）拖動此圖片到Scene視圖，便可在當前的遊戲場景中添加此對象，爲此對象添加RigidBody 2D組件，並設置組件的下列屬性，如圖2-24所示。

• q   Gravity Scale：0。表示子彈對象將不受重力的影響，因此不會偏離預約的發射軌道；

圖2-24  設置子彈對象上各組件的屬性

（3）在Project視圖裏，新建一個C#腳本，命名爲PlayerBulletController，爲此腳本添加下面的代碼：

• 01     using UnityEngine;

• 02     using System.Collections;

• 03    

• 04     public class PlayerBulletController : MonoBehaviour

• 05     {

• 06              public GameObject playerObject = null;            //表示精靈對象

• 07              public float bulletSpeed = 15.0f;                                    //表示子彈的速度

• 08              private float selfDestructTimer = 0.0f;                 //表示子彈自我銷燬的時間

• 09              void Update()

• 10              {

• 11                       //在一段時間之後銷燬子彈對象

• 12                       if(selfDestructTimer > 0.0f)

• 13                       {

• 14                                 if(selfDestructTimer < Time.time)

• 15                                          Destroy(gameObject);

• 16                       }

• 17              }       

• 18              //調用此函數發射子彈

• 19              public void launchBullet()

• 20              {

• 21                       //肯定精靈對象的朝向

• 22                       float mainXScale = playerObject.transform.localScale.x;

• 23                       Vector2 bulletForce;                                                //對子彈施加的力的方向

• 24                       //若是精靈對象面朝左，則向左發射子彈

• 25                       if(mainXScale < 0.0f)

• 26                       {

• 27                                 bulletForce = new Vector2(bulletSpeed * -1.0f,0.0f);

• 28                       }

• 29                       //若是精靈對象面朝右，則向右發射子彈

• 30                       else

• 31                       {

• 32                                 bulletForce = new Vector2(bulletSpeed,0.0f);

• 33                       }

• 34                       //施加給子彈對象一個指定方向的力

• 35                       rigidbody2D.velocity = bulletForce;

• 36                       //在1秒後銷燬子彈對象

• 37                       selfDestructTimer = Time.time + 1.0f;

• 38              }

• 39     }

將此腳本賦予場景中的子彈對象，選中後者，而後在Inspector視圖裏能夠設置此腳本組件的Bullet Speed屬性，用於修改子彈的發射速度，如圖2-25所示。

圖2-25  腳本組件的屬性設置

將Hierarchy視圖裏的子彈對象，拖動到Project視圖，便可建立一個子彈對象的預置資源，以備後面腳本中的代碼使用。

（4）在PlayerStateController腳本中，添加精靈開火的狀態，且指定當玩家按下鼠標左鍵的時候，精靈將進入開火狀態，要添加的代碼以下：

• 01     using UnityEngine;

• 02     using System.Collections;

• 03    

• 04     public class PlayerStateController : MonoBehaviour

• 05     {

• 06              //定義遊戲人物的各類狀態

• 07              public enum playerStates

• 08              {

• 09                       …                                                             //省略

• 10                       falling,                                                     //表示降落過程

• 11                       firingWeapon                                        //表示開火

• 12              }

• 13              //定義委託和事件      

• 14              public delegate void playerStateHandler(PlayerStateController.playerStates newState);

• 15              public static event playerStateHandler onStateChange;

• 16              void LateUpdate ()

• 17              {

• 18                       …                                                             //省略

• 19                       //當玩家按下鼠標的左鍵時，進入開火狀態

• 20                       float firing = Input.GetAxis("Fire1");

• 21                       if(firing > 0.0f)

• 22                       {

• 23                                 if(onStateChange != null)

• 24                                         onStateChange(PlayerStateController.playerStates.firingWeapon);

• 25                       }

• 26              }

• 27     }

（5）在Hierarchy視圖裏，新建一個Empty對象，命名爲BulletSpawnPoint。拖動它到Player對象下，使其成爲Player對象的子對象。而後調整BulletSpawnPoint對象的位置，使其位於精靈發射子彈時，子彈的出現位置。在本示例中，它們的相對位置如圖2-26所示。

圖2-26  設置開火時，子彈的發射位置

（6）在PlayerStateListener腳本中，添加代碼用於處理精靈進入開火狀態時，開火的遊戲邏輯，要添加的代碼以下：

• 01     using UnityEngine;

• 02     using System.Collections;

• 03    

• 04     [RequireComponent(typeof(Animator))]

• 05     public class PlayerStateListener : MonoBehaviour

• 06     {

• 07              …                                                                                         //省略

• 08              public GameObject bulletPrefab = null;                    //表示子彈對象

• 09              public Transform bulletSpawnTransform;               //表示建立子彈的位置

• 10              …                                                                                         //省略

• 11              //當角色的狀態發生改變的時候，調用此函數

• 12              public void onStateChange(PlayerStateController.playerStates newState)

• 13              {

• 14                       //若是狀態沒有發生變化，則無需改變狀態

• 15                       if(newState == currentState)

• 16                                 return;

• 17                       //判斷精靈可否由當前的動畫狀態，直接轉換爲另外一個動畫狀態

• 18                       if(!checkForValidStatePair(newState))

• 19                                 return;

• 20                       //經過修改Parameter中Walking的值，修改精靈當前的狀態

• 21                       switch(newState)

• 22                       {

• 23                       …                                                                       //省略

• 24                       case PlayerStateController.playerStates.firingWeapon:

• 25                                 //實例化一個子彈對象

• 26                                 GameObject newBullet = (GameObject)Instantiate(bulletPrefab);

• 27                                 //設置子彈的起始位置

• 28                                 newBullet.transform.position = bulletSpawnTransform.position;

• 29                                 //創建與子彈對象上PlayerBulletController組件的聯繫

• 30                                 PlayerBulletController bullCon = newBullet.GetComponent<PlayerBulletController>();

• 31                                 //設定子彈對象上的PlayerBulletController組件的player object屬性

• 32                                 bullCon.playerObject = gameObject;

• 33                                 //發射子彈

• 34                                 bullCon.launchBullet();

• 35                                 break;

• 36                       }

• 37                       //記錄角色當前的狀態

• 38                       currentState = newState;

• 39              }   

• 40              //用於確認當前的動畫狀態可否直接轉換爲另外一動畫狀態的函數

• 41              bool checkForValidStatePair(PlayerStateController.playerStates newState)

• 42              {

• 43                       bool returnVal = false;

• 44                       //比較兩種動畫狀態

• 45                       switch(currentState)

• 46                       {

• 47                       …                                                                                         //省略

• 48                       case PlayerStateController.playerStates.jump:

• 49                                 if(    newState == PlayerStateController.playerStates.landing

• 50                                          || newState == PlayerStateController.playerStates.kill

• 51                                          || newState == PlayerStateController.playerStates.firingWeapon

• 52                                          )

• 53                                          returnVal = true;

• 54                                 else

• 55                                          returnVal = false;

• 56                                 break;

• 57                       case PlayerStateController.playerStates.landing:

• 58                                 if(    newState == PlayerStateController.playerStates.left

• 59                                          || newState == PlayerStateController.playerStates.right

• 60                                          || newState == PlayerStateController.playerStates.idle

• 61                                          || newState == PlayerStateController.playerStates.firingWeapon

• 62                                          )

• 63                                          returnVal = true;

• 64                                 else

• 65                                          returnVal = false;

• 66                                 break;             

• 67                       case PlayerStateController.playerStates.falling:   

• 68                                 if(

• 69                                          newState == PlayerStateController.playerStates.landing

• 70                                          || newState == PlayerStateController.playerStates.kill

• 71                                          || newState == PlayerStateController.playerStates.firingWeapon

• 72                                          )

• 73                                          returnVal = true;

• 74                                 else

• 75                                          returnVal = false;

• 76                                 break;             

• 77                       case PlayerStateController.playerStates.firingWeapon:

• 78                                 returnVal = true;

• 79                                 break;

• 80                       }          

• 81                       return returnVal;

• 82              }

• 83     }

對於此腳本，有如下幾點須要說明：

• q   腳本08、09行的代碼，使得腳本組件中多出了兩個屬性設置框，如圖2-27所示。須要依次設置爲子彈預置對象和子彈的生成位置。

圖2-27  腳本組件上增長的兩個屬性，須要手動設置屬性值

• q   腳本12行，定義的方法onStateChange()裏面添加的代碼，表示精靈處於開火狀態時，將在指定位置上實例化一個子彈的預置對象，而後經過給子彈施加一個力來將它發射出去。

• q   腳本41行，定義的方法checkForValidStatePair()裏面添加的代碼，表示處於jump、landing和falling狀態的精靈，能夠轉換爲firingWeapon，即開火狀態。

（7）運行遊戲，當按下鼠標的左鍵時，精靈將發射子彈，並且精靈能夠在任何狀態下發射子彈，如圖2-28所示。

圖2-28  精靈開火狀態的運行效果

本文選自：Unity 2D遊戲開發快速入門大學霸內部資料，轉載請註明出處，尊重技術尊重IT人！