Unity 2D游戏开发教程之游戏精灵的开火状态

Unity 2D游戏开发教程之游戏精灵的开火状态

精灵的开火状态

“开火”就是发射子弹的意思，在战争类型的电影或者电视剧中，主角们就爱这么说！本节打算为精灵添加发射子弹的能力。因为本游戏在后面会引入敌人，而精灵最好具备开火的能力，否则会被敌人轻易干掉！具体的实现方法是：

（1）导入一个表示子弹的图片到Unity，本示例中选用的子弹图片，名为PlayerBullet，如图2-23所示。

图2-23  导入到游戏项目的表示子弹的图片

（2）拖动此图片到Scene视图，即可在当前的游戏场景中添加此对象，为此对象添加RigidBody 2D组件，并设置组件的下列属性，如图2-24所示。

• q   Gravity Scale：0。表示子弹对象将不受重力的影响，所以不会偏离预定的发射轨道；

图2-24  设置子弹对象上各组件的属性

（3）在Project视图里，新建一个C#脚本，命名为PlayerBulletController，为此脚本添加下面的代码：

• 01     using UnityEngine;

• 02     using System.Collections;

• 03    

• 04     public class PlayerBulletController : MonoBehaviour

• 05     {

• 06              public GameObject playerObject = null;            //表示精灵对象

• 07              public float bulletSpeed = 15.0f;                                    //表示子弹的速度

• 08              private float selfDestructTimer = 0.0f;                 //表示子弹自我销毁的时间

• 09              void Update()

• 10              {

• 11                       //在一段时间以后销毁子弹对象

• 12                       if(selfDestructTimer > 0.0f)

• 13                       {

• 14                                 if(selfDestructTimer < Time.time)

• 15                                          Destroy(gameObject);

• 16                       }

• 17              }       

• 18              //调用此函数发射子弹

• 19              public void launchBullet()

• 20              {

• 21                       //确定精灵对象的朝向

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

• 23                       Vector2 bulletForce;                                                //对子弹施加的力的方向

• 24                       //如果精灵对象面朝左，则向左发射子弹

• 25                       if(mainXScale < 0.0f)

• 26                       {

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

• 28                       }

• 29                       //如果精灵对象面朝右，则向右发射子弹

• 30                       else

• 31                       {

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

• 33                       }

• 34                       //施加给子弹对象一个指定方向的力

• 35                       rigidbody2D.velocity = bulletForce;

• 36                       //在1秒后销毁子弹对象

• 37                       selfDestructTimer = Time.time + 1.0f;

• 38              }

• 39     }

将此脚本赋予场景中的子弹对象，选中后者，然后在Inspector视图里可以设置此脚本组件的Bullet Speed属性，用于修改子弹的发射速度，如图2-25所示。

图2-25  脚本组件的属性设置

将Hierarchy视图里的子弹对象，拖动到Project视图，即可创建一个子弹对象的预置资源，以备后面脚本中的代码使用。

（4）在PlayerStateController脚本中，添加精灵开火的状态，且指定当玩家按下鼠标左键的时候，精灵将进入开火状态，要添加的代码如下：

• 01     using UnityEngine;

• 02     using System.Collections;

• 03    

• 04     public class PlayerStateController : MonoBehaviour

• 05     {

• 06              //定义游戏人物的各种状态

• 07              public enum playerStates

• 08              {

• 09                       …                                                             //省略

• 10                       falling,                                                     //表示降落过程

• 11                       firingWeapon                                        //表示开火

• 12              }

• 13              //定义委托和事件      

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

• 15              public static event playerStateHandler onStateChange;

• 16              void LateUpdate ()

• 17              {

• 18                       …                                                             //省略

• 19                       //当玩家按下鼠标的左键时，进入开火状态

• 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视图里，新建一个Empty对象，命名为BulletSpawnPoint。拖动它到Player对象下，使其成为Player对象的子对象。然后调整BulletSpawnPoint对象的位置，使其位于精灵发射子弹时，子弹的出现位置。在本示例中，它们的相对位置如图2-26所示。

图2-26  设置开火时，子弹的发射位置

（6）在PlayerStateListener脚本中，添加代码用于处理精灵进入开火状态时，开火的游戏逻辑，要添加的代码如下：

• 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;                    //表示子弹对象

• 09              public Transform bulletSpawnTransform;               //表示创建子弹的位置

• 10              …                                                                                         //省略

• 11              //当角色的状态发生改变的时候，调用此函数

• 12              public void onStateChange(PlayerStateController.playerStates newState)

• 13              {

• 14                       //如果状态没有发生变化，则无需改变状态

• 15                       if(newState == currentState)

• 16                                 return;

• 17                       //判断精灵能否由当前的动画状态，直接转换为另一个动画状态

• 18                       if(!checkForValidStatePair(newState))

• 19                                 return;

• 20                       //通过修改Parameter中Walking的值，修改精灵当前的状态

• 21                       switch(newState)

• 22                       {

• 23                       …                                                                       //省略

• 24                       case PlayerStateController.playerStates.firingWeapon:

• 25                                 //实例化一个子弹对象

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

• 27                                 //设置子弹的起始位置

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

• 29                                 //建立与子弹对象上PlayerBulletController组件的联系

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

• 31                                 //设定子弹对象上的PlayerBulletController组件的player object属性

• 32                                 bullCon.playerObject = gameObject;

• 33                                 //发射子弹

• 34                                 bullCon.launchBullet();

• 35                                 break;

• 36                       }

• 37                       //记录角色当前的状态

• 38                       currentState = newState;

• 39              }   

• 40              //用于确认当前的动画状态能否直接转换为另一动画状态的函数

• 41              bool checkForValidStatePair(PlayerStateController.playerStates newState)

• 42              {

• 43                       bool returnVal = false;

• 44                       //比较两种动画状态

• 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     }

对于此脚本，有以下几点需要说明：

• q   脚本08、09行的代码，使得脚本组件中多出了两个属性设置框，如图2-27所示。需要依次设置为子弹预置对象和子弹的生成位置。

图2-27  脚本组件上增加的两个属性，需要手动设置属性值

• q   脚本12行，定义的方法onStateChange()里面添加的代码，表示精灵处于开火状态时，将在指定位置上实例化一个子弹的预置对象，然后通过给子弹施加一个力来将它发射出去。

• q   脚本41行，定义的方法checkForValidStatePair()里面添加的代码，表示处于jump、landing和falling状态的精灵，可以转换为firingWeapon，即开火状态。

（7）运行游戏，当按下鼠标的左键时，精灵将发射子弹，而且精灵可以在任何状态下发射子弹，如图2-28所示。

图2-28  精灵开火状态的运行效果

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