Unity 2D游戏开发教程之游戏中精灵的跳跃状态

Unity 2D游戏开发教程之游戏中精灵的跳跃状态

精灵的跳跃状态

为了让游戏中的精灵有更大的活动范围,上一节为游戏场景添加了多个地面,于是精灵可以从高的地面移动到低的地面处,如图2-14所示。但是却无法从低的地面移动到高的地面,因为当前的游戏精灵只能左右移动,即leftright。为了解决这个问题,本节就来为精灵添加跳跃状态。


2-14  精灵从一个地面移动到另一个地面

1如果要为精灵添加跳跃状态,即jump,就不得不再引入其它状态:

  • q   landing:用于表示精灵接触到地面的这种状态。为了阻止精灵在跳跃到空中的时候再次跳跃,就需要在精灵做跳跃动作之前,确认其接触到了地面。

提示:有些游戏允许精灵在空中的时候再跳跃一次,也就是所谓的二级跳。例如,《天天酷跑》中,精灵就需要有二级跳的能力,因为有些场景光是跳跃一次无法跳过悬崖,或者吃到金币,如图2-15所示。


2-15  《天天酷跑》中,需要连续跳跃来越过断崖的精灵

  • q   falling:用于表示精灵在空中的状态,处于此种状态下的精灵只可能过渡到landingkill状态,也就是说精灵在空中的时候,无法产生其它动作行为,如leftright

2为脚本PlayerStateController中定义的动画状态枚举类型添加3种新的状态:jumplandingfalling,并且设置当玩家按下键盘上的空格键时,精灵会进入跳跃状态。脚本PlayerStateController中的部分代码如下:

  • 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                       jump,                                                       //表示跳跃

  • 11                       landing,                                                   //表示落地

  • 12                       falling,                                                     //表示降落过程

  • 13              }

  • 14              …                                                                       //省略

  • 15              void LateUpdate ()

  • 16              {

  • 17                       …                                                             //省略

  • 18                       //当玩家按下键盘上的空格键时,进入跳跃状态

  • 19                       float jump = Input.GetAxis("Jump");

  • 20                       if(jump > 0.0f)

  • 21                       {

  • 22                                 if(onStateChange != null)

  • 23                                          onStateChange(PlayerStateController.playerStates.jump);

  • 24                       }

  • 25              }

  • 26     }

3Hierarchy视图里,新建一个Empty对象,命名为SceneryToggler,并拖动它到Player对象下,使其成为Player对象的子对象。为其添加Box Collider 2D组件,并在Inspector视图里,设置此组件的属性,如图2-16所示。

  • q   选中Is Trigger复选框;

  • q   Sizex:1,y:2

  • q   Centerx:0,y:1


2-16  SceneryToggler对象上,组件属性的设置

如此这般设置,相当于为Player对象添加了一个Collider检测框,如图2-17所示,可以看出除了精灵自身的Polygon Collider 2D的线框外,外层还包裹了矩形的线框。它在后面将用于检测精灵与场景中其它对象的碰撞。


2-17  精灵对象外层包裹的矩形线框

读者此时心中一定在疑惑,既然精灵本身就有Collider,为什么还要添加一个Collider呢?答案是,精灵是有实体的,因此即使其它对象与精灵发生了接触,它们也不会“交叉”,因此就永远不会触发我们期望的landing状态。但是对于Empty对象而言,就没有这种担心了,因为它根本没有实体,因此会与其它对象发生“交叉”,然后触发landing状态。

4Unity里,单击Edit|Project Settings|Tags and Layers命令,打开Tag&Layers对话框,为Tags属性添加两个元素:PlatformDeathTrigger,如图2-18所示。


2-18  Tag&Layers对话框里,为Tags属性添加两个元素

然后修改场景里地面对象的Tag属性为PlatformDeath Trigger对象的Tag属性为DeathTrigger

5Project视图里的Scripts文件夹下,新建一个C#脚本,命名为PlayerColliderListener,为此脚本添加下面的代码:

  • 01     using UnityEngine;

  • 02     using System.Collections;

  • 03    

  • 04     public class PlayerColliderListener : MonoBehaviour

  • 05     {

  • 06              public PlayerStateListener targetStateListener = null;                          //表示精灵对象

  • 07         //进入碰撞检测区域时,调用此函数

  • 08              void OnTriggerEnter2D( Collider2D collidedObject )

  • 09         {

  • 10                       switch(collidedObject.tag)

  • 11             {

  • 12                                 //当精灵落到地面上时,触发landing动画状态

  • 13                                 case "Platform":

  • 14                                         targetStateListener.onStateChange(PlayerStateController.playerStates.landing);

  • 15                                 break;

  • 16                       }

  • 17              }

  • 18              //离开碰撞检测区域时,调用此函数

  • 19              void OnTriggerExit2D( Collider2D collidedObject)

  • 20              {

  • 21                       switch(collidedObject.tag)

  • 22                       {

  • 23                                 //当精灵离开地面是,触发falling动画状态

  • 24                                 case "Platform":

  • 25                                         targetStateListener.onStateChange(PlayerStateController.playerStates.falling);

  • 26                                 break;

  • 27                                 //当精灵离开的是Death Trigger对象,则触发kill动画状态

  • 28                                 case "DeathTrigger":

  • 29                                         targetStateListener.onStateChange(PlayerStateController.playerStates.kill);

  • 30                                 break;      

  • 31                       }        

  • 32              }

  • 33     }

将此脚本赋予Player对象的子对象SceneryToggler,选中后者,然后在Inspector视图里设置此脚本组件的Target State Listener属性为Player对象,如图2-19所示。


2-19  设置脚本组件里的属性

对于此脚本,有以下几点需要说明:

  • q   脚本08行定义的OnTriggerEnter2D(),说明当与SceneryToggler对象发生碰撞的对象的Tag属性是Platform的时候(精灵与地面接触),精灵就会进入landing状态;

  • q   脚本19行定义的OnTriggerExit2D(),说明当离开SceneryToggler对象检测范围的对象的Tag属性是Platform的时候(精灵离开地面),精灵就会进入falling状态;Tag属性为DeathTrigger的时候(精灵离开场景中的Death Trigger对象),精灵就会进入kill状态;

提示:如果读者再回头细细的查看精灵的死亡逻辑的话,就会发现精灵的死亡只是表象!本质上是精灵在一瞬间转移到了重生点所在的位置。正是因为游戏中是如此实现精灵死亡逻辑的,所以才需要检测碰撞对象的Tag属性是否为Death Trigger

6)为脚本PlayerStateListener添加对jumplandingfalling这些状态的处理,如下:

  • 01     using UnityEngine;

  • 02     using System.Collections;

  • 03    

  • 04     [RequireComponent(typeof(Animator))]

  • 05     public class PlayerStateListener : MonoBehaviour

  • 06     {

  • 07              public float playerWalkSpeed = 3f;                               //表示精灵移动的速度

  • 08              public GameObject playerRespawnPoint = null;                 //表示重生的点

  • 09              public float playerJumpForceVertical = 300f;          //表示跳跃时,水平方向上,力的大小

  • 10              public float playerJumpForceHorizontal = 200f;     //表示跳跃时,垂直方向上,力的大小

  • 11              private bool playerHasLanded = true;                       //表示精灵是否落地

  • 12              …                                                                                         //省略

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

  • 14              public void onStateChange(PlayerStateController.playerStates newState)

  • 15              {

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

  • 17                       if(newState == currentState)

  • 18                                 return;

  • 19                       //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

  • 20                       if(!checkForValidStatePair(newState))

  • 21                                 return;

  • 22                       //通过修改ParameterWalking的值,修改精灵当前的状态

  • 23                       switch(newState)

  • 24                       {

  • 25                       …                                                             //省略

  • 26                       case PlayerStateController.playerStates.jump:

  • 27                                 if(playerHasLanded)

  • 28                                 {

  • 29                                          //确定精灵的跳跃方向

  • 30                                          float jumpDirection = 0.0f;

  • 31                                          if(currentState == PlayerStateController.playerStates.left)

  • 32                                                   jumpDirection = -1.0f;

  • 33                                          else if(currentState == PlayerStateController.playerStates.right)

  • 34                                                   jumpDirection = 1.0f;

  • 35                                          else

  • 36                                                   jumpDirection = 0.0f;

  • 37                                          //给精灵施加一个特定方向的力

  • 38                                          rigidbody2D.AddForce(new Vector2(jumpDirection * playerJumpForceHorizontal,

  • 39                                                                      playerJumpForceVertical));

  • 40                                          playerHasLanded = false;

  • 41                                 }

  • 42                                 break;

  • 43                       case PlayerStateController.playerStates.landing:

  • 44                                 playerHasLanded = true;

  • 45                                 break;

  • 46                       }

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

  • 48                       currentState = newState;

  • 49              }   

  • 50              //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

  • 51              bool checkForValidStatePair(PlayerStateController.playerStates newState)

  • 52              {

  • 53                       bool returnVal = false;

  • 54                       //比较两种动画状态

  • 55                       switch(currentState)

  • 56                       {

  • 57                       …                                                    //省略

  • 58                       case PlayerStateController.playerStates.jump:

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

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

  • 61                                          )

  • 62                                          returnVal = true;

  • 63                                 else

  • 64                                          returnVal = false;

  • 65                                 break;

  • 66                       case PlayerStateController.playerStates.landing:

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

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

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

  • 70                                          )

  • 71                                          returnVal = true;

  • 72                                 else

  • 73                                          returnVal = false;

  • 74                                 break;             

  • 75                       case PlayerStateController.playerStates.falling:   

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

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

  • 78                                          )

  • 79                                          returnVal = true;

  • 80                                 else

  • 81                                          returnVal = false;

  • 82                                 break;             

  • 83                       }         

  • 84                       return returnVal;

  • 85              }

  • 86              …                                                             //省略

  • 87     }

修改后的脚本,在脚本组件里就会多出两个属性,分别用于决定精灵跳跃时水平和垂直方向受到的力,如图2-20所示。


2-20  修改后的脚本组件

对于此脚本里新加入的代码,有以下几点需要说明:

  • q   脚本09~11行,定义了3个变量:playerJumpForceVerticalplayerJumpForceHorizontalplayerHasLanded,用于辅助新加入状态的逻辑实现;

  • q   脚本14行,onStateChange()里添加的代码说明,精灵只有在落地的时候才能继续跳跃,而且脚本会依据精灵当前的运动朝向,来决定是朝左跳还是朝右跳,具体的方法是,给精灵的刚体施加一个力,精灵将在此力的作用下产生类似于跳跃的行为。

  • q   脚本51行,checkForValidStatePair()里添加的代码说明,jump状态只能转换为landingkill状态;landing状态只能转换为leftrightidle状态;falling状态只能转换为landingkill状态;

7运行游戏,按下空格的时候,精灵就会进入jump状态了。当精灵处于idle状态时,精灵会原地起跳;处于left状态时,会朝左跳,同理right状态;最终,精灵可以在多个地面间上窜下跳,如图2-21所示。


2-21  精灵的跳跃状态(原地起跳、左跳和右跳)

提示:当精灵与Death Trigger对象接触,并进入死亡状态时,Unity里的Console视图里会弹出一条警告信息:hitDeathTrigger has no receiver!,如图2-22所示。


2-22  Console视图里弹出的警告信息

这是由于脚本PlayerColliderListener里包含了方法OnTriggerExit2D(),代码如下:

  • 01              //离开碰撞检测区域时,调用此函数

  • 02              void OnTriggerExit2D( Collider2D collidedObject)

  • 03              {

  • 04                       switch(collidedObject.tag)

  • 05                       {

  • 06                                 //当精灵离开地面是,触发falling动画状态

  • 07                                 case "Platform":

  • 08                                         targetStateListener.onStateChange(PlayerStateController.playerStates.falling);

  • 09                                 break;

  • 10                                 //当精灵离开的是Death Trigger对象,则触发kill动画状态

  • 11                                 case "DeathTrigger":

  • 12                                          targetStateListener.onStateChange(PlayerStateController.playerStates.kill);

  • 13                                 break;

  • 14                       }

  • 15              }

代码中加粗的部分直接激活了精灵的kill状态,因此不再需要hitDeathTrigger()方法去激活这个状态。因此,读者可以做两步操作,来解决Console视图里提示的警告信息。首先,移除Death Trigger对象上的Death Trigger Script组件,然后,移除脚本PlayerStateListener里定义的hitDeathTrigger()方法:

  • 01              public void hitDeathTrigger()

  • 02              {

  • 03                       onStateChange(PlayerStateController.playerStates.kill);

  • 04              }

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