godot4制作2D游戏03———添加人物状态机

添加状态机接口

• 创建一个script，名称为state.gd

class_name State extends Node

static var player: Player

func _ready() -> void:
	pass

func  Enter() -> void:
	pass
	
func Exit() -> void:
	pass
	
func Process(delta: float) -> State:
	return null

func PhysicsProcess(delta: float) -> State:
	return null

func HandleInput(event: InputEvent) -> State:
	return null

这个接口是各个状态机方法属性的定义

为Player添加StateMachine节点

• 在Player下创建一个StateMachine的节点
  • 在StateMachine下新添加两个子节点Idle和Walk
• 创建 player_state_machine.gd

  class_name PlayerStateMachine extends Node
  
  var states: Array[ State ]
  var prev_state: State
  var current_state: State
  
  // 禁用所有StateMachine以及子节点的_process和_physics_process方法
  func _ready() -> void:
  	process_mode = Node.PROCESS_MODE_DISABLED
  	pass
  
  func _process(delta: float) -> void:
  	ChangeState(current_state.Process( delta ))
  	
  func _physics_process(delta: float) -> void:
  	ChangeState(current_state.PhysicsProcess( delta ))
  	
  func _unhandled_input(event: InputEvent) -> void:
  	ChangeState(current_state.HandleInput( event ))
  
  // 获取所有子节点状态机并将第一个作为初始状态
  func Initialize(player: Player) -> void:
  	for c in get_children():
  		if c is State:
  			states.append(c)
  	if states.size() > 0:
  		states[0].player = player
  		ChangeState(states[0])
  		process_mode = Node.PROCESS_MODE_INHERIT
  	
  func ChangeState(new_state: State) -> void:
  	if new_state == null || new_state  == current_state:
  		return
  	if current_state:
  		current_state.Exit()
  		
  	prev_state = current_state
  	current_state = new_state
  	current_state.Enter()	

  • 将 player_state_machine.md 挂载到StateMachine节点上

创建两个子状态的脚本

• state_idle.gd

  class_name StateIdle extends State
  
  @onready var walk: StateWalk = $"../Walk"
  
  func _ready() -> void:
  	pass
  
  func  Enter() -> void:
  	player.UpdateAnimation("idle")
  	pass
  	
  func Exit() -> void:
  	pass
  	
  func Process(delta: float) -> State:
  	if player.direction != Vector2.ZERO:
  		return walk
  	player.velocity = Vector2.ZERO
  	return null
  
  func PhysicsProcess(delta: float) -> State:
  	return null
  
  func HandleInput(event: InputEvent) -> State:
  	return null
  class_name StateIdle extends State
  
  @onready var walk: StateWalk = $"../Walk"
  
  func _ready() -> void:
  	pass
  
  func  Enter() -> void:
  	player.UpdateAnimation("idle")
  	pass
  	
  func Exit() -> void:
  	pass
  	
  func Process(delta: float) -> State:
  	if player.direction != Vector2.ZERO:
  		return walk
  	player.velocity = Vector2.ZERO
  	return null
  
  func PhysicsProcess(delta: float) -> State:
  	return null
  
  func HandleInput(event: InputEvent) -> State:
  	return null

• state_walk.gd

  class_name StateWalk extends State
  
  @onready var idle: StateIdle = $"../Idle"
  var move_speed: float = 100.0
  
  func _ready() -> void:
  	pass
  
  func  Enter() -> void:
  	player.UpdateAnimation("walk")
  	pass
  	
  func Exit() -> void:
  	pass
  	
  func Process(delta: float) -> State:
  	if player.direction == Vector2.ZERO:
  		return idle
  	
  	player.velocity = player.direction * move_speed
  	if player.SetDirection():
  		player.UpdateAnimation("walk")
  	return null
  
  func PhysicsProcess(delta: float) -> State:
  	return null
  
  func HandleInput(event: InputEvent) -> State:
  	return null

修改Player节点的脚本

• player.gd

  class_name Player extends CharacterBody2D
  
  var direction: Vector2 = Vector2.ZERO
  var cardinal_direction: Vector2 = Vector2.DOWN
  
  @onready var animation_player: AnimationPlayer = $AnimationPlayer
  @onready var sprite: Sprite2D = $Sprite2D
  @onready var state_machine: PlayerStateMachine = $StateMachine
  
  
  func _ready() -> void:
  	state_machine.Initialize(self)
  	pass
  	
  func _process(delta: float) -> void:
  	direction.x = Input.get_action_strength("right") - Input.get_action_strength("left")
  	direction.y = Input.get_action_strength("down") - Input.get_action_strength("up")
  	pass
  
  func _physics_process(delta: float) -> void:
  	move_and_slide()
  
  func SetDirection() -> bool:
  	var new_dir: Vector2 = cardinal_direction
  	if direction == Vector2.ZERO:
  		return false
  	if direction.y == 0:
  		new_dir = Vector2.LEFT if direction.x < 0 else Vector2.RIGHT
  	if direction.x == 0:
  		new_dir = Vector2.UP if direction.y < 0 else Vector2.DOWN
  	if cardinal_direction == direction:
  		return false
  	cardinal_direction = new_dir
  	sprite.scale.x = -1 if cardinal_direction == Vector2.LEFT else 1
  	return true
  	
  func UpdateAnimation(state: String) -> void:
  	animation_player.play(state + "_" + AnimationDirection())
  	
  func AnimationDirection() -> String:
  	if cardinal_direction == Vector2.DOWN:
  		return "down"
  	elif cardinal_direction == Vector2.UP:
  		return "up"
  	else:
  		return "side"

总结

• 创建一个StateMachine的节点，下面挂载多个子节点，通过获取子节点的方式动态扩展
• 用户节点脚本不再直接调用动画渲染，只修改direction
• 在执行StateMachine的_process和_physics_process方法时，调用当前State的对应方法来处理动画