实例2 爬梯子

用状态枚举和状态变量重构了代码，稍微清晰了一些。

extends KinematicBody2D
var speed = 120.0 # 速度 像素/秒
var velocity = Vector2.ZERO # 速度向量
var gravity = 5000 # 重力加速度
var jump_force = 1000.0 # 单次跳跃高度
enum state {
    STATE_ON_WALL,
    STATE_ON_AIR,
    STATE_ON_FLOOR,
    STATE_ON_TIZI, # 在爬梯
}
var n_state = state.STATE_ON_AIR
func _physics_process(delta):
    match n_state:
        state.STATE_ON_AIR:
            # 掉到地板
            if is_on_floor():
                n_state = state.STATE_ON_FLOOR
            else:
                # 实现下落
                velocity.y += gravity * delta
                velocity = move_and_slide(velocity,Vector2.UP)
        state.STATE_ON_FLOOR:
            velocity.y = 0
            # 左右移动
            velocity.x = Input.get_axis("ui_left","ui_right") * speed
            # 跳跃
            if Input.is_action_just_pressed("ui_accept"):  # 按空格键
                velocity.y = -jump_force
                n_state = state.STATE_ON_AIR
            velocity = move_and_slide(velocity,Vector2.UP)
            if is_on_wall():
                n_state = state.STATE_ON_WALL
        state.STATE_ON_TIZI:
            if is_on_floor():
                velocity.x = velocity.x * 0.9
            else:
                velocity.x = Input.get_axis("ui_left","ui_right") * speed
            velocity.y = Input.get_axis("ui_up","ui_down") * speed
            move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
        state.STATE_ON_WALL:
            velocity.y = Input.get_axis("ui_up","ui_down") * speed
            velocity.x = Input.get_axis("ui_left","ui_right") * speed
            if Input.is_action_just_pressed("ui_accept"):  # 按空格键
                velocity.y = -jump_force
                velocity = move_and_slide(velocity,Vector2.UP)
            if velocity.x != 0:
                velocity = move_and_slide(velocity,Vector2.UP)
                n_state = state.STATE_ON_AIR
            else:
                velocity = move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
            if not is_on_wall():
                n_state = state.STATE_ON_AIR

改进后的代码

extends KinematicBody2D
var speed = 120.0 # 速度 像素/秒
var velocity = Vector2.ZERO # 速度向量
var gravity = 5000 # 重力加速度
var jump_force = 1000.0 # 单次跳跃高度
enum state {
    STATE_ON_WALL,
    STATE_ON_AIR,
    STATE_ON_FLOOR,
    STATE_ON_TIZI, # 在爬梯
}
var n_state = state.STATE_ON_AIR
func input_x():
    velocity.x = Input.get_axis("ui_left","ui_right") * speed
func input_y():
    velocity.y = Input.get_axis("ui_up","ui_down") * speed
func input_jump() -> bool:
    return Input.is_action_just_pressed("ui_accept")
func change_stage(new_state:int):
    n_state = new_state
func _physics_process(delta):
    match n_state:
        state.STATE_ON_AIR:
            # 掉到地板
            if is_on_floor():
                change_stage(state.STATE_ON_FLOOR)
            else:
                # 实现下落
                velocity.y += gravity * delta
                velocity = move_and_slide(velocity,Vector2.UP)
        state.STATE_ON_FLOOR:
            velocity.y = 0
            # 左右移动
            velocity.x = Input.get_axis("ui_left","ui_right") * speed
            # 跳跃
            if input_jump():  # 按空格键
                velocity.y = -jump_force
                change_stage(state.STATE_ON_AIR)
            velocity = move_and_slide(velocity,Vector2.UP)
            if is_on_wall():
                change_stage(state.STATE_ON_WALL)
        state.STATE_ON_TIZI:
            if is_on_floor():
                velocity.x = velocity.x * 0.9
            else:
                input_x()
            input_y()
            move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
        state.STATE_ON_WALL:
            input_x()
            input_y()
            if input_jump():  # 按空格键
                velocity.y = -jump_force / 2 # 在墙上时只能跳地面的一半
                velocity = move_and_slide(velocity,Vector2.UP)
                change_stage(state.STATE_ON_AIR)
            if velocity.x != 0:  # 按左右键
                velocity = move_and_slide(velocity,Vector2.UP)
                change_stage(state.STATE_ON_AIR)
            else:
                velocity = move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
            if not is_on_wall():
                change_stage(state.STATE_ON_AIR)

可以看到我们可以将按键语句封装为简单函数，这样对判断非常有利。
比如下面的形式

func input_jump() -> bool:
    return Input.is_action_just_pressed("ui_accept")

或者干脆我们可以封装一个单例

# mInput.gd 单例 用于统一处理按键输入
extends Node
var left_action = "ui_left"
var right_action = "ui_right"
var up_action = "ui_up"
var down_action = "ui_down"
var jump_action = "ui_accept"
func just_pressed(action:String) -> bool:
    return Input.is_action_just_pressed(action)
func pressed(action:String) -> bool:
    return Input.is_action_pressed(action)
# 跳跃
func input_jump() -> bool:
    return just_pressed(jump_action)
func get_x():
    return Input.get_axis(left_action,right_action)
func get_y():
    return Input.get_axis(left_action,right_action)
func get_dir():
    return Input.get_vector(left_action,right_action,up_action,down_action)

此时，我们的玩家代码中将彻底看不到各种按键检测。

extends KinematicBody2D
var speed = 120.0 # 速度 像素/秒
var velocity = Vector2.ZERO # 速度向量
var gravity = 5000 # 重力加速度
var jump_force = 1000.0 # 单次跳跃高度
enum state {
    STATE_ON_WALL,
    STATE_ON_AIR,
    STATE_ON_FLOOR,
    STATE_ON_TIZI, # 在爬梯
}
var n_state = state.STATE_ON_AIR
func input_x():
    velocity.x = MInput.get_x() * speed
func input_y():
    velocity.y = MInput.get_y() * speed
func change_stage(new_state:int):
    n_state = new_state
func _physics_process(delta):
    match n_state:
        state.STATE_ON_AIR:
            # 掉到地板
            if is_on_floor():
                change_stage(state.STATE_ON_FLOOR)
            else:
                # 实现下落
                velocity.y += gravity * delta
                velocity = move_and_slide(velocity,Vector2.UP)
        state.STATE_ON_FLOOR:
            velocity.y = 0
            # 左右移动
            input_x()
            # 跳跃
            if MInput.input_jump():  # 按空格键
                velocity.y = -jump_force
                change_stage(state.STATE_ON_AIR)
            velocity = move_and_slide(velocity,Vector2.UP)
            if is_on_wall():
                change_stage(state.STATE_ON_WALL)
        state.STATE_ON_TIZI:
            if is_on_floor():
                velocity.x = velocity.x * 0.9
            else:
                input_x()
            input_y()
            move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
        state.STATE_ON_WALL:
            input_x()
            input_y()
            if MInput.input_jump():  # 按空格键
                velocity.y = -jump_force / 2 # 在墙上时只能跳地面的一半
                velocity = move_and_slide(velocity,Vector2.UP)
                change_stage(state.STATE_ON_AIR)
            if velocity.x != 0:  # 按左右键
                velocity = move_and_slide(velocity,Vector2.UP)
                change_stage(state.STATE_ON_AIR)
            else:
                velocity = move_and_slide_with_snap(velocity,get_floor_normal(),Vector2.UP)
            if not is_on_wall():
                change_stage(state.STATE_ON_AIR)