Unity 2D平台游戏下蹲问题：角色蹲伏时穿模掉落出地图

问题场景 #

开发2D平台游戏时，长按下蹲键（1秒内）角色会穿过地面掉落出地图，尝试过教程和重写脚本都没解决，需要实现蹲伏时不穿模的效果。

问题根源 #

1. 碰撞体偏移量在Update里被重复赋值覆盖，蹲伏时没正确调整碰撞体位置
2. 蹲伏只改了碰撞体大小，没同步改偏移，导致碰撞体位置和角色模型不匹配，触发穿模
3. 部分Sprite变量没初始化，可能引发额外异常

修复后的完整代码 #

using UnityEngine;

public class PlayerMovement : MonoBehaviour
{
    private Rigidbody2D rb;
    private Animator anim;
    private SpriteRenderer sprite;
    private int jumpCount = 0;
    private int maxJumps = 2;
    private bool grounded = false;
    private float dirX;
    private new BoxCollider2D collider;
    // 直接在Inspector面板拖入对应的Sprite
    public Sprite crouchingSprite;
    public Sprite standingSprite;
    private Vector2 crouchingSize = new Vector2(1, 0.5f);
    private Vector2 crouchingOffset = new Vector2(0, -0.25f);
    private Vector2 standingSize = new Vector2(1, 1);
    private Vector2 standingOffset = Vector2.zero;


    private void Start()
    {
        rb = GetComponent<Rigidbody2D>();
        anim = GetComponent<Animator>();
        sprite = GetComponent<SpriteRenderer>();
        collider = GetComponent<BoxCollider2D>();
        // 初始化默认显示站立Sprite
        if(standingSprite != null)
            sprite.sprite = standingSprite;
    }

    private void Update()
    {
        dirX = Input.GetAxisRaw("Horizontal");
        rb.velocity = new Vector3(dirX * 7f, rb.velocity.y, 0);

        // 跳跃与二段跳逻辑
        if (Input.GetButtonDown("Jump") && jumpCount < maxJumps)
        {
            rb.velocity = new Vector3(rb.velocity.x, 14f, 0);
            grounded = false;
            jumpCount++;
        }

        if (grounded)
        {
            jumpCount = 0;
        }

        // 蹲伏输入处理
        if (Input.GetButtonDown("Crouch"))
        {
            if(crouchingSprite != null)
                sprite.sprite = crouchingSprite;
            collider.size = crouchingSize;
            collider.offset = crouchingOffset;
        }

        if (Input.GetButtonUp("Crouch"))
        {
            if(standingSprite != null)
                sprite.sprite = standingSprite;
            collider.size = standingSize;
            collider.offset = standingOffset;
        }

        UpdateAnimationState();
    }

    private void UpdateAnimationState()
    {
        dirX = Input.GetAxisRaw("Horizontal");

        anim.SetBool("running", dirX != 0);
        if (dirX > 0f)
        {
            sprite.flipX = false;
        }
        else if (dirX < 0f)
        {
            sprite.flipX = true;
        }
    }

    private void OnCollisionEnter2D(Collision2D other)
    {
        if (other.gameObject.CompareTag("Ground"))
        {
            grounded = true;
            jumpCount = 0; // 落地重置跳跃次数，逻辑更合理
        }
    }

    private void OnCollisionExit2D(Collision2D other)
    {
        if (other.gameObject.CompareTag("Ground"))
        {
            grounded = false;
        }
    }
}

关键修改说明 #

• 碰撞体偏移修复：把碰撞体的大小、偏移改成类成员变量，不在Update里重复赋值，蹲伏时同时设置collider.offset，让碰撞体跟着角色模型下移，保证和地面的碰撞检测正常
• Sprite变量优化：把蹲伏、站立Sprite改成公开变量，直接在Unity编辑器拖入，还加了空值判断，避免空引用报错
• 地面碰撞逻辑完善：新增OnCollisionExit2D，离开地面时更新grounded状态；落地时把jumpCount设为0，跳跃逻辑更严谨
• 动画代码简化：跑步状态判断直接用dirX != 0，减少冗余代码

内容的提问来源于stack exchange，提问作者Magatsu