Unity横版游戏移动脚本报错CS1503：无法将Vector2转换为float

错误error CS1503: Argument 2: cannot convert from 'UnityEngine.Vector2' to 'float'的原因很明确：你在FixedUpdate方法中创建Vector2时，第二个参数传了整个rb.velocity（Vector2类型），但new Vector2的第二个参数要求是float类型，类型不匹配导致报错。

修正方案 #

把FixedUpdate里的代码修改为：

private void FixedUpdate()
{
    rb.velocity = new Vector2(horizontal * speed, rb.velocity.y);
}

说明 #

rb.velocity.y是Rigidbody2D当前速度的y轴分量，属于float类型，刚好符合new Vector2的参数要求。这样修改既解决了类型错误，还能保留角色竖直方向的原有运动状态（比如下落、跳跃的速度不会被重置），不影响后续的跳跃等逻辑。

完整修正后的代码 #

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Player_Movement : MonoBehaviour
{
    private float horizontal;
    private float speed = 8f;
    private bool isFacingRight = true;

    [SerializeField] private Rigidbody2D rb;
    [SerializeField] private Transform groundCheck;
    [SerializeField] private LayerMask groundLayer;

    // Update is called once per frame
    void Update()
    {
        horizontal = Input.GetAxisRaw("Horizontal");

        Flip();
    }

    private void FixedUpdate()
    {
        rb.velocity = new Vector2(horizontal * speed, rb.velocity.y);
    }

    private void Flip()
    {
        if (isFacingRight && horizontal < 0f || !isFacingRight && horizontal > 0f)
        {
            isFacingRight = !isFacingRight;
            Vector3 localScale = transform.localScale;
            localScale.x *= -1f;
            transform.localScale = localScale;
        }
    }
}

内容的提问来源于stack exchange，提问作者bald_man_