Unity 教學 2D 遊戲角色移動 程式篇

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Unity 2D遊戲角色移動控制 程式篇
用淺顯易懂的方式解說如何實作2D角色移動的控制 包含走路與跳躍
而且能用 Physics2D.Linecast 判定是否在地板上，是的話才能跳躍(也就是不能在空中連跳)
並且附上2D platform Effector 的簡易說明

延伸閱讀：
Unity 5.5 2D Effectors 力場教學：2D平台, 橫向捲軸, 風吹, 瀑布, 漂浮, 黑洞, 爆炸, 輸送帶
http://www.morningfungame.com/2017/01/unity-55-2d-effectors-2d.html

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

public class Player : MonoBehaviour
{
    Rigidbody2D playerRigidbody2D;

    [Header("目前的水平速度")]
    public float speedX;

    [Header("目前的水平方向")]
    public float horizontalDirection;//數值會在 -1~1之間

    const string HORIZONTAL = "Horizontal";

    [Header("水平推力")]
    [Range(0, 150)]
    public float xForce;

    //目前垂直速度
    float speedY;

    [Header("最大水平速度")]
    public float maxSpeedX;

    [Header("垂直向上推力")]
    public float yForce;

    [Header("感應地板的距離")]
    [Range(0, 0.5f)]
    public float distance;

    [Header("偵測地板的射線起點")]
    public Transform groundCheck;

    [Header("地面圖層")]
    public LayerMask groundLayer;

    public bool grounded;

    public void ControlSpeed()
    {
        speedX = playerRigidbody2D.velocity.x;
        speedY = playerRigidbody2D.velocity.y;
        float newSpeedX = Mathf.Clamp(speedX, -maxSpeedX, maxSpeedX);
        playerRigidbody2D.velocity = new Vector2(newSpeedX, speedY);
    }

    public bool JumpKey
    {
        get
        {
            return Input.GetKeyDown(KeyCode.Space);
        }
    }

    void TryJump()
    {
        if (IsGround && JumpKey)
        {
            playerRigidbody2D.AddForce(Vector2.up * yForce);
        }
    }

    //在玩家的底部射一條很短的射線 如果射線有打到地板圖層的話 代表正在踩著地板
    bool IsGround
    {
        get
        {
            Vector2 start = groundCheck.position;
            Vector2 end = new Vector2(start.x, start.y - distance);

            Debug.DrawLine(start, end, Color.blue);
            grounded = Physics2D.Linecast(start, end, groundLayer);
            return grounded;
        }
    }

    void Start()
    {
        playerRigidbody2D = GetComponent<Rigidbody2D>();
    }

    /// <summary>水平移動</summary>
    void MovementX()
    {
        horizontalDirection = Input.GetAxis(HORIZONTAL);
        playerRigidbody2D.AddForce(new Vector2(xForce * horizontalDirection, 0));
    }

    void Update()
    {
        MovementX();
        ControlSpeed();
        TryJump();
        //speedX = playerRigidbody2D.velocity.x;
    }
}