要在角色开始移动时将动画切换为 walk，可以通过添加一个 Animator 组件和相应的 Animator Controller 来实现。首先，在 Unity 中创建一个 Animator Controller，然后将其分配给角色的 Animator 组件。在这个控制器中，创建两个动画状态：walk 和 idle，并将它们分别与名为 IsWalking 和 IsIdle 的布尔参数关联起来。

接下来，在 PlayerController1 脚本中，在 MoveToTarget 协程中设置 IsWalking 参数为 true，在协程结束时将其设回 false。还可以使用 GetAxisRaw 函数检测玩家是否按下了左右箭头键（或者 A/D 键），并设置相应的参数来播放行走动画。

以下是修改后的代码：

using UnityEngine;
using System.Collections;

public class PlayerController1 : MonoBehaviour
{
    public GameObject circlePrefab;
    private GameObject currentCircle;
    private Vector3 targetPosition;
    private bool facingRight = true;

    // 新增变量：限制角色移动范围
    public Rect moveRange;

    Coroutine currentCoroutine;

    // 新增变量：Animator 组件
    private Animator animator;

    void Start()
    {
        // 获取角色上的 Animator 组件
        animator = GetComponent<Animator>();
    }

    void Update()
    {
        if (Input.touchCount > 0)
        {
            Touch touch = Input.GetTouch(0);

            switch (touch.phase)
            {
                case TouchPhase.Began:
                    if (IsTouchedOnPlayer(touch.position))
                    {
                        currentCircle = Instantiate(circlePrefab, transform.position, Quaternion.identity);
                        return;
                    }
                    break;

                case TouchPhase.Moved:
                    if (currentCircle != null)
                    {
                        Vector3 touchPos = Camera.main.ScreenToWorldPoint(touch.position);
                        touchPos.z = 0;
                        currentCircle.transform.position = touchPos;
                    }
                    break;

                case TouchPhase.Ended:
                    if (currentCircle != null)
                    {
                        HandleTouchEndedOrCanceled(touch);
                        Destroy(currentCircle);
                    }
                    break;

                case TouchPhase.Canceled:
                    break;
            }
        }

        // 新增：检测玩家是否按下左右箭头键（或者 A/D 键）
        float horizontalInput = Input.GetAxisRaw("Horizontal");
        animator.SetBool("IsWalking", horizontalInput != 0);
    }

    private bool IsTouchedOnPlayer(Vector2 screenPosition)
    {
        Vector2 worldPosition = Camera.main.ScreenToWorldPoint(screenPosition);
        Collider2D[] colliders = GetComponents<Collider2D>();
        foreach (var collider in colliders)
        {
            if (collider.OverlapPoint(worldPosition))
            {
                return true;
            }
        }
        return false;
    }

    void HandleTouchEndedOrCanceled(Touch touch)
    {
        if (!IsTouchedOnPlayer(touch.position))
        {
            Vector2 targetPos = Camera.main.ScreenToWorldPoint(touch.position);
            // 新增限制：将目标位置限制在 moveRange 范围内
            targetPosition.x = Mathf.Clamp(targetPos.x, moveRange.xMin, moveRange.xMax);
            targetPosition.y = Mathf.Clamp(targetPos.y, moveRange.yMin, moveRange.yMax);

            if (currentCoroutine != null)
                StopCoroutine(currentCoroutine);

            currentCoroutine = StartCoroutine(MoveToTarget());
        }
    }

    IEnumerator MoveToTarget()
    {
        float moveSpeed = 2.5f;
        float bufferDistance = 0.01f;
        Vector3 targetDirection;

        // 新增：设置 IsWalking 参数为 true
        animator.SetBool("IsWalking", true);

        while (Vector3.Distance(transform.position, targetPosition) > bufferDistance)
        {
            if (transform.position == targetPosition)
                yield break;

            // 新增限制：检查角色是否超出了移动范围
            Vector3 clampedPos = transform.position;
            clampedPos.x = Mathf.Clamp(clampedPos.x, moveRange.xMin, moveRange.xMax);
            clampedPos.y = Mathf.Clamp(clampedPos.y, moveRange.yMin, moveRange.yMax);
            transform.position = clampedPos;

            targetDirection = (targetPosition - transform.position).normalized;

            if (targetDirection.x > 0 && !facingRight)
            {
                Flip();
            }
            else if (targetDirection.x < 0 && facingRight)
            {
                Flip();
            }

            if (Vector3.Distance(transform.position, targetPosition) < moveSpeed * Time.deltaTime)
            {
                transform.position = targetPosition;
                yield break;
            }

            transform.position = Vector3.MoveTowards(transform.position, targetPosition, moveSpeed * Time.deltaTime);

            yield return null;
        }

        // 新增：设置 IsWalking 参数为 false
        animator.SetBool("IsWalking", false);
    }

    void Flip()
    {
        facingRight = !facingRight;

        Vector3 scale = transform.localScale;
        scale.x *= -1;
        transform.localScale = scale;
    }
}

现在，当玩家按下左右箭头键（或者 A/D 键）时，角色会播放行走动画。当角色到达目标位置后，动画将切换为闲置状态。