public class PlayerController : MonoBehaviour {

    public float speed = 1;
    private Rigidbody2D rigidbody;
    private Animator animator;
    private int key;


    public float jumpForce = 240.0f;
    private float walkForce = 20.0f;
    private float MaxWalkSpeed = 10.0f;

    // Use this for initialization
    void Start () {
        rigidbody = GetComponent<Rigidbody2D>();
        animator = GetComponent<Animator>();
    }

    // Update is called once per frame
    void Update () {
        key = 0;

        //ジャンプ
        if (Input.GetKeyDown(KeyCode.Space))
        {
            animator.SetTrigger("JumpTrigger");
            rigidbody.AddForce(transform.up * jumpForce);
            //jump_ = true;
        }

        if(Input.GetKey(KeyCode.RightArrow))
        {
            key = 1;
        }

        if (Input.GetKey(KeyCode.LeftArrow))
        {
            key = -1;
        }


        if ( key != 0)
        {
            transform.localScale = new Vector3(key,1,1);
        }

        float speedx = Mathf.Abs(rigidbody.velocity.x);//ここです。
        //Debug.Log(speedx);

        if(speedx < MaxWalkSpeed)
        {
            rigidbody.AddForce(transform.right * key * walkForce);
        }


        if(rigidbody.velocity.y == 0)
        {
            animator.speed = speedx / 2.0f;
        }
        else
        {
            animator.speed = 1.0f;
        }
    }
}