Rigidbody2D.velocity

描述

刚体的线性速度，采用单位/秒形式。

速度被指定为具有 X 和 Y 方向（在 2D 物理中，没有 Z 方向）分量的矢量。我们通常不直接设置该值，而是使用 forces。在 Inspector 中，禁用阻力可停止速度的逐渐衰减。

Additional resources: Rigidbody2D.angularVelocity, Rigidbody2D.AddForce and Rigidbody2D.drag.

//Create a new 2D Sprite GameObject and attach this script to it.

//This script moves a GameObject up or down when you press the up or down arrow keys.
//The velocity is set to the Vector2() value.  Unchanging the Vector2() keeps the
//GameObject moving at a constant rate.

using UnityEngine;

public class ExampleClass : MonoBehaviour
{
    private Rigidbody2D rb;

    private float t = 0.0f;
    private bool moving = false;

    void Awake()
    {
        rb = gameObject.AddComponent<Rigidbody2D>() as Rigidbody2D;
        rb.bodyType = RigidbodyType2D.Kinematic;
    }

    void Start()
    {
        gameObject.GetComponent<SpriteRenderer>().sprite = Resources.Load<Sprite>("image128x128");
        gameObject.transform.Translate(0.0f, 0.0f, 0.0f);
    }

    void Update()
    {
        //Press the Up arrow key to move the RigidBody upwards
        if (Input.GetKey(KeyCode.UpArrow))
        {
            rb.velocity = new Vector2(0.0f, 2.0f);
            moving = true;
            t = 0.0f;
        }

        //Press the Down arrow key to move the RigidBody downwards
        if (Input.GetKey(KeyCode.DownArrow))
        {
            rb.velocity = new Vector2(0.0f, -1.0f);
            moving = true;
            t = 0.0f;
        }

        if (moving)
        {
            // Record the time spent moving up or down.
            // When this is 1sec then display info
            t = t + Time.deltaTime;
            if (t > 1.0f)
            {
                Debug.Log(gameObject.transform.position.y + " : " + t);
                t = 0.0f;
            }
        }
    }
}