Time.deltaTime

描述

完成上一帧所用的时间（以秒为单位）（只读）。

此属性提供当前帧和上一帧之间的时间。

使用 Time.deltaTime 可在 y 方向以 n 单位/秒的速度移动 GameObject。将 n 乘以 Time.deltaTime，然后与 y 分量相加。

MonoBehaviour.FixedUpdate 使用 fixedDeltaTime，而非 deltaTime。不依赖于 MonoBehaviour.OnGUI 中的 Time.deltaTime。Unity 可以每帧多次调用 OnGUI。应用程序每次调用使用相同的 deltaTime 值。

以下示例将实现一个 timer。timer 在每一帧增加 deltaTime。该示例声明 timer 值，并在达到 2 秒时将其重置为零。当 MonoBehaviour.Update 增加 deltaTime 时，timer 不会达到 2.0。相应的测试适用于移动 2 秒的 timer。脚本代码将删除报告的时间，然后 timer 重新启动。重新启动时间并不总是精确到 0.0。速度在 0.5 到 2.0 秒之间变化。Time.timeScale 用于存储所选择的时间流逝标度。

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

// Time.deltaTime example.
//
// Wait two seconds and display waited time.
// This is typically just beyond 2 seconds.
// Allow the speed of the time to be increased or decreased.
// It can range between 0.5 and 2.0. These changes only
// happen when the timer restarts.

public class ScriptExample : MonoBehaviour
{
    private float waitTime = 2.0f;
    private float timer = 0.0f;
    private float visualTime = 0.0f;
    private int width, height;
    private float value = 10.0f;
    private float scrollBar = 1.0f;

    void Awake()
    {
        width = Screen.width;
        height = Screen.height;
        Time.timeScale = scrollBar;
    }

    void Update()
    {
        timer += Time.deltaTime;

        // Check if we have reached beyond 2 seconds.
        // Subtracting two is more accurate over time than resetting to zero.
        if (timer > waitTime)
        {
            visualTime = timer;

            // Remove the recorded 2 seconds.
            timer = timer - waitTime;
            Time.timeScale = scrollBar;
        }
    }

    void OnGUI()
    {
        GUIStyle sliderDetails = new GUIStyle(GUI.skin.GetStyle("horizontalSlider"));
        GUIStyle sliderThumbDetails = new GUIStyle(GUI.skin.GetStyle("horizontalSliderThumb"));
        GUIStyle labelDetails = new GUIStyle(GUI.skin.GetStyle("label"));

        // Set the size of the fonts and the width/height of the slider.
        labelDetails.fontSize = 6 * (width / 200);
        sliderDetails.fixedHeight = height / 32;
        sliderDetails.fontSize = 12 * (width / 200);
        sliderThumbDetails.fixedHeight = height / 32;
        sliderThumbDetails.fixedWidth = width / 32;

        // Show the slider. Make the scale to be ten times bigger than the needed size.
        value = GUI.HorizontalSlider(new Rect(width / 8, height / 4, width - (4 * width / 8), height - (2 * height / 4)),
            value, 5.0f, 20.0f, sliderDetails, sliderThumbDetails);

        // Show the value from the slider. Make sure that 0.5, 0.6... 1.9, 2.0 are shown.
        float v = ((float)Mathf.RoundToInt(value)) / 10.0f;
        GUI.Label(new Rect(width / 8, height / 3.25f, width - (2 * width / 8), height - (2 * height / 4)),
            "timeScale: " + v.ToString("f1"), labelDetails);
        scrollBar = v;

        // Display the recorded time in a certain size.
        labelDetails.fontSize = 14 * (width / 200);
        GUI.Label(new Rect(width / 8, height / 2, width - (2 * width / 8), height - (2 * height / 4)),
            "Timer value is: " + visualTime.ToString("f4") + " seconds.", labelDetails);
    }
}