Time.deltaTime

描述

从上一帧到当前帧的时间间隔（秒）（只读）。

当从 MonoBehaviour.FixedUpdate 内部调用此方法时，它将返回 Time.fixedDeltaTime。 deltaTime 的最大值由 Time.maximumDeltaTime 定义。

deltaTime 在 MonoBehaviour.OnGUI 中不可靠，因为 Unity 可能会在每一帧中多次调用它。

以下示例以恒定速度围绕其 z 轴旋转一个 GameObject。

请参阅用户手册中的 时间和帧率管理，以获取有关此属性与其他 Time 属性之间关系的更多信息。

using UnityEngine;
// Rotate around the z axis at a constant speed
public class ConstantRotation : MonoBehaviour
{
    public float degreesPerSecond = 2.0f;
    void Update()
    {
        transform.Rotate(0, 0, degreesPerSecond * Time.deltaTime);
    }
}

以下示例实现了一个计时器。计时器在每一帧中添加 deltaTime。该示例显示计时器值，并在其达到 2 秒时重置它。 Time.timeScale 控制时间流逝的速度以及计时器重置的速度。

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);
    }
}