I've sorted it out today Time class ！

+ An interesting understanding API Graph

（ This picture is inspired by   How to understand API,API How it works _ Brother Renjie's blog -CSDN Blog _api）

Catalog

Time

practice ： Use Text Make a countdown prefab

* stay Update In the method executed per frame , Individual statements are executed once at a specified interval

Time

Time.time In seconds , From the beginning of the game

Time.deltaTime Time consumed per frame （ Time interval of each frame ）

Public void Update()// Rendering update

{ Move at a constant speed in the rendered frame 、 rotate

// Execute once per rendered frame , Spin one degree

// Multiple frames —>1 Second rotation speed is fast hope 1 Frame rotation is small

// Fewer frames —>1 Second rotation speed is slow hope 1 Frame rotation is large

This.transform.Rotate(0,1*Time.deltaTime,0)

}

Rotation speed * Time consumed per frame , It can ensure that the rotation speed is not affected by rendering

perhaps

public void FixedUpdate()// Physical update

{

this.transform.Rotate(0,1,0);

)

Time.timeScale Every frame interval affected by scaling

Time.timeScale=0 Game pause  Time.timeScale=1 Keep playing

The object is in FixedUpdate() Move , spot “ Pause ”、“ continue ” All good.

（ Even if Time.timeScale Not in the FixedUpdate() in ）

because FixedUpdate() Execute once at a fixed time , It has nothing to do with rendering , suffer Time.timeScale influence

stay Update() It's hard to work in , because Update() When rendering a scene , Not subject to Time.timeScale influence , but Time.deltaTime Will receive Time.timeScale influence

demand ： After the game pauses , Individual objects are not affected

stay Updete In doing

use this.transform.Rotatel(0,1*Time.unscaledDeltaTime,0)

Time.unscaledDeltaTime Every frame interval unaffected by scaling

practice ： Use Text Make a countdown prefab

from 02:00 Start , Last 10 The second font is red , Time is 00:00 Stop after

Last 10 The second font is red —>

Hierachy Right click —>UI—>Text

quote using UnityEngine.UI;

If(second<=0)

txtTimer.color=Color.red;

Time is 00:00 Stop after —>

If(second<=0)

CancelInvoke(“Timer”)// Cancel calling a method

Ideas ：

1. Find component references

2. Defining variables ： second

3.120—>02:00

       119—>01:59

4. Modify the text

5. How to modify once per second

* stay Update In the method executed per frame , Individual statements are executed once at a specified interval

Method 1 ：Time.time

 private float nextTime = 1;// Next modification time

 private void Update()

    {

       if (Time.time >= nextTime)

        {

            second--;

            txtTimer.text = string.Format("{0:d2}:{1:d2}", second / 60, second % 60);

            if (second <= 10)

                txtTimer.color = Color.red;

            // Set the next modification time

            nextTime = Time.time + 1;// Every other second

        }

}

Suitable for firing bullets , Press the left button to launch , Then accumulate strength （ Waiting time ） Limit the frequency

Method 2 ：Time.deltaTime

private float totalTime;// Cumulative The interval of each frame

private void Update()

    {

         totalTime += Time.deltaTime;

        if (totalTime >= 1)

        {

            second--;

            txtTimer.text = string.Format("{0:d2}:{1:d2}", second / 60, second % 60);

            totalTime = 0;

        }

}

Wait before you do

Method 3 ：InvokeRepeating()

// Repeated calls to （ Name of the method to be executed , The first execution time , Every execution interval ）

 void Start()

    {

 InvokeRepeating("Timer", 1, 1);

    }

private void Timer()

    {

            second--;

            txtTimer.text = string.Format("{0:d2}:{1:d2}", second / 60, second % 60);

    }

Invoke( The method to be carried out , The time when the call started )

Code implementation ：

using System.Collections;

using System.Collections.Generic;

using UnityEngine ;

using UnityEngine.UI;

public class TimeDemo : MonoBehaviour

{

    private Text txtTimer;

    public int second = 120;

private float nextTime = 1;// Next modification time 

void Start()

    {

        txtTimer = this.GetComponent<Text>();

    }

    private void Update()

    {

        Timer1();

}

 void Timer1()

    {

        if (Time.time >= nextTime)

        {

            second--;

            txtTimer.text = string.Format("{0:d2}:{1:d2}", second / 60, second % 60);

            if (second <= 10)

                txtTimer.color = Color.red;

            // Set the next modification time 

            nextTime = Time.time + 1;

            if(second<=0)

            {

                CancelInvoke("Timer");

            }

        }

}

}