当我未在代码中调用它时，为什么我的方法被Unity调用？

Question

I can not understand why the method OnDrawGizmos() executes while it is not called in both the Start() method and Update() method, but it is executed when I run the Unity project.

using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour 
{
    public Transform grounder;


    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

    }

    void OnDrawGizmos(){
        Gizmos.color = Color.white;
        Gizmos.DrawSphere (grounder.position, 1);
    }
}

Answer 1

As the name suggests, OnDrawGizmozs gets called by the unity engine. It's a message function that gets called on classes that implement MonoBehaviour. Excert from the documentation:

Description

Implement OnDrawGizmos if you want to draw gizmos that are also pickable and always drawn.

http://docs.unity3d.com/ScriptReference/MonoBehaviour.OnDrawGizmos.html

This means you don't need to call the function yourself.

Answer 2

根据文档 ，因为它是由Unity在实现MonoBehaviour的类上调用的。