Unity之DontDestroyOnLoad的使用

发表于2019-01-14
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Unity中的一个方法DontDestroyOnLoad可以让某些游戏对象在切换场景的时候不是释放,听上去很好用的方法,

了解一下官方文档:
public static void DontDestroyOnLoad(Object target);
Parameters
target An Object not destroyed on Scene change.
Description
Do not destroy the target Object when loading a new Scene.

The load of a new Scene destroys all current Scene objects. Call Object.DontDestroyOnLoad to preserve an Object during level loading. If the target Object is a component or GameObject, Unity will also preserve all of the Transform’s children. Object.DontDestroyOnLoad does not return a value. Change the argument type using the typeof operator.

公共静态空洞DontDestroyOnLoad(对象目标);

参数

目标:场景改变时未被摧毁的物体。
描述:加载新场景时不要销毁目标对象。

新场景的负载会破坏所有当前场景对象。调用Object.DontDestroyOnLoad在级别加载期间保存对象。如果目标对象是组件或游戏对象,Unity还将保留Transform的所有子对象。对象。DontDestroyOnLoad不返回值。使用typeof操作符更改参数类型。

官方的举例:当我从游戏scence1开始播放背景音乐,而切换到scence2的时候还希望继续播放这个音乐,那么久可以使用这个DontDestroyLoad这种形式,

(请创建两个新的场景,命名为scene1和scene2。打开scene1并添加SceneSwap.cs脚本为空游戏对象给它起个名字Menu。接下来,添加DontDestroy.cs换一个新的游戏对象给它起个名字BackgroundMusic。添加一个音频源到BackgroundMusic - Add Component > Audio > Audio Source-并进口AudioClip进入你的项目。分配AudioClip到音频源氏AudioClip场。创建一个标签,称之为music,并将其添加到BackgroundMusic。切换到scene2。再加SceneSwap.cs换一个新的游戏对象给它起个名字Menu。拯救计划。回到scene1并从Editor.)
using UnityEngine;
using UnityEngine.SceneManagement;
// Object.DontDestroyOnLoad example.
//
// Two scenes call each other. This happens when OnGUI button is clicked.
// scene1 will load scene2; scene2 will load scene1. Both scenes have
// the Menu GameObject with the SceneSwap.cs script attached.
//
// AudioSource plays an AudioClip as the game runs. This is on the
// BackgroundMusic GameObject which has a music tag.  The audio
// starts in AudioSource.playOnAwake. The DontDestroy.cs script
// is attached to BackgroundMusic.
public class SceneSwap : MonoBehaviour
{
    private void OnGUI()
    {
        int xCenter = (Screen.width / 2);
        int yCenter = (Screen.height / 2);
        int width = 400;
        int height = 120;
        GUIStyle fontSize = new GUIStyle(GUI.skin.GetStyle("button"));
        fontSize.fontSize = 32;
        Scene scene = SceneManager.GetActiveScene();
        if (scene.name == "scene1")
        {
            // Show a button to allow scene2 to be switched to.
            if (GUI.Button(new Rect(xCenter - width / 2, yCenter - height / 2, width, height), "Load second scene", fontSize))
            {
                SceneManager.LoadScene("scene2");
            }
        }
        else
        {
            // Show a button to allow scene1 to be returned to.
            if (GUI.Button(new Rect(xCenter - width / 2, yCenter - height / 2, width, height), "Return to first scene", fontSize))
            {
                SceneManager.LoadScene("scene1");
            }
        }
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
// Object.DontDestroyOnLoad example.
//
// This script example manages the playing audio. The GameObject with the
// "music" tag is the BackgroundMusic GameObject. The AudioSource has the
// audio attached to the AudioClip.
public class DontDestroy : MonoBehaviour
{
    void Awake()
    {
        GameObject[] objs = GameObject.FindGameObjectsWithTag("music");
        if (objs.Length > 1)
        {
            Destroy(this.gameObject);
        }
        DontDestroyOnLoad(this.gameObject);
    }
}

其实真的使用起来并没有想象的那么简单,当你从一个场景切换到另一个然后在切回来的时候,会多了一个DontDestroyOnLoad的游戏对象,建议把需要DontDestroyOnLoad的游戏对象放到一个在游戏逻辑中不会返回的一个场景,比如说放到登录时加载的那个场景,或者代码使用一个静态变量做标志,(static bool isHave )是否DontDestroyOnLoad过,若DontDestroyOnLoad就将其赋值为True,想要找到这个游戏物体的话,搜索Find 是可以找到的,或者使用标签的形式FindGameObjectWithTag。

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