UGUI_游戏菜单场景切换

事件委托

GameManger（空物体）+GameManger脚本——重要的方式

public class GameManger : MonoBehaviour {

    public void OnStartGame(string sceneName)
    {
        Application.LoadLevel(sceneName);
    }

}

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

public class GameManger : MonoBehaviour
 {
    public void OnStartGame(int sceneIndex)
    {
        //Application.LoadLevel(sceneIndex);
         SceneManager.LoadScene(1);
    }
}

Unity3D  SceneManager场景管理用法总结

一、Unity关卡

Unity 使用过程中关卡加载和卸载是大多数三维引擎都要提供的基本功能。 
因为关卡切换在游戏中非常常用。 
在之前的版本中Unity的关卡切换使用的是：

Application.loadedLevel()；

• 1看看Application类，此时这个类的功能比较繁杂，比较多。只看与关卡相关的：

 [Obsolete("Use SceneManager.LoadScene")]
        public static void LoadLevel(string name);

        [Obsolete("Use SceneManager.LoadScene")]
        public static void LoadLevel(int index);

        [Obsolete("Use SceneManager.LoadScene")]
        public static void LoadLevelAdditive(string name);

        [Obsolete("Use SceneManager.LoadScene")]
        public static void LoadLevelAdditive(int index);
  //
        // 摘要:
        //     ///
        //     Unloads all GameObject associated with the given scene. Note that assets are
        //     currently not unloaded, in order to free up asset memory call Resources.UnloadAllUnusedAssets.
        //     ///
        //
        // 参数:
        //   index:
        //     Index of the scene in the PlayerSettings to unload.
        //
        //   scenePath:
        //     Name of the scene to Unload.
        //
        // 返回结果:
        //     ///
        //     Return true if the scene is unloaded.
        //     ///
        [Obsolete("Use SceneManager.UnloadScene")]
        public static bool UnloadLevel(string scenePath);
        //
        // 摘要:
        //     ///
        //     Unloads all GameObject associated with the given scene. Note that assets are
        //     currently not unloaded, in order to free up asset memory call Resources.UnloadAllUnusedAssets.
        //     ///
        //
        // 参数:
        //   index:
        //     Index of the scene in the PlayerSettings to unload.
        //
        //   scenePath:
        //     Name of the scene to Unload.
        //
        // 返回结果:
        //     ///
        //     Return true if the scene is unloaded.
        //     ///
        [Obsolete("Use SceneManager.UnloadScene")]
        public static bool UnloadLevel(int index);

注解： 
这是之前的Application中的关卡的加载和卸载。 
当然现在在新版本（Unity5.3以上）中，有了新的变化，那就是SceneManager类了处理。

二、Untiy的SceneManager类

自从Unity5.3版本，Unity 的关卡切换就添加了新的SceneManager的类来处理。 
当然要安装过了Unity文档帮助，并且给下面路径一样，就可以知道在本地打开。 
本地链接： 
file:///C:/Program%20Files/Unity5.3.0/Editor/Data/Documentation/en/Manual/UpgradeGuide53.html 
也可以在Unity中搜索SceneManager来查看。

#region 程序集 UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null
// H:UnityUnityProjectShiftLevelsLibraryUnityAssembliesUnityEngine.dll
#endregion

using UnityEngine.Internal;

namespace UnityEngine.SceneManagement
{
    //
    // 摘要:
    //     ///
    //     Scene management at run-time.
    //     ///
    public class SceneManager
    {
        public SceneManager();


        public static int sceneCount { get; }
        //

        public static int sceneCountInBuildSettings { get; }


        public static Scene GetActiveScene();

        public static Scene[] GetAllScenes();
        // 参数:
        //   index:
        //     Index of the scene to get. Index must be greater than or equal to 0 and less
        //     than SceneManager.sceneCount.
        public static Scene GetSceneAt(int index);

        // 返回结果:
        //     ///
        //     The scene if found or an invalid scene if not.
        //     ///
        public static Scene GetSceneByName(string name);

        //     Searches all scenes added to the SceneManager for a scene that has the given
        //     asset path.
        //     ///
        //
        // 参数:
        //   scenePath:
        //     Path of the scene. Should be relative to the project folder. Like: "AssetsMyScenesMyScene.unity".
        public static Scene GetSceneByPath(string scenePath);
        [ExcludeFromDocs]
        public static void LoadScene(int sceneBuildIndex);
        [ExcludeFromDocs]
        public static void LoadScene(string sceneName);

        // 参数:
        //   sceneName:
        //     Name of the scene to load.
        //
        //   sceneBuildIndex:
        //     Index of the scene in the Build Settings to load.
        //
        //   mode:
        //     Allows you to specify whether or not to load the scene additively. See SceneManagement.LoadSceneMode
        //     for more information about the options.
        public static void LoadScene(int sceneBuildIndex, [DefaultValue("LoadSceneMode.Single")] LoadSceneMode mode);

        // 参数:
        //   sceneName:
        //     Name of the scene to load.
        //
        //   sceneBuildIndex:
        //     Index of the scene in the Build Settings to load.
        //
        //   mode:
        //     Allows you to specify whether or not to load the scene additively. See SceneManagement.LoadSceneMode
        //     for more information about the options.
        public static void LoadScene(string sceneName, [DefaultValue("LoadSceneMode.Single")] LoadSceneMode mode);
        [ExcludeFromDocs]
        public static AsyncOperation LoadSceneAsync(int sceneBuildIndex);
        [ExcludeFromDocs]
        public static AsyncOperation LoadSceneAsync(string sceneName);

        // 参数:
        //   sceneName:
        //     Name of the scene to load.
        //
        //   sceneBuildIndex:
        //     Index of the scene in the Build Settings to load.
        //
        //   mode:
        //     If LoadSceneMode.Single then all current scenes will be unloaded before loading.
        public static AsyncOperation LoadSceneAsync(int sceneBuildIndex, [DefaultValue("LoadSceneMode.Single")] LoadSceneMode mode);

        // 参数:
        //   sceneName:
        //     Name of the scene to load.
        //
        //   sceneBuildIndex:
        //     Index of the scene in the Build Settings to load.
        //
        //   mode:
        //     If LoadSceneMode.Single then all current scenes will be unloaded before loading.
        public static AsyncOperation LoadSceneAsync(string sceneName, [DefaultValue("LoadSceneMode.Single")] LoadSceneMode mode);
        //

        // 参数:
        //   sourceScene:
        //     The scene that will be merged into the destination scene.
        //
        //   destinationScene:
        //     Existing scene to merge the source scene into.
        public static void MergeScenes(Scene sourceScene, Scene destinationScene);
        //
        // 摘要:
        //     ///
        //     Move a GameObject from its current scene to a new scene. /// It is required that
        //     the GameObject is at the root of its current scene.
        //     ///
        //
        // 参数:
        //   go:
        //     GameObject to move.
        //
        //   scene:
        //     Scene to move into.
        public static void MoveGameObjectToScene(GameObject go, Scene scene);
        //

        // 返回结果:
        //     ///
        //     Returns false if the scene is not loaded yet.
        //     ///
        public static bool SetActiveScene(Scene scene);

        //     ///
        public static bool UnloadScene(string sceneName);
        //
        // 摘要:
        //     ///
        //     Unloads all GameObjects associated with the given scene. Note that assets are
        //     currently not unloaded, in order to free up asset memory call Resources.UnloadAllUnusedAssets.
        //     ///
        //
        // 参数:
        //   sceneBuildIndex:
        //     Index of the scene in the Build Settings to unload.
        //
        //   sceneName:
        //     Name of the scene to unload.
        //
        // 返回结果:
        //     ///
        //     Returns true if the scene is unloaded.
        //     ///
        public static bool UnloadScene(int sceneBuildIndex);
    }
}

三、SceneManager对于获取场景的一些操作

（一） 
SceneManager 
class in UnityEngine.SceneManagement 
描述：运行时的场景管理。 
静态变量sceneCount: 当前加载的场景的总数。 
前加载的场景的数量将被返回。 
sceneCountInBuildSettings : 在BuildSettings的号码。

（二） 
CreateScene：在运行时创建一个空的新场景，使用给定的名称。 
在运行时创建一个空的新场景，使用给定的名称。 
新的场景将开放相加到层次与现有已经打开的场景。新场景的路径将是空的。此函数用于在运行时创建场景。创建一个场景编辑时间（例如，使编辑脚本或工具需要创建场景时），使用editorscenemanager.newscene。

（三） 
public static SceneManagement.Scene GetActiveScene() 
现场的活动场景。 
描述：获取当前活动场景。 
当前活动的场景将被用来作为目标由脚本实例化新的游戏对象现场。

using UnityEngine;
using UnityEngine.SceneManagement;

public class GetActiveSceneExample : MonoBehaviour
{
    void Start()
    {
        Scene scene = SceneManager.GetActiveScene();

        Debug.Log("Active scene is '" + scene.name + "'.");
    }
}

（四） 
public static SceneManagement.Scene GetSceneAt(int index); 
index：场景索引。指数必须大于或等于0和小于scenemanager.scenecount。

返回： 
根据给定的参数返回一个场景引用。 
获取现场在添加场景的场景管理器的列表索引：

using UnityEditor;
using UnityEditor.SceneManagement;
using UnityEngine.SceneManagement;
using UnityEngine;
public class Example
{
    // adds a menu item which gives a brief summary of currently open scenes
    [MenuItem("SceneExample/Scene Summary")]
    public static void ListSceneNames()
    {
        string output = "";
        if (SceneManager.sceneCount > 0)
        {
            for (int n = 0; n < SceneManager.sceneCount; ++n)
            {
                Scene scene = SceneManager.GetSceneAt(n);
                output += scene.name;
                output += scene.isLoaded ? " (Loaded, " : " (Not Loaded, ";
                output += scene.isDirty ? "Dirty, " : "Clean, ";
                output += scene.buildIndex >=0 ? " in build)
" : " NOT in build)
";
            }
        }
        else
        {
            output = "No open scenes.";
        }
        EditorUtility.DisplayDialog("Scene Summary",output, "Ok");
    }
}

（五）

public static SceneManagement.Scene GetActiveScene(); 
获取当前活动场景。 
当前活动的场景将被用来作为目标由脚本实例化新对象。

using UnityEngine;
using UnityEngine.SceneManagement;

public class GetActiveSceneExample : MonoBehaviour
{
    void Start()
    {
        Scene scene = SceneManager.GetActiveScene();

        Debug.Log("Active scene is '" + scene.name + "'.");
    }
}

public static void LoadScene(int sceneBuildIndex, SceneManagement.LoadSceneMode mode = LoadSceneMode.Single);
public static void LoadScene(string sceneName, SceneManagement.LoadSceneMode mode = LoadSceneMode.Single);

sceneName: 需发加载的场景名称或路径。

sceneBuildIndex：在“ Build Settings”加载中的场景的索引。

Mode：允许您指定是否要加载相加现场。见LoadScene模式有关选项的详细信息。 
LoadSceneMode：在播放器加载一个场景时使用。 
Single：关闭所有当前场景和加载一个新场景。 
Additive：将场景添加到当前加载的场景中。 
你可以使用这个异步版本：LoadSceneAsync。

using UnityEngine;
using UnityEngine.SceneManagement;

public class ExampleClass : MonoBehaviour {
    void Start () {
        // Only specifying the sceneName or sceneBuildIndex will load the scene with the Single mode
        SceneManager.LoadScene ("OtherSceneName", LoadSceneMode.Additive);
    }
}

四、5.3的实现代码

上代码：

/**************************************************************************
Copyright:@maxdong
Author: maxdong
Date: 2017-07-04
Description:加载关卡，可以分组加载和卸载。使用Unity版本为5.3.0.
因为里面使用了场景管理的一个类，这个类在5.3.0以上版本才添加的。
测试操作：使用空格键来切换场景，然后间隔5秒后才开始卸载。
**************************************************************************/
using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;

[System.Serializable]
public class LevelOrder
{

    [Header("每组关卡名称")]
    public string[] LevelNames;
}

public class ChangLevelsHasMain : MonoBehaviour
{
    [Header("所有关卡列表")]
    public LevelOrder[] levelOrder;
    private static int index;
    private int totalLevels = 0;
    private int levelOrderLength;

    void Start ()
    {
        for (int i = 0; i < levelOrder.Length; i++)
        {
            totalLevels += levelOrder[i].LevelNames.Length;
        }

        if (totalLevels != SceneManager.sceneCountInBuildSettings)
        {

        }
        levelOrderLength = levelOrder.Length;
    }

    // Update is called once per frame
    void Update ()
    {
        if (Input.GetKeyDown(KeyCode.Space))
        {
            bool isOk = LoadNextLevels();
            if (isOk)
            {
                InvokeRepeating("UnloadLastLevel", 2.0f, 5);
            }
        }
    }

    bool LoadNextLevels()
    {
        bool bResult = true;
        //index = index % levelOrderLength;
        if (index < 0 || index >= levelOrderLength)
        {
            bResult = false;
            return bResult;
        }

        int LoadTimes = levelOrder[index].LevelNames.Length;
        for (int i = 0; i < LoadTimes; i++)
        {
            SceneManager.LoadSceneAsync(levelOrder[index].LevelNames[i], LoadSceneMode.Additive);
        }
        return bResult;
    }

    void UnloadLastLevel()
    {
        if (index == 0)
        {
            index++;
            CancelInvoke("UnloadLastLevel");
            return;
        }
        // 上一組的關卡
        int TmpLast = (index - 1) >= 0 ? (index - 1) : levelOrderLength - 1;
        int LoadTimes = levelOrder[index].LevelNames.Length;
        for (int i = 0; i < LoadTimes; i++)
        {
            Scene Tmp = SceneManager.GetSceneByName(levelOrder[index].LevelNames[i]);
            if (!Tmp.isLoaded)
            {
                return;
            }
        }

        // 下一關卡全部加載完畢後，卸載之前關卡
        for (int i = 0; i < levelOrder[TmpLast].LevelNames.Length; i++)
        {
            SceneManager.UnloadScene(levelOrder[TmpLast].LevelNames[i]);
        }
        index++;
        CancelInvoke("UnloadLastLevel");
    }
}

就这样就可以了。 
代码主要是按组来加载关卡，然后按组来卸载。 
测试中，按下空格键来加载，每组关卡在一定时间后，（这里设置的5秒）自动卸载前一组关卡。这里主地图是不卸载的，会一直存在的。

怎么设置的呢？首先需要在Build setting中中把所有要处理的关卡放进来。要不就会在加载过程中报错。 
如下图： 

然后把代码挂在主地图的任意对象对象上就可以了.