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1、什么是引用计数规则？

当通过加载使用可寻址资源时，Addressables会在内部帮助我们进行引用计数，使用资源时，引用计数+1，释放资源时，引用计数-1，当可寻址资源的引用为0时，就可以卸载它了

为了避免内存泄露（不需要使用的内容残留在内存中），我们要保证加载资源和卸载资源是配对使用的

注意：释放的资源不一定立即从内存中卸载，在卸载资源所属的AB包之前，不会释放资源使用的内存(比如自己所在的AB包 被别人使用时，这时AB包不会被卸载，所以自己还在内存中)，我们可以使用Resources.UnloadUnusedAssets卸载资源（建议在切换场景时调用）

AB包也有自己的引用计数（Addressables把它也视为可寻址资源）从AB包中加载资源时，引用计数+1，从AB包中卸载资源时，引用计数-1，当AB包引用计数为0时，意味着不再使用了，这时会从内存中卸载

总结：Addressables内部会通过引用计数帮助我们管理内存，我们只需要保证 加载和卸载资源配对使用即可

2、AddressableMgr 

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using NUnit.Framework;
using Unity.VisualScripting;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.ResourceManagement.AsyncOperations;public class AddresssablesInfo
{public AsyncOperationHandle handle;public uint count;public AddresssablesInfo(AsyncOperationHandle handle){this.handle = handle;count += 1;}
}public class AddressableMgr
{public static AddressableMgr instance = new AddressableMgr();public static AddressableMgr Instance => instance;// 有一个容帮助存储异步加载的返回值public Dictionary<string, AddresssablesInfo> resDic = new Dictionary<string, AddresssablesInfo>();private AddressableMgr() { }public void LoadAssetAsync<T>(string name, Action<AsyncOperationHandle<T>> callback){// 由于存在同名，不同类型资源区分加载，所以通过名字和类型进行拼接作为 Keystring keyName = name + "_" + typeof(T).Name;AsyncOperationHandle<T> handle;// 已经加载过该资源if (resDic.ContainsKey(keyName)){// 获取异步加载返回的 handlehandle = resDic[keyName].handle.Convert<T>();resDic[keyName].count += 1;if (handle.IsDone){callback(handle);}// 还没有加载完成else {// 如果还没有异步加载完成，只需要添加委托告诉完成后做什么handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Succeeded)callback(obj);};}return;}// 如果没有加载过该资源，直接进行异步加载并记录handle = Addressables.LoadAssetAsync<T>(name);handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Succeeded)callback(obj);else{Debug.LogWarning(keyName + " load asset failed");if (resDic.ContainsKey(keyName))resDic.Remove(keyName);}};AddresssablesInfo info = new AddresssablesInfo(handle);resDic.Add(keyName, info);}public void Release<T>(string name){string keyName = name + "_" + typeof(T).Name;if (resDic.ContainsKey(keyName)){resDic[keyName].count -= 1;if (resDic[keyName].count == 0){AsyncOperationHandle<T> handle = resDic[keyName].handle.Convert<T>();Addressables.Release(handle);resDic.Remove(keyName);}}}// 异步加载多个资源 或者 加载指定资源private string FormatKeyName<T>(List<string> keys){string keyName = "";foreach (string key in keys)keyName += key + "_";keyName += typeof(T).Name;return keyName;}public void LoadAssetAsync<T>(Addressables.MergeMode mode, Action<T> callBack, params string[] keys){// 1.构建一个 keyName 之后存入到字典中List<string> list = new List<string>(keys);string keyName = FormatKeyName<T>(list);// 2.判断是否存在已经加载过的内容AsyncOperationHandle<IList<T>> handle;if (resDic.ContainsKey(keyName)){handle = resDic[keyName].handle.Convert<IList<T>>();resDic[keyName].count += 1;// 异步加载是否结束if (handle.IsDone){foreach(T item in handle.Result) callBack(item);}else{handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Succeeded){foreach (T item in handle.Result)callBack(item);}};}return;}handle = Addressables.LoadAssetsAsync<T>(list, callBack, mode);handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Failed){Debug.LogWarning(keyName + " load asset failed");if (resDic.ContainsKey(keyName))resDic.Remove(keyName);}};AddresssablesInfo info = new AddresssablesInfo(handle);resDic.Add(keyName, info);}public void LoadAssetAsync<T>(Addressables.MergeMode mode, Action<AsyncOperationHandle<IList<T>>> callBack, params string[] keys){// 1.构建一个 keyName 之后存入到字典中List<string> list = new List<string>(keys);string keyName = FormatKeyName<T>(list);// 2.判断是否存在已经加载过的内容AsyncOperationHandle<IList<T>> handle;if (resDic.ContainsKey(keyName)){handle = resDic[keyName].handle.Convert<IList<T>>();resDic[keyName].count += 1;// 异步加载是否结束if (handle.IsDone){callBack(handle);}else{handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Succeeded){callBack(handle);}};}return;}handle = Addressables.LoadAssetsAsync<T>(list, null, mode);handle.Completed += (obj) =>{if (obj.Status == AsyncOperationStatus.Failed){Debug.LogWarning(keyName + " load asset failed");if (resDic.ContainsKey(keyName))resDic.Remove(keyName);}else{callBack(handle);}};AddresssablesInfo info = new AddresssablesInfo(handle);resDic.Add(keyName, info);}public void Release<T>(params string[] keys){List<string> list = new List<string>(keys);string keyName = FormatKeyName<T>(list);if ( resDic.ContainsKey(keyName)){resDic[keyName].count -= 1;if (resDic[keyName].count == 0){AsyncOperationHandle<IList<T>> handle = resDic[keyName].handle.Convert<IList<T>>();Addressables.Release(handle);resDic.Remove(keyName);}}}public void Clear(){foreach (var item in resDic.Values){Addressables.Release(item.handle);}resDic.Clear();AssetBundle.UnloadAllAssetBundles(true);Resources.UnloadUnusedAssets();GC.Collect();}}