純個人筆記，有錯誤歡迎指正，學習階段基本看到不會的就寫一寫，最后有時間會梳理整體結構

先看完了官方的演講

1 地圖加載流程

1.1 默認Experience的加載

??這里先不從GameInstance開始，中間的CommonUser等流程暫時不談（有點多暫時不想看0w0），編輯器默認地圖L_DefaultEditorOverview中沒有重載游戲模式，所以用項目默認的B_LyraGameMode。
??ALyraGameMode::InitGame()

// Wait for the next frame to give time to initialize startup settings
GetWorld()->GetTimerManager().SetTimerForNextTick(this, &ThisClass::HandleMatchAssignmentIfNotExpectingOne);

可見邏輯轉到了ALyraGameMode::HandleMatchAssignmentIfNotExpectingOne()
(這里走的默認分支）

void ALyraGameMode::HandleMatchAssignmentIfNotExpectingOne()
{...ExperienceId = FPrimaryAssetId(FPrimaryAssetType("LyraExperienceDefinition"), FName("B_LyraDefaultExperience"));ExperienceIdSource = TEXT("Default");...OnMatchAssignmentGiven(ExperienceId, ExperienceIdSource);
}

??之后的調用棧大概是

OnMatchAssignmentGiven(ExperienceId, ExperienceIdSource)->
void ULyraExperienceManagerComponent::SetCurrentExperience(ExperienceId)->
void ULyraExperienceManagerComponent::StartExperienceLoad()->
void ULyraExperienceManagerComponent::OnExperienceLoadComplete()

??過程大體是設置當前ExperienceId，異步加載Experience相關資源，調用加載完成的回調.
??OnExperienceLoadComplete()函數收集GameFeaturePluginURL，最終調用

UGameFeaturesSubsystem::Get().
LoadAndActivateGameFeaturePlugin(PluginURL,  
FGameFeaturePluginLoadComplete::CreateUObject(this, 
&ThisClass::OnGameFeaturePluginLoadComplete));

??觸發默認Feature的Action

這里記錄一下幾個Action函數的調用順序， 防止我忘了
在這個函數中：
void ULyraExperienceManagerComponent::OnExperienceFullLoadCompleted()
ActivateListOfActions的定義

	auto ActivateListOfActions = [&Context](const TArray<UGameFeatureAction*>& ActionList){for (UGameFeatureAction* Action : ActionList){if (Action != nullptr){//@TODO: The fact that these don't take a world are potentially problematic in client-server PIE// The current behavior matches systems like gameplay tags where loading and registering apply to the entire process,// but actually applying the results to actors is restricted to a specific worldAction->OnGameFeatureRegistering();Action->OnGameFeatureLoading();Action->OnGameFeatureActivating(Context);}}};

逐一調用順序
自己的Actions先調用，再遍歷調用ActionSets

ActivateListOfActions(CurrentExperience->Actions);for (const TObjectPtr<ULyraExperienceActionSet>& ActionSet : CurrentExperience->ActionSets){if (ActionSet != nullptr){ActivateListOfActions(ActionSet->Actions);}}

三個多播順序

	OnExperienceLoaded_HighPriority.Broadcast(CurrentExperience);OnExperienceLoaded_HighPriority.Clear();OnExperienceLoaded.Broadcast(CurrentExperience);OnExperienceLoaded.Clear();OnExperienceLoaded_LowPriority.Broadcast(CurrentExperience);OnExperienceLoaded_LowPriority.Clear();

1.2 加載角色

B_LyraDefaultExperience中：

SimplePawnData：

可以發現通過這個就找到了創建的金屬Pawn，而不是GameMode中的角色類（是其藍圖子類）

但是為什么這里的配置能夠生效呢？
因為ALyraGameMode重寫了這個實現：

APawn* ALyraGameMode::SpawnDefaultPawnAtTransform_Implementation(AController* NewPlayer, const FTransform& SpawnTransform){
...
if (UClass* PawnClass = GetDefaultPawnClassForController(NewPlayer)){if (APawn* SpawnedPawn = GetWorld()->SpawnActor<APawn>(PawnClass, SpawnTransform, SpawnInfo))
...
}UClass* ALyraGameMode::GetDefaultPawnClassForController_Implementation(AController* InController)
{if (const ULyraPawnData* PawnData = GetPawnDataForController(InController)){if (PawnData->PawnClass){return PawnData->PawnClass;}}
...
}const ULyraPawnData* ALyraGameMode::GetPawnDataForController(const AController* InController) const
{
...
return Experience->DefaultPawnData;
...
}

1.3 加載場景中的幾個傳送點

由場景中這個Actor控制：

生成邏輯沒什么該注意的，注意生成時傳入了LyraUserfacingExperienceDefinition類型的變量，Widget信息都是根據這個配置的。
主要看加載地圖：

可見信息都在LyraUserfacingExperienceDefinition中，例如這個下邊這個，可以看到
要去的地圖信息都有。

2 幾個內建類的筆記

2.1 UDataAsset

剛拿到項目無從下手，就去看了啟動默認地圖L_LyraFrontEnd,沒有重載GameMode，即用的項目設置的B_LyraGameMode,暫時先不看GameMode，然后基于演講去看了DefaultGameplayExperience，一路看過去

B_LyraFrontEnd_Experience->
ULyraExperienceDefinition->
UPrimaryDataAsset->
UDataAsset->
UObject

這時候我發現我對DataAsset沒什么了解，只好先去學習一下：

UCLASS(abstract, MinimalAPI, Meta = (LoadBehavior = "LazyOnDemand"))
class UDataAsset : public UObject

abstract：

MinimalAPI沒太看懂，大概是優化編譯相關的：

LoadBehavior
UPrimaryDataAsset：
UE5–PrimaryDataAsset資產包更新UpdateAssetBundleData源碼分析
看完這幾篇后我的理解這個類就是數據資產。

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2.2 UAssetManager

暫時停留在使用層理解。
UE5 AssetManager類使用詳解

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參考文章：
UE5 Lyra項目學習（零） 開篇&目錄