前言
大多数人应该是会通过学习UE4的ActionRPG项目来入门GAS框架的。但在最近自己做Demo的过程中才发现里面的部分不适用网络联机。比如ActionRPG将Character与Controller的指针存在GameMode，因为Server与Client只有一个GameMode的关系，就不符合多人联机游戏的规则。所以在经过实践之后这里我分享一些要点仅供抛砖引玉。这里我再推荐各位读者去看一下GASDocument以及附带的工程，它展现了正确的设计思路。
GASDocument中的处理方式
将AbilitySystemComponent以及AttributeSet放在PlayerState中，之后再Character类中的PossesseBy()事件(ServerOnly)与OnRep_PlayerState()事件(Client)给角色类的ASC弱智能指针与AttributeSet弱智能指针赋值。
AGDPlayerState::AGDPlayerState()
{
AbilitySystemComponent = CreateDefaultSubobject<UGDAbilitySystemComponent>(TEXT("AbilitySystemComponent"));
AbilitySystemComponent->SetIsReplicated(true);
// Mixed mode means we only are replicated the GEs to ourself, not the GEs to simulated proxies. If another GDPlayerState (Hero) receives a GE,
// we won't be told about it by the Server. Attributes, GameplayTags, and GameplayCues will still replicate to us.
AbilitySystemComponent->SetReplicationMode(EGameplayEffectReplicationMode::Mixed);
AttributeSetBase = CreateDefaultSubobject<UGDAttributeSetBase>(TEXT("AttributeSetBase"));
NetUpdateFrequency = 100.0f;
}
// TWeakObjectPtr<class UGDAbilitySystemComponent> AbilitySystemComponent;
// TWeakObjectPtr<class UGDAttributeSetBase> AttributeSetBase;
// Server only
void AGDHeroCharacter::PossessedBy(AController * NewController)
{
Super::PossessedBy(NewController);
AGDPlayerState* PS = GetPlayerState<AGDPlayerState>();
if (PS)
{
// Set the ASC on the Server. Clients do this in OnRep_PlayerState()
AbilitySystemComponent = Cast<UGDAbilitySystemComponent>(PS->GetAbilitySystemComponent());
// AI won't have PlayerControllers so we can init again here just to be sure. No harm in initing twice for heroes that have PlayerControllers.
PS->GetAbilitySystemComponent()->InitAbilityActorInfo(PS, this);
AttributeSetBase = PS->GetAttributeSetBase();
}
//...
}
// Client only
void AGDHeroCharacter::OnRep_PlayerState()
{
Super::OnRep_PlayerState();
AGDPlayerState* PS = GetPlayerState<AGDPlayerState>();
if (PS)
{
// Set the ASC for clients. Server does this in PossessedBy.
AbilitySystemComponent = Cast<UGDAbilitySystemComponent>(PS->GetAbilitySystemComponent());
// Init ASC Actor Info for clients. Server will init its ASC when it possesses a new Actor.
AbilitySystemComponent->InitAbilityActorInfo(PS, this);
AttributeSetBase = PS->GetAttributeSetBase();
}
// ...
}
PlayerState
PlayerState只在开发多人游戏时有用，在设计上负责管理角色的变量(PlayerId、UniqueId、SessionName与自己定义的变量)。
指定与初始化
在GameMode中设置实现的PlayerState类，之后在AController::InitPlayerState()中Spawn。
访问方法
- Pawn->PlayerState
- Controller->PlayerState(一般用这个)
另外还可以通过GameState->PlayerArray获取所有有效的GameState实例。
PlayerState
PlayerState在切换地图时会默认销毁，为了解决这个问题可以通过实现CopyProperties方法来解决。
class ARPGPlayerState : public APlayerState
{
GENERATED_BODY()
public:
UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "ActionRPG")
ARPGCharacterBase* Character;
protected:
/** 这里是为了解决切换地图时的属性丢失问题 */
/** Copy properties which need to be saved in inactive PlayerState */
virtual void CopyProperties(APlayerState* PlayerState);
};
void ARPGPlayerState::CopyProperties(APlayerState* PlayerState)
{
//如果不是因为断线
if (IsFromPreviousLevel())
{
ARPGPlayerState* RPGPlayerState=Cast<ARPGPlayerState>(PlayerState);
RPGPlayerState->Character = Character;
}
}
NetUpdateFrequency
PlayerState的NetUpdateFrequency和角色类的效果是一样的，都是调节更新频率。默认数值对于GAS太低了，会导致滞后性。100是个比较高的数值，你也可以按照需求自己调节。
Controller
获取PlayerControllers
- GetWorld()->GetPlayerControllerIterator()
- PlayerState->GetOwner()
- Pawn->GetController()
BeginPlay里不做任何与GAS相关的操作
因为在服务端，Possession会发生在在BeginPlay前，客户端Possession发生在BeginPlay后，所以我们不能在BeginPlay中写任何有关ASC的逻辑除非PlayerState已经同步。
相关判断服务端客户端状态函数
在Ability类中一些操作可能需要判断是服务端还是客户端，比如应用GameplayEffect就在服务端执行(使用HasAuthority())，而创建UI就需要在客户端执行(使用IsLocallyControlled())。
蓝图
- HasAuthority()判断是否是服务端或是作为主机的玩家
- IsLocallyControlled()判断是否是本地控制器
- IsServer()通过World的ENetMode来段是服务端
c++
- 蓝图函数HasAuthority()在c++中为
return (GetLocalRole() == ROLE_Authority); - IsLocallyControlled(),c++中有对应函数。
NetSecurityPolicy
GameplayAbility的网络安全策略决定了Ability应该在网络的何处执行. 它为尝试执行限制Ability的客户端提供了保护.
- ClientOrServer：没有安全需求. 客户端或服务端可以自由地触发该Ability的执行和终止.
- ServerOnlyExecution：客户端对该Ability请求的执行会被服务端忽略, 但客户端仍可以请求服务端取消或结束该Ability.
- ServerOnlyTermination：客户端对该Ability请求的取消或结束会被服务端忽略, 但客户端仍可以请求执行该Ability.
- ServerOnly：服务端控制该Ability的执行和终止, 客户端的任何请求都会被忽略.
NetExecutionPolicy
推荐看这位大佬的文章：https://zhuanlan.zhihu.com/p/143637846
属性集属性UI更新
这里推荐使用GASDocument中的GameplayTasks更新方法。
#pragma once
#include "CoreMinimal.h"
#include "Kismet/BlueprintAsyncActionBase.h"
#include "AbilitySystemComponent.h"
#include "AsyncTaskAttributeChanged.generated.h"
DECLARE_DYNAMIC_MULTICAST_DELEGATE_ThreeParams(FOnAttributeChanged, FGameplayAttribute, Attribute, float, NewValue, float, OldValue);
/**
* Blueprint node to automatically register a listener for all attribute changes in an AbilitySystemComponent.
* Useful to use in UI.
*/
UCLASS(BlueprintType, meta=(ExposedAsyncProxy = AsyncTask))
class RPGGAMEPLAYABILITY_API UAsyncTaskAttributeChanged : public UBlueprintAsyncActionBase
{
GENERATED_BODY()
public:
UPROPERTY(BlueprintAssignable)
FOnAttributeChanged OnAttributeChanged;
// Listens for an attribute changing.
UFUNCTION(BlueprintCallable, meta = (BlueprintInternalUseOnly = "true"))
static UAsyncTaskAttributeChanged* ListenForAttributeChange(UAbilitySystemComponent* AbilitySystemComponent, FGameplayAttribute Attribute);
// Listens for an attribute changing.
// Version that takes in an array of Attributes. Check the Attribute output for which Attribute changed.
UFUNCTION(BlueprintCallable, meta = (BlueprintInternalUseOnly = "true"))
static UAsyncTaskAttributeChanged* ListenForAttributesChange(UAbilitySystemComponent* AbilitySystemComponent, TArray<FGameplayAttribute> Attributes);
// You must call this function manually when you want the AsyncTask to end.
// For UMG Widgets, you would call it in the Widget's Destruct event.
UFUNCTION(BlueprintCallable)
void EndTask();
protected:
UPROPERTY()
UAbilitySystemComponent* ASC;
FGameplayAttribute AttributeToListenFor;
TArray<FGameplayAttribute> AttributesToListenFor;
void AttributeChanged(const FOnAttributeChangeData& Data);
};
#include "Abilities/AsyncTasks/AsyncTaskAttributeChanged.h"
UAsyncTaskAttributeChanged* UAsyncTaskAttributeChanged::ListenForAttributeChange(UAbilitySystemComponent* AbilitySystemComponent, FGameplayAttribute Attribute)
{
UAsyncTaskAttributeChanged* WaitForAttributeChangedTask = NewObject<UAsyncTaskAttributeChanged>();
WaitForAttributeChangedTask->ASC = AbilitySystemComponent;
WaitForAttributeChangedTask->AttributeToListenFor = Attribute;
if (!IsValid(AbilitySystemComponent) || !Attribute.IsValid())
{
WaitForAttributeChangedTask->RemoveFromRoot();
return nullptr;
}
AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(Attribute).AddUObject(WaitForAttributeChangedTask, &UAsyncTaskAttributeChanged::AttributeChanged);
return WaitForAttributeChangedTask;
}
UAsyncTaskAttributeChanged * UAsyncTaskAttributeChanged::ListenForAttributesChange(UAbilitySystemComponent * AbilitySystemComponent, TArray<FGameplayAttribute> Attributes)
{
UAsyncTaskAttributeChanged* WaitForAttributeChangedTask = NewObject<UAsyncTaskAttributeChanged>();
WaitForAttributeChangedTask->ASC = AbilitySystemComponent;
WaitForAttributeChangedTask->AttributesToListenFor = Attributes;
if (!IsValid(AbilitySystemComponent) || Attributes.Num() < 1)
{
WaitForAttributeChangedTask->RemoveFromRoot();
return nullptr;
}
for (FGameplayAttribute Attribute : Attributes)
{
AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(Attribute).AddUObject(WaitForAttributeChangedTask, &UAsyncTaskAttributeChanged::AttributeChanged);
}
return WaitForAttributeChangedTask;
}
void UAsyncTaskAttributeChanged::EndTask()
{
if (IsValid(ASC))
{
ASC->GetGameplayAttributeValueChangeDelegate(AttributeToListenFor).RemoveAll(this);
for (FGameplayAttribute Attribute : AttributesToListenFor)
{
ASC->GetGameplayAttributeValueChangeDelegate(Attribute).RemoveAll(this);
}
}
SetReadyToDestroy();
MarkPendingKill();
}
void UAsyncTaskAttributeChanged::AttributeChanged(const FOnAttributeChangeData & Data)
{
OnAttributeChanged.Broadcast(Data.Attribute, Data.NewValue, Data.OldValue);
}