UE4基础：Gameplay框架（三）Actor 类（5月27日 更新）

本文是老王学习UE4的笔记，如有错误敬请指正

概述

AActor继承于UObject是所有可以放置到场景中的对象的基类。Gameplay框架的核心基类之一。

UCLASS声明

AActor的UCLASS已经声明了BlueprintType, Blueprintable这两个属性都可以传递给子类。

UCLASS(BlueprintType, Blueprintable, config=Engine, meta=(ShortTooltip="An Actor is an object that can be placed or spawned in the world."))
class ENGINE_API AActor : public UObject
{
	GENERATED_BODY()
	...
}

生命周期

protected:
	virtual void BeginPlay() override;
	virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
public:	
	virtual void Tick(float DeltaTime) override;

Tick相当于Unity中的Update，UE4中的Tick可以通过PrimaryActorTick.bCanEverTick来开关。

virtual void Tick( float DeltaSeconds );
FORCEINLINE bool CanEverTick() const { return PrimaryActorTick.bCanEverTick; }
UPROPERTY(EditDefaultsOnly, Category=Tick)
	struct FActorTickFunction PrimaryActorTick;

获取ULevel和UGameInstance

UWorld在UObject中就可以获取

• 获取所属ULevel

ULevel* GetLevel() const;

• 获取UGameInstance

class UGameInstance* GetGameInstance() const;

Actor的名字

//定义在基类UObjectBaseUtility中
public：
FORCEINLINE FString GetName() const
	{
		return GetFName().ToString();
	}

和组件相关的一些内容

AActor有3个管理组件的容器

• OwnedComponents：集合
• InstanceComponents：数组
• BlueprintCreatedComponents数组

另外还有一个重要的RootComponent组件

• 它是所有其它组件的根组件
• 它一定是USceneComponent类型即带有变换的组件

private:
	TSet<UActorComponent*> OwnedComponents;
	UPROPERTY(Instanced)
	TArray<UActorComponent*> InstanceComponents;
public:
	UPROPERTY(TextExportTransient, NonTransactional)
	TArray<UActorComponent*> BlueprintCreatedComponents;
protected:
	UPROPERTY(BlueprintGetter=K2_GetRootComponent, Category="Utilities|Transformation")
	USceneComponent* RootComponent;
public:
	FORCEINLINE USceneComponent* GetRootComponent() const { return RootComponent; }

和场景中的AActor树相关的一些内容

private:
	UPROPERTY(ReplicatedUsing=OnRep_Owner)
	AActor* Owner;
public:
	UPROPERTY(Transient)
	TArray<AActor*> Children;

	UFUNCTION(BlueprintCallable, Category=Actor)
	AActor* GetOwner() const;

	UFUNCTION(BlueprintCallable, Category=Actor)
	virtual void SetOwner( AActor* NewOwner );
	

和蓝图中的AActor树相关的一些内容

	UFUNCTION(BlueprintCallable, Category="Actor")
	AActor* GetParentActor() const;

	UFUNCTION(BlueprintCallable, Category="Actor")
	UChildActorComponent* GetParentComponent() const;

一些奇葩的地方

• AActor应该是抽象层次很高的类，里面竟然有关于伤害的定义
• 竟然还引用了子类APawn和ACharacter
• UInputComponent也应该是在APawn层级才有交集

/**
	 * Whether this actor can take damage. Must be true for damage events (e.g. ReceiveDamage()) to be called.
	 * @see https://www.unrealengine.com/blog/damage-in-ue4
	 * @see TakeDamage(), ReceiveDamage()
	 */
	UPROPERTY(EditAnywhere, BlueprintReadWrite, SaveGame, Replicated, Category=Actor, meta=(AllowPrivateAccess="true"))
	uint8 bCanBeDamaged:1;
private:
	/** Pawn responsible for damage and other gameplay events caused by this actor. */
	UPROPERTY(BlueprintReadWrite, ReplicatedUsing=OnRep_Instigator, meta=(ExposeOnSpawn=true, AllowPrivateAccess=true), Category=Actor)
	class APawn* Instigator;
	UPROPERTY(DuplicateTransient)
	class UInputComponent* InputComponent;
	/**
	 * Return true if the given Pawn can be "based" on this actor (ie walk on it).
	 * @param Pawn - The pawn that wants to be based on this actor
	 */
	virtual bool CanBeBaseForCharacter(class APawn* Pawn) const;

	/**
	 * Apply damage to this actor.
	 * @see https://www.unrealengine.com/blog/damage-in-ue4
	 * @param DamageAmount		How much damage to apply
	 * @param DamageEvent		Data package that fully describes the damage received.
	 * @param EventInstigator	The Controller responsible for the damage.
	 * @param DamageCauser		The Actor that directly caused the damage (e.g. the projectile that exploded, the rock that landed on you)
	 * @return					The amount of damage actually applied.
	 */
	virtual float TakeDamage(float DamageAmount, struct FDamageEvent const& DamageEvent, class AController* EventInstigator, AActor* DamageCauser);

protected:
	virtual float InternalTakeRadialDamage(float Damage, struct FRadialDamageEvent const& RadialDamageEvent, class AController* EventInstigator, AActor* DamageCauser);
	virtual float InternalTakePointDamage(float Damage, struct FPointDamageEvent const& PointDamageEvent, class AController* EventInstigator, AActor* DamageCauser);