(UE4 4.20)UE4的Actor添加,删除ActorComponent

Actor添加ActorComponent

总结Actor添加组件(ActorComponent)的常用三种方式：

[1] 在蓝图编辑器中直接添加

[2] 在Actor构造函数中创建添加

[3] 在游戏运行时(GameRunTime)进行添加

[1][2]方式相当于在编辑器层面预先添加组件，[3]是游戏运行时的层面上添加组件

编辑器直接添加

 

不过C++创建的ActorComponent变成可编辑器可直接添加的组件得在 UCLASS 宏这样设置

"UCLASS(meta=(BlueprintSpawnableComponent) )"

UCLASS(meta=(BlueprintSpawnableComponent) )
class MYPROJECT3_API UTestActorComponent : public UActorComponent
{
}

在Actor构造函数中创建添加

UCLASS()
class MYPROJECT3_API ATestActor : public AActor
{
	GENERATED_BODY()
	
public:	
	// Sets default values for this actor's properties
	ATestActor();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;

	UPROPERTY(VisibleAnywhere)
		class UStaticMeshComponent* staticMeshComponent;
};

ATestActor::ATestActor()
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;
	staticMeshComponent = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("StaitcMeshComponent"));
	RootComponent = staticMeshComponent;
}

上面比较注意的是，UPROPERTY里得用“VisibleAnywhere”，不要用EditAnywhere或者EditDefaultsOnly等等其他的。

如果创建的这个组件是USceneComponent并且又不作为RootComponent，得调用AttachToComponent绑定到某个sceneComponent之下，不过在构造函数中SetupAttachment 就能起到类似作用，可以看看SetupAttachment 函数的 源码注释

if (ensureMsgf(!bRegistered, TEXT("SetupAttachment should only be used to initialize AttachParent and AttachSocketName for a future AttachToComponent. Once a component is registered you must use AttachToComponent.")))
	{
		if (ensureMsgf(InParent != this, TEXT("Cannot attach a component to itself.")))

 

在游戏运行时(GameRunTime)进行添加

const FName actorComponentName = FName("TestActorComponent");
UTestActorComponent* actorComponent = NewObject<UTestActorComponent>(character, actorComponentName);
actorComponent->RegisterComponent();

这个 NewObject函数的第一参数为目标“Actor”,至于网上不少资料说还要用AddOwnedComponent，其实是不必要的。

character->AddOwnedComponent(actorComponent);

如果创建的这个组件是USceneComponent并且又不作为RootComponent，得调用AttachToComponent绑定到某个sceneComponent之下,

这里顺便说一下，很多时候项目开发中，由于我们某些组件是游戏运行时添加的，并且经常性添加的那个组件有大量的参数，我们不可能在添加的时候再设置参数，往往"动态添加组件的开发模式"是遵循下面几步：

(1)组件变成蓝图类，并设置好参数

(2)用LoadClass加载组件蓝图类为UClass*

(3)在NewObject传入UClass*

下面演示个例子：

 

[1]UCLASS(Blueprintable）代表了一个UObject可以变为蓝图类

UCLASS(Blueprintable, ClassGroup=(Custom), meta=(BlueprintSpawnableComponent) )
class MYPROJECT3_API UTestActorComponent : public UActorComponent
{
	GENERATED_BODY()

public:	
	// Sets default values for this component's properties
	UTestActorComponent();

protected:
	// Called when the game starts
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction) override;

		
	UPROPERTY(EditAnywhere)
		float a;

	UPROPERTY(EditAnywhere)
		float b;

	UPROPERTY(EditAnywhere)
		float c;
	
};

[2]蓝图化

 

[3]代码动态添加蓝图化的组件

 

void ATestActor::BeginPlay()
{
	Super::BeginPlay();

	APlayerController* 	playerController = GetWorld()->GetFirstPlayerController();
	if (nullptr == playerController)
		return;
	AActor* character = playerController->GetPawn();
	if (nullptr == character)
		return;
	const FString testComponentBPFilePath = "/Game/Geometry/TestActorComponent.TestActorComponent_C";
	UClass* testComponentClass = LoadClass<UTestActorComponent>(character, *testComponentBPFilePath);
	if (nullptr == testComponentClass)
		return;
	const FName actorComponentName = FName("TestActorComponent");
	UTestActorComponent* actorComponent = NewObject<UTestActorComponent>(character, testComponentClass);
	if (nullptr == actorComponent)
		return;
	actorComponent->RegisterComponent();
}

运行截图：

Actor移除ActorComponent

主要是先调用UnregisterComponent， 然后再DestroyComponent

if (MyActorComponent)
{
	MyActorComponent->UnregisterComponent();
	MyActorComponent->DestroyComponent();
}