在UE中实现一个交互组件

¶先创建一个交互接口(UInterface)

// This class does not need to be modified.
UINTERFACE()
class USGameplayInterface : public UInterface
{
    GENERATED_BODY()
};

/**
 * 
 */
class ACTIONROGUELIKE_API ISGameplayInterface
{
    GENERATED_BODY()

    // Add interface functions to this class. This is the class that will be inherited to implement this interface.
public:
    UFUNCTION(BlueprintCallable, BlueprintNativeEvent)
    void Interact(APawn* InstigatorPawn);
};

¶在创建一个交互组件

// .h
class ACTIONROGUELIKE_API USInteractionComponent : public UActorComponent

¶事件交互检测

当开始交互时，检测到可交互的物品（这里的检测规则需要设置Actor碰撞为WorldDynamic）。再查看可交互物品是否实现对应的交互接口。(用if (HitActor->Implements<USGameplayInterface>())查看)，实现对用接口后通过ISGameplayInterface::Execute_Interact(HitActor, MyPawn);调用对应的实现。

// .h
class ACTIONROGUELIKE_API USInteractionComponent : public UActorComponent
{
    GENERATED_BODY()

			...

public:
    void PrimaryInteract();
};

// .cpp
void USInteractionComponent::PrimaryInteract()
{
    FCollisionObjectQueryParams ObjectQueryParams;
    ObjectQueryParams.AddObjectTypesToQuery(ECC_WorldDynamic);

    AActor* MyOwner = GetOwner();

    FVector EyeLocation;
    FRotator EyeRotation;
    MyOwner->GetActorEyesViewPoint(EyeLocation, EyeRotation);
    FVector End = EyeLocation + (EyeRotation.Vector() * 1000);

#if 0 // 眼睛看到的位置，适用于大物体，小物体此方式检测不太适用
    FHitResult HitResult;
    GetWorld()->LineTraceSingleByObjectType(HitResult, EyeLocation, End, ObjectQueryParams);

    AActor* HitActor = HitResult.GetActor();
    if (HitActor)
    {
        if (HitActor->Implements<USGameplayInterface>())
        {
            APawn* MyPawn = Cast<APawn>(MyOwner);
            ISGameplayInterface::Execute_Interact(HitActor, MyPawn);
        }
    }
    DrawDebugLine(GetWorld(), EyeLocation, End, FColor::Red, false, 2.0f, 0, 2.0f);
#elif 1 // 眼睛前方范围内碰撞检测
    TArray<FHitResult> HitResults;
    float Radius = 30.f;
    FCollisionShape CollisionShape;
    CollisionShape.SetSphere(Radius);
    bool bBlockingHit = GetWorld()->SweepMultiByObjectType(HitResults, EyeLocation, End, FQuat::Identity,
                                                           ObjectQueryParams, CollisionShape);
    FColor LineColor = bBlockingHit ? FColor::Green : FColor::Red;

    for (FHitResult Hit : HitResults)
    {
        AActor* HitActor = Hit.GetActor();
        if (HitActor)
        {
            if (HitActor->Implements<USGameplayInterface>())
            {
                APawn* MyPawn = Cast<APawn>(MyOwner);

                ISGameplayInterface::Execute_Interact(HitActor, MyPawn);
                DrawDebugSphere(GetWorld(), Hit.ImpactPoint, Radius, 32, LineColor, false, 2.0f);
                break;
            }
        }
        DrawDebugSphere(GetWorld(), Hit.ImpactPoint, Radius, 32, LineColor, false, 2.0f);
    }

    DrawDebugLine(GetWorld(), EyeLocation, End, LineColor, false, 2.0f, 0, 2.0f);
#else // 角色范围内进行碰撞检测，不做眼睛前视检测
    TArray<FOverlapResult> Overlaps;
    FCollisionQueryParams Params;
    Params.AddIgnoredActor(MyOwner);
    bool bBlockingHit = GetWorld()->OverlapMultiByObjectType(Overlaps, MyOwner->GetActorLocation(), FQuat::Identity,
                                                             ObjectQueryParams, FCollisionShape::MakeSphere(200.f),
                                                             Params);
    FColor LineColor = bBlockingHit ? FColor::Green : FColor::Red;
    for (FOverlapResult& Overlap : Overlaps)
    {
        AActor* HitActor = Overlap.GetActor();
        if (HitActor)
        {
            if (HitActor->Implements<USGameplayInterface>())
            {
                APawn* MyPawn = Cast<APawn>(MyOwner);

                ISGameplayInterface::Execute_Interact(HitActor, MyPawn);
                DrawDebugSphere(GetWorld(), HitActor->GetActorLocation(), 30.f, 32, LineColor, false, 2.0f);
                break;
            }
        }
        DrawDebugSphere(GetWorld(), HitActor->GetActorLocation(), 30.f, 32, LineColor, false, 2.0f);
    }
    DrawDebugLine(GetWorld(), EyeLocation, End, LineColor, false, 2.0f, 0, 2.0f);
#endif
}

¶什么时候触发交互呢？

这个以玩家按下F时进行交互,给玩家添加交互组件后，玩家就拥有交互的能力。

class ACTIONROGUELIKE_API ASCharacter : public ACharacter
{
  ...
    UPROPERTY(VisibleAnywhere)
    USInteractionComponent* InteractionComp;
  ...
}

void ASCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
    Super::SetupPlayerInputComponent(PlayerInputComponent);


    // Action
    UPlayerInput::AddEngineDefinedActionMapping(FInputActionKeyMapping("PrimaryInteract", EKeys::F));
    PlayerInputComponent->BindAction("PrimaryInteract", IE_Pressed, this, &ASCharacter::PrimaryInteract);
 }

void ASCharacter::PrimaryInteract()
{
    if (InteractionComp)
    {
        InteractionComp->PrimaryInteract();
    }
}

¶玩家可以交互了，还差可以交互的Actor

¶C++中的交互

直接继承接口类，实现重载接口实现逻辑。

class ACTIONROGUELIKE_API ASItemChest : public AActor, public ISGameplayInterface
{
  ...
  virtual void Interact_Implementation(APawn* InstigatorPawn) override;
  ...
}