尝试更改 TargetArmLength 时崩溃（虚幻引擎 C++）

Question

每当我尝试更改 SpringArmComponent->TargetArmLength 时，它都会崩溃， 即使我这样做：UE_LOG(LogTemp, Warning, TEXT("%f"), SpringArmComponent->TargetArmLength);

我做错了什么？

它在ZoomIn() 和ZoomOut() 函数中崩溃，但它在构造函数中有效。如果我只做SpringArmComponent->TargetArmLength 它不会崩溃，但如果我尝试记录它就会崩溃。

.h 文件片段：

class UCameraComponent;
class USpringArmComponent;

UCLASS()
class WELT_API ATPWBaseCharacter : public ACharacter
{
    GENERATED_BODY()

public:
    UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Camera", meta = (AllowPrivateAccess = "true"))
    UCameraComponent* CameraComponent;

    UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Camera", meta = (AllowPrivateAccess = "true"))
    USpringArmComponent* SpringArmComponent;

public:
    // Sets default values for this character's properties
    ATPWBaseCharacter(const FObjectInitializer& ObjInit);

protected:
    virtual void BeginPlay() override;

public: 
    virtual void Tick(float DeltaTime) override;

    virtual void SetupPlayerInputComponent(class UInputComponent* PlayerInputComponent) override;

    UFUNCTION(BlueprintCallable, Category = "Movement")
    bool IsRunning() const;

private:
    bool WantsToRun = false;
    bool IsMovingForward = false;

    void MoveForward(float Amount);
    void MoveRight(float Amount);

    void OnStartRunning();
    void OnStopRunning();

    void LookUp(float Amount);
    void TurnAround(float Amount);
    
    void ChangeCameraLen(bool bAmount);

public:
    UFUNCTION(BlueprintCallable, Category = "Movement")
    void ZoomIn();
    UFUNCTION(BlueprintCallable, Category = "Movement")
    void ZoomOut();
};

.cpp 文件片段：

ATPWBaseCharacter::ATPWBaseCharacter(const FObjectInitializer& ObjInit) : 
    Super(ObjInit.SetDefaultSubobjectClass<UTPWCharacterMovementComponent>(ACharacter::CharacterMovementComponentName))
{
    PrimaryActorTick.bCanEverTick = true;

    SpringArmComponent = CreateDefaultSubobject<USpringArmComponent>(TEXT("SpringArmComponent"));
    SpringArmComponent->SetupAttachment(GetRootComponent());
    // SpringArmComponent->SocketOffset.Set(0, 0, 80);
    SpringArmComponent->TargetArmLength = 400.0f;
    SpringArmComponent->bUsePawnControlRotation = true;

    CameraComponent = CreateDefaultSubobject<UCameraComponent>(TEXT("CameraComponent"));
    CameraComponent->SetupAttachment(SpringArmComponent, USpringArmComponent::SocketName);
    CameraComponent->bUsePawnControlRotation = false;

    bUseControllerRotationPitch = false;
    bUseControllerRotationYaw = false;
    bUseControllerRotationRoll = false;
}
void ATPWBaseCharacter::BeginPlay()
{
    Super::BeginPlay();
}
void ATPWBaseCharacter::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

    // AddActorLocalRotation(QuatRotation, false, 0, ETeleportType::None);
    FRotator NewRotationVector = FRotator(0.0f, GetVelocity().Rotation().Yaw, 0.0f);    // pitch, yaw, roll
    if (!NewRotationVector.IsZero())
    {
        FRotator NewRotation = FRotator(NewRotationVector);
        FQuat QuatRotation = FQuat(NewRotation);
        SetActorRotation(QuatRotation, ETeleportType::None);
    }
}
void ATPWBaseCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
    Super::SetupPlayerInputComponent(PlayerInputComponent);

    PlayerInputComponent->BindAxis("MoveForward", this, &ATPWBaseCharacter::MoveForward);
    PlayerInputComponent->BindAxis("MoveRight", this, &ATPWBaseCharacter::MoveRight);
    PlayerInputComponent->BindAxis("LookUp", this, &ATPWBaseCharacter::LookUp);
    PlayerInputComponent->BindAxis("TurnAround", this, &ATPWBaseCharacter::TurnAround);

    PlayerInputComponent->BindAction("WheelUp", IE_Pressed, this, &ATPWBaseCharacter::ZoomIn);
    PlayerInputComponent->BindAction("WheelDown", IE_Pressed, this, &ATPWBaseCharacter::ZoomOut);

    PlayerInputComponent->BindAction("Jump", IE_Pressed, this, &ATPWBaseCharacter::Jump);
    PlayerInputComponent->BindAction("Run", IE_Pressed, this, &ATPWBaseCharacter::OnStartRunning);
    PlayerInputComponent->BindAction("Run", IE_Released, this, &ATPWBaseCharacter::OnStopRunning);
}

void ATPWBaseCharacter::MoveForward(float Amount)
{
    IsMovingForward = Amount > 0.0f;
    // AddMovementInput(GetActorForwardVector(), Amount);
    if ((Controller != nullptr) && (Amount != 0.0f))
    {
        const FRotator Rotation = Controller->GetControlRotation();
        const FRotator YawRotation(0, Rotation.Yaw, 0);
        const FVector Direction = FRotationMatrix(YawRotation).GetUnitAxis(EAxis::X);
        AddMovementInput(Direction, Amount);
    }
}

void ATPWBaseCharacter::MoveRight(float Amount)
{
    // AddMovementInput(GetActorRightVector(), Amount);
    if ((Controller != nullptr) && (Amount != 0.0f))

        const FRotator Rotation = Controller->GetControlRotation();
        const FRotator YawRotation(0, Rotation.Yaw, 0);
        const FVector Direction = FRotationMatrix(YawRotation).GetUnitAxis(EAxis::Y);
        AddMovementInput(Direction, Amount);
    }
}

void ATPWBaseCharacter::LookUp(float Amount)
{
    AddControllerPitchInput(Amount);
}

void ATPWBaseCharacter::TurnAround(float Amount)
{
    AddControllerYawInput(Amount);
}

void ATPWBaseCharacter::OnStartRunning()
{
    WantsToRun = true;
}
void ATPWBaseCharacter::OnStopRunning()
{
    WantsToRun = false;
}

void ATPWBaseCharacter::ZoomIn()
{
    // SpringArmComponent->TargetArmLength;
    UE_LOG(LogTemp, Warning, TEXT("%f"), SpringArmComponent->TargetArmLength);
    SpringArmComponent->TargetArmLength = 200.0f;
    // UE_LOG(LogTemp, Warning, TEXT("%f"), SpringArmComponent->TargetArmLength);
    // SpringArmComponent->SocketOffset = FVector(0, 0, 80);
}

void ATPWBaseCharacter::ZoomOut()
{
    // SpringArmComponent->TargetArmLength;
    UE_LOG(LogTemp, Warning, TEXT("%f"), SpringArmComponent->TargetArmLength);
    
    SpringArmComponent->SocketOffset = FVector(0, 0, 80);
}

Answer 1

您是否有可能在派生自此类的蓝图 act​​or 中运行它？如果是这样，我注意到这可能会导致组件创建出现问题，并会导致引擎崩溃并为正在正确设置的组件返回 NULL。

我建议也许尝试创建一个新的派生类，看看是否可行。我知道这是一个奇怪的建议，但它对我有用。