Question

我正在尝试发出从相机位置开始到一定距离的光线。这是我制造的“枪”。当我尝试访问除构造器之外的其他任何地方的摄像头时，我得到的摄像头为空。

当我运行调试器时，摄像机在到达第一个“ BeginPlay”功能之前返回null。 CameraSpringArm仍然附着在对象上。

我尝试重新整理头文件中的函数和指针，但仍然卡住了。

cpp：

 #include "MyCharacter.h"

// Sets default values
AMyCharacter::AMyCharacter()
{
 ThirdPerson = 2;
 FirstPerson = 1;

 // Set this character to call Tick() every frame.  You can turn this off 
 to improve performance if you don't need it.
 PrimaryActorTick.bCanEverTick = true;
 // Create a first person camera component.
 CameraSpringArm = CreateDefaultSubobject<USpringArmComponent> 
 (TEXT("CameraSpringArm"));

 CharacterCamera = 
 CreateDefaultSubobject<UCameraComponent(TEXT("FirstPersonCamera"));

 // Attach the camera component to our capsule component.
 CameraSpringArm->SetupAttachment(RootComponent);
 CharacterCamera->SetupAttachment(CameraSpringArm);

 // Allow the pawn to control camera rotation.
 CharacterCamera->bUsePawnControlRotation = true;
 SwitchCamera(CharacterCamera, CameraSpringArm, ThirdPerson);

 bPressedCameraSwap = false;
 bFire = false;
}


 // Called to bind functionality to input
void AMyCharacter::SetupPlayerInputComponent(UInputComponent* 
 PlayerInputComponent)
 {
 Super::SetupPlayerInputComponent(PlayerInputComponent);

 PlayerInputComponent->BindAxis("MoveForward", this, 
 &AMyCharacter::MoveForward);

 PlayerInputComponent->BindAxis("MoveSide", this, &AMyCharacter::MoveSide);

 PlayerInputComponent->BindAxis("TurnUp", this, 
 &AMyCharacter::AddControllerYawInput);

 PlayerInputComponent->BindAxis("TurnSide", this, 
 &AMyCharacter::AddControllerPitchInput);

 PlayerInputComponent->BindAction("CameraSwap", IE_Pressed, this, 
 &AMyCharacter::CameraSwap);

 PlayerInputComponent->BindAction("CameraSwap", IE_Released, this, 
 &AMyCharacter::CameraSwapStop);

 PlayerInputComponent->BindAction("Fire", IE_Pressed, this, 
 &AMyCharacter::Fire);
 }

void AMyCharacter::Fire()
 {
 bFire = true;
 float Distance = 1000.0f;
 FHitResult HitResult;
 FVector StartTrace = CharacterCamera->GetComponentLocation(); //Its 
 breaking here
 FVector ForwardVector = CharacterCamera->GetForwardVector();
 FVector EndTrace = ((ForwardVector * Distance) + StartTrace);
 FCollisionQueryParams TraceParams;

 GetWorld()->LineTraceSingleByChannel(HitResult, StartTrace, EndTrace, 
 ECC_Visibility, TraceParams);
 DrawDebugLine(GetWorld(), StartTrace, EndTrace,FColor(255,0,0), true);

 }

标题

#pragma once

#include "CoreMinimal.h"
#include "EngineGlobals.h"
#include "Engine/Engine.h"
#include "Components/InputComponent.h"
#include "GameFramework/CharacterMovementComponent.h"
#include "Camera/CameraComponent.h"
#include "GameFramework/Controller.h"
#include "GameFramework/Character.h"
#include "GameFramework/SpringArmComponent.h"
#include "DrawDebugHelpers.h"
#include "MyCharacter.generated.h"


UCLASS()
class LEARNING_API AMyCharacter : public ACharacter
{
GENERATED_BODY()

public:
// Sets default values for this character's properties
AMyCharacter();

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


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

// Called to bind functionality to input
void SetupPlayerInputComponent(class UInputComponent* 
PlayerInputComponent) override;

UPROPERTY(VisibleAnywhere)
    UCameraComponent* CharacterCamera;
UPROPERTY(VisibleAnywhere)
    USpringArmComponent* CameraSpringArm;
UPROPERTY()
    bool bPressedCameraSwap;
UPROPERTY()
    bool bFirstPersonEnabled{};
UPROPERTY()
    bool bThirdPersonEnabled{};
UPROPERTY()
    bool bFire;
protected:
UFUNCTION()
    void MoveForward(float Val);
//handles strafing
UFUNCTION()
    void MoveSide(float Val);
//Handles swaping camera on press
UFUNCTION()
    void CameraSwap();
//Clears swaping camera Flag
UFUNCTION()
    void CameraSwapStop();

UFUNCTION()
    void Fire();
UFUNCTION()
    void FireStop();

Answer 1

您的CharacterCamera是一个指针，而不是实际的对象。因此，在构造函数内部，您将AMyCharacter.CharacterCamera设置为临时对象的地址，并且当构造函数的作用域结束时，该临时对象将被解构且指针变为无效。

有几种解决方法，一种是将CharacterCamera更改为实际的UCameraComponent，而不仅仅是一个指针。

另一种解决方案是在函数外部实例化UCameraComponent，以免在构造函数的末尾对其进行解构。

Answer 2

答案是虚幻引擎中存在一个非常讨厌的错误。我必须更改CharacterCamera变量的名称。我认为这是因为我在“ CreateDefaultSubobject”函数中编辑了字符串。

除了构造函数以外的其他地方访问相机时，我的相机指针返回null

2 个答案: