最简单的 UE 4 C++ 教程 —— 触发区域内的键盘响应开关灯【二十五】

男娘i 2022-09-02 00:44 142阅读 0赞

**原教程是基于 UE 4.18，我是基于 UE 4.25】**

[英文原地址][Link 1]

接上一节教程，创建一个新的 C++ Actor 子类并将其命名为 **LightSwitchPushButton** 。我们将在头文件中定义四个东西 —— 我们将定义一个 **UPointLightComponent**、**USphereComponent**、**float** 变量和 **void** 函数。

下面是最终的头代码。

### LightSwitchPushButton.h ###

#pragma once
    
    #include "CoreMinimal.h"
    #include "GameFramework/Actor.h"
    #include "LightSwitchPushButton.generated.h"
    
    UCLASS()
    class UNREALCPP_API ALightSwitchPushButton : public AActor
    {
    	GENERATED_BODY()
    	
    public:	
    	// Sets default values for this actor's properties
    	ALightSwitchPushButton();
    
    protected:
    	// Called when the game starts or when spawned
    	virtual void BeginPlay() override;
    
    public:	
    	// Called every frame
    	// virtual void Tick(float DeltaTime) override;
    
    	// declare point light comp
    	UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    	class UPointLightComponent* PointLight;
    
    	// declare sphere comp
    	UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    	class USphereComponent* LightSphere;
    
    	// declare light intensity variable
    	UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    	float LightIntensity;
    
    	// declare ToggleLight function
    	UFUNCTION(BlueprintCallable, Category = "Light Switch")
    	void ToggleLight();
    	
    };

接下来，在我们的 .cpp 文件中，让我们首先 \#include 我们将在代码中使用的必要脚本。包括**Components / PointLightComponent.h** 和 **Components/ spherecomcomponent .h** 两个文件。

#include "LightSwitchPushButton.h"
    // include these header files
    #include "Components/PointLightComponent.h"
    #include "Components/SphereComponent.h"

我们将在构造函数中设置 actor 的所有默认属性。首先让我们设置我们的 float 变量 **LightIntensity** 为 3000.0f，它将使光相对于其他对象看起来足够明亮。接下来，我们将创建我们的**UPointLightComponent** 并将它设置为我们的 **RootComponent** 。之后，我们将创建**USphereComponent**，当我们的玩家在半径内时，它将作为碰撞球体。然后，我们将创建简单的**ToggleLight()** 函数来切换灯光的可见性状态。稍后我们将从玩家代码中调用该函数。下面是**LightSwitchPushButton** 角色的最后一个 .cpp 文件。

### LightSwitchPushButton.cpp ###

#include "LightSwitchPushButton.h"
    #include "Components/PointLightComponent.h"
    #include "Components/SphereComponent.h"
    
    // Sets default values
    ALightSwitchPushButton::ALightSwitchPushButton()
    {
     	// 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;
    
    	LightIntensity = 3000.0f;
    
    	PointLight = CreateDefaultSubobject<UPointLightComponent>(TEXT("Point Light"));
    	PointLight->Intensity = LightIntensity;
    	//PointLight->bVisible = true; ///< 过时了
        //PointLight->SetVisibleFlag(true);
        PointLight->SetVisibility(true);
    	RootComponent = PointLight;
    
    	LightSphere = CreateDefaultSubobject<USphereComponent>(TEXT("Light Sphere Component"));
    	LightSphere->InitSphereRadius(300.0f);
    	LightSphere->SetCollisionProfileName(TEXT("Trigger"));
    	LightSphere->SetCollisionResponseToChannel(ECC_Pawn, ECR_Ignore);
    	LightSphere->SetupAttachment(RootComponent);
    }
    
    // Called when the game starts or when spawned
    void ALightSwitchPushButton::BeginPlay()
    {
    	Super::BeginPlay();
    }
    
    void ALightSwitchPushButton::ToggleLight()
    {
        PointLight->ToggleVisibility();
    }

接下来，和上一节类似，让我们向项目添加一个 **Action** 输入。在本例中，我们将把 **Action** 输入绑定到键盘的 **F**键。转到 **编辑>项目设置 ( Edit > Project Settings**)。然后选择 Input 选项。单击 **Action Mappings** 旁边的加号。调用新的输入 **Action** 并从下拉菜单中选择 **F** 。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1][]

【**以下我们把目光转到 xxxCharacter.h / .cpp 上**】

在 xxxCharacter.h文件中，在 **OnFire** 方法下添加 **OnAction** 方法。

protected:
    	
    	/** Fires a projectile. */
    	void OnFire();
    
    	// on action 
    	void OnAction();

此外，我们还必须包含 **LightSwitchPushButton** 头文件，这样我们的角色才能访问它的功能。

#include "CoreMinimal.h"
    #include "GameFramework/Character.h"
    // include our new LightSwitchPushButton header file
    #include "LightSwitchPushButton/LightSwitchPushButton.h"
    #include "UnrealCPPCharacter.generated.h"

然后为玩家当前重叠的灯开关声明一个变量 **CurrentLightSwitch** 。此外，我们还需要声明重叠事件，来使得当玩家处于光的球体组件的半径内时，触发我们想要运行的函数。

// declare overlap begin function
    UFUNCTION()
    void OnOverlapBegin(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult);
    
    // declare overlap end function
    UFUNCTION()
    void OnOverlapEnd(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex);
    // declare current light switch
    class ALightSwitchPushButton* CurrentLightSwitch;

同时还声明了 **`UCapsuleComponent`**来处理我们的触发事件

UPROPERTY(VisibleAnywhere, Category = "Trigger Capsule")
    class UCapsuleComponent* TriggerCapsule;

在构造函数中添加触发器胶囊并将其绑定到重叠事件。接着设置变量 **CurrentLightSwitch** 为**NULL**。

AUnrealCPPCharacter::AUnrealCPPCharacter()
    {
        ...
        // create trigger capsule
        TriggerCapsule = CreateDefaultSubobject<UCapsuleComponent>(TEXT("Trigger Capsule"));
        TriggerCapsule->InitCapsuleSize(55.f, 96.0f);;
        TriggerCapsule->SetCollisionProfileName(TEXT("Trigger"));
        TriggerCapsule->SetupAttachment(RootComponent);
    
        // bind trigger events
        TriggerCapsule->OnComponentBeginOverlap.AddDynamic(this, &AUnrealCPPCharacter::OnOverlapBegin); 
        TriggerCapsule->OnComponentEndOverlap.AddDynamic(this, &AUnrealCPPCharacter::OnOverlapEnd); 
    
         // set current light switch to null
         CurrentLightSwitch = NULL;
    }

进一步，将 **Action** 输入绑定连接到玩家

void AUnrealCPPCharacter::SetupPlayerInputComponent(class UInputComponent* PlayerInputComponent)
    {
        ...
        // Bind action event
        PlayerInputComponent->BindAction("Action", IE_Pressed, this, &AUnrealCPPCharacter::OnAction);
    
    }

将 **OnAction()** 函数添加到玩家脚本中。该函数将检查 **CurrentLightSwitch** 是否为 **NULL** 。如果**CurrentLightSwitch** 不为 **NULL**，那么当玩家按下动作键 F 时，将切换灯光的可见性（开关灯）。然后，添加重叠函数来设置和取消 **CurrentLightSwitch**

void AUnrealCPPCharacter::OnAction() 
    {
    	if(CurrentLightSwitch) 
    	{
    		CurrentLightSwitch->ToggleLight();
    	}
    }
    
    // overlap on begin function
    void AUnrealCPPCharacter::OnOverlapBegin(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
    {
    	if (OtherActor && (OtherActor != this) && OtherComp && OtherActor->GetClass()->IsChildOf(ALightSwitchPushButton::StaticClass())) 
    	{
    		CurrentLightSwitch = Cast<ALightSwitchPushButton>(OtherActor);
    	}
    } 
    
    // overlap on end function
    void AUnrealCPPCharacter::OnOverlapEnd(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
    {
    	if (OtherActor && (OtherActor != this) && OtherComp) 
    	{
    		CurrentLightSwitch = NULL;
    	}
    }

编译代码。拖放 actor （**LightSwitchPushButton**）到场景中，当玩家进入球形触发区域，点击 **F** 键开关灯。

最后的效果图如下

![20210729105023405.gif][]

[Link 1]: https://unrealcpp.com/light-switch-push-button/
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1]: /images/20220829/c21a64dc97894f909faa25988494e9af.png
[20210729105023405.gif]: /images/20220829/43618febaa73422ca8de1a34ae825721.png