最简单的 UE 4 C++ 教程 —— 指定 Actor 的触发器框【二十一】

待我称王封你为后i 2022-09-01 15:54 308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，本教程将通过**特定**的 actor 触发重叠事件。

创建一个新的 C++ TriggerBox 类，并将其命名为 **TriggerBoxSpecificActor**。在头文件中，我们将为特定的 actor 声明两个 void 重叠函数和 **AActor** 类。

下面是最终的头代码。

### TriggerBoxSpecificActor.h ###

#pragma once
    
    #include "CoreMinimal.h"
    #include "Engine/TriggerBox.h"
    #include "TriggerBoxSpecificActor.generated.h"
    
    
    UCLASS()
    class UNREALCPP_API ATriggerBoxSpecificActor : public ATriggerBox
    {
    	GENERATED_BODY()
    
    protected:
    
    	// Called when the game starts or when spawned
    	virtual void BeginPlay() override;
    	
    public:
    
    	// constructor sets default values for this actor's properties
    	ATriggerBoxSpecificActor();
    
    	// overlap begin function
    	UFUNCTION()
    	void OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor);
    
    	// overlap end function
    	UFUNCTION()
    	void OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor);
    
    	// specific actor for overlap
    	UPROPERTY(EditAnywhere)
    	class AActor* SpecificActor;
    	
    };

在 .cpp 文件中，为了帮助我们可视化触发器框，我们必须 **\#include DrawDebugHelpers.h** 文件。

#include "TriggerBoxSpecificActor.h"
    // include draw debug helpers header file
    #include "DrawDebugHelpers.h"

我们也可以 **\#define** 一些调试日志的快捷方式。

#define print(text) if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 1.5, FColor::Green,text)
    #define printFString(text, fstring) if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Green, FString::Printf(TEXT(text), fstring))

在 actor 的构造函数中，我们将向 **OnActorBeginOverlap.AddDynamic** 和 **OnActorEndOverlap.AddDynamic** 注册重叠事件。

ATriggerBoxSpecificActor::ATriggerBoxSpecificActor()
    {
        //Register Events
        OnActorBeginOverlap.AddDynamic(this, &ATriggerBoxSpecificActor::OnOverlapBegin);
        OnActorEndOverlap.AddDynamic(this, &ATriggerBoxSpecificActor::OnOverlapEnd);
    }

在 **BeginPlay** 上，我们将使用 **DrawDebugBox** 绘制调试框。

// Called when the game starts or when spawned
    void ATriggerBoxSpecificActor::BeginPlay()
    {
    	Super::BeginPlay();
    
        DrawDebugBox(GetWorld(), GetActorLocation(), GetComponentsBoundingBox().GetExtent(), FColor::Green, true, -1, 0, 5);
    	
    }

接下来，我们将编写重叠函数，当特定的 actor 进入和退出 TriggerBox 时，它将向屏幕打印一条消息。在重叠函数中，我们通过 **OtherActor == SpecificActor** 来检查 TriggerBox 中的 actor 是否是我们的特定 actor。

void ATriggerBoxSpecificActor::OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        //if the overlapping actor is the specific actor we identified in the editor
        if (OtherActor && (OtherActor != this) && OtherActor == SpecificActor )
        {
            print("Overlap Begin");
            printFString("Overlapping Actor = %s", *OtherActor->GetName());
        }
    }
    
    void ATriggerBoxSpecificActor::OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        //if the overlapping actor is the specific actor we identified in the editor
        if (OtherActor && (OtherActor != this) && OtherActor == SpecificActor )
        {
            print("Overlap End");
            printFString("%s has left the Trigger Box", *OtherActor->GetName());
        }
    }

编译代码。将新 actor 拖放到游戏中。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70][]

运行起来是这样的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1][]

在 actor 的详细信息面板中添加一个 actor，即特定 actor。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 2][]

点击播放按钮，将特定的 actor **进进出出** TriggerBox 中以触发重叠事件。

下面是**进进出出**的效果图

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 3][]

[Link 1]: https://unrealcpp.com/trigger-box-specific-actor/
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1]: /images/20220829/89df45e9cfcb46b396a8724cbce56f0c.png
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