最简单的 UE 4 C++ 教程 —— 触发器框【二十】

谁践踏了优雅 2022-09-01 14:52 267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，在本教程中，当角色与一个触发器框（Trigger Box）发生重叠时将触发一个事件。

创建一个新的 C++ **TriggerBox** 子类【**它继承自 TriggerBase 类，而它又继承自 Actor 类**】并将其命名为 **MyTriggerBox** 。在头文件中添加 **OnOverlapBegin** 和 **OnOverlapEnd** 函数。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70][]

下面是最终的 .h 头文件【**原教程的头文件代码错了，已修复**】。

#pragma once
    
    #include "CoreMinimal.h"
    #include "Engine/TriggerBox.h"
    #include "MyTriggerBox.generated.h"
    
    /**
     *
     */
    UCLASS()
    class HELLOUNREAL_API AMyTriggerBox : 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
        AMyTriggerBox();
    
        // declare overlap begin function
        UFUNCTION()
        void OnOverlapBegin(AActor* OverlappedActor, AActor* OtherActor);
    
        // declare overlap end function
        UFUNCTION()
        void OnOverlapEnd(AActor* OverlappedActor, AActor* OtherActor);
    };

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 "MyTriggerBox.h"
    // include draw debu helpers header file
    #include "DrawDebugHelpers.h"

我们也可以 **\#define** 一些调试日志的快捷方式。

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

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

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

void AMyTriggerBox::BeginPlay()
    {
    	Super::BeginPlay();
    
        DrawDebugBox(GetWorld(), GetActorLocation(), GetComponentsBoundingBox().GetExtent(), FColor::Purple, true, -1, 0, 5);
    	
    }

接下来，我们将编写重叠函数，它将向屏幕打印一条消息，指示进入和退出**触发器框**的 actor 。

void AMyTriggerBox::OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        // check if Actors do not equal nullptr and that 
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor enters trigger box
            print("Overlap Begin");
            printFString("Overlapped Actor = %s", *OverlappedActor->GetName());
        }
    }
    
    void AMyTriggerBox::OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor leaves trigger box
            print("Overlap Ended");
            printFString("%s has left the Trigger Box", *OtherActor->GetName());
        }
    }

编译代码，将新 actor 拖放到游戏中，如下所示

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1][]

运行起来的框是这样的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 2][]

下面是最后的 .cpp 文件。

#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))
    
    #include "MyTriggerBox.h"
    // include draw debu helpers header file
    #include "DrawDebugHelpers.h"
    
    AMyTriggerBox::AMyTriggerBox()
    {
        //Register Events
        OnActorBeginOverlap.AddDynamic(this, &AMyTriggerBox::OnOverlapBegin);
        OnActorEndOverlap.AddDynamic(this, &AMyTriggerBox::OnOverlapEnd);
    }
    
    // Called when the game starts or when spawned
    void AMyTriggerBox::BeginPlay()
    {
    	Super::BeginPlay();
    
        DrawDebugBox(GetWorld(), GetActorLocation(), GetComponentsBoundingBox().GetExtent(), FColor::Purple, true, -1, 0, 5);
    	
    }
    
    void AMyTriggerBox::OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        // check if Actors do not equal nullptr and that 
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor enters trigger box
            print("Overlap Begin");
            printFString("Overlapped Actor = %s", *OverlappedActor->GetName());
        }
    }
    
    void AMyTriggerBox::OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor leaves trigger box
            print("Overlap Ended");
            printFString("%s has left the Trigger Box", *OtherActor->GetName());
        }
    }

最后，按下播放键，操控玩家在触发器框里**进进出出**，得到的最终效果图如下所示。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 3][]

[Link 1]: https://unrealcpp.com/trigger-box/
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1]: /images/20220829/0bb41b84acb54ee9a0e6957ccc7c00af.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 2]: /images/20220829/6ef2914d41fe40e2bc6314497d0b70b1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 3]: /images/20220829/f9650bf602f24660b72a6c9b8b64a593.png