最简单的 UE 4 C++ 教程 —— 触发器体【二十二】

约定不等于承诺〃 2022-09-01 15:55 199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 actor 与 TriggerVolume 重叠时将触发一个事件。本教程使用了TriggerBox，但过程应该是相似的。

创建一个新的 C++ **TriggerVolume** 子类并将其命名为 **MyTriggerVolume** 。在头文件中添加**OnOverlapBegin** 和 **OnOverlapEnd** 函数。

下面是最终的头文件。

### MyTriggerVolume.h ###

#pragma once
    
    #include "CoreMinimal.h"
    #include "Engine/TriggerVolume.h"
    #include "MyTriggerVolume.generated.h"
    
    /**
     * 
     */
    UCLASS()
    class UNREALCPP_API AMyTriggerVolume : public ATriggerVolume
    {
    	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
    	AMyTriggerVolume();
    
    	// overlap begin function
    	UFUNCTION()
    	void OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor);
    
    	// overlap end function
    	UFUNCTION()
    	void OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor);
    	
    };

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

#include "MyTriggerVolume.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。

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

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

void AMyTriggerVolume::BeginPlay()
    {
    	Super::BeginPlay();
    
    	DrawDebugBox(GetWorld(), GetActorLocation(), GetActorScale()*100, FColor::Cyan, 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 TriggerVolume 的 actor 。

void AMyTriggerVolume::OnOverlapBegin(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor enters trigger volume
            print("Overlap Begin");
            printFString("Other Actor = %s", *OtherActor->GetName());
        }
    }
    
    void AMyTriggerVolume::OnOverlapEnd(class AActor* OverlappedActor, class AActor* OtherActor)
    {
        if (OtherActor && (OtherActor != this)) {
            // print to screen using above defined method when actor leaves trigger volume
            print("Overlap Ended");
            printFString("%s has left the Trigger Volume", *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][]

按下播放按钮，并进进出出触发器体。

下面是最后运行的效果图

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 2][]

[Link 1]: https://unrealcpp.com/trigger-volume/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70]: /images/20220829/aedeef3d36a0447dac6cbebcd831744c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 1]: /images/20220829/85c13c69247941089062b6a06f0cd6fa.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70 2]: /images/20220829/b9be9fee175c45859276a5479b1d7ee6.png