最简单的 UE 4 C++ 教程 —— 触发器框【二十】

原教程是基于 UE 4.18，我是基于 UE 4.25】

英文原地址

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。

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。

#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

 运行起来的框是这样的

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。 

最后

以上就是风中招牌为你收集整理的最简单的 UE 4 C++ 教程 —— 触发器框【二十】的全部内容，希望文章能够帮你解决最简单的 UE 4 C++ 教程 —— 触发器框【二十】所遇到的程序开发问题。

如果觉得靠谱客网站的内容还不错，欢迎将靠谱客网站推荐给程序员好友。