概述

简单的说，接口提供一组公共的方法，不同的对象中继承这些方法后可以有不同的具体实现。
任何使用接口的类都必须实现这些接口。
实现解耦
解决多继承的问题

蓝图使用

使用方法

三种调用方法的区别

调用流关卡蓝图的接口函数

C++ 使用接口

本例使用一个Box Trigger 出发overlap 调用 Drone实例的接口

添加接口类

定义接口

声明蓝图可调用接口函数

用UFUNCTION 宏 BlueprintCallable 声明蓝图可调用，还必须使用 BlueprintImplementableEvent 或 BlueprintNativeEvent 说明，而且函数不能为虚函数
如果不想蓝图重载，只是想使用 BlueprintCallable 以支持蓝图起到单纯的调用作用，可以通过将接口标记为 UINTERFACE(meta = (CannotImplementInterfaceInBlueprint)) 来解决
通过声明 virtual 虚函数，使得派生类可重载

代码

ReactToTriggerInterface.h

#pragma once

#include "CoreMinimal.h"

#include "UObject/Interface.h"

#include "ReactToTriggerInterface.generated.h"

// 无需更改

// UINTERFACE类不是实际的接口；它是一个空白类，它的存在只是为了向虚幻引擎反射系统确保可见性。

UINTERFACE(MinimalAPI)

class UReactToTriggerInterface : public UInterface

{

	GENERATED_BODY()

};

//开头字母"U"必须改为"I"。

class TIPS_API IReactToTriggerInterface

{

	GENERATED_BODY()

public:

	// 纯虚函数，实现类必须实现接口

	virtual void ReactToTrigger_PureVirtual() = 0;

	// 虚函数，在接口本身的 .h 或 .cpp 文件中提供默认实现.实现类可覆盖

	virtual void ReactToTrigger_Virtual();

	//实现类可以在蓝图和C++中实现接口

	UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category="Trigger Reaction")

		void ReactToTrigger_NativeEvent1(int32 number);

	//实现类可以在蓝图和C++中实现接口

	UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category = "Trigger Reaction")

		bool ReactToTrigger_NativeEvent2(int32 number);

	//实现类在蓝图中实现接口

	UFUNCTION(BlueprintCallable, BlueprintImplementableEvent, Category = "Trigger Reaction")

		void ReactToTrigger_ImplementableEvent();

};

ReactToTriggerInterface.cpp

#include "ReactToTriggerInterface.h"

void IReactToTriggerInterface::ReactToTrigger_Virtual()

{

	// unimplemented(); //该宏将在执行代码行时发出调试语句, 中断

	UE_LOG(LogTemp, Warning, TEXT("ReactToTrigger_Virtual 被调用, From 接口本身"));

}

实现接口

MyDrone.h 此类继承自Pawn类，无关本文主题

#include "ReactToTriggerInterface.h"

#include "MyDrone.generated.h"

UCLASS()

class TIPS_API AMyDrone : public ADrone, public IReactToTriggerInterface

{

	GENERATED_BODY()

public:

	virtual void ReactToTrigger_PureVirtual() override;

	//可蓝图调用，貌似通用写法

	UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category = "Trigger Reaction")

		void ReactToTrigger_NativeEvent1(int32 number);

		virtual void ReactToTrigger_NativeEvent1_Implementation(int32 number) override;

	//蓝图可调用,,貌似和上面没区别

	virtual bool ReactToTrigger_NativeEvent2_Implementation(int32 number) override;

	//void ReactToTrigger_ImplementableEvent();需要在蓝图实现

};

MyDrone.cpp

#include "MyDrone.h"

void AMyDrone::ReactToTrigger_PureVirtual()

{

	UE_LOG(LogTemp, Warning, TEXT("ReactToTrigger_PureVirtual 被调用, From MyDrone"));

}

void AMyDrone::ReactToTrigger_NativeEvent1_Implementation(int32 number)

{

	UE_LOG(LogTemp, Warning, TEXT("ReactToTrigger_NativeEvent1 被调用, From MyDrone"));

}

bool AMyDrone::ReactToTrigger_NativeEvent2_Implementation(int32 number)

{

	UE_LOG(LogTemp, Warning, TEXT("ReactToTrigger_NativeEvent2 被调用, From MyDrone"));

	return true;

}

也可以蓝图重载

调用接口的类

c++ 调用接口可以先判断该类是否有实现接口

// 如果OriginalObject实现了UReactToTriggerInterface，则bisimplemated将为true。

bool bIsImplemented = OriginalObject->GetClass()->ImplementsInterface(UReactToTriggerInterface::StaticClass()); 

// 如果OriginalObject实现了UReactToTrigger，bIsImplemented将为true。

bIsImplemented = OriginalObject->Implements<UReactToTriggerInterface>(); 

// 如果OriginalObject实现了UReactToTriggerInterface，则ReactingObject将为非空。

IReactToTriggerInterface* ReactingObject = Cast<IReactToTriggerInterface>(OriginalObject);

原生虚函数调用按照原生C++调用即可
UFUCNTION()修饰的接口函数则以 I接口名::Execute_函数名( 接口实例, 函数参数) 调用

代码

MyTriggerBox.h

#pragma once

#include "CoreMinimal.h"

#include "Engine/TriggerBox.h"

#include "MyTriggerBox.generated.h"

UCLASS()

class TIPS_API AMyTriggerBox : public ATriggerBox

{

	GENERATED_BODY()

public:

	virtual void BeginPlay() override;

	UFUNCTION()

	void HandleOverlap(AActor* OverlappedActor, AActor* OtherActor );

};

MyTriggerBox.cpp

#include "MyTriggerBox.h"

#include "Components/BoxComponent.h"

#include "ReactToTriggerInterface.h"

void AMyTriggerBox::BeginPlay()

{

	//放在构造函数好像不起作用

	OnActorBeginOverlap.AddDynamic(this, &AMyTriggerBox::HandleOverlap);

}

void AMyTriggerBox::HandleOverlap(AActor* OverlappedActor, AActor* OtherActor )

{

	UClass* ActorClass = OtherActor->GetClass();

	if (ActorClass->ImplementsInterface(UReactToTriggerInterface::StaticClass()))

	{

		UE_LOG(LogTemp, Warning, TEXT("是否实现接口判断方法一"));

		IReactToTriggerInterface* ReactToTriggerInterface1 = CastChecked<IReactToTriggerInterface>(OtherActor);

		ReactToTriggerInterface1->ReactToTrigger_PureVirtual();

		ReactToTriggerInterface1->ReactToTrigger_Virtual();

		IReactToTriggerInterface::Execute_ReactToTrigger_NativeEvent1(OtherActor, 16);

		IReactToTriggerInterface::Execute_ReactToTrigger_NativeEvent2(OtherActor, 32);

		IReactToTriggerInterface::Execute_ReactToTrigger_ImplementableEvent(OtherActor);

	}

	if (OtherActor->Implements<UReactToTriggerInterface>())

	{

		UE_LOG(LogTemp, Warning, TEXT("是否实现接口判断方法二"));

		IReactToTriggerInterface::Execute_ReactToTrigger_NativeEvent1(OtherActor, 16);

		IReactToTriggerInterface::Execute_ReactToTrigger_NativeEvent2(OtherActor, 32);

	}

	IReactToTriggerInterface* ReactToTriggerInterface2 = Cast<IReactToTriggerInterface>(OtherActor);

	if (ReactToTriggerInterface2)

	{

		UE_LOG(LogTemp, Warning, TEXT("是否实现接口判断方法三"));

		IReactToTriggerInterface::Execute_ReactToTrigger_ImplementableEvent(OtherActor);

	}

}

巴特西

【UE4 C++ 基础知识】<9> Interface 接口

概述

蓝图使用

使用方法

三种调用方法的区别

调用流关卡蓝图的接口函数

C++ 使用接口

添加接口类

定义接口

声明蓝图可调用接口函数

代码

实现接口

调用接口的类

代码

测试结果

参考

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