UE4 zooms the camera by clicking the right mouse button

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Pawn.h"
#include "CameraPawn.generated.h"

UCLASS()
class TRUEFPSPROJECT_API ACameraPawn : public APawn {
    
    
	GENERATED_BODY()

public:
	// Sets default values for this pawn's properties
	ACameraPawn();

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "AAA")
	class UStaticMeshComponent* staticMeshComponent;

	//摄像机的摇臂
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "AAA")
	class USpringArmComponent* springArm;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "AAA")
	class UCameraComponent* myCamera;
protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:
	// Called every frame
	virtual void Tick(float DeltaTime) override;

	// Called to bind functionality to input
	virtual void SetupPlayerInputComponent(class UInputComponent* PlayerInputComponent) override;

	void ZoomIn();
	void ZoomOut();

private:
	bool bZoomIn = false;
	float zoomScale = 1.0;
};

// Fill out your copyright notice in the Description page of Project Settings.


#include "CameraPawn.h"
#include "GameFramework/SpringArmComponent.h"
#include "Camera/CameraComponent.h"

// Sets default values
ACameraPawn::ACameraPawn() {
    
    
	// Set this pawn to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;
	 
	staticMeshComponent = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("staticMeshComponent"));
	RootComponent = staticMeshComponent;

	springArm = CreateDefaultSubobject<USpringArmComponent>(TEXT("springArm"));
	springArm->SetupAttachment(RootComponent);

	springArm->SetRelativeLocationAndRotation(FVector(0.0, 0.0, 50.0), FRotator(-45, 0.0, 0.0));

	//摇臂的长度
	springArm->TargetArmLength = 400.0;
	//开启摄像机延迟
	springArm->bEnableCameraLag = true;
	//摄像机延迟速度
	springArm->CameraLagSpeed = 3.0f;

	myCamera = CreateDefaultSubobject<UCameraComponent>(TEXT("myCamera"));
	myCamera->SetupAttachment(springArm, USpringArmComponent::SocketName);

	//设置默认玩家
	AutoPossessPlayer = EAutoReceiveInput::Player0;
}

// Called when the game starts or when spawned
void ACameraPawn::BeginPlay() {
    
    
	Super::BeginPlay();

}

// Called every frame
void ACameraPawn::Tick(float DeltaTime) {
    
    
	Super::Tick(DeltaTime);
	if (bZoomIn){
    
    
		zoomScale += DeltaTime;
	} else {
    
    
		zoomScale -= DeltaTime;
	}

	zoomScale = FMath::Clamp<float>(zoomScale, 0.0f, 1.0f);
	/**
	基于 zoomScale 混合相机的FOV和SpringArm的长度
	基于两个量之间的线型差值，在数字from和to之间的值
	*/
	myCamera->FieldOfView = FMath::Lerp<float>(90.0f, 60.0, zoomScale);
	springArm->TargetArmLength = FMath::Lerp<float>(400.0, 300.0, zoomScale);
}

// Called to bind functionality to input
void ACameraPawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent) {
    
    
	Super::SetupPlayerInputComponent(PlayerInputComponent);

	PlayerInputComponent->BindAction("ZoomIn", IE_Pressed, this, &ACameraPawn::ZoomIn);
	PlayerInputComponent->BindAction("ZoomIn", IE_Released, this, &ACameraPawn::ZoomOut);
}

void ACameraPawn::ZoomIn() {
    
    
	bZoomIn = true;
}

void ACameraPawn::ZoomOut() {
    
    
	bZoomIn = false;
}

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