UE5 C++跑酷练习（Part2）

一.首先GameMode里有Actor数组，组装直线路，和左右路

#include "CoreMinimal.h"
#include "GameFramework/GameModeBase.h"
#include "RunGANGameMode.generated.h"

UCLASS(minimalapi)
class ARunGANGameMode : public AGameModeBase
{
    GENERATED_BODY()
    UPROPERTY()
    TArray<TSubclassOf<class AActor>> StraitArray;
    UPROPERTY()
    TArray<TSubclassOf<class AActor>> LeftRightArray;
    UPROPERTY()
    TSubclassOf<AActor> NewRoad;
    UPROPERTY()
    FTransform NextTransforms;
public:
    ARunGANGameMode();
    TSubclassOf<AActor> RandomInputFloor();
    virtual void BeginPlay();
    //添加我们地板
    void AddFloor();
};

UPROPERTY（）不会被GC掉

TSubclassOf

在Unreal中经常会有在蓝图或者C++中声明某些UClass，便于后续用来创建对应的对象，但是如果只是填了一个UClass指针的话，这并不好用。这是因为UClass*可以指代任意UObject，所以在蓝图或者编辑器中选择对应的UClass的时候不好选择，因为基本上所有的UClass都会出现在下拉框内。Unreal也提出对应的解决方案，那就是TSubclassOf，它能够避免能上面说的问题，TSubclassOf能够约束下拉框中只会出现继承于T的类或者T本身，并且C++层面也能实现类型安全，如果给TSubclassOf对象赋值一个类型不兼容的UClass，则会得到编译错误。

二.在GameMode构造函数时，可以使用动态加载 Actor到路面类型。静态加载主角到PlayerPawnBPClass类中，再设置到Gamemode默认的Pawn里(DefaultPawnClass)。

#include "RunGANGameMode.h"
#include "RunGANCharacter.h"
#include "UObject/ConstructorHelpers.h"
#include "Actor/CollisionInteraction/RunRoad.h"
ARunGANGameMode::ARunGANGameMode()
{
    // set default pawn class to our Blueprinted character
    static ConstructorHelpers::FClassFinder<APawn> PlayerPawnBPClass(TEXT("/Game/ThirdPerson/Blueprints/BP_ThirdPersonCharacter"));
    if (PlayerPawnBPClass.Class != NULL)
    {
        DefaultPawnClass = PlayerPawnBPClass.Class;
    }
    StraitArray.Add(LoadClass<AActor>(NULL,TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_StraightRoad_1.BP_StraightRoad_1_C'")));
    StraitArray.Add(LoadClass<AActor>(NULL, TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_StraightRoad_2.BP_StraightRoad_2_C'")));
    StraitArray.Add(LoadClass<AActor>(NULL, TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_StraightRoad_3.BP_StraightRoad_3_C'")));
    StraitArray.Add(LoadClass<AActor>(NULL, TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_StraightRoad_4.BP_StraightRoad_4_C'")));
    LeftRightArray.Add(LoadClass<AActor>(NULL, TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_TurnLeftRoad.BP_TurnLeftRoad_C'")));
    LeftRightArray.Add(LoadClass<AActor>(NULL, TEXT("/Script/Engine.Blueprint'/Game/Environment/BP/BP_TurnRightRoad_2.BP_TurnRightRoad_2_C'")));
}

ConstructorHelpers::FClassFinder()和FObjectFinder()

静态加载指的是在构造函数中完成的加载方式，这种方式的弊端明显，就是需要写死路径，一旦改变路径读取失败很容易造成程序崩溃。

**LoadObject<UClass>**。

也就是说LoadObject和LoadClass函数都用于在运行时加载UObject派生的对象，但是它们的用途和返回值有所不同。

LoadObject用于加载单个对象，可以是任何UObject派生类的实例，包括UClass、UTexture、UMaterial等。它会返回加载的对象，或者在加载失败时返回nullptr

同时，如果使用LoadClass（）方法，路径名也必须带_C后缀（LoadObject不需要带_C后缀），例如，蓝图路径是：Blueprint'/Game/Blueprints/Test'， 加后缀以后，则是：Blueprint'/Game/Blueprints/Test_C'

三.通过FMath::RandRange随机数从不同的类型中生成下个路面。并在一开始设置生成一个路面的位置。

TSubclassOf<AActor> ARunGANGameMode::RandomInputFloor()
{
    int32 i = FMath::RandRange(1,100);
    if (i <= 80)
    {
        int32 Index = FMath::RandRange(0,StraitArray.Num()-1);
        return StraitArray[Index];
    }
    else
    {
        int32 Index = FMath::RandRange(0, LeftRightArray.Num() - 1);
        return LeftRightArray[Index];
    }
    return TSubclassOf<AActor>();
}
void ARunGANGameMode::BeginPlay()
{
    Super::BeginPlay();
    if (GetWorld())
    {
        NextTransforms = GetWorld()->GetFirstPlayerController()->GetPawn()->GetTransform();
        FVector InLocation = NextTransforms.GetLocation();
        InLocation.Y += 100.f;
        InLocation.Z -= 200.f;
        NextTransforms.SetLocation(InLocation);
        for (int32 i = 0; i < 9; i++)
        {
            AddFloor();
        }
    }
}

四.添加地板逻辑，拼贴点位。

//添加我们的地板
void ARunGANGameMode::AddFloor()
{
    NewRoad = RandomInputFloor();
    if (NewRoad != NULL)
    {
        FVector const MyLocation = NextTransforms.GetLocation();
        FRotator MyRotation(NextTransforms.Rotator());
        if (ARunRoad* MyRunRoad = GetWorld()->SpawnActor<ARunRoad>(NewRoad, MyLocation, MyRotation))
        {
            MyRunRoad->SetActorScale3D(FVector(10.f));
            NextTransforms = MyRunRoad->GetAttackToTransform(MyLocation);
        }
    }
}

五.AddFloor里使用的GetAttackToTransform是使用每个，路面自己对准的下一个路面的位置。

FTransform ARunRoad::GetAttackToTransform(const FVector& MyLocation)
{
    FTransform Transform;
    Transform.SetLocation(SpawnPointMiddle->GetComponentToWorld().GetLocation());
    Transform.SetRotation(SpawnPointMiddle->GetComponentQuat());
    return Transform;
}

六.通过跑步碰撞，判断。开启角色可以转弯的功能，

#include "TurnBox.h"
#include "Components/BoxComponent.h"
#include "../../RunGANCharacter.h"

// Sets default values
ATurnBox::ATurnBox()
{
     // Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
    PrimaryActorTick.bCanEverTick = false;
    Box = CreateDefaultSubobject<UBoxComponent>(TEXT("TurnBox"));
    RootComponent = Box;
}

// Called when the game starts or when spawned
void ATurnBox::BeginPlay()
{
    Super::BeginPlay();    
    Box->OnComponentBeginOverlap.AddDynamic(this,&ATurnBox::CharacterOverlapStart);
    Box->OnComponentEndOverlap.AddDynamic(this, &ATurnBox::CharacterOverlapEnd);
}

// Called every frame
void ATurnBox::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

}

void ATurnBox::CharacterOverlapStart(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
{
    if (ARunGANCharacter* InCharacter =  Cast<ARunGANCharacter>(OtherActor))
    {
        InCharacter->bTurn = true;
    }
}

void ATurnBox::CharacterOverlapEnd(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
{
    if (ARunGANCharacter* InCharacter = Cast<ARunGANCharacter>(OtherActor))
    {
        InCharacter->bTurn = false;
    }
}

TurnBox，位置不对。可以用蓝图具象化调整。

碰撞显示

BP_TurnBox 的位置就是Arrow的位置，记住Dlay延迟一下，预防Scale位置会有问题偏差。