【UE4 C++】Tick的三種方式、異步藍圖節點、Latent Action

Tick的三種方式

• 包括
  • 默認 Tick （Actor、Component、UMG）
  • TimerManager 定時器
  • FTickableGameObject
    • 可以寫原生 Object
    • 也可以繼承UObject 使用
• 下面利用 AActor 直接實現三種 Tick

class  FTickableObject :public FTickableGameObject
{
public:
	bool bEnableTick = false;
	int32 TickCounter = 0;

	virtual void Tick(float DeltaTime)override {
		UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__"\t [TickCounter]%d"), TickCounter);
	}
	virtual bool IsTickable()const override { return bEnableTick; }
	virtual TStatId GetStatId() const override { RETURN_QUICK_DECLARE_CYCLE_STAT(UTickableObject, STATGROUP_Tickables); }
};

UCLASS()
class DESIGNPATTERNS_API AAsyncTickActor : public AActor
{
	GENERATED_BODY()
public:	
	// Sets default values for this actor's properties
	AAsyncTickActor();

	// Called every frame
	virtual void Tick(float DeltaTime) override;
	void TimerTick();
protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

private:
	int32 TickCounter = 0;
	FTimerHandle TimeHandle;
	TSharedPtr<FTickableObject> TickableObject;
};

AAsyncTickActor::AAsyncTickActor()
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;	
}

// Called when the game starts or when spawned
void AAsyncTickActor::BeginPlay()
{
	Super::BeginPlay();
	TickableObject = MakeShareable(new FTickableObject());
	TickableObject->bEnableTick = true;
	GetWorld()->GetTimerManager().SetTimer(TimeHandle, this, &AAsyncTickActor::TimerTick, 0.1f, true);
}

// Called every frame
void AAsyncTickActor::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__"\t[TickCounter]%d"), TickCounter);
	if (TickableObject.IsValid())
	{
		TickableObject->TickCounter = TickCounter;
	}

}

void AAsyncTickActor::TimerTick()
{
	TickCounter++;
	UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__"%\t [TickCounter]%d"), TickCounter);
}

---

異步藍圖節點

• 原博客地址

使用方法

• 繼承 UBlueprintAsyncActionBase

  • 成員函數 Activate 用於內部觸發委托綁定的事件
  • 成員函數 RegisterWithGameInstance 允許將該對象注冊到 GameInstance，防止GC
  • 注冊后，調用成員方法 SetReadyToDestroy 銷毀、釋放，從 GameInstance 注銷
  • 源碼

    class UGameInstance;
    
    UCLASS()
    class ENGINE_API UBlueprintAsyncActionBase : public UObject
    {
    	GENERATED_UCLASS_BODY()
    
    	/** Called to trigger the action once the delegates have been bound */
    	UFUNCTION(BlueprintCallable, meta=(BlueprintInternalUseOnly="true"))
    	virtual void Activate();
    
    	/**
    	 * Call to globally register this object with a game instance, it will not be destroyed until SetReadyToDestroy is called
    	 * This allows having an action stay alive until SetReadyToDestroy is manually called, allowing it to be used inside loops or if the calling BP goes away
    	 */
    	virtual void RegisterWithGameInstance(UObject* WorldContextObject);
    	virtual void RegisterWithGameInstance(UGameInstance* GameInstance);
    
    	/** Call when the action is completely done, this makes the action free to delete, and will unregister it with the game instance */
    	virtual void SetReadyToDestroy();
    
    protected:
    	TWeakObjectPtr<UGameInstance> RegisteredWithGameInstance;
    };
    

• 聲明靜態函數

• 需要動態多播委托，作為多個輸出節點

代碼實現

• 代碼

  UCLASS()
  class DESIGNPATTERNS_API AAsyncTickActor : public AActor
  {
  public:
  	UPROPERTY(BlueprintReadWrite)
  		TArray<int32>CountdownNums;
  };
  
  // 定義委托類型
  DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FCompleteHandleDelegate, int32, Result);
  
  UCLASS()
  class DESIGNPATTERNS_API UMyBPAsyncAction : public UBlueprintAsyncActionBase
  {
  	GENERATED_BODY()
  public:
  	UMyBPAsyncAction() { UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__"")); }
  	~UMyBPAsyncAction() { UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__"")); }
  
  	// 自定義的異步藍圖節點
  	UFUNCTION(BlueprintCallable, meta = (WorldContext = "WorldContextObject"), Category = "MyBPAsyncAction")
  		static UMyBPAsyncAction* AsyncCountdown(UObject* WorldContextObject, AAsyncTickActor* AsyncTickActor, int32 StartNum);
  public:
  	//輸出節點
  	UPROPERTY(BlueprintAssignable)
  		FCompleteHandleDelegate OnSucceeded;
  	
  	//輸出節點
  	UPROPERTY(BlueprintAssignable)
  		FCompleteHandleDelegate OnFailed;
  private:
  	FTimerHandle TimerHandle;
  	
  protected:
  	virtual void Activate() override;
  };
  

  void UMyBPAsyncAction::Activate()
  {
  	// 開新的線程，測試 Activate 調用情況
  	Async(EAsyncExecution::ThreadPool, [&]()
  		{
  			UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Start Delay 1s."));
  			FPlatformProcess::Sleep(1.0f);
  			UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Delay Finished."));
  		});
  }
  
  UMyBPAsyncAction* UMyBPAsyncAction::AsyncCountdown(UObject* WorldContextObject, AAsyncTickActor* AsyncTickActor, int32 StartNum)
  {
  	if (WorldContextObject == nullptr)
  	{
  		FFrame::KismetExecutionMessage(TEXT("Invalid WorldContextObject"), ELogVerbosity::Error);
  		UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Invalid WorldContextObject."));
  		return nullptr;
  	}
  
  	UMyBPAsyncAction* MyBPAsyncActionNode = NewObject<UMyBPAsyncAction>();
  	// Lambda 表達式
  	auto CountdownFunc = [&,MyBPAsyncActionNode, WorldContextObject, AsyncTickActor, StartNum]() {
  		if (IsValid(AsyncTickActor))
  		{
  			if (AsyncTickActor->CountdownNums.Num() == StartNum)
  			{
  				// OnSucceeded輸出節點
  				MyBPAsyncActionNode->OnSucceeded.Broadcast(1);	
  				
  				// 清空定時器
  				WorldContextObject->GetWorld()->GetTimerManager().ClearTimer(MyBPAsyncActionNode->TimerHandle);
  				
  				// 如果不使用，則銷毀
  				MyBPAsyncActionNode->SetReadyToDestroy();
  				UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Countdown Completed."));
  			}
  			else
  			{
  				int32 length = AsyncTickActor->CountdownNums.Num();
  				AsyncTickActor->CountdownNums.Add(length + 1);
  				UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Counting down... %d"), length + 1);
  			}
  		}
  		else
  		{
  			// OnFailed 輸出節點
  			MyBPAsyncActionNode->OnFailed.Broadcast(-1);
  			WorldContextObject->GetWorld()->GetTimerManager().ClearTimer(MyBPAsyncActionNode->TimerHandle);
  			UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Invalid AsyncTickActor."));
  			FFrame::KismetExecutionMessage(TEXT("Invalid AsyncTickActor"), ELogVerbosity::Error);
  		}
  	};
  	
  	// 設置定時器並開始
  	WorldContextObject->GetWorld()->GetTimerManager().SetTimer(MyBPAsyncActionNode->TimerHandle, FTimerDelegate::CreateLambda(CountdownFunc), 1.0f, true);
  	UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" Countdown Starting."));
  	return MyBPAsyncActionNode;
  }
  

  

---

Latent Action

• 參考：UE4 Latent Action(潛在事件)節點的基礎創建方法