斯坦福CS193U-虚幻4C++课程学习笔记(6)

UE4 - UPROPERTY Specifier

• EditAnywhere - 可以在蓝图编辑器中和地图中的每个实例进行修改

• VisibleAnywhere - 在蓝图编辑器中和地图中只读

• EditDefaultOnly - 实例中隐藏，蓝图编辑器中可修改

• VisibleDefaultOnly - 变量只读，且仅在蓝图编辑器中 (不常用)

• BlueprintReadOnly - 蓝图脚本只读 (不影响details面板)

• BlueprintReadWrite - 蓝图脚本读写

• Category = "" - 蓝图中的分类显示

UMG

UE4 "STRING" Types

• FString

• 通常用于Debug

• 支持string操作

• FName

• Hashed从而能够快速比较string

• system和gameplay使用

• assigned之后无法改变

• FText

• UI显示的前端文本

• 更容易地本地化成为不同语言

Binding

• 每一帧运行

• 性能开销大

Event-Based

• 触发时才调用

• 可以自定义触发表现

• C++中添加代理

Construct vs. Pre-Construct

Construct在Widget添加到视口中时才会调用，而Pre-Construct每一次编译都会调用

Tips

• 组件添加到使用的类中，默认规范要求添加 Category = "Components"

• 不建议在变量变化时调用更新UI的函数，而是使用UI单方面监听变量的变化，避免双向调用

• 当制作UI动画时不小心修改了默认值，可以点击动画上的Action->Restore Pre-Animated State查看并恢复

项目代码

Github: https://github.com/yufeige4/ActionRoguelike

• 实现属性组件

• 实现魔法弹伤害功能

• 血条Widget显示

• 生命值变化表现

// 代理声明
DECLARE_DYNAMIC_MULTICAST_DELEGATE_FourParams(FOnHealthChanged, AActor*, InstigatorActor, UGAttributeComponent*, OwningComp, float, NewHealth, float, Delta);

UCLASS( ClassGroup=(Custom), meta=(BlueprintSpawnableComponent) )
class ACTIONROGUELIKE_API UGAttributeComponent : public UActorComponent
{
	GENERATED_BODY()

protected:
	// 生命值
	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = "Attributes")
	float Health;

public:	
	// 对生命值进行修改
	UFUNCTION(BlueprintCallable, Category = "Attributes")
	bool ApplyHealthChange(float Delta);
	// 包含代理
	UPROPERTY(BlueprintAssignable)
	FOnHealthChanged OnHealthChanged;

}

UGAttributeComponent::UGAttributeComponent()
{
	Health = 100;
}

bool UGAttributeComponent::ApplyHealthChange(float Delta)
{
	Health += Delta;
	// 调用代理
	OnHealthChanged.Broadcast(nullptr,this,Health,Delta);
	return true;
}

protected:

	// ...

	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Components")
	UGAttributeComponent* AttributeComp;

AGCharacter::AGCharacter(){

	// ...
	// 添加属性组件
	AttributeComp = CreateDefaultSubobject("AttributeComp");
}

AGMagicProjectile::AGMagicProjectile()
{
	// ...

	SphereComp->OnComponentBeginOverlap.AddDynamic(this,&AGMagicProjectile::OnActorOverlap);
	DamageAmount = 20.0f;
}

void AGMagicProjectile::OnActorOverlap(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor,
	UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
{
	if(OtherActor && OtherActor!=GetInstigator())
	{
		UGAttributeComponent* AttributeComp = Cast (OtherActor->GetComponentByClass(UGAttributeComponent::StaticClass()));
		if(AttributeComp)
		{
			AttributeComp->ApplyHealthChange(-DamageAmount);
		}
		Explode();
	}
}