UE4 中Struct Emum 类型的定义方式 笔记

时间:2021-02-15 02:11:42

记录一些UE4文档以外编程相关的底层基础的概念和使用方法,如GC和Gameplay,各种宏/配置项等说明和使用

备查

文档:http://api.unrealengine.com/INT/Programming/index.html

Q.UE4怎么打开系统文件对话框(OpenFileDialog):

FString UCommonBPLibrary::OpenFileDialog()
{
void* ParentWindowPtr = FSlateApplication::Get().GetActiveTopLevelWindow()->GetNativeWindow()->GetOSWindowHandle();
IDesktopPlatform* DesktopPlatform = FDesktopPlatformModule::Get(); FJsonSerializableArray OutFileNames;
if (DesktopPlatform)
{ EFileDialogFlags::Type SelectionFlag = EFileDialogFlags::None; //A value of 0 represents single file selection while a value of 1 represents multiple file selection DesktopPlatform->OpenFileDialog(ParentWindowPtr, TEXT("选取一张图片"), TEXT("D:/"), FString(""), TEXT("(Image Files)|*.BMP;*.JPG;*.PNG;*.JPEG;)"), SelectionFlag, OutFileNames);
} if (OutFileNames.Num() > )
{
return FString (OutFileNames[]);
}
else
{
return TEXT("");
} }

Q. UE4 第三人称(SpringArm控制下)设置初始视口位置 :

UE4 中Struct Emum 类型的定义方式 笔记

Q. UE4的委托和事件(Delegate):

  记一下,开发方便Copy.

  吐槽:UE4 的Delegate得定义宏又臭又长又多,C#的委托和事件不知道比UE4高到哪里去了!(UE5请务必砍掉从新实现!)

  快速索引:委托文档:https://docs.unrealengine.com/en-US/Programming/UnrealArchitecture/Delegates/index.html

  概念:

    从设计模式上来说 多播Delegate就是 观察者模式得实现,只不过C#集成到了语言特性上,刚好C#(QT single-slot)得方式 被UE4借鉴到了引擎里

    Q0:C++是怎么去实现委托的?

      链接:C++实现的类C# Delegate 参考: https://*.com/questions/23973914/c-like-delegates-in-c

      实现委托的代码:      

/* 代码来着上述* */
#include <algorithm>
#include <iostream>
#include <memory>
#include <utility>
#include <vector> template <typename Signature>
struct delegate; template <typename... Args>
struct delegate<void(Args...)>
{
struct base
{
virtual ~base() {}
virtual bool do_cmp(base* other) = ;
virtual void do_call(Args... args) = ;
};
template <typename T>
struct call : base
{
T d_callback;
template <typename S>
call(S&& callback) : d_callback(std::forward<S>(callback))
{ } bool do_cmp(base* other)
{
call<T>* tmp = dynamic_cast<call<T>*>(other); return tmp && this->d_callback == tmp->d_callback;
}
void do_call(Args... args)
{
return this->d_callback(std::forward<Args>(args)...);
}
};
std::vector<std::unique_ptr<base>> d_callbacks; delegate(delegate const&) = delete;
void operator=(delegate const&) = delete;
public:
delegate()
{ }
template <typename T>
delegate& operator+= (T&& callback)
{
this->d_callbacks.emplace_back(new call<T>(std::forward<T>(callback)));
return *this;
} template <typename T>
delegate& operator-= (T&& callback)
{
call<T> tmp(std::forward<T>(callback));
auto it = std::remove_if(this->d_callbacks.begin(),
this->d_callbacks.end(),
[&](std::unique_ptr<base>& other) {
return tmp.do_cmp(other.get());
});
this->d_callbacks.erase(it, this->d_callbacks.end());
return *this;
} void operator()(Args... args)
{
for (auto& callback : this->d_callbacks)
{
callback->do_call(args...);
}
}
}; // ---------------------------------------------------------------------------- template <typename RC, typename Class, typename... Args>
class member_call
{
Class* d_object;
RC(Class::* d_member)(Args...);
public:
member_call(Class* object, RC(Class::* member)(Args...))
: d_object(object)
, d_member(member)
{
} RC operator()(Args... args)
{
return (d_object->*d_member)(std::forward<Args>(args)...);
} bool operator== (member_call const& other) const
{
return (this->d_object == other.d_object) && (this->d_member == other.d_member);
} bool operator!= (member_call const& other) const
{
return !(*this == other);
}
}; /**
* @prarms RC 返回类型, Class
**/
template <typename RC, typename Class, typename... Args>
member_call<RC, Class, Args...> mem_call(Class& object,
RC(Class::* member)(Args...))
{
return member_call<RC, Class, Args...>(&object, member);
} // ---------------------------------------------------------------------------- void f(char const* str) { std::cout << "f(" << str << ")\n"; }
void g(char const* str) { std::cout << "g(" << str << ")\n"; }
void h(char const* str) { std::cout << "h(" << str << ")\n"; } // ---------------------------------------------------------------------------- struct foo
{
int d_id;
explicit foo(int id) : d_id(id)
{ } void bar(char const* str)
{
std::cout << "foo(" << this->d_id << ")::bar(" << str << ")\n";
} void cbs(char const* str)
{
std::cout << "foo(" << this->d_id << ")::cbs(" << str << ")\n";
} }; // ---------------------------------------------------------------------------- int main()
{
delegate<void(char const*)> d0; foo f0();
foo f1(); d0 += f;
d0 += g;
d0 += g;
d0 += h; d0 += mem_call(f0, &foo::bar);
d0 += mem_call(f0, &foo::cbs);
d0 += mem_call(f1, &foo::bar);
d0 += mem_call(f1, &foo::cbs);
d0("first call");
d0 -= g;
d0 -= mem_call(f0, &foo::cbs);
d0 -= mem_call(f1, &foo::bar);
d0("second call");
}

      

      C++触发时调用的假设:

#include <iostream>

class DemonstrateClass
{
public:
int a = ;
//绑定函数
void Func( std::string a)
{
std::cout << "hi : [ "<< a << " ] " << std::endl;
}
}; /**
*
* Qt或UE4实现绑定成员函数核心调用代码Demo:
*
**/
int main()
{
// 假设 pa 为绑定对象
DemonstrateClass* pa = new DemonstrateClass(); // &DemonstrateClass::Func为绑定函数
void(DemonstrateClass::* func_ref)(std::string) = &DemonstrateClass::Func; //委托触发时,实际调用以下代码
(pa->*(func_ref))(" linqing demonstrate "); std::cout << "exam complated.... " << std::endl;
}

  

    Q1.什么是单播委托/什么是多播委托/什么是事件:

      wait

    Q1.什么是动态委托:

      wait

Q. UE4的Input全局钩子,全局监听鼠标键盘等外设输入事件:

  方式一:

  可继承GameViewportClient类实现

  

  例子(全局监听鼠标左键并打印Log):

  .h:

UCLASS()
class BJ_YourProject_API UGameViewportClient_Demonstrate : public UGameViewportClient
{
GENERATED_BODY() public:
UGameViewportClient_Demonstrate();
public:
virtual EMouseCaptureMode CaptureMouseOnClick() override; /*
输入设备的全局钩子函数
*/
virtual bool InputKey
(
const FInputKeyEventArgs & EventArgs
) override;
};

.cpp

UGameViewportClient_Demonstrate::UGameViewportClient_Demonstrate()
{
} EMouseCaptureMode UGameViewportClient_Demonstrate::CaptureMouseOnClick()
{
UE_LOG(LogTemp, Log, TEXT("[GVC:] CaptureMouseOnClick"));
return Super::CaptureMouseOnClick();
} bool UGameViewportClient_Demonstrate::InputKey(const FInputKeyEventArgs & EventArgs)
{
if (EKeys::LeftMouseButton == EventArgs.Key)
{
UE_LOG(LogTemp, Log, TEXT("[GVC:] InputKey is left mouse button"));
} return Super::InputKey(EventArgs);
}

  最后在Editor中的Project Setttings里修改默认的GameViewportClient即可

  UE4 中Struct Emum 类型的定义方式 笔记

Q. UE4 关于 C++中使用或设置组件的自定义 Trace Response/Object Type的问题:

UE4关于这块配置是用的枚举映射.

自定义Collision:

UE4 中Struct Emum 类型的定义方式 笔记

打开Config/DefaultEngine.ini

在[/Script/Engine.CollisionProfile]下可以找到:

类似如:

UE4 中Struct Emum 类型的定义方式 笔记

的设置项.其中ECC_GameTraceChannel1就是映射的ECollisionChannel枚举项:

C++例子:

        //因为QingResponse映射到ECC_GameTraceChannel1,所以这里修改的是 QingResponse的Collision值
Dynamic_Com->SetCollisionResponseToChannel(ECollisionChannel::ECC_EngineTraceChannel1, ECollisionResponse::ECR_Block);

Q. UE4 Skeletal Mesh模型 个别视角莫名消失隐藏的问题背后原因:

  问题:UE4的场景剔除优化渲染算法(可参考DX里的视锥体优化算法)引起的问题./UE4SketalMesh无法正常显示可见

  剔除和遮挡的相关文档:https://docs.unrealengine.com/en-US/Engine/Rendering/VisibilityCulling/VisibilityCullingReference/index.html

  解决:剔除算法在Skeletal Mesh上,用的是Physics Asset 的碰撞资源来做的运算的,把Physics Asset刷正确就OK。(也可以使用UE4 两个 Precomputed Volume处理或关闭遮挡剔除)

UE4 中Struct Emum 类型的定义方式 笔记

Q.UE4 Blueprint(蓝图) Template Function实现(蓝图中的模板函数实现):

  Meta文档:https://docs.unrealengine.com/en-US/Programming/UnrealArchitecture/Reference/Metadata/index.html

  其实就是加meta标签,只是官方的meta的说明文档标签不够完善o(╥﹏╥)o

  具体的可以翻源码里的ObjectMacros.h 头文件查看标签意义.

  这里顺便记录一下比较常用的Meta标签:

  UFUNCTION:

  1. DefaultToSelf            指定参数默认值为调用本函数类实例的self(类似于javascript的this,谁调用指向谁)
  2. HidePin                指定BP里要隐藏成员参数,通常配合DefaultToSelf标签一起食用

  解决:

  根据蓝图中传入的类返回类的实例.

  可以参考SpawnActor的代码实现.

  栗子:

    note:这是个 BPLibraryFunction类,所有声明的static

    UFUNCTION(BlueprintCallable, meta = (DeterminesOutputType = "actorClass"))
static class AActor* TestActor(class TSubclassOf<class AActor> actorClass);

Q.UE4中使用dynamic_cast,编译报错问题.

  UE4 默认是关闭RTTI的,如果要使用dynamic_cast,需要在build.cs中启用rtti;

  UE4 中Struct Emum 类型的定义方式 笔记

using UnrealBuildTool;

public class MyAPP : ModuleRules
{
public MyAPP(ReadOnlyTargetRules Target) : base(Target)
{
PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
bUseRTTI = true;
bEnableExceptions = true; PublicDependencyModuleNames.AddRange(
new string[]
{
""
}); PrivateDependencyModuleNames.AddRange(new string[]
{
""
});
}
}

Q.BP 蓝图宏 (Macros)和函数(functions)的区别:

  记录一下 具体描述

  BP下的function不支持delay,AI Move to的等时间Latent型节点的,但是Macro支持.

  总体来说编译上function是静态编译,而Macro就是c++的动态宏,是动态编译的.

Q.跨平台相关宏:

  如果需要编写平台相关的代码段的话,需要使用宏来约定。

  跨平台相关的宏定义都在Platform.h里。

  例如:

#if PLATFORM_WINDOWS
UE_LOG(LogTemp, Error, TEXT("hi ,windows"));
#elif PLATFORM_MAC
UE_LOG(LogTemp, Error, TEXT("hi ,MAC"));
#endif

Q.关于C++使用LoadClass加载资源的路径问题:

  一般平常加载Texture或mesh时,都是采用例如TEXT("/Game/Blueprints/MyMesh.MyMesh")的路径形式,

  但是如果是用LoadClass加载BP类或UMG类的话需要在路径后面加上_C的后缀:例如

LoadClass<UUserWidget>(NULL,TEXT("/Game/Blueprints/BaseWgt.BaseWgt_C"));

  文档里没有详细介绍,但是这问题几乎会困扰所有刚使用LoadClass这个函数小伙伴。

Q.保存游戏/应用信息到本地:

  USaveGame的应用:

  发现UE4已经写了相关文档,之前没有找到:

  http://api.unrealengine.com/INT/Gameplay/SaveGame/index.html

Q.Struct 和Emum 类型的定义方式 :

UE4 基础,但是不经常用总是忘记,做个笔记马一下:

Note:虽然USTRUCT可以定义函数,但是不能加UFUNCTION 标签喔

结构体:

USTRUCT(BlueprintType)
struct FData_PageInfo
{
GENERATED_USTRUCT_BODY() FData_PageInfo();
FData_PageInfo(UChildActorComponent *parent_Com); void reInit(); UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "struct_Variants")
class UChildActorComponent *Parent_Com; UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "struct_Variants")
class ACpp_PagerActor *PageActor; UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "struct_Variants")
class UChildActorComponent *FrontCanvas_Com; UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "struct_Variants")
class UChildActorComponent *BackCanvas_Com;
};

枚举:

UENUM(BlueprintType)
enum class GroupActorState : uint8
{
EM_Expand UMETA(DisplayName = "Expand"),
EM_Merge UMETA(DisplayName = "Merge")
};

Q.C++ DatatableRow的定义方式:(经常忘,留底Copy用):

#include "Runtime/Engine/Classes/Engine/DataTable.h"
#include "DTOData_AssetItem.generated.h"
USTRUCT(BlueprintType)
struct FDTOData_AssetItem : public FTableRowBase
{
GENERATED_USTRUCT_BODY()
public:
FDTOData_AssetItem()
{
}
public: UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "FDTO_AssetItem")
int Id = ;
};

Q.C++ Interface 的定义方式 :(经常忘,留底Copy用)

UE4的interface 分蓝图可继承和不可集成两种:

文档:http://api.unrealengine.com/CHN/Programming/UnrealArchitecture/Reference/Interfaces/

可继承:

#include "CoreMinimal.h"
#include "Demonstrate.generated.h"
/**
*
*/ UINTERFACE(BlueprintType)
class BJ_3DDESIGNAPP_API UDemonstrate : public UInterface
{
GENERATED_BODY() };
class BJ_3DDESIGNAPP_API IDemonstrate
{
GENERATED_BODY()
public:
UFUNCTION(BlueprintImplementableEvent, Category = "Trigger Reaction")
void Hi();
};

不可继承:

UINTERFACE(meta = (CannotImplementInterfaceInBlueprint) )
class BJ_3DDESIGNAPP_API UDemonstrateGameMode : public UInterface
{
GENERATED_BODY() }; class BJ_3DDESIGNAPP_API IDemonstrateGameMode
{
GENERATED_BODY()
public :
UFUNCTION(BlueprintCallable, Category = "IDemonstrateGameMode")
virtual class ACppCharacter_Demonstrate * GetCurrentDemonstrateActor() const { return nullptr; }
};