Unreal Engine 4 常用功能引导

1、UE4的调试输出

//*1 调试输出*///*case a、快速使用 不设置log类别 默认为LogTemp*/UE_LOG(LogTemp,Log,TEXT("Your message"));UE_Log(LogTemp,Warning,TEXT("You Number type of float value is %f"),YourFloatTypeValue);UE_Log(LogTemp,Error,TEXT("Your Number type of FString value is %s"),YourFStringTypeValue);//Log:输出日志字体颜色为灰色 Warning:输出字体颜色为黄色 Error：输出字体颜色为红色/*case b、设置自定义Log类别*///在YourCode.h文件中声明自定义Log类别@parm YourLogDECLARE_LOG_CATEGORY_EXTERN(YourLog, Log, All);//在YourCode.cpp文件中定义DEFINE_LOG_CATEGORY(YourLog);UE_LOG(YourLog, Log, TEXT("This is a message to yourself during runtime!"));/*case c、触发严重中断 程序执行到此时会触发程序中断*/UE_LOG(YourLog, Fatal, TEXT("This fringe case was reached! Debug this!"));//log输出在output log面板中显示/*case d、 向屏幕打印消息 显示在屏幕上*/if(GEngine){    GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("This is an on screen message!"));    GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, FString::Printf(TEXT("Some variable values: x: %f, y: %f"), x, y));}//我们可以在.cpp文件下进行如下宏定义以快速使用该方法#define print(text) if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 1.5, FColor::White,text)
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2、在场景中查找对象

#include "EngineUtils.h"/*case a、Actor 迭代*/for (TActorIterator<AStaticMeshActor> ActorItr(GetWorld()); ActorItr; ++ActorItr){    AStaticMeshActor *Mesh = *ActorItr；}/*case b、Object迭代*/for (TObjectIterator<AActor> Itr; Itr; ++Itr){    AActor *Component = *Itr;}//Object 迭代可以迭代的内容包括Actor可迭代的内容
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3、射线的使用

//GetHitResultAtScreenPosition函数为引擎框架下APlayerController的方法  //顾名思义是以屏幕为起点向鼠标所在坐标发出射线，进行碰撞检测//可查看APlayerController下此函数的定义  FVector2D cursorPosition(0,0);  this->GetMousePosition(cursorPosition.X, cursorPosition.Y);  FHitResult hitInfo(ForceInit);  FCollisionQueryParams collisionParms(false);  this->GetHitResultAtScreenPosition(cursorPosition,ECC_PhysicsBody,collisionParms,hitInfo);//在此处理hitInfo;/*GetWorld()->LineTraceSingleByObjectType等一系列函数用于处理更多的射线类功能，但APlayerController下已经封装好很多常用的方法。*/
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4、场景捕获组件的使用
将SceneCapture2D组件拖入场景

选中SceneCapture2D找到Texture Target属性 并为其赋值

/*此处实现将SceneCapture2D看到的视角复制到Texture中 */ /*方式一、 *//*sceneCapture为SceneCapture2D组件的引用 */ /*renderTexture为上图所示textureTarget的引用*/ UTexture2D *Texture = UTexture2D::CreateTransient(TextureRenderTarget->SizeX,TextureRenderTarget->SizeY, PF_B8G8R8A8);  sceneCapture->GetCaptureComponent2D()->UpdateContent();  TArray<FColor> SurfData;FRenderTarget *RenderTarget = renderTexture->GameThread_GetRenderTargetResource();RenderTarget->ReadPixels(SurfData);void* TextureData = Texture->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE);const int32 TextureDataSize = SurfData.Num() * 4;FMemory::Memcpy(TextureData, SurfData.GetData(), TextureDataSize);Texture->PlatformData->Mips[0].BulkData.Unlock();Texture->UpdateResource();
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/*方式二、*//*使用ConstructTexture2D函数，该函数每次返回的是同一块内存地址*/sceneCapture->GetCaptureComponent2D()->UpdateContent();  Texture = renderTexture->ConstructTexture2D(this,"AlphaTex",EObjectFlags::RF_NoFlags,CTF_DeferCompression);  Texture->CompressionSettings = TextureCompressionSettings::TC_VectorDisplacementmap;  Texture->UpdateResource();
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5、XML文件的使用
initgameValue.xml文件内容如下
需要在build.cs文件中添加模块”XmlParser”，在YourCode.h中包含XmlParser.h

<?xml version="1.0" encoding="UTF-8"?>  <Value>      <ChildrenSex>Girl</ChildrenSex>      <SceneIndex>0</SceneIndex>  </Value>  
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解析代码如下

#include "XmlParser.h" /*写数据*/    FXmlFile InitVariable(L"X:\\initgameValue.xml");      FXmlNode* root = InitVariable.GetRootNode();      TArray<FXmlNode*> VarArray = root->GetChildrenNodes();      VarArray[0]->SetContent("Your content");      VarArray[1]->SetContent("Your content");      InitVariable.Save(L"X:\\initgameValue.xml");      InitVariable.Clear();  /*读数据*/    FXmlFile InitVariable(L"X:\\initgameValue.xml");      FXmlNode* root = InitVariable.GetRootNode();      TArray<FXmlNode*> VarArray = root->GetChildrenNodes();      FString tempContent=VarArray[0]->GetContent();//一般情况下 文件加载路径不应该是绝对路径 我们可以使用FPaths::GameUserDir()得到项目路径根路径，从而便可以使用相对路径来进行配置文件的加载
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6、UE4字符类型到基本数据类型的转换
UnrealString.h下的内联函数如下

/** Covert a string buffer to intrinsic types */    inline void FromString(int8& OutValue,      const TCHAR* Buffer)    {   OutValue = FCString::Atoi(Buffer);      }    inline void FromString(int16& OutValue,     const TCHAR* Buffer)    {   OutValue = FCString::Atoi(Buffer);      }    inline void FromString(int32& OutValue,     const TCHAR* Buffer)    {   OutValue = FCString::Atoi(Buffer);      }    inline void FromString(int64& OutValue,     const TCHAR* Buffer)    {   OutValue = FCString::Atoi64(Buffer);    }    inline void FromString(uint8& OutValue,     const TCHAR* Buffer)    {   OutValue = FCString::Atoi(Buffer);      }    inline void FromString(uint16& OutValue,    const TCHAR* Buffer)    {   OutValue = FCString::Atoi(Buffer);      }    inline void FromString(uint32& OutValue,    const TCHAR* Buffer)    {   OutValue = FCString::Atoi64(Buffer);    }   //64 because this unsigned and so Atoi might overflow    inline void FromString(uint64& OutValue,    const TCHAR* Buffer)    {   OutValue = FCString::Strtoui64(Buffer, nullptr, 0); }    inline void FromString(float& OutValue,     const TCHAR* Buffer)    {   OutValue = FCString::Atof(Buffer);      }    inline void FromString(double& OutValue,    const TCHAR* Buffer)    {   OutValue = FCString::Atod(Buffer);      }    inline void FromString(bool& OutValue,      const TCHAR* Buffer)    {   OutValue = FCString::ToBool(Buffer);    }
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例：

#include "UnrealString.h"using namespace LexicalConversion;FString temp = "3.1415926":float outFloat; FromString(outFloat, *temp);
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7、UMG拖拽图标的实现
a、重载On Mouse Button Down函数
新建UserWidget组件,在Graph事件图表中重载该函数实现检测是否触发拖拽事件

b、重载OnDrag Detected函数
重载OnDrag Detected函数，处理拖拽逻辑
@parm payload是用于传递的参数 会在On Drop函数中用到
@parm defaultdragvisual是用于拖拽时跟随的图标

c、重载On Drop函数
此时Operation中的Payload参数便是CreateDragDropOperation中的传递过来的Payload参数

8、UE4官方文档&Answer Hub
1、官方文档 :https://docs.unrealengine.com/latest/INT/
2、Answer Hub :https://answers.unrealengine.com/index.html