Unreal Engine 4：学习笔记（四）字符串处理及日志显示

男娘i 2022-05-20 07:53 31阅读 0赞

FString类是由存放TCHAR的TArray构成的。TCHAR是unicode编码的。

FString class is built upon a TArray of TCHARs. TCHAR (native Unicode encoding).

设置字面量时要用TEXT()，它会将ANSI的字面量转换成TCHAR。例如：

FString txt = TEXT("中国人");

**std::string to FString**

// uft8编码的string
    std::string str_uft8 = u8"中国人";
    FString txt = UTF8_TO_TCHAR(str_uft8.c_str());

// 若只含ASCII
    std::string TestString = "Happy";
    FString HappyString(TestString.c_str());

**FString to std::string**

FString txt = TEXT("中国人");
    
    // uft8编码的string
    std::string str_uft8 = TCHAR_TO_UTF8(*txt);

**FString to std::wstring**

FString txt = TEXT("中国人");
    std::wstring ws = txt.GetCharArray().GetData();

**std::wstring to FString**

std::wstring ws = L"中国人";
    FString txt(ws.c_str());

**To FString**

// float
    FString::SanitizeFloat(FloatVariable);
    // int
    FString::FromInt(IntVariable);
    // bool
    InBool ? TEXT("true") : TEXT("false");
    // FVector
    VectorVariable.ToString();
    // FVector2D
    Vector2DVariable.ToString();
    // FRotator
    RotatorVariable.ToString();
    // FLinearColor
    LinearColorVariable.ToString();
    // UObject
    (InObj != NULL) ? InObj->GetName() : FString(TEXT("None"));
    // FName
    TestHUDString = TestHUDName.ToString();
    // FText
    TestHUDString = TestHUDText.ToString(); 
    // int64
    FString::Printf(TEXT("%lld"), int64_val);
    // uint64
    FString::Printf(TEXT("%llu"), uint64_val);

**From FString**

// bool
    TestHUDString.ToBool();
    // int
    FCString::Atoi(*TestHUDString);
    // float
    FCString::Atof(*TestHUDString);
    // FName
    TestHUDName = FName(*TestHUDString);
    // FText
    TestHUDText = FText::FromString(TestHUDString);
    // int64
    FCString::Atoi64(*TestHUDString);

**Print to Canvas**

FCanvas::DrawText()
    Canvas->DrawText(BigFont, TestHUDString, 110.0f,110.0f);

**Print to Viewport**

// UEngine::AddOnScreenDebugMessage(int Key, float TimeToDisplay, FColor DisplayColor, FString DebugMessage)
    GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Blue, TestHUDString);

**Print to Output Log**

UE_LOG(CategoryName, Verbosity, Format, ...);

全局可用的LogCategory可以在如下文件中找到：  
UE\_4.18\\Engine\\Source\\Runtime\\Core\\Public\\CoreGlobals.h  
UE\_4.18\\Engine\\Source\\Runtime\\Core\\Private\\Misc\\CoreGlobals.cpp

其中定义的全局LogCategory为：

LogHAL
    LogMac
    LogLinux
    LogIOS
    LogAndroid
    LogPS4
    LogXboxOne
    LogWindows
    LogSwitch
    LogSerialization
    LogUnrealMath
    LogUnrealMatrix
    LogContentComparisonCommandlet
    LogNetPackageMap
    LogNetSerialization
    LogMemory
    LogProfilingDebugging
    LogCore
    LogOutputDevice
    LogSHA
    LogStats
    LogStreaming
    LogInit
    LogExit
    LogExec
    LogScript
    LogLocalization
    LogLongPackageNames
    LogProcess
    LogLoad
    LogTemp

如果要声明并定义全局LogCategory，可以使用DECLARE\_LOG\_CATEGORY\_EXTERN来声明，使用DEFINE\_LOG\_CATEGORY定义。  
如果只声明并定义单个文件使用的LogCategory，只需在源码中使用DEFINE\_LOG\_CATEGORY\_STATIC来定义。  
  
DECLARE\_LOG\_CATEGORY\_EXTERN  
DEFINE\_LOG\_CATEGORY  
DEFINE\_LOG\_CATEGORY\_STATIC  
这三个宏的定义可以在如下文件中找到：  
UE\_4.18\\Engine\\Source\\Runtime\\Core\\Public\\Logging\\LogMacros.h  
  
LogVerbosity is the verbosity level

enum ELogVerbosity {
    Fatal, Error, Warning, Display, Log, Verbose, VeryVerbose
    }

Log an FString,Int,Float

UE_LOG(YourLog,Warning,TEXT("%s has health %d, which is %f percent of total health"), 
    *MyCharacter->GetName(), MyCharacter->Health, MyCharacter->HealthPercent);

Log an FVector

UE_LOG(YourLog,Warning,TEXT("MyCharacter's Location is %s"), *MyCharacter->GetActorLocation().ToString());