[UE4]输出LOG及定义

在.h 文件中，填写如下代码：

DECLARE_LOG_CATEGORY_EXTERN(YourLog, Log, All);

在.cpp文件中，填写如下代码：

DEFINE_LOG_CATEGORY(YourLog);

输出格式如下：

（1）UE_LOG(LogTemp, Warning, TEXT("Problem on load Province Message!"));

（2）UE_LOG(LogTemp, Warning, TEXT("Content:%s"), *(Response->GetContentAsString()));

UE_LOG(CategoryName,Warning,TEXT("MyCharacter's Health is %d"), MyCharacter->Health );
UE_LOG(CategoryName,Warning,TEXT("MyCharacter's Health is %f"), MyCharacter->Health );
UE_LOG(CategoryName,Warning,TEXT("MyCharacter's Name is %s"), *MyCharacter->GetName() );

https://www.cnblogs.com/blueroses/p/6037981.html

GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Blue, TestHUDString);

GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Blue, FString::Printf(TEXT("Some variable values: x: %d, y: %d"), HitX, HitY) )

游戏模式：

在游戏模式下，你需要在游戏的快捷方式后面加 -Log，才会在游戏中显示。

编辑器模式（Play In Editor）：

你可以在Output窗口中看到log信息。

如果想在游戏中看到，需要到Engin.ini中修改参数添加"GameCommandLine=-log，如果没有，则需要按~，输入-Log命令开启。

快速使用：

UE_LOG(LogTemp, Warning, TEXT("Your message"));

不用设置标签，简单快速。

设置拥有自己标签的Log：

在你的游戏头文件中加入：

//General Log
DECLARE_LOG_CATEGORY_EXTERN(YourLog, Log, All);
 
//Logging during game startup
DECLARE_LOG_CATEGORY_EXTERN(YourInit, Log, All);
 
//Logging for your AI system
DECLARE_LOG_CATEGORY_EXTERN(YourAI, Log, All);
 
//Logging for Critical Errors that must always be addressed
DECLARE_LOG_CATEGORY_EXTERN(YourCriticalErrors, Log, All);

这样输出的Log你就可以知道是哪个部分的，这也是UE_Log很有用的原因。

在你的游戏Cpp文件中：

//General Log
DEFINE_LOG_CATEGORY(YourLog);
 
//Logging during game startup
DEFINE_LOG_CATEGORY(YourInit);
 
//Logging for your AI system
DEFINE_LOG_CATEGORY(YourAI);
 
//Logging for Critical Errors that must always be addressed
DEFINE_LOG_CATEGORY(YourCriticalErrors);

Log格式：

Log Message

//"This is a message to yourself during runtime!"
UE_LOG(YourLog,Warning,TEXT("This is a message to yourself during runtime!"));

Log an FString

 %s strings are wanted as TCHAR* by Log, so use *FString()
//"MyCharacter's Name is %s"
UE_LOG(YourLog,Warning,TEXT("MyCharacter's Name is %s"), *MyCharacter->GetName() );

Log an Int

//"MyCharacter's Health is %d"
UE_LOG(YourLog,Warning,TEXT("MyCharacter's Health is %d"), MyCharacter->Health );

Log a Float

//"MyCharacter's Health is %f"
UE_LOG(YourLog,Warning,TEXT("MyCharacter's Health is %f"), MyCharacter->Health );

Log an FVector

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

Log an FName

//"MyCharacter's FName is %s"
UE_LOG(YourLog,Warning,TEXT("MyCharacter's FName is %s"), 
    *MyCharacter->GetFName().ToString());

Log an FString,Int,Float

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

Log的颜色设置：

//"this is Grey Text"
UE_LOG(YourLog,Log,TEXT("This is grey text!"));
//"this is Yellow Text"
UE_LOG(YourLog,Warning,TEXT("This is yellow text!"));
//"This is Red Text"
UE_LOG(YourLog,Error,TEXT("This is red text!"));

可以看得出第二个参数是是用来控制颜色的。

传递客户端信息（网络模式）：

PlayerController->ClientMessage("Your Message");

命令行命令以及Engine.ini配置：

Log conventions (in the console, ini files, or environment variables)

[cat] = a category for the command to operate on, or 'global' for all categories.
标签，没有设置就显示所有的Log
[level] = verbosity level, one of: none, error, warning, display, log, verbose, all, default
关卡，显示某某关卡的Log

At boot time, compiled in default is overridden by ini files setting, which is overridden by command line

Log console command usage

Log list - list all log categories
Log list [string] - list all log categories containing a substring
Log reset - reset all log categories to their boot-time default
Log [cat] - toggle the display of the category [cat]
Log [cat] off - disable display of the category [cat]
Log [cat] on - resume display of the category [cat]
Log [cat] [level] - set the verbosity level of the category [cat]
Log [cat] break - toggle the debug break on display of the category [cat]

Log command line

-LogCmds=\"[arguments],[arguments]...\"           - applies a list of console commands at boot time
-LogCmds=\"foo verbose, bar off\"         - turns on the foo category and turns off the bar category

Environment variables

Any command line option can be set via the environment variable UE-CmdLineArgs

set UE-CmdLineArgs=\"-LogCmds=foo verbose breakon, bar off\"

Config file

In DefaultEngine.ini or Engine.ini:

[Core.Log]
global=[default verbosity for things not listed later]
[cat]=[level]
foo=verbose break

/**
* A macro to declare a logging category as a C++ "extern"
* @param CategoryName, category to declare
* @param DefaultVerbosity, default run time verbosity
* @param CompileTimeVerbosity, maximum verbosity to compile into the code
**/
#define DECLARE_LOG_CATEGORY_EXTERN(CategoryName, DefaultVerbosity, CompileTimeVerbosity)
externstructFLogCategory##CategoryName : public FLogCategory<ELogVerbosity::DefaultVerbosity, ELogVerbosity::CompileTimeVerbosity>
{
FORCEINLINEFLogCategory##CategoryName() : FLogCategory(TEXT(#CategoryName)) {}
}CategoryName;

/**
* A macro to define a logging category, usually paired with DECLARE_LOG_CATEGORY_EXTERN from the header.
* @param CategoryName, category to define
**/
#define DEFINE_LOG_CATEGORY(CategoryName) FLogCategory##CategoryName CategoryName;

/**
* A macro to define a logging category as a C++ "static"
* @param CategoryName, category to declare
* @param DefaultVerbosity, default run time verbosity
* @param CompileTimeVerbosity, maximum verbosity to compile into the code
**/
#define DEFINE_LOG_CATEGORY_STATIC(CategoryName, DefaultVerbosity, CompileTimeVerbosity)
staticstructFLogCategory##CategoryName : public FLogCategory<ELogVerbosity::DefaultVerbosity, ELogVerbosity::CompileTimeVerbosity>
{
FORCEINLINEFLogCategory##CategoryName() : FLogCategory(TEXT(#CategoryName)) {}
}CategoryName;

/**
* A macro to declare a logging category as a C++ "class static"
* @param CategoryName, category to declare
* @param DefaultVerbosity, default run time verbosity
* @param CompileTimeVerbosity, maximum verbosity to compile into the code
**/
#define DECLARE_LOG_CATEGORY_CLASS(CategoryName, DefaultVerbosity, CompileTimeVerbosity)
DEFINE_LOG_CATEGORY_STATIC(CategoryName,DefaultVerbosity,CompileTimeVerbosity)

/**
* A macro to define a logging category, usually paired with DECLARE_LOG_CATEGORY_CLASS from the header.
* @param CategoryName, category to definee
**/
#define DEFINE_LOG_CATEGORY_CLASS(Class, CategoryName) Class::FLogCategory##CategoryName Class::CategoryName;

namespaceELogVerbosity
{
enumType
{
/** Not used */
NoLogging=0,

/** Always prints s fatal error to console (and log file) and crashes (even if logging is disabled) */
Fatal,

/**
* Prints an error to console (and log file).
* Commandlets and the editor collect and report errors. Error messages result in commandlet failure.
*/
Error,

/**
* Prints a warning to console (and log file).
* Commandlets and the editor collect and report warnings. Warnings can be treated as an error.
*/
Warning,

/** Prints a message to console (and log file) */
Display,

/** Prints a message to a log file (does not print to console) */
Log,

/**
* Prints a verbose message to a log file (if Verbose logging is enabled for the given category,
* usually used for detailed logging)
*/
Verbose,

/**
* Prints a verbose message to a log file (if VeryVerbose logging is enabled,
* usually used for detailed logging that would otherwise spam output)
*/
VeryVerbose,

// Log masks and special Enum values

All=VeryVerbose,
NumVerbosity,
VerbosityMask=0xf,
SetColor=0x40,// not actually a verbosity, used to set the color of an output device
BreakOnLog=0x80
};
}

https://wiki.unrealengine.com/index.php?title=Logs,_Printing_Class_Name,_Function_Name,_Line_Number_of_your_Calling_Code!