最简单的 UE 4 C++ 教程 —— 打印调试信息【五】

柔光的暖阳◎ 2022-08-31 14:21 15阅读 0赞

**【原教程是基于 UE 4.18，我是基于 UE 4.25】**

[英文原地址][Link 1]

接上一节，我们新创建一个名为 **ConsoleLog** 的新 Actor 子类（我们不需要在头文件中执行任何操作）。

### ConsoleLog.h ###

#pragma once
    
    #include "CoreMinimal.h"
    #include "GameFramework/Actor.h"
    #include "ConsoleLog.generated.h"
    
    UCLASS()
    class UNREALCPP_API AConsoleLog : public AActor
    {
    	GENERATED_BODY()
    	
    public:	
    	// Sets default values for this actor's properties
    	AConsoleLog();
    
    protected:
    	// Called when the game starts or when spawned
    	virtual void BeginPlay() override;
    
    public:	
    	// Called every frame
    	virtual void Tick(float DeltaTime) override;
    	
    };

接着我们将在 .cpp 文件中打印日志消息。对于这个例子，我们将在 **BeginPlay** 方法中打印该消息。所以，当游戏开始时，消息将打印出来。

下面是打印消息的三种方法。

*  打印到控制台
 *  打印到屏幕
 *  打印的数据格式为向量

分别如下所示

UE_LOG(LogTemp, Warning, TEXT("I just started running"));

GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("Screen Message"));

GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Orange, FString::Printf(TEXT("My Location is: %s"), *GetActorLocation().ToString()));

下面是完整的.cpp文件（使用宏定义可以简化打印调试信息的步骤）

// define a print message function to print to screen
    #define print(text) if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 1.5, FColor::Green,text)
    #define printFString(text, fstring) if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Magenta, FString::Printf(TEXT(text), fstring))
    #include "ConsoleLog.h"
    
    // Sets default values
    AConsoleLog::AConsoleLog()
    {
     	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
    	PrimaryActorTick.bCanEverTick = true;
    
    }
    
    // Called when the game starts or when spawned
    void AConsoleLog::BeginPlay()
    {
    	Super::BeginPlay();
    
    	// Standard way to log to console.
    	UE_LOG(LogTemp, Warning, TEXT("I just started running"));
    
    	// Log to Screen
    	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("Screen Message"));
    
    	FVector MyVector = FVector(200,100,900);
    
    	// log vector
    	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Orange, FString::Printf(TEXT("My Location is: %s"), *GetActorLocation().ToString()));
    
    	// Use the shortcut defined above
    	print("Hello Unreal");	
    	printFString("My Variable Vector is: %s", *MyVector.ToString());
    	
    }
    
    // Called every frame
    void AConsoleLog::Tick(float DeltaTime)
    {
    	Super::Tick(DeltaTime);
    
    }

执行的结果如下所示

![20210726081333655.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70][] 先打印的在下，后打印的在上

[Link 1]: https://unrealcpp.com/debug-logging/
[20210726081333655.png]: /images/20220829/66c443af0a4342afaaf200f25a972f19.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3BhbmRhMTIzNGxlZQ_size_16_color_FFFFFF_t_70]: /images/20220829/c1f00e379646441fa5bfc4c73184f156.png