如何在Unreal C++中解析Pandas DataFrame输出的JSON格式字符串

前置依赖配置 #

首先打开项目的.Build.cs文件，在公共依赖模块中新增Json模块，示例如下：

PublicDependencyModuleNames.AddRange(new string[] 
{ 
    "Core", 
    "CoreUObject", 
    "Engine", 
    "InputCore", 
    "HTTP", // 你已有的HTTP模块
    "Json"  // 新增JSON解析模块
});

1. 修改HttpActor.h头文件 #

新增JSON相关头文件引用，可自定义3D点存储结构体方便后续使用：

#pragma once

#include "GameFramework/Actor.h"
#include "Runtime/Online/HTTP/Public/Http.h"
#include "Dom/JsonObject.h" // 新增JSON对象头
#include "CoreMinimal.h"
#include "HttpActor.generated.h"

// 自定义3D标注点结构体，可选定义
USTRUCT(BlueprintType)
struct F3DLabeledPoint
{
    GENERATED_BODY()

    UPROPERTY(BlueprintReadWrite, Category = "3D Point")
    double X;
    UPROPERTY(BlueprintReadWrite, Category = "3D Point")
    double Y;
    UPROPERTY(BlueprintReadWrite, Category = "3D Point")
    double Z;
    UPROPERTY(BlueprintReadWrite, Category = "3D Point")
    int32 Label;
    UPROPERTY(BlueprintReadWrite, Category = "3D Point")
    FString PointId;
};

UCLASS()
class UE4CPPEXAMPLE_API AHttpActor : public AActor
{
    GENERATED_BODY()
    
public: 
    AHttpActor(const class FObjectInitializer& ObjectInitializer);

    virtual void BeginPlay() override;

    FHttpModule* Http;

    void OnResponseReceived(FHttpRequestPtr Request, FHttpResponsePtr Response, bool bWasSuccessful);
};

2. 修改HttpActor.cpp的OnResponseReceived实现 #

直接对应你给出的Python逻辑实现解析遍历：

#include "UE4CPPExample.h"
#include "HttpActor.h"
#include "Templates/SharedPointer.h"
#include "Serialization/JsonReader.h" // 新增JSON读取头
#include "Serialization/JsonSerializer.h" // 新增JSON序列化头

// 原有构造函数、BeginPlay代码不变，仅修改OnResponseReceived
void AHttpActor::OnResponseReceived(
    FHttpRequestPtr Request,
    FHttpResponsePtr Response,
    bool bWasSuccessful
){
    // 先判断请求是否成功、响应是否有效
    if (!bWasSuccessful || !Response.IsValid() || Response->GetResponseCode() != 200)
    {
        GEngine->AddOnScreenDebugMessage(1, 2.0f, FColor::Red, TEXT("请求失败"));
        return;
    }

    FString ResponseStr = Response->GetContentAsString();

    // 解析JSON字符串，对应Python的json.loads
    TSharedPtr<FJsonObject> RootJsonObject;
    TSharedRef<TJsonReader<>> Reader = TJsonReaderFactory<>::Create(ResponseStr);
    if (!FJsonSerializer::Deserialize(Reader, RootJsonObject) || !RootJsonObject.IsValid())
    {
        GEngine->AddOnScreenDebugMessage(1, 2.0f, FColor::Red, TEXT("JSON解析失败"));
        return;
    }

    // 分别取出x/y/z/label四个二级对象
    TSharedPtr<FJsonObject> XObject = RootJsonObject->GetObjectField(TEXT("x"));
    TSharedPtr<FJsonObject> YObject = RootJsonObject->GetObjectField(TEXT("y"));
    TSharedPtr<FJsonObject> ZObject = RootJsonObject->GetObjectField(TEXT("z"));
    TSharedPtr<FJsonObject> LabelObject = RootJsonObject->GetObjectField(TEXT("label"));

    // 校验四个对象是否都存在
    if (!XObject.IsValid() || !YObject.IsValid() || !ZObject.IsValid() || !LabelObject.IsValid())
    {
        GEngine->AddOnScreenDebugMessage(1, 2.0f, FColor::Red, TEXT("JSON格式不符合预期"));
        return;
    }

    // 遍历x的所有键，对应Python的for key in data_dictionary['x'].keys()
    TArray<FString> PointIds;
    XObject->Values.GetKeys(PointIds);
    for (const FString& PointId : PointIds)
    {
        // 取出对应字段的值
        double X = XObject->GetNumberField(PointId);
        double Y = YObject->GetNumberField(PointId);
        double Z = ZObject->GetNumberField(PointId);
        int32 Label = LabelObject->GetIntegerField(PointId);

        // 输出到屏幕，对应Python的print
        FString PointInfo = FString::Printf(TEXT("点ID:%s | X:%.6f | Y:%.6f | Z:%.6f | 标签:%d"), 
            *PointId, X, Y, Z, Label);
        GEngine->AddOnScreenDebugMessage(-1, 5.0f, FColor::Green, PointInfo);

        // 也可以存入结构体数组供后续使用
        // F3DLabeledPoint NewPoint;
        // NewPoint.PointId = PointId;
        // NewPoint.X = X;
        // NewPoint.Y = Y;
        // NewPoint.Z = Z;
        // NewPoint.Label = Label;
        // PointArray.Add(NewPoint);
    }
}

内容的提问来源于stack exchange，提问作者Bengt