基于QGC4.1.2版本进行添加，首先由于QGC的原来对FactGroup定义均写在Vehicle.h和Vehicle.cc两个文件中，个人感觉都写在Vehicle文件下回导致文件过大，所以将FactGroup定义进行分离，写在各自的.h和.cc文件下，然后在Vehicle中include。

进入正题，添加自定义的FactGroup有一下几步（以VehicleGPSFactGroup为例）：

1. 新建.h文件然后定义FactGroup类

#pragma once#include "FactGroup.h"
#include "QGCMAVLink.h"class VehicleGPSFactGroup : public FactGroup
{Q_OBJECTpublic:VehicleGPSFactGroup(QObject* parent = nullptr);Q_PROPERTY(Fact* lat                READ lat                CONSTANT)Q_PROPERTY(Fact* lon                READ lon                CONSTANT)Q_PROPERTY(Fact* mgrs               READ mgrs               CONSTANT)Q_PROPERTY(Fact* hdop               READ hdop               CONSTANT)Q_PROPERTY(Fact* vdop               READ vdop               CONSTANT)Q_PROPERTY(Fact* courseOverGround   READ courseOverGround   CONSTANT)Q_PROPERTY(Fact* count              READ count              CONSTANT)Q_PROPERTY(Fact* lock               READ lock               CONSTANT)Fact* lat               () { return &_latFact; }Fact* lon               () { return &_lonFact; }Fact* mgrs              () { return &_mgrsFact; }Fact* hdop              () { return &_hdopFact; }Fact* vdop              () { return &_vdopFact; }Fact* courseOverGround  () { return &_courseOverGroundFact; }Fact* count             () { return &_countFact; }Fact* lock              () { return &_lockFact; }static const char* _latFactName;static const char* _lonFactName;static const char* _mgrsFactName;static const char* _hdopFactName;static const char* _vdopFactName;static const char* _courseOverGroundFactName;static const char* _countFactName;static const char* _lockFactName;private:Fact        _latFact;Fact        _lonFact;Fact        _mgrsFact;Fact        _hdopFact;Fact        _vdopFact;Fact        _courseOverGroundFact;Fact        _countFact;Fact        _lockFact;
};

2. 新建.cc文件，进行类的初始化（不太确定这个是不是叫初始化）

#include "VehicleGPSFactGroup.h"const char* VehicleGPSFactGroup::_latFactName =                 "lat";
const char* VehicleGPSFactGroup::_lonFactName =                 "lon";
const char* VehicleGPSFactGroup::_mgrsFactName =                "mgrs";
const char* VehicleGPSFactGroup::_hdopFactName =                "hdop";
const char* VehicleGPSFactGroup::_vdopFactName =                "vdop";
const char* VehicleGPSFactGroup::_courseOverGroundFactName =    "courseOverGround";
const char* VehicleGPSFactGroup::_countFactName =               "count";
const char* VehicleGPSFactGroup::_lockFactName =                "lock";VehicleGPSFactGroup::VehicleGPSFactGroup(QObject* parent): FactGroup(1000, ":/json/Vehicle/GPSFact.json", parent), _latFact              (0, _latFactName,               FactMetaData::valueTypeDouble), _lonFact              (0, _lonFactName,               FactMetaData::valueTypeDouble), _mgrsFact             (0, _mgrsFactName,              FactMetaData::valueTypeString), _hdopFact             (0, _hdopFactName,              FactMetaData::valueTypeDouble), _vdopFact             (0, _vdopFactName,              FactMetaData::valueTypeDouble), _courseOverGroundFact (0, _courseOverGroundFactName,  FactMetaData::valueTypeDouble), _countFact            (0, _countFactName,             FactMetaData::valueTypeInt32), _lockFact             (0, _lockFactName,              FactMetaData::valueTypeInt32)
{_addFact(&_latFact,                 _latFactName);_addFact(&_lonFact,                 _lonFactName);_addFact(&_mgrsFact,                _mgrsFactName);_addFact(&_hdopFact,                _hdopFactName);_addFact(&_vdopFact,                _vdopFactName);_addFact(&_courseOverGroundFact,    _courseOverGroundFactName);_addFact(&_lockFact,                _lockFactName);_addFact(&_countFact,               _countFactName);_latFact.setRawValue(std::numeric_limits::quiet_NaN());_lonFact.setRawValue(std::numeric_limits::quiet_NaN());_mgrsFact.setRawValue("");_hdopFact.setRawValue(std::numeric_limits::quiet_NaN());_vdopFact.setRawValue(std::numeric_limits::quiet_NaN());_courseOverGroundFact.setRawValue(std::numeric_limits::quiet_NaN());
}

3. 添加对应的json文件，这一步有点问题，需要手动修改qgroundcontrol.qrc文件中文件别名

[
{"name":             "lat","shortDescription": "Latitude","type":             "double","decimalPlaces":    7
},
{"name":             "lon","shortDescription": "Longitude","type":             "double","decimalPlaces":    7
},
{"name":             "mgrs","shortDescription": "MGRS Position","type":             "string"
},
{"name":             "hdop","shortDescription": "HDOP","type":             "double","decimalPlaces":    1
},
{"name":             "vdop","shortDescription": "VDOP","type":             "double","decimalPlaces":    1
},
{"name":             "courseOverGround","shortDescription": "Course Over Ground","type":             "double","decimalPlaces":    1,"units":            "deg"
},
{"name":             "lock","shortDescription": "GPS Lock","type":             "uint32","enumStrings":      "None,None,2D Lock,3D Lock,3D DGPS Lock,3D RTK GPS Lock (float),3D RTK GPS Lock (fixed),Static (fixed)","enumValues":       "0,1,2,3,4,5,6,7","decimalPlaces":    0
},
{"name":             "count","shortDescription": "Sat Count","type":             "uint32"
}
]

4. 在CMakeList.txt文件中添加新建的类文件，文件路径：qgroundcontrol\src\Vehicle

以上准备好之后开始在Vehicle.h和Vehicle.cc中添加FactGroup

5. 在Vehicle.h文件中include FactGroup.h

6. 在Vehicle.h文件中声明FactGroup

7. 在Vehicle.h文件中添加FactGrounp对应的Q_PROPERTY，在qml读取数据使用

8. 在Vehicle.h文件中定义Q_PROPERTY对应的READ 函数

9. 在Vehicle.h中定义FactGroup对应的FactGroupName

10. 在Vehicle.cc中初始化FactGroupName

11. 在Vehicle.cc中Vehicle类初始化部分添加FactGroup

12. 在Vehicle.cc中_commonInit函数中添加_addFactGroup()

13. 对FactGroup成员赋值

完成以上内容后即完成了FactGroup 的添加，就可以在显示页面进行数据显示了。同时添加FactGroup后程序会将数据保存，和其他FactGroup存储在csv中。