c++ - 使用带有 wxEvtHandler::Bind 的模板自定义 wxEvent

Question

在下面的代码中，我执行以下操作:

• 我创建了一个新的模板 wxCommandEvent 类，它包含模板指定的一些有效载荷。
• 然后我继承了一个 wxStringPayloadEvent 类。
• 最后，我创建了一个示例应用程序，它只发出一个 wxStringPayloadEvent，然后事件处理程序被触发并在屏幕上的消息框中显示负载。

如果我使用稍微过时的 wxEvtHandler::Connect 方法(正如我在下面评论的那样)，那么一切正常。但是如果我使用 wxEvtHandler::Bind 方法，我会收到一系列非常神秘的错误消息(在代码之后发布)。

因为 Bind 允许更多的自由并且更容易使用(它不需要创建笨拙的宏)，所以我想使用它而不是 Connect ...有什么想法吗？

代码如下:

#include <wx/wx.h>

//Creating my own custom event which will hold a payload of some templated type
template <class Payload_type>
class TemplatedPayloadEvent : public wxCommandEvent
{
public:
 TemplatedPayloadEvent(){}
 TemplatedPayloadEvent(wxEventType eventType) : wxCommandEvent(eventType){}

 TemplatedPayloadEvent(const TemplatedPayloadEvent& event)
 : wxCommandEvent(event)  
 {
  this->mPayload = event.mPayload;
 }

 virtual TemplatedPayloadEvent* Clone() const {return new TemplatedPayloadEvent(*this);}

 void setPayload(Payload_type payload) {mPayload = payload;}
 Payload_type getPayload() {return mPayload;}

private:
 Payload_type mPayload;
};


//instantiating new event along with associated elements
class wxStringPayloadEvent : public TemplatedPayloadEvent<wxString>
{
public:
 wxStringPayloadEvent() : TemplatedPayloadEvent<wxString>(wxEVT_STRING_PAYLOAD){};
};
typedef void (wxEvtHandler::*wxStringPayloadEventFunction)(wxStringPayloadEvent&);
#define wxStringPayloadEventHandler(func) \
 (wxObjectEventFunction)(wxEventFunction)(wxCommandEventFunction)\
 wxStaticCastEvent(wxStringPayloadEventFunction, &func)
const wxEventType wxEVT_STRING_PAYLOAD = wxNewEventType();


//implementing test application
class MyApp : public wxApp
{
public:
 virtual bool OnInit();
 void OnProcessCustom(wxStringPayloadEvent& event);
};

bool
MyApp::OnInit()
{
 //Connect event
 //Connect(wxEVT_STRING_PAYLOAD, wxStringPayloadEventHandler(MyApp::OnProcessCustom));
 Bind(wxEVT_STRING_PAYLOAD, &MyApp::OnProcessCustom, this);///< wish I could use this

    wxStringPayloadEvent eventCustom;
 eventCustom.SetEventObject(this);
 eventCustom.setPayload(wxT("Test payload."));
 wxPostEvent(this, eventCustom);

 return true;
}

void MyApp::OnProcessCustom(wxStringPayloadEvent& event)
{
 wxMessageBox(wxT("Event received.  Payload = \"") + event.getPayload() + wxT("\""));
}

IMPLEMENT_APP(MyApp);

这是错误信息:

/ThirdParty/Includes/wx/event.h: In constructor 'wxEventFunctorMethod<EventTag, Class, EventArg, EventHandler>::wxEventFunctorMethod(void (Class::*)(EventArg&), EventHandler*) [with EventTag = int, Class = MyApp, EventArg = wxStringPayloadEvent, EventHandler = MyApp]':
/ThirdParty/Includes/wx/event.h:587:   instantiated from 'wxEventFunctorMethod<EventTag, Class, EventArg, EventHandler>* wxNewEventFunctor(const EventTag&, void (Class::*)(EventArg&), EventHandler*) [with EventTag = int, Class = MyApp, EventArg = wxStringPayloadEvent, EventHandler = MyApp]'
/ThirdParty/Includes/wx/event.h:3182:   instantiated from 'void wxEvtHandler::Bind(const EventTag&, void (Class::*)(EventArg&), EventHandler*, int, int, wxObject*) [with EventTag = wxEventType, Class = MyApp, EventArg = wxStringPayloadEvent, EventHandler = MyApp]'
../src/program.cpp:29:   instantiated from here
/ThirdParty/Includes/wx/event.h:382: error: invalid conversion from 'wxEvent*' to 'wxStringPayloadEvent*'
/ThirdParty/Includes/wx/event.h:382: error:   initializing argument 1 of 'static void wxEventFunctorMethod<EventTag, Class, EventArg, EventHandler>::CheckHandlerArgument(EventArg*) [with EventTag = int, Class = MyApp, EventArg = wxStringPayloadEvent, EventHandler = MyApp]'

---

更新更多线索:

• This might be a clue,但我的 C++ 仍然不够好，无法确定。
• 查看 event.h:382 我发现以下注释:

if you get an error here it means that the signature of the handler you're trying to use is not compatible with (i.e. is not the same as or a base class of) the real event class used for this event type

Answer 1

这可能是应该记录的内容，但据我所知，当您使用 Bind() 时，您不能仅使用“const wxEventType ...”来声明您的事件类型。 Bind() 需要使用 wxDEFINE_EVENT() 时提供的事件类型类。因此，您实际上需要在此处进行一些更改。

1) 使用它来定义您的事件类型(替换“const wxEventType ...”):

wxDEFINE_EVENT(wxEVT_STRING_PAYLOAD, wxStringPayloadEvent);

2) 显然需要在 wxStringPayloadEvent 定义之后完成上述操作，因此您的 wxStringPayloadEvent 构造函数不能仅默认为您的自定义事件类型。所以这里是 wxStringPayloadEvent 的构造函数应该看起来更像:

wxStringPayloadEvent() : TemplatedPayloadEvent<wxString>(){};
wxStringPayloadEvent(wxEventType eventType) : TemplatedPayloadEvent<wxString>(eventType){};

3) 因为你不能默认你的事件类型，你需要在你的自定义事件对象构造中指定它:

wxStringPayloadEvent eventCustom(wxEVT_STRING_PAYLOAD);

我已经用 SVN trunk 测试了这些变化，它似乎工作得很好。