C++ Builder XE，传递和处理用户定义的消息

Question

我想了解如何传递和处理VCL表单应用程序中的消息。 我已经挖上网一段时间后，发现this

假设我有一个进度条，我想用消息（顺便说一句，如果有任何其他更好的办法，我渴望听到它）来更新 所以我做了一个简单的项目来测试这些东西，这里是我的东西（RECEIVER是一个带有进度条的表单的名称，SENDER是用来发送消息的按钮，updBar是一个更新进度条的函数，123456是我想要的消息ID使用）： Unit1.cpp：

#include <vcl.h> 
#pragma hdrstop 

#include "Unit1.h" 
//--------------------------------------------------------------------------- 
#pragma package(smart_init) 
#pragma resource "*.dfm" 
TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
__fastcall TRECIEVER::TRECIEVER(TComponent* Owner) 
    : TForm(Owner) 
{ 
} 
void __fastcall TRECIEVER::barUPD(TMessage& msg){ 
    BAR->StepIt(); 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::SENDERClick(TObject *Sender) 
{ 
//BAR->StepIt(); 
PostMessage(FindWindow(0,(wchar_t*)"RECIEVER"),123456,0,0); 
} 

Unit1.h：

#ifndef Unit1H 
#define Unit1H 
//--------------------------------------------------------------------------- 
#include <System.Classes.hpp> 
#include <Vcl.Controls.hpp> 
#include <Vcl.StdCtrls.hpp> 
#include <Vcl.Forms.hpp> 
#include <Vcl.ComCtrls.hpp> 
//--------------------------------------------------------------------------- 
class TRECIEVER : public TForm 
{ 
__published: // IDE-managed Components 
    TButton *SENDER; 
    TProgressBar *BAR; 
    void __fastcall SENDERClick(TObject *Sender); 
private: // User declarations 
public:  // User declarations 
    void __fastcall barUPD(TMessage& msg); 
    __fastcall TRECIEVER(TComponent* Owner); 
    BEGIN_MESSAGE_MAP 
    MESSAGE_HANDLER(123456,TMessage,barUPD); 
    END_MESSAGE_MAP(TForm) 
}; 
//--------------------------------------------------------------------------- 
extern PACKAGE TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
#endif 

正如您所看到的，我已经为我的消息定义了处理函数和适当的消息处理函数。但是当我通过调试器查看它时（使用按钮发送消息之后），执行点似乎永远不会去我的函数和处理程序行。 预先感谢

Answer 1

有两个问题与您的代码：

1）123456（0x1E240）不是有效的用户级消息ID。操作系统保留0xFFFF以上的值。自定义消息必须在WM_USER（0x0400-0x7FFF），WM_APP（0x8000-0xBFFF）或RegisterWindowMessage()（0xC000-0xFFFF）范围内。

2）你传递一个坏字符串指针到FindWindow()。您正在将char[]转换为wchar_t*，这是一种无效的类型转换。要指定字符串文字应该使用wchar_t而不是char，则必须改为在L修饰符前加上文字。或者更一般地说，当使用任何TCHAR敏感API（如FindWindow()）时，请使用TEXT()宏。

另外，虽然不是严格的错误，但应该用VCL_MESSAGE_HANDLER()而不是MESSAGE_HANDLER()，这是因为MESSAGE_HANDLER()的定义与ATL不同。如果您的项目中没有使用ATL，则不会遇到问题，但使用VCL_MESSAGE_HANDLER()只是为了确保绝对安全，并且要记录代码使用的是VCL的版本MESSAGE_HANDLER()而不是其他版本。

试试这个：

Unit1.h：

#ifndef Unit1H 
#define Unit1H 
//--------------------------------------------------------------------------- 
#include <System.Classes.hpp> 
#include <Vcl.Controls.hpp> 
#include <Vcl.StdCtrls.hpp> 
#include <Vcl.Forms.hpp> 
#include <Vcl.ComCtrls.hpp> 
//--------------------------------------------------------------------------- 
#define WM_BAR_STEP_IT (WM_USER+1) 
//--------------------------------------------------------------------------- 
class TRECIEVER : public TForm 
{ 
__published: // IDE-managed Components 
    TButton *SENDER; 
    TProgressBar *BAR; 
    void __fastcall SENDERClick(TObject *Sender); 
private: // User declarations 
    void __fastcall barUPD(TMessage&); 
public:  // User declarations 
    __fastcall TRECIEVER(TComponent* Owner); 
    BEGIN_MESSAGE_MAP 
     VCL_MESSAGE_HANDLER(WM_BAR_STEP_IT, TMessage, barUPD); 
    END_MESSAGE_MAP(TForm) 
}; 
//--------------------------------------------------------------------------- 
extern PACKAGE TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
#endif 

Unit1.cpp：

#include <vcl.h> 
#pragma hdrstop 

#include "Unit1.h" 
//--------------------------------------------------------------------------- 
#pragma package(smart_init) 
#pragma resource "*.dfm" 
TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
__fastcall TRECIEVER::TRECIEVER(TComponent* Owner) 
    : TForm(Owner) 
{ 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::barUPD(TMessage&) 
{ 
    BAR->StepIt(); 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::SENDERClick(TObject *Sender) 
{ 
    // this assumes the Form's Caption is set to "RECEIVER" 
    // also specifying the class type for good measure... 
    PostMessage(FindWindow(TEXT("TRECEIVER"), TEXT("RECIEVER")), WM_BAR_STEP_IT, 0, 0); 

    //Alternatively: 
    //PostMessage(FindWindowW(ClassName().c_str(), Caption.c_str()), WM_BAR_STEP_IT, 0, 0); 
} 
//--------------------------------------------------------------------------- 

虽这么说，因为消息是私有的应用程序，也没有必要根本不使用FindWindow()，而是使用TForm::Handle属性。我甚至会更进一步，完全摆脱MESSAGE_HANDLER()。该消息是私有的TRECEIVER的内部，所以这是它应该呆在：

Unit1.h：

#ifndef Unit1H 
#define Unit1H 
//--------------------------------------------------------------------------- 
#include <System.Classes.hpp> 
#include <Vcl.Controls.hpp> 
#include <Vcl.StdCtrls.hpp> 
#include <Vcl.Forms.hpp> 
#include <Vcl.ComCtrls.hpp> 
//--------------------------------------------------------------------------- 
class TRECIEVER : public TForm 
{ 
__published: // IDE-managed Components 
    TButton *SENDER; 
    TProgressBar *BAR; 
    void __fastcall SENDERClick(TObject *Sender); 
private: // User declarations 
protected: 
    void __fastcall WndProc(TMessage& Message); 
public:  // User declarations 
    __fastcall TRECIEVER(TComponent* Owner); 
}; 
//--------------------------------------------------------------------------- 
extern PACKAGE TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
#endif 

1单元。CPP：

#include <vcl.h> 
#pragma hdrstop 

#include "Unit1.h" 
//--------------------------------------------------------------------------- 
#pragma package(smart_init) 
#pragma resource "*.dfm" 
TRECIEVER *RECIEVER; 
#define WM_BAR_STEP_IT (WM_USER+1) 
//--------------------------------------------------------------------------- 
__fastcall TRECIEVER::TRECIEVER(TComponent* Owner) 
    : TForm(Owner) 
{ 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::WndProc(TMessage& Message) 
{ 
    if (Message.Msg == WM_BAR_STEP_IT) 
     BAR->StepIt(); 
    else 
     TForm::WndProc(Message); 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::SENDERClick(TObject *Sender) 
{ 
    PostMessage(Handle, WM_BAR_STEP_IT, 0, 0); 
} 
//--------------------------------------------------------------------------- 

如果你想其他部分你的应用程序的发布消息到Revceiver，你会暴露为一个公共方法：

Unit1.h：

#ifndef Unit1H 
#define Unit1H 
//--------------------------------------------------------------------------- 
#include <System.Classes.hpp> 
#include <Vcl.Controls.hpp> 
#include <Vcl.StdCtrls.hpp> 
#include <Vcl.Forms.hpp> 
#include <Vcl.ComCtrls.hpp> 
//--------------------------------------------------------------------------- 
class TRECIEVER : public TForm 
{ 
__published: // IDE-managed Components 
    TButton *SENDER; 
    TProgressBar *BAR; 
    void __fastcall SENDERClick(TObject *Sender); 
private: // User declarations 
protected: 
    void __fastcall WndProc(TMessage& Message); 
public:  // User declarations 
    __fastcall TRECIEVER(TComponent* Owner); 
    void __fastcall PostBarStepIt(); 
}; 
//--------------------------------------------------------------------------- 
extern PACKAGE TRECIEVER *RECIEVER; 
//--------------------------------------------------------------------------- 
#endif 

1单元。 CPP：

#include <vcl.h> 
#pragma hdrstop 

#include "Unit1.h" 
//--------------------------------------------------------------------------- 
#pragma package(smart_init) 
#pragma resource "*.dfm" 
TRECIEVER *RECIEVER; 
#define WM_BAR_STEP_IT (WM_USER+1) 
//--------------------------------------------------------------------------- 
__fastcall TRECIEVER::TRECIEVER(TComponent* Owner) 
    : TForm(Owner) 
{ 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::WndProc(TMessage& Message) 
{ 
    if (Message.Msg == WM_BAR_STEP_IT) 
     BAR->StepIt(); 
    else 
     TForm::WndProc(Message); 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::SENDERClick(TObject *Sender) 
{ 
    PostBarStepIt(); 
} 
//--------------------------------------------------------------------------- 
void __fastcall TRECIEVER::PostBarStepIt() 
{ 
    PostMessage(Handle, WM_BAR_STEP_IT, 0, 0); 
} 
//--------------------------------------------------------------------------- 

SomeOtherFile.cpp：

#include "Unit1.h" 

void __fastcall TSomeOtherClass::SomeMethod() 
{ 
    RECIEVER->PostBarStepIt(); 
}