小贝子编程

C++Builder XE，传递和处理用户定义的消息



我正在尝试学习如何在VCL表单应用程序中传递和处理消息。我在网上搜索了一段时间，发现了这个

假设我有一个进度条，我想用消息更新(顺便说一句，如果有其他更好的方法，我很想听(所以我做了一个简单的项目来测试这些东西，下面是我所拥有的(RECEIVER是一个带有进度条的表单的名称，SENDER是一个用于发送消息的按钮，updBar是一个更新进度条的函数，123456是我想使用的消息ID(：单元1.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);
}

第一单元.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程序。但是，当我通过调试器查看它时(在使用按钮发送消息之后(，执行点似乎从来没有到达我的函数或处理程序行。提前感谢

您的代码有两个问题：

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

2( 您正在向FindWindow()传递一个错误的字符串指针。您正在将char[]类型转换为wchar_t*，这是一个无效的类型转换。要指定字符串文字应使用wchar_t而不是char，必须在文字前面加上L说明符。或者更一般地，当使用任何TCHAR敏感的API(如FindWindow()(时，请改用TEXT()宏。

此外，虽然不是严格意义上的错误，但应该使用VCL_MESSAGE_HANDLER()而不是MESSAGE_HANDLER()，因为ATL对MESSAGE_HANDLER()的定义不同。如果您在项目中不使用ATL，您不会遇到问题，但最好使用VCL_MESSAGE_HANDLER()来确保绝对正确，并记录代码使用的是MESSAGE_HANDLER()的VCL版本，而不是其他版本。

试试这个：

第一单元.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

单元1.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); 
} 
//---------------------------------------------------------------------------

话虽如此，由于消息对应用程序是私有的，因此根本不需要使用FindWindow()，而是使用TForm::Handle属性。我甚至会更进一步，完全去掉MESSAGE_HANDLER()。该消息对于TRECEIVER的内部是私有的，因此它应该留在那里：

第一单元.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

单元1.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); 
} 
//---------------------------------------------------------------------------

如果你想让你的应用程序的其他部分向Revceiver发布消息，你可以公开一个公共方法：

第一单元.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

单元1.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(); 
}

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