Question

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。我已经挖了一段时间互联网，发现this

假设我有一个进度条我想用消息更新（顺便说两句，如果还有其他更好的方式，我很想听到它）所以我做了一个简单的项目来测试这些东西，这就是我所拥有的（RECEIVER是带有进度条的表单的名称，SENDER是用于发送消息的按钮，updBar是用于更新进度条的函数，123456是一条消息ID我想用）： 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程序。但是当我通过调试器查看它（在使用按钮发送消息之后）时，执行点似乎永远不会转到我的函数和处理程序行。提前致谢

Answer 1

您的代码存在两个问题：

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

2）您将错误的字符串指针传递给FindWindow()。您正在将char[]压缩为wchar_t*，这是一种无效的类型转换。要指定字符串文字应使用wchar_t而不是char，您必须在文字前面添加L说明符。或者更一般地，当使用任何TCHAR敏感API（如FindWindow()）时，请改用TEXT()宏。

此外，虽然不是严格意义上的错误，但您应该使用VCL_MESSAGE_HANDLER()而不是MESSAGE_HANDLER()，这只是因为ATL对MESSAGE_HANDLER()的定义不同。如果您没有在项目中使用ATL，则不会遇到问题，但最好只使用VCL_MESSAGE_HANDLER()来确保，并记录代码使用的是VCL版本的{{ 1}}而不是其他版本。

试试这个：

Unit1.h：

MESSAGE_HANDLER()

Unit1.cpp：

#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

话虽如此，由于该消息是应用程序的私有消息，因此根本不需要使用#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); } //---------------------------------------------------------------------------，而是使用FindWindow()属性。我甚至可以更进一步摆脱TForm::Handle。该消息对于MESSAGE_HANDLER()的内部是私有的，因此它应该保留在哪里：

Unit1.h：

TRECEIVER

Unit1.cpp：

#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

如果您希望应用的其他部分向Revceiver发布消息，您可以为此公开一种公共方法：

Unit1.h：

#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); 
} 
//---------------------------------------------------------------------------

Unit1.cpp：

#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

SomeOtherFile.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); 
} 
//---------------------------------------------------------------------------

C ++ Builder XE，传递和处理用户定义的消息

1 个答案: