Windows编程-自己发送消息

这里我们讨论两种消息传递的方法：SendMessage()和PostMessage();

(1)SendMessage

Sends the specified message to a window or windows. The SendMessage function calls the window procedure for the specified window and does not return until the window procedure has processed the message.

函数的定义如下：

LRESULT WINAPI SendMessage( _In_  HWND hWnd, _In_  UINT Msg, _In_  WPARAM wParam, _In_  LPARAM lParam );

Parameters
hWnd [in]  Type: HWND

A handle to the window whose window procedure will receive the message. If this parameter is HWND_BROADCAST ((HWND)0xffff), the message is sent to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows; but the message is not sent to child windows.

Message sending is subject to UIPI. The thread of a process can send messages only to message queues of threads in processes of lesser or equal integrity level.

Msg [in]  Type: UINT

The message to be sent. For lists of the system-provided messages, see System-Defined Messages.

wParam [in]  Type: WPARAM

Additional message-specific information.

lParam [in]  Type: LPARAM

Additional message-specific information.

Return value Type: LRESULT

The return value specifies the result of the message processing; it depends on the message sent.

SendMessage() 可向窗口传递一个要求立即处理的消息。当窗口接收这个消息后，立即执行WinProc()并返回。

 

(2)PostMessage

Places (posts) a message in the message queue associated with the thread that created the specified window and returns without waiting for the thread to process the message.

函数定义如下：

BOOL WINAPI PostMessage( _In_opt_  HWND hWnd, _In_      UINT Msg, _In_      WPARAM wParam, _In_      LPARAM lParam );

Parameters

hWnd [in, optional]   Type: HWND

A handle to the window whose window procedure is to receive the message. The following values have special meanings.

Msg [in]   Type: UINT

The message to be posted.

For lists of the system-provided messages, see System-Defined Messages.

wParam [in]   Type: WPARAM

Additional message-specific information.

lParam [in]   Type: LPARAM

Additional message-specific information.

Return value  Type: BOOL

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

PostMessage() 可向窗口的消息队列发消息，而后直接返回。

下面的例子给出SendMessage()的简单用法。

// INCLUDES ///////////////////////////////////////////////
#define WIN32_LEAN_AND_MEAN  // just say no to MFC

#include <windows.h>   // include all the windows headers
#include <windowsx.h>  // include useful macros
#include <mmsystem.h>  // very important and include WINMM.LIB too!
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

// DEFINES ////////////////////////////////////////////////

// defines for windows 
#define WINDOW_CLASS_NAME "WINCLASS1"

// MACROS /////////////////////////////////////////////////

#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)

#define KEYUP(vk_code)   ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)

// GLOBALS ////////////////////////////////////////////////
HWND      main_window_handle = NULL; // globally track main window
HINSTANCE hinstance_app      = NULL; // globally track hinstance
char buffer[80];                     // general printing buffer

// FUNCTIONS //////////////////////////////////////////////
LRESULT CALLBACK WindowProc(HWND hwnd, 
                            UINT msg, 
                            WPARAM wparam, 
                            LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT        ps;        // used in WM_PAINT
HDC                hdc;    // handle to a device context
char buffer[80];        // used to print strings

// what is the message 
switch(msg)
    {    
    case WM_CREATE: 
        {
        // do initialization stuff here
        // return success
        return(0);
        } break;
   
    case WM_PAINT: 
        {
        // simply validate the window 
           hdc = BeginPaint(hwnd,&ps);     
        
        // end painting
        EndPaint(hwnd,&ps);

        // return success
        return(0);
           } break;

    case WM_DESTROY: 
        {

        // kill the application, this sends a WM_QUIT message 
        PostQuitMessage(0);

        // return success
        return(0);
        } break;

    default:break;

    } // end switch

// process any messages that we didn't take care of 
return (DefWindowProc(hwnd, msg, wparam, lparam));

} // end WinProc

// WINMAIN ////////////////////////////////////////////////
int WINAPI WinMain(    HINSTANCE hinstance,
                    HINSTANCE hprevinstance,
                    LPSTR lpcmdline,
                    int ncmdshow)
{

WNDCLASSEX winclass; // this will hold the class we create
HWND       hwnd;     // generic window handle
MSG           msg;         // generic message
HDC        hdc;      // graphics device context

// first fill in the window class stucture
winclass.cbSize         = sizeof(WNDCLASSEX);
winclass.style            = CS_DBLCLKS | CS_OWNDC | 
                          CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc    = WindowProc;
winclass.cbClsExtra        = 0;
winclass.cbWndExtra        = 0;
winclass.hInstance        = hinstance;
winclass.hIcon            = LoadIcon(NULL, IDI_APPLICATION);
winclass.hCursor        = LoadCursor(NULL, IDC_ARROW); 
winclass.hbrBackground    = (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName    = NULL;
winclass.lpszClassName    = WINDOW_CLASS_NAME;
winclass.hIconSm        = LoadIcon(NULL, IDI_APPLICATION);

// save hinstance in global
hinstance_app = hinstance;

// register the window class
if (!RegisterClassEx(&winclass))
    return(0);

// create the window
if (!(hwnd = CreateWindowEx(NULL,                  // extended style
                            WINDOW_CLASS_NAME,     // class
                            "WM_DESTROY Message Sending Demo", // title
                            WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                             0,0,      // initial x,y
                            400,300,  // initial width, height
                            NULL,      // handle to parent 
                            NULL,      // handle to menu
                            hinstance,// instance of this application
                            NULL)))    // extra creation parms
return(0);

// save main window handle
main_window_handle = hwnd;


// enter main event loop, but this time we use PeekMessage()
// instead of GetMessage() to retrieve messages
while(TRUE)
    {
    // test if there is a message in queue, if so get it
    if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
       { 
       // test if this is a quit
       if (msg.message == WM_QUIT)
           break;
    
       // translate any accelerator keys
       TranslateMessage(&msg);

       // send the message to the window proc
       DispatchMessage(&msg);
       } // end if
    
       // main game processing goes here
    if (KEYDOWN(VK_ESCAPE)){    
        //SendMessage(hwnd, WM_CLOSE, 0,0);
        PostMessage(hwnd, WM_CLOSE, 0,0);
    }   

    } // end while

// return to Windows like this
return(msg.wParam);

} // end WinMain

///////////////////////////////////////////////////////////