In the process of learning First, figure out two points: (1) Whoever wants to send this message (2) Whoever wants this news. Use a simple example to explain. Object A sends a message to B (or may be a to a). 1 Send a message First define this message in the header file of A: #define WM_USERMESSAGE WM_USER 30 All custom messages are represented by a WM_USER message based on an arbitrary natural number. A is an object to send a message outward, so a function of sending a message is called in a method (function) of A. B: postMessage (), because it is B accept the message, so Yes, as above. 2 accept messages Objects accept a message, there should be three parts: the prototype of the processing function of the message in the header file; the macro in which the message map is received; and the specific implementation of the processing function of the message. 2.1 Processing function prototypes with custom messages in header files Before the DECLARE_MESSAGE_MAP () statement, a pair of AFX_MSG plus the following form of function prototype: AFX_MSG LRESULT OnPROCNAME (WPARAM WPARAM, LPARAM LPARAM); For Win32, WPARAM, LPARAM is the most commonly used means of passing messages. 2.2 Macro in the implementation of the message In the CPP file, after the Begin_MESSAGE_MAP statement, the following form is added between a pair of AFX_MSG_MAP: ON_MESSAGE (WM_USERMESSAGE, ONPROCNAME) The above is the end of the semicolon. 2.3 Specific implementation of the message processing function is given in the implementation file.
