钩子(Hook)，是Windows消息处理机制的一个平台,应用程序可以在上面设置子程以监视指定窗口的某种消息，而且所监视的窗口可以是其他进程所创建的。当消息到达后，在目标窗口处理函数之前处理它。钩子机制允许应用程序截获处理window消息或特定事件。该代码包含较为全面的示例。(Hook (Hook), Windows message processing mechanism is a platform, applications can be set on the procedure to monitor some messages of specified window, and the monitoring window can be created by other processes. When the message arrives, handle it before the target window handler. Hook mechanism allows applications to intercept window messages or specific events. This code contains a comprehensive sample.)