等待Win32应用程序中的特定键

Question

At some point in my program, I want to wait for the user to either press [return] or [escape]. This is what I did:

while(1)
{
    Sleep(100);
    if( GetAsyncKeyState( VK_RETURN ) )
    {
        //do something
    }
    if( GetAsyncKeyState( VK_ESCAPE ) )
    {
        //do something else 
    }   
}

But (only in the release build) after waiting for about 2 seconds, Windows says it's not responding, and it crashes. What should I do?

Answer 1

Your application is a GUI subsystem application and its main thread must regularly pump its message queue. You are not doing that because you enter a tight loop looking for specific key state. Because you don't service your queue, the system concludes that your application is broken and ghosts your window.

Before we go on to how to do it right, your existing approach is broken in other ways. Suppose that the key is pressed and released during the Sleep(100). Then you miss that event. Or suppose your app is not in the foreground. Then it responds to key presses meant for other applications.

To solve the problem you simply need to let your normal message loop process and dispatch messages. When you get a WM_KEYDOWN message for the appropriate key you can react accordingly.

Using the message loop in the intended way not only fixes the behaviour you observe in the question, but also the issues I describe above.