Key listener not firing (MouseKeyHook)

Question

I'm starting out in C#, coded a lot in Java but having some trouble here. I'm trying to learn how to use MouseKeyHook for an application I'm developing. I cannot get the actual listener to fire off an event. Here's my listener code:

using System;
using System.Windows.Forms;
using Gma.System.MouseKeyHook;

namespace ChromaHeatmap
{
    class keyListener
    {
        private IKeyboardMouseEvents m_GlobalHook;

        public void Subscribe()
        {
            // Note: for the application hook, use the Hook.AppEvents() instead
            m_GlobalHook = Hook.GlobalEvents();
            m_GlobalHook.KeyPress += GlobalHookKeyPress;
        }

        private void GlobalHookKeyPress(object sender, KeyPressEventArgs e)
        {
            Console.WriteLine("blah");
        }

        public void Unsubscribe()
        {
            m_GlobalHook.KeyPress -= GlobalHookKeyPress;

            //It is recommened to dispose it
            m_GlobalHook.Dispose();
        }
    }
}

And here's the part of my application code where I attempt to do something with the listener. If anyone can let me know what the best way is to loop here and wait for events, I'd appreciate it.

    //Listen for key presses
    keyListener heyListen = new keyListener();
    heyListen.Subscribe();

    while(true)
    {
    }

I'd like to note that this is mostly sample code from the developer (for the listener) — segfault, Jun 06 '15 at 02:42
Where is this code running from? The `while` loop is sure to mess up the message pump, get rid of it. — Idle_Mind, Jun 06 '15 at 02:56

score 2 · Answer 1 · edited May 23 '17 at 11:43

    while(true) {}

This is a hold-and-catch-fire statement, the thread will burn 100% core and cannot execute the hook callback. You'll notice that the machine goes dead for 5 seconds when you press a key, the operating system is waiting for an opportunity to invoke the callback. But it won't wait forever and unceremoniously will destroy the hook so you regain control over the machine. Also the kind of mishap that will occur when you try to debug your event handler.

Windows needs an opportunity to safely call the hook callback. That requires your program to be "idle", not executing any code. The technical term for this is "pumping the message loop", your program must wait for a notification from the operating system that something interesting happened.

A very simple way is to use the Winforms project template as-is, you'll also get a window. Note how the Main() method in the project makes the call that you need instead of the while() loop. You must call Application.Run().

Check this post for code that avoids displaying a window.

Thanks! This helps a lot. Gonna go try this out now. – segfault Jun 06 '15 at 21:45 — segfault, Jun 06 '15 at 21:45

Key listener not firing (MouseKeyHook)

1 Answers1