如果程序最小化或在系统托盘中，如何检测ctrl键两次

Question

How to detect the ctrl key is pressed twice if the program is minimized or in system tray

I am trying to develop ac# program where the main form will be shown to the user when the control key is pressed twice. I found samples for hotkey combinations but this is not hotkey with combination, like control+ some other key. This is like google desktop app where the search box is displayed when control key is pressed twice.

Answer 1

这似乎是键盘挂钩 （ WH_KEYBOARD ）的情况。

Answer 2

What you could do is capture each time the key is pressed, and perhaps in a background worker compare the difference in time.

Set yourself a threshold and if it is less than that, you would consider it a double press and do what you need to.

Untested the components could look something like:

    private readonly DateTime _originDateTime = new DateTime(0);
    private DateTime _lastKeyPress;

Hook up worker:

        _backgroundWorker = new BackgroundWorker { WorkerSupportsCancellation = false };
        _backgroundWorker.DoWork += DoBackgroundWork;
        _backgroundWorker.RunWorkerAsync();

Implement DoBackgroundWork method:

    private void DoBackgroundWork(object sender, DoWorkEventArgs doWorkEventArgs)
    {
        do
        { 
                if (_lastKeyPress != _originDateTime)
                {
                    Thread.Sleep(DelayInMilliseconds);
                    DateTime now = DateTime.Now;

                    TimeSpan delta = now - _lastKeyPress;

                    if (delta < new TimeSpan(0, 0, 0, 0, DelayInMilliseconds))
                    {
                        continue;
                    }
                }

                //do stuff

        } while (true);
    }

And don't forget to capture the key:

    private void SomeEvent_KeyDown(object sender, KeyEventArgs e)
    {
        _lastKeyPress = DateTime.Now;
    }

This is based on XPath Visualizer

Answer 3

Use keyboard hooks like foxx1337 suggested, then do something like this:

int triggerThreshold = 500; //This would be equivalent to .5 seconds
int lastCtrlTick = 0;

private void OnCtrlPress()
{
    int thisCtrlTick = Environment.TickCount;
    int elapsed = thisCtrlTick - lastCtrlTick;
    if (elapsed <= triggerThreshold)
    {
        LaunchYourAppOrWhatever();
    }
    lastCtrlTick = thisCtrlTick;
}

Answer 4

Keyboard hooking as suggested. It's been nicely wrapped for you at CodePlex , where you get a .NET API simply raising Key and Mouse events, regardless of the state your app is in.

Answer 5

UPDATE: The managed wrapper .NET library library mentioned in an accepted answer has moved here . Now there is also a nuget package MouseKeyHook available.

Recently support for detecting shortcuts, key combinations and sequences was added. Here is a usage example:

void DoSomething()
{
    Console.WriteLine("You pressed UNDO");
}

Hook.GlobalEvents().OnCombination(new Dictionary<Combination, Action>
{
    {Combination.FromString("Control+Z"), DoSomething},
    {Combination.FromString("Shift+Alt+Enter"), () => { Console.WriteLine("You Pressed FULL SCREEN"); }}
});

For more information see: Detecting Key Combinations and Seuqnces