WPF: Button single click + double click issue

mouseclick-eventtimerwpf

I have to handle both the single click and the double click of a button in a WPF application with different reaction.
Unfortunately, on a doubleclick, WPF fires two click event and a double click event, so it's hard to handle this situation.

It tried to solve it using a timer but without success…I hope you can help me.

Lets see the code:

private void delayedBtnClick(object statInfo)
{
    if (doubleClickTimer != null)
        doubleClickTimer.Dispose();
    doubleClickTimer = null;

    this.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal, new VoidDelegate(delegate()
    {
        // ... DO THE SINGLE CLICK ACTION
    }));
}

private void btn_Click(object sender, RoutedEventArgs e)
{
    if (doubleClickTimer == null)
        doubleClickTimer = new Timer(delayedBtnClick, null, System.Windows.Forms.SystemInformation.DoubleClickTime, Timeout.Infinite);
        }
    }
}

private void btnNext_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    if (doubleClickTimer != null)
        doubleClickTimer.Change(Timeout.Infinite, Timeout.Infinite);    // disable it - I've tried it with and without this line
        doubleClickTimer.Dispose();
    doubleClickTimer = null;

    //.... DO THE DOUBLE CLICK ACTION
}

The problem is that the 'SINGLE CLICK ACTION' called after the 'DOUBLE CLICK ACTION' on doubleclick. It's strange that I set thedoubleClickTimer to null on double click but in the delayedBtnClick it's true :O

I've already tried to use longer time, a bool flag and lock…

Do you have any ideas?

Best!

Best Answer

If you set the RoutedEvent's e.Handled to true after handling the MouseDoubleClick event then it will not call the Click Event the second time after the MouseDoubleClick.

There's a recent post which touches on having different behaviors for SingleClick and DoubleClick which may be useful.

However, if you are sure you want separate behaviors and want/need to block the first Click as well as the second Click, you can use the DispatcherTimer like you were.

private static DispatcherTimer myClickWaitTimer = 
    new DispatcherTimer(
        new TimeSpan(0, 0, 0, 1), 
        DispatcherPriority.Background, 
        mouseWaitTimer_Tick, 
        Dispatcher.CurrentDispatcher);

private void Button_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    // Stop the timer from ticking.
    myClickWaitTimer.Stop();

    Trace.WriteLine("Double Click");
    e.Handled = true;
}

private void Button_Click(object sender, RoutedEventArgs e)
{
    myClickWaitTimer.Start();
}

private static void mouseWaitTimer_Tick(object sender, EventArgs e)
{
    myClickWaitTimer.Stop();

    // Handle Single Click Actions
    Trace.WriteLine("Single Click");
}

UPDATE

As of 8/1/2014, the article I linked to above is still active, but the blog hasn't been updated in a while. That makes me worry that eventually it might disappear, and with it, the advocated solution. I'm reproducing the content of the article here for posterity. The words belong solely to the blog owner at Sanity Free Coding.

Today I wanted to refactor some code that prohibited my application from running multiple instances of itself.

Previously I had use System.Diagnostics.Process to search for an instance of my myapp.exe in the process list. While this works, it brings on a lot of overhead, and I wanted something cleaner.

Knowing that I could use a mutex for this (but never having done it before) I set out to cut down my code and simplify my life.

In the class of my application main I created a static named Mutex:

static class Program
{
    static Mutex mutex = new Mutex(true, "{8F6F0AC4-B9A1-45fd-A8CF-72F04E6BDE8F}");
    [STAThread]
    ...
}

Having a named mutex allows us to stack synchronization across multiple threads and processes which is just the magic I'm looking for.

Mutex.WaitOne has an overload that specifies an amount of time for us to wait. Since we're not actually wanting to synchronizing our code (more just check if it is currently in use) we use the overload with two parameters: Mutex.WaitOne(Timespan timeout, bool exitContext). Wait one returns true if it is able to enter, and false if it wasn't. In this case, we don't want to wait at all; If our mutex is being used, skip it, and move on, so we pass in TimeSpan.Zero (wait 0 milliseconds), and set the exitContext to true so we can exit the synchronization context before we try to aquire a lock on it. Using this, we wrap our Application.Run code inside something like this:

static class Program
{
    static Mutex mutex = new Mutex(true, "{8F6F0AC4-B9A1-45fd-A8CF-72F04E6BDE8F}");
    [STAThread]
    static void Main() {
        if(mutex.WaitOne(TimeSpan.Zero, true)) {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
            mutex.ReleaseMutex();
        } else {
            MessageBox.Show("only one instance at a time");
        }
    }
}

So, if our app is running, WaitOne will return false, and we'll get a message box.

Instead of showing a message box, I opted to utilize a little Win32 to notify my running instance that someone forgot that it was already running (by bringing itself to the top of all the other windows). To achieve this I used PostMessage to broadcast a custom message to every window (the custom message was registered with RegisterWindowMessage by my running application, which means only my application knows what it is) then my second instance exits. The running application instance would receive that notification and process it. In order to do that, I overrode WndProc in my main form and listened for my custom notification. When I received that notification I set the form's TopMost property to true to bring it up on top.

Here is what I ended up with:

Program.cs

static class Program
{
    static Mutex mutex = new Mutex(true, "{8F6F0AC4-B9A1-45fd-A8CF-72F04E6BDE8F}");
    [STAThread]
    static void Main() {
        if(mutex.WaitOne(TimeSpan.Zero, true)) {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
            mutex.ReleaseMutex();
        } else {
            // send our Win32 message to make the currently running instance
            // jump on top of all the other windows
            NativeMethods.PostMessage(
                (IntPtr)NativeMethods.HWND_BROADCAST,
                NativeMethods.WM_SHOWME,
                IntPtr.Zero,
                IntPtr.Zero);
        }
    }
}

NativeMethods.cs

// this class just wraps some Win32 stuff that we're going to use
internal class NativeMethods
{
    public const int HWND_BROADCAST = 0xffff;
    public static readonly int WM_SHOWME = RegisterWindowMessage("WM_SHOWME");
    [DllImport("user32")]
    public static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam);
    [DllImport("user32")]
    public static extern int RegisterWindowMessage(string message);
}

Form1.cs (front side partial)

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    protected override void WndProc(ref Message m)
    {
        if(m.Msg == NativeMethods.WM_SHOWME) {
            ShowMe();
        }
        base.WndProc(ref m);
    }
    private void ShowMe()
    {
        if(WindowState == FormWindowState.Minimized) {
            WindowState = FormWindowState.Normal;
        }
        // get our current "TopMost" value (ours will always be false though)
        bool top = TopMost;
        // make our form jump to the top of everything
        TopMost = true;
        // set it back to whatever it was
        TopMost = top;
    }
}

.net – Stop double click from happening after single click

RaymondChen is once again a valuable source.

I suggest you read the linked half second delay article for deeper details but that one shows how the delay manifests itself to the user.

Best Answer

Related Solutions

C# – the correct way to create a single-instance WPF application

UPDATE

.net – Stop double click from happening after single click

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