Question

I’m creating a WinForm application that takes a person’s photo with a webcam and am trying to now create a countdown effect. I have 4 images that i would like to cycle through but this is proving quite tricky to accomplish.

I’m using a timer for the seconds, but all that’s happening is the app lags a bit and then the last image shows. Does anybody know how i might accomplish this?

Here’s my code:

        int counter = 0;
        // start the counter to swap the images
        tmCountDown.Start();
        while (counter < 4)
        {
            // holding off picture taking
        }
        // reset counter for timer
        counter = 0;
        tmCountDown.Stop();

    /// <summary>
    /// timer event to switch between the countdown images
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void tmCountDown_Tick(object sender, EventArgs e)
    {
        counter++;
        //MessageBox.Show("c:/vrfid/apppics/" + counter + ".jpg");
        pbCountDown.Image = new Bitmap("c:/vrfid/apppics/" + counter + ".jpg");
    }

Answer 1

The Windows Timer class uses the message queue for notifying the timer has expired. And so you need to have the message loop running in order to get the correct number of timer expires occuring. So you should set the counter variable to be a class field and then you can increment it inside the event handler. Something like this…

    // Main Code
    _counter = 0;
    tmCountDown.Start();

    // Event Handler
    private void tmCountDown_Tick(object sender, EventArgs e)    
    {
        _counter++;
        if (_counter == 4)
            tmCountDown.Stop();
        else
            pbCountDown.Image = new Bitmap("c:/vrfid/apppics/" + _counter + ".jpg");
    }