WPF子类捕获按键事件

Question

I am new to WPF and am building a test application. In my application I have a user control that is calling another class to capture the fingerprint from the device. The class that captures the fingerprint from the device is running on a do while loop, that constantly keeps reading from the device. I want to introduce an event that can break the do while. In my user control I can capture the KeyDown event. But the class that is capturing the fingerprint is unable to capture the keypress. Any thing that I am missing on?

This is my Sample File.Xaml.cs code

   protected override void OnKeyDown(KeyEventArgs e)
    {
        if (e.Key == Key.LeftCtrl || e.Key == Key.RightCtrl)
        {

        }
        else
            base.OnKeyDown(e);
    }

 private void button_Click(object sender, RoutedEventArgs e)
    {


            TNTFMT220 tntFmt220 = new TNTFMT220();
            string fingerPrintId = "";
            var data = tntFmt220.ContiniousCaptureFingerPrint(ref fingerPrintId);                          

    }

This is my code to capture the fingerprint

   public bool ContiniousCaptureFingerPrint(ref string FingerPrintScanned)
    {
      do
       {
         //get data from device
        }  while(dataReturned);
     return true;
    }

Answer 1

UserControl is made by a window and a class, when the UserControl window is focused and you press a key, you can get a OnKeyDown event.

I think your TNTFMT220 class has not a window, so you can generate the event in UserControl or in Main Window and propagate it to the class in different ways, I suggest you a couple:

1. Class Property

    protected override void OnKeyDown(KeyEventArgs e) { if (e.Key == Key.LeftCtrl || e.Key == Key.RightCtrl) { tntFmt220.doStop= true; } else base.OnKeyDown(e); } private TNTFMT220 tntFmt220; private void button_Click(object sender, RoutedEventArgs e) { tntFmt220 = new TNTFMT220(); string fingerPrintId = ""; var data = tntFmt220.ContiniousCaptureFingerPrint(ref fingerPrintId); } 

2. Class Method

    protected override void OnKeyDown(KeyEventArgs e) { if (e.Key == Key.LeftCtrl || e.Key == Key.RightCtrl) { tntFmt220.DoStop(); } else base.OnKeyDown(e); } private TNTFMT220 tntFmt220; private void button_Click(object sender, RoutedEventArgs e) { tntFmt220 = new TNTFMT220(); string fingerPrintId = ""; var data = tntFmt220.ContiniousCaptureFingerPrint(ref fingerPrintId); } 

Above all:

First of all, I probably think again if that do while is needed or if TNTFMT220 can generate an event when data is read.

Then, if you don't want that do While will block you window, you have to run it in a different thread.