Keyboard input delay Flex/AIR

Question

I've build an AIR desktop app that uses an USB barcode scanner. To capture the token provided by the barcode scanner an input field is used.
When testing the barcode input was only partially captured by the scanner. This was caused by the barcode scanner's input coming in the fast. Increasing the key stroke delay of the barcode scanner (config tool from motorola) solved the problem however this is not ideal.
Does anyone has experience with this type of problems? What is an approach to solve this? Maybe by writing an Java compagnion app that captures the keyboard input?

Answer 1

I just ran into this same problem. Our users are scanning barcodes from various labels using various types of scanners (changing the delay using scanner software wasn't an option). We also have to allow them to scan to a TextInput within a DataGrid, which created even more problems. There were 2 very interesting things I learned in coming up with a solution for this one:
1. As mentioned previously, the scanner inputs the data so quickly that the enter key event is often processed before the change event for the text. I tried several solutions (like trying to force the change event before the enter key is processed), but learned that the best solution was just to add the delay as mentioned in previous posts.
2. When adding to a DataGrid control, I learned that both the DataGrid's & the TextInput's key down events are fired by the same SystemManager event. Though you can override the TextInput's keyDownHandler, you can't override the DataGrid's because it's a private method. So, even though my delay was being processed in the TextInput, the DataGrid was forcing control away from it and moving to the next item in the grid. To get around this one, I had to stop propagation of the event from the TextInput, then re-start the DataGrid's event once the delay was complete. I also had to process a focus-out event to get it to move to the next item in the DataGrid.
Here's the code I used inside a custom TextInput control to handle processing both stand-alone and inside a DataGrid:
override protected function keyDownHandler(event:KeyboardEvent):void
      // If the enter key was pressed, then we need to add a delay.
      // Barcode scanners quite often process the enter key before the TextInput
      // control has time to finish processing all the text. (e.g., Instead of
      // getting 12345 as a text entry, you could get 123 or 1234.)
      if (event.charCode == Keyboard.ENTER)
           // If this is the first time we've processed the enter key, we need to
           // add the delay.
           if (_keyboardEvent == null)
           _keyboardEvent = new KeyboardEvent(event.type, event.bubbles,
           event.cancelable, event.charCode, event.keyCode, event.keyLocation,
           event.ctrlKey, event.altKey, event.shiftKey);
           event.stopImmediatePropagation();
           barcodeTimer(_keyboardEvent);
                      return;
           // If the enter key is pressed while we are still in the delay, ignore
           // it.
           else if (_keyboardEvent != null && _keyboardEvent != event)
                     return;
           // If the delay is complete, then we need to restart events related to
           // the enter key so the control is handled properly.
           else
                super.keyDownHandler(event);
                // If the TextInput is inside a DataGrid, then we need to dispatch the
                // DataGrid's key down event. We also need to make sure the proper
                // focus change happens (since this was stopped in the original event
                // propagation).
                if (parent != null && parent.parent != null &&
           parent.parent is mx.controls.DataGrid)
           parent.parent.dispatchEvent(event);
           dispatchEvent(new FocusEvent(FocusEvent.KEY_FOCUS_CHANGE, true,
                          false, null, event.shiftKey, Keyboard.TAB));
        _keyboardEvent = null;
                return;
      super.keyDownHandler(event);
* This is a copy of the keyboard event to be processed once the barcode
* delay is complete.
private var _keyboardEvent:KeyboardEvent = null;
* This method launches a timer of sufficient length to allow barcode
* scanner text to be processed before it re-launches the keyboard event.
* @param event This is the key-down event to be restarted once the timer is
* complete.
private function barcodeTimer(event:KeyboardEvent):void
      var t:Timer = new Timer(30, 1); // 30 ms
   t.addEventListener(TimerEvent.TIMER,
           function():void
           keyDownHandler(event);
   t.start();