将键盘输入保存到变量中

Question

I wrote a Firefox extension that gets input from a Barcode Tag Scanner, calls a page and writes it into a field. The scanner is programmed to send a keystroke after reading a tag. I added an event on the window object that is listening for CTRL K . My problem is the focus on the textbox, when it's lost it's not working. My question is: is it possibile to get the value of the scanned tag without using the textbox element? Scanner input comes in via keyboard interface.

BrowserOverlay.xul :

<window id="main-window">
<script type="application/x-javascript">

window.addEventListener("keydown", barcodeInit, false);

function sel(){
var textbox = document.getElementById("editIndex");
textbox.focus();
}
</script>
<hbox>
  <spacer flex="1"/>
<textbox id="editIndex" value="" size="1" maxlength="25" oncommand="sel()" />
<statusbar id="status-bar" class="chromeclass-status"> 
<statusbarpanel label="Barcode AddOn" class="statusbarpanel-iconic"
      onclick="openPreferences('barcodePane');" align="left" 
          src="chrome://topas/content/images/icon18.png" />
</statusbar>

</hbox>

When I get the textbox content I'm calling the openURI method to open the page in the actual window and post data to it .

BrowserOverlay.js :

if (event.ctrlKey && pressedKey == prefKey ){
  if(typeof editIndex != "undefined"){
    var dataString = "barcodeValue=" + editIndex;
    immidiate = true;
    document.getElementById("editIndex").value = "";
    window.loadURI(stringURL, null, dataString, false);
  }

Answer 1

You can receive keys pressed by listening for the keypress events on the window object - you will get them as long as the browser window is focused, no matter which element of the window is active. Along these lines:

var data = "";
window.addEventListener("keypress", processKeyPress, false);
window.addEventListener("keydown", processKeyDown, false);

function processKeyPress(event)
{
  data += String.fromCharCode(event.charCode);
}

function processKeyDown(event)
{
  if (event.ctrlKey && event.keyCode == prefKey)
  {
    var dataString = "barcodeValue=" + data;
    data = "";
    ...
  }
}

Documentation: event.charCode