UIEngine "Listens" to User Input

Use the <event name="onselect"> tag to capture key presses and mouse/stylus clicks/taps.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ujml PUBLIC "-//UIEVOLUTION//DTD UJML 
    1.5//EN" "http://www.uievolution.com/dtd/ujml-1.5.dtd" []>

<ujml>
  <application>   
    <!-- paint background -->
    <display>
      <box>
        <width>
          <eval>_getIntProperty(&_PROPERTY_INT_SCREEN_WIDTH;)</eval>
        </width>
        <height>
          <eval>_getIntProperty(&_PROPERTY_INT_SCREEN_HEIGHT;)</eval>
        </height>
        <bg>&_COLOR_BLACK;</bg>
      </box>            
      <!-- draw text -->
      <label>
        <text>Hello World!</text>
        <fg>&_COLOR_YELLOW;</fg>
        <!-- wait for keypress or mouse click -->
        <event name="onselect">
          <accelerators>
            <key>FIRE</key>
          </accelerators>
          <script>
            // User pressed FIRE or clicked on label
          </script>
        </event>
      </label>
    </display>
  </application>
</ujml>

Learn more about UIEvolution's UIEngine.