FocusManager.java 文件源码

/**
 * Installs a key handler for key events on this window.
 *
 * @param handler handler to receive key events.
 */
static void install(KeySignalHandler handler) {
  //
  // NOTE: There are three potential candidate elements for sinking keyboard
  // events: the window, the document, and the document body. IE7 does not
  // fire events on the window element, and GWT's RootPanel is already a
  // listener on the body, leaving the document as the only cross-browser
  // whole-window event-sinking 'element'.
  //
  DocumentPanel panel = new DocumentPanel(handler);
  panel.setElement(Document.get().<Element>cast());
  panel.addDomHandler(panel, KeyDownEvent.getType());
  panel.addDomHandler(panel, KeyPressEvent.getType());
  panel.addDomHandler(panel, KeyUpEvent.getType());
  RootPanel.detachOnWindowClose(panel);
  panel.onAttach();
}