import com.google.gwt.event.dom.client.HasMouseOverHandlers; //导入依赖的package包/类
public void add(Widget widget) {
    if (widget instanceof HasClickHandlers && clickHandler!=null) {
        ((HasClickHandlers) widget).addClickHandler(clickHandler);
    }
    if (widget instanceof HasDoubleClickHandlers && doubleClickHandler!=null) {
        ((HasDoubleClickHandlers) widget).addDoubleClickHandler(doubleClickHandler);
    }
    if (widget instanceof HasErrorHandlers && errorHandler!=null) {
        ((HasErrorHandlers) widget).addErrorHandler(errorHandler);
    }
    if (widget instanceof HasMouseOutHandlers && mouseOutHandler!=null) {
        ((HasMouseOutHandlers) widget).addMouseOutHandler(mouseOutHandler);
    }
    if (widget instanceof HasMouseOverHandlers && mouseOverHandler!=null) {
        ((HasMouseOverHandlers) widget).addMouseOverHandler(mouseOverHandler);
    }
    flowpanel.add(widget);
}
 

import com.google.gwt.event.dom.client.HasMouseOverHandlers; //导入依赖的package包/类
public void setMouseEntered(JavaScriptObject aValue) {
	if (mouseEntered != aValue) {
		if (mouseOverReg != null) {
			mouseOverReg.removeHandler();
			mouseOverReg = null;
		}
		mouseEntered = aValue;
		if (mouseEntered != null) {
			MouseOverHandler handler = new MouseOverHandler() {
				@Override
				public void onMouseOver(MouseOverEvent event) {
					if (mouseEntered != null) {
						event.stopPropagation();
						executeEvent(mouseEntered, EventsPublisher.publish(event));
					}
				}
			};
			if (component instanceof Widget) {
				mouseOverReg = ((Widget) component).addDomHandler(handler, MouseOverEvent.getType());
			} else if (component instanceof HasMouseOverHandlers) {
				mouseOverReg = ((HasMouseOverHandlers) component).addMouseOverHandler(handler);
			}
		}
	}
}