问GWT Disclosure面板错误

EN

DisclosurePanel disclosurePanel = new DisclosurePanel("Reset password");
    disclosurePanel.setAnimationEnabled(true);
    disclosurePanel.setContent(passwordGrid);
    disclosurePanel.addOpenHandler(new OpenHandler<DisclosurePanel>() {

        public void onOpen(OpenEvent<DisclosurePanel> event) {
            saveButton.setEnabled(false);//enable on close or after verifying current password

        }
    });
    disclosurePanel.addCloseHandler(new CloseHandler<DisclosurePanel>() {

        public void onClose(CloseEvent<DisclosurePanel> event) {
            saveButton.setEnabled(true);

        }
    });