GWT Round up!

• String[] can't serialize!
• You can't use "new" to widget variable that was attached to panel already! You will lose reference to that widget because "new" will generate new reference differ from old one. So, use other function to change content inside the widget.
• Use "implements IsSerializable" to make your class serializable.
• Use show and hide methods in PopupPanel to make PopupPanel modal. Otherwise, it will not be modal.
• [Client] GWT.log(str, null), [Server] this.log(str)