Override这个configureShell可以设置和窗口相关的属性.
protected void configureShell(Shell newShell) {
super.configureShell(newShell);
newShell.setText("用户登录");
newShell.setSize(300, 200);
newShell.setImage(ImageUtils.getImage("icons/logo.gif"));
SWTUtil.centerShell(newShell);
}