code: function(args) {
          args = args || [];
          var that = this;
          var html = '';
          var number = 0;
          this.callbacks = {};
  
  
          if (typeof args === 'string') {
              html = args;
              number++;
          } else {
              $.each(args, function(i, val) {
  
                  var id = val.id = val.id || val.value;
                  var style = '';
                  that.callbacks[id] = val.callback;
  
  
                  if (val.display === false) {
                      style = ' style="display:none"';
                  } else {
                      number++;
                  }
  
                  html +=
                      '<button' +
                      ' type="button"' +
                      ' i-id="' + id + '"' +
                      style +
                      (val.disabled ? ' disabled' : '') +
                      (val.autofocus ? ' autofocus class="ui-dialog-autofocus"' : '') +
                      '>' +
                      val.value +
                      '</button>';
  
                  that._$('button')
                      .on('click', '[i-id=' + id + ']', function(event) {
                          var $this = $(this);
                          if (!$this.attr('disabled')) { // IE BUG
                              that._trigger(id);
                          }
  
                          event.preventDefault();
                      });
  
              });
          }
  
          this._$('button').html(html);
          this._$('footer')[number ? 'show' : 'hide']();
  
          return this;
      }
docs: 设置按钮组
  @param   {Array, String}
  Options: value, callback, autofocus, disabled