Handle back key in some dialog node

Cocos Creator
#1

Hi
In my project, there are some dialog, and i wanna to close them one by one when user press back key.
How can i implement it?

show : function() {
    this.node.active = true;
...
    cc.systemEvent.once(cc.SystemEvent.EventType.KEY_DOWN,
      this.onKeyPressed,
      this);
...
}

onKeyPressed: function (event) {
 if (event.keyCode === cc.KEY.back || event.keyCode === cc.KEY.backspace || event.keyCode === cc.KEY.escape) {
      this.hide();
      event.stopPropagation();
    }
  }

hide : function() {
    this.node.active = false;
}

But when i press back key, all dialog close.
I want to close some dialog one by one.
How???

Thanks.