dart - 将监听器添加到DART lang中的自定义元素

Question

在JavaScript中，我们可以通过here将侦听器添加到自定义元素中，方法是:

proto.createdCallback = function() {
   this.addEventListener('click', function(e) {
   alert('Thanks!');
  });
};

我尝试将等效的DART代码制作为:

    Element launchElement(){
       this.onClick.listen((e)=>print('Thanks!'));
       return (shadow);  
    }

我在这里做错什么了吗？

我的自定义元素的完整代码为:

class MegaButton extends ButtonElement  {
  static final tag = 'mega-button';
  factory MegaButton()=>new Element.tag('button', tag);

MegaButton.created() : super.created() {
  var shadow = this.createShadowRoot();
  shadow.text='save'; 

  Element launchElement(){
    this.onClick.listen((e)=>print('Thanks!'));
    return (shadow);  
  }

}

注册为:

document.registerElement(MegaButton.tag, MegaButton, extendsTag: 'button');

并通过以下方式调用它:

myDiv.nodes.add(new Element.tag('button', 'mega-button'));

Answer 1

class MegaButton extends ButtonElement {
  static final tag = 'mega-button';

  factory MegaButton()=> new Element.tag('button', tag);

  MegaButton.created() : super.created() {
    var shadow = this.createShadowRoot();
    shadow.text = 'save';
  }

  void attached() {
    this.onClick.listen((e)=>print('Thanks!'));
  }
}