dart - Dart 自定义元素中的extendTag

Question

来自this link在javascript中，自定义元素扩展按钮制作为:

var MegaButton = document.registerElement('mega-button', {
  prototype: Object.create(HTMLButtonElement.prototype),
  extends: 'button'
});

<button is="mega-button">

我尝试使用 dart 通过以下代码进行相同的操作:

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';
  }
}
 document.registerElement(MegaButton.tag, MegaButton);

在html文件中

    <button  is="mega-button"></button>
    <mega-button>click me</mega-button>

但出现此错误:

Exception: Unsupported operation: Class must provide extendsTag if base native class is not HTMLElement

请提供任何帮助。谢谢

Answer 1

document.registerElement 应该如下所示:

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

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

另请参阅Custom Polymer element extending AElement in Dart