一段时间内没有元素注册，但仍在等待 1 个元素被注册

Question

我正在试用聚合物飞镖。我想构建一个简单的自定义元素。我基于 dart 编辑器中的聚合物示例应用程序中提供的自定义元素。

不幸的是，我收到以下错误：

No elements registered in a while, but still waiting on 1 elements to be registered. Check that you have a class with an @CustomTag annotation for each of the following tags: 'send-card'

'send-card' 元素的代码如下所示：

send_card.html

<!-- send card -->


<!-- import polymer-element's definition -->
<link rel="import" href="../../packages/polymer/polymer.html">

<link rel="import" href="../../packages/paper_elements/paper_input.html">
<link rel="import" href="../../packages/paper_elements/paper_fab.html">

<link rel="import" href="../../packages/core_elements/core_icons.html">

<polymer-element name="send-card">
  <template>
    <style>
      #input-wrapper {
        width: 500px;
        padding: 5px;
        margin: 10px;
      }
      paper-input {
        color:#5677fc;
      }
      paper-fab {
        background: #5677fc;
        position: relative;
        right: -5px;
        bottom: -5px;
      }
    </style>

    <div id="input-wrapper">
      <paper-input multiline label="Your message"></paper-input>
      <paper-fab icon="add" on-click="{{sendMessage}}"></paper-fab>
    </div>

  </template>
</polymer-element>

send_card.dart

import 'package:paper_elements/paper_input.dart';
import 'package:paper_elements/paper_fab.dart';
import 'package:polymer/polymer.dart';

@CustomTag('send-card')
class SendCard extends PolymerElement {

  /// Constructor used to create instance of MainApp.
  SendCard.created() : super.created();

  void sendMessage(){}
}

在我看来，这里一切都已到位。谁能解释一下这个错误？

PS：当我运行代码时，浏览器中没有任何显示。

Answer 1

在模板中 send_card.dart 添加脚本元素：

send_card.html:

  <!-- ... -->
  </template>
  <script type="application/dart" src="send_card.dart"></script>
</polymer-element>

Answer 2

我上次遇到这个是因为我忘记将入口页面添加到 Polymer 变压器配置中。

另见 What are dart polymer transformer entry_points actually for?

一段时间内没有元素注册，但仍在等待 1 个元素被注册

No elements registered in a while, but still waiting on 1 elements to be registered

dart

polymer

dart-polymer