dart - 现在，使用CoreScaffold和CoreTabs类会导致异常

Question

我有一个称为main-app的聚合物元素:

    <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_input.html">
    <link rel="import" href="../../packages/paper_elements/paper_tabs.html">
    <link rel="import" href="../../packages/paper_elements/paper_dialog.html">
    <link rel="import" href="../../packages/paper_elements/paper_icon_button.html">
    <link rel="import" href="../../packages/core_elements/core_toolbar.html">
    <link rel="import" href="../../packages/core_elements/core_scaffold.html">
    <link rel="import" href="../../packages/core_elements/core_header_panel.html">
    <link rel="import" href="../../packages/core_elements/core_menu.html">
    <link rel="import" href="../../packages/core_elements/core_item.html">
    <link rel="import" href="../../packages/paper_elements/paper_input.html">
    <link rel="import" href="../../packages/paper_elements/paper_button.html">
    <link rel="import" href="../../packages/paper_elements/paper_dialog.html">
    <link rel="import" href="../../packages/core_elements/core_scaffold.html">
    <link rel="import" href="../../packages/core_elements/core_pages.html">

    <polymer-element name="main-app" class="dark-primary-color">
        <template>
            <style type="text/css">
                :host {
                    display: block;
                }
            </style>
            <core-scaffold>

                <core-header-panel id="menu-panel" navigation flex>

                    <core-toolbar id="navheader">
                        <span>Menu</span>
                    </core-toolbar>
                    <core-menu>
                        <core-item label="Home" on-click="{{homeClicked}}"></core-item>
                        <core-item label="About Us" on-click="{{aboutClicked}}"></core-item>
                        <core-item label="Contact Us" on-click="{{contactClicked}}"></core-item>
                    </core-menu>
                </core-header-panel>

                <span tool>{{title}}</span>
                <paper-tabs class="main-menu bottom fit" selected="0">
                    <paper-tab on-click="{{homeClicked}}">Home</paper-tab>
                    <paper-tab on-click="{{aboutClicked}}">About Us</paper-tab>
                    <paper-tab on-click="{{contactClicked}}">Contact Us</paper-tab>
                </paper-tabs>
                <div class="content" forceNarrow>
                    <p>Lorem ipsum ...</p>
                </div>

                ...
            </core-scaffold>
        </template>
        <script type="application/dart" src="main-app.dart"></script>
    </polymer-element>

main-app.dart:

import 'package:polymer/polymer.dart';
import 'util/util.dart';
import 'event/event.dart';

import 'dart:html';

import 'page/home-page.dart';
import 'page/about-page.dart';
import 'page/contact-page.dart';

@CustomTag('main-app')
class MainApp extends PolymerElement {

  @observable String page = "home";
  @observable String title = "Home";

  MainApp.created() : super.created();

  ...

  homeClicked(event, detail, target) {
    CoreScaffold e = shadowRoot.querySelector('core-scaffold');
    e.doSomething <<-- fails
    ...
  }

  ...

}

这是我得到的异常(exception):

Exception: 'package:falm/main-app.dart': malformed type: line 73 pos 5: type 'CoreScaffold' is not loaded
    CoreScaffold e = shadowRoot.querySelector('core-scaffold');
    ^
type 'CoreScaffold' is not a subtype of type 'malformed' of 'e'. 

为了摆脱异常，我现在必须做:

  homeClicked(event, detail, target) {
    Element e = shadowRoot.querySelector('core-scaffold');
    e.doSomething <<-- works
    ...
  }

失败的代码在昨天早晨进行 Dart 更新之前一直有效(不确定在更新完整的pub，进行pub缓存修复和pub下载之前完全重新安装SDK时是从哪个版本更新的)，PaperTabs在做同样的事情。

这是否意味着我不能再在Dart代码中使用CoreElement和PaperTabs类？

更新:这是来自pubspec.lock的相关内容:

core_elements:
    description: core_elements
    source: hosted
    version: "0.6.0+4"
paper_elements:
    description: paper_elements
    source: hosted
    version: "0.6.0+4"
  polymer:
    description: polymer
    source: hosted
    version: "0.15.5"
  polymer_expressions:
    description: polymer_expressions
    source: hosted
    version: "0.13.0+1"
  web_components:
    description: web_components
    source: hosted
    version: "0.10.1"

Answer 1

您需要导入定义了类的库。

import 'package:core_elements/core_scaffold.dart'; 
import 'package:paper_elements/paper_tabs.dart';

已选中/未选中

从 命令行运行Dart脚本时，默认为生产模式(未选中模式)。 dart bin/somescript.dart，或明确设置为 dart -c bin/somescript.dart时的检查模式。

从 启动Dart脚本或Web应用程序时，DartEditor 默认为选中模式。 DartEditor允许(停用) Run in checked mode中的 Manage Launches(运行配置)。

我假设 Dart插件中有Eclipse 的类似设置(请勿自己使用)。

WebStorm 允许在 Run > Edit Configurations ...中为命令行应用程序设置它。对于Web应用程序，您可以创建一个新的浏览器配置，并在 --checked中添加 Command line options。

我认为它与 IntelliJ IDEA 类似，但我自己尚未使用过。

另请参阅 https://stackoverflow.com/a/21658630/217408