My first DART polymer project: No execution / testing possible, nothing works?

Question

I have created a polymer project. It generates a default app which reverses text entered into an input field. This works.

Then I tried to add a core-header-panel. I copied the code from the description page into the index.html file of the project:

<body unresolved fullbleed layout vertical>
  <core-header-panel flex>
    <core-toolbar>
      <div>Hello World!</div>
    </core-toolbar>
  </core-header-panel>

  <main-app>
  </main-app>

  <script type="application/dart">export 'package:polymer/init.dart';</script>
</body>

This gets me 3 warnings on the displayed web page. Two say:

Custom element found in document body without an "unresolved" attribute on it or one of its parents.

I have inserted an unresolved attribute after the body tag. I do not understand why the error does not go away.

The third messages is:

custom element with name core-toolbar not found

I added a line

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

but the error message did not go away.

Finally I outcommented the complete core-header-panel and nevertheless the page in Dartium still shows "Hello world" and all the error messages.

I'm lost here. The DART editor / Dartium "development system" seems to be useless. I can not even test the simplest things. What am I doing wrong? How do you work with this system???

BTW: I get exactly the same behaviour when I try to run this as Javascript in Firefox browser ...

You can ignore the unresolved message at first. This is just about FOUC. You can care about it when you got the app and elements working. — Günter Zöchbauer

Günter Zöchbauer Günter Zöchbauer · Accepted Answer · 2014-12-05T21:57:15

You need to add an import for core-toolbar and core-header-panel.

You also need to add a dependency to the pubspec.yaml file.

dependencies:
  core_elements: any

Otherwise I can't see anything wrong.
If this doesn't work, please try to run pub cache repair in your project directory (from command line). If this still doesn't work please add the complete content of your pubspec.yaml, pubspec.lock and index.html to your question.

My first DART polymer project: No execution / testing possible, nothing works?

2 Answers