javascript - 引用错误 : KeyframeEffect is not defined in paper component

Question

我正在构建一个 Web 应用程序，对于下拉列表，我使用的是 paper-dropdown-menu我的代码非常简单，并且紧跟展示的演示 here

代码片段如下:

<link rel="import" href="/polymer/polymer-element.html">
<link rel="import" href="/paper-dropdown-menu/paper-dropdown-menu.html">
<link rel="import" href="/paper-item/paper-icon-item.html">
<link rel="import" href="/paper-listbox/paper-listbox.html">
<link rel="import" href="/iron-icons/maps-icons.html">

<dom-module id="isochrone-settings-element">
    <template>
     ...

        <div id="settings">
            <paper-dropdown-menu label="Travel mode">
                <paper-listbox slot="dropdown-content" attr-for-selected="value" selected={{selectedItem}}>
                    <paper-icon-item value="auto">
                        <iron-icon icon="maps:directions-car" slot="item-icon"></iron-icon>Driving
                    </paper-icon-item >
                    <paper-icon-item value="bicycle">
                        <iron-icon icon="maps:directions-bike" slot="item-icon"></iron-icon>Cycling
                    </paper-icon-item>
                    <paper-icon-item value="bus">
                        <iron-icon icon="maps:directions-bus" slot="item-icon"></iron-icon>Bus
                    </paper-icon-item>
                    <paper-icon-item value="pedestrian">
                        <iron-icon icon="maps:directions-walk" slot="item-icon"></iron-icon>Walking
                    </paper-icon-item>
                </paper-listbox>                
         </paper-dropdown-menu>
       </div>

    </template>
    .....

   </dom-module>

问题是，当我尝试使用 webapp 中的下拉菜单时，出现以下错误:

neon-animation-runner-behavior.html:40 Couldnt play ( fade-in-animation ). ReferenceError: KeyframeEffect is not defined
    at HTMLElement.configure (fade-in-animation.html:39)
    at HTMLElement._configureAnimations (neon-animation-runner-behavior.html:33)
    at HTMLElement.playAnimation (neon-animation-runner-behavior.html:93)
    at HTMLElement._renderOpened (iron-dropdown.html:233)
    at HTMLElement.__openedChanged (iron-overlay-behavior.html:541)
    at nextAnimationFrame (iron-overlay-behavior.html:566)

每次使用菜单时，至少会抛出 3 次相同的错误。

我现在正在调查组件本身，但由于我没有发现很多在网络上看起来相关的问题，我认为问题可能出在我身上。

这段代码有什么明显的错误吗？

谢谢

Answer 1

您需要包含 WebAnimation API 的 polyfill。您尝试使用的动画仅在 Chrome Canary 中可用。只需添加:

<link rel="import" href="../../neon-animation/web-animations.html">

The documented line in the source code can be found here.

And here you will receive updates if the need to include this changes