聚合物querySelector在DartVM上工作，但编译后不在Chrome中 [英] Polymer querySelector working on DartVM but not in Chrome after compile

问题描述

有一个奇怪的问题。在我的Dart代码中，我在屏幕上有一些聚合物组件，其中一个有我从main（）调用的方法。

Having a weird issue. In my Dart code I have some polymer components on the screen and one of them has a method I call from my main().

我通过做

PolyComp poly = querySelector("#idOfPolymer");
poly.flash();

这在dart中完美地工作。页面加载并且PolyComp开始闪烁。但是，当我通过从Dart IDE运行Build Polymer应用程序在Chrome中运行这个程序时，我得到一个错误，说无法在null上调用flash（）。

This works perfectly in dart. The page loads up and PolyComp starts to flash. However when I run this in Chrome by running Build Polymer app from the Dart IDE, I get an error that says cannot call flash() on null.

它只是使用一个事件总线闪光，让PolyComp听我的事件，但这是过度杀伤。

I ended up making it flash by just using an event bus and letting PolyComp listen to my event, but this is overkill.

我做错了什么？这发生在最新的Chrome，Firefox和Safari中。

What am I doing wrong? This happens in the latest Chrome, Firefox and Safari.

编辑：

JS也碰到了同样的问题。
https：// github .com / sethladd / dart-polymer-dart-examples / blob / master / web / todo_element / todo.html

I built the following polymer app to JS also and ran into the same issue. https://github.com/sethladd/dart-polymer-dart-examples/blob/master/web/todo_element/todo.html

适用于DartVM因为它调用一个空元素上的方法。

Works on DartVM, not in Chrome because its calling a method on a null element.

推荐答案

当你从 main ）方法，这可能是一个时间问题。
您可以尝试类似

When you run this code from the main() method it is probably a timing issue. You can try something like

import "package:polymer/polymer.dart";

main() {
  initPolymer().run(() {
    // code here works most of the time
    Polymer.onReady.then((e) {     
      // some things must wait until onReady callback is called
    });
  });
}

另请参阅如何在聚合物应用程序中实现主要功能

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