聚合查询选择器在 DartVM 上运行，但在编译后不在 Chrome 中运行 [英] Polymer querySelector working on DartVM but not in Chrome after compile

问题描述

遇到一个奇怪的问题.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().

我通过执行获取对它的引用

I grab a reference to it by doing

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

这在 dart 中非常有效.页面加载完毕，PolyComp 开始闪烁.但是，当我通过从 Dart IDE 运行 Build Polymer 应用程序在 Chrome 中运行它时，我收到一条错误消息，提示无法在 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.

我最终仅通过使用事件总线并让 PolyComp 监听我的事件来使其闪烁，但这太过分了.

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?这种情况发生在最新的 Chrome、Firefox 和 Safari 中.

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

我也为 JS 构建了以下聚合物应用程序，但遇到了同样的问题.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，不适用于 Chrome，因为它在空元素上调用方法.

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

推荐答案

当您从 main() 方法运行此代码时，可能是时间问题.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
    });
  });
}

另见如何在聚合物应用中实现一个主要功能

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