2

为了从孩子到父母进行交流,事件似乎是最优雅的方式。父母与孩子沟通的方式有哪些?

更具体地说,我想要一个在孩子可见时调用的方法。这些是我提出的想法:

  • xtag - 优雅而有效
  • 观察“隐藏” - 无法使其正常工作,隐藏在元素中未标记为可观察
  • 在子级中发布触发变量,在​​父级中绑定和更改它 - 丑陋

还有其他选择吗?

4

2 回答 2

0

我还没有尝试过,但也许MutationObserver 可以满足您的要求。

Seth Ladd 的聚合物示例包含两个示例:第一个监听 onMutation 事件 https://github.com/sethladd/dart-polymer-dart-examples/blob/master/web/onmutation-mutation-observer/my_element.dart

library my_element;

import 'package:polymer/polymer.dart';
import 'dart:html';
import 'dart:async';

@CustomTag('my-element')
class MyElement extends PolymerElement {
  MyElement.created() : super.created() {

    // NOTE this only fires once,
    // see https://groups.google.com/forum/#!topic/polymer-dev/llfRAC_cMIo
    // This is useful for waiting for a node to change in response
    // to some data change. Since we don't know when the node will
    // change, we can use onMutation.
    onMutation($['list']).then((List<MutationRecord> records) {
      $['out'].text = 'Change detected at ${new DateTime.now()}';
    });

    new Timer(const Duration(seconds:1), () {
      $['list'].children.add(new LIElement()..text='hello from timer');
    });
  }
}

第二个示例使用 MutationObserver 类 https://github.com/sethladd/dart-polymer-dart-examples/blob/master/web/mutation_observers/my_element.dart

=== 编辑 ===

您是否尝试过链接的示例?观察方法允许指定应该观察什么:

  /**
   * Observes the target for the specified changes.
   *
   * Some requirements for the optional parameters:
   *
   * * Either childList, attributes or characterData must be true.
   * * If attributeOldValue is true then attributes must also be true.
   * * If attributeFilter is specified then attributes must be true.
   * * If characterDataOldValue is true then characterData must be true.
   */
  void observe(Node target,
               {bool childList,
                bool attributes,
                bool characterData,
                bool subtree,
                bool attributeOldValue,
                bool characterDataOldValue,
                List<String> attributeFilter}) {
于 2013-12-02T12:28:37.047 回答
0

为了从母聚合物到子聚合物进行通信,这个解决方案对我很有用。

如果我们有一个像这样的子聚合物元素:

library my_element;

import 'package:polymer/polymer.dart';
import 'dart:html';
import 'dart:async';

@CustomTag('my-element')
class MyElement extends PolymerElement {
  MyElement.created() : super.created() {
  }

  myCustomMethod(param){
    print("pass-in param = $param");
  }

}

要从父元素访问您的子元素:

  1. 在父元素中查询您的子聚合物元素(是的,首先访问 HTML 元素)
  2. 将其转换为绑定类(例如:在我们的示例中为 MyElement.dart)
  (theParentClass.querySelector("my-element") as MyElement).myCustomMethod({"done":true});
于 2015-07-19T06:07:44.147 回答