为了便于说明,我创建了一个继承自WebComponent的类FancyOption,该类在单击另一个子元素时更改为由一个子元素中的文本指定的背景颜色.
import 'package:web_ui/web_ui.dart';
import 'dart:html';
class FancyOptionComponent extends WebComponent {
ButtonElement _button;
TextInputElement _textInput;
FancyOptionComponent() {
// obtain reference to button element
// obtain reference to text element
// failed attempt
//_button = this.query('.fancy-option-button');
// error: Bad state: host element has not been set. (no idea)
// make the background color of this web component the specified color
final changeColorFunc = (e) => this.style.backgroundColor = _textInput.value;
_button.onClick.listen(changeColorFunc);
}
}
FancyOption HTML:
<!DOCTYPE html>
<html>
<body>
<element name="x-fancy-option" constructor="FancyOptionComponent" extends="div">
<template>
<div>
<button class='fancy-option-button'>Click me!</button>
<input class='fancy-option-text' type='text'>
</div>
</template>
<script type="application/dart" src="fancyoption.dart"></script>
</element>
</body>
</html>
我在这样的页面上有三个.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Sample app</title>
<link rel="stylesheet" href="myapp.css">
<link rel="components" href="fancyoption.html">
</head>
<body>
<h3>Type a color name into a fancy option textbox, push the button and
see what happens!</h3>
<div is="x-fancy-option" id="fancy-option1"></div>
<div is="x-fancy-option" id="fancy-option2"></div>
<div is="x-fancy-option" id="fancy-option3"></div>
<script type="application/dart" src="myapp.dart"></script>
<script src="packages/browser/dart.js"></script>
</body>
</html>
只需使用getShadowRoot()和查询它:
import 'package:web_ui/web_ui.dart';
import 'dart:html';
class FancyOptionComponent extends WebComponent {
ButtonElement _button;
TextInputElement _textInput;
inserted() {
// obtain references
_button = getShadowRoot('x-fancy-option').query('.fancy-option-button');
_textInput = getShadowRoot('x-fancy-option').query('.fancy-option-text');
// make the background color of this web component the specified color
final changeColorFunc = (e) => this.style.backgroundColor = _textInput.value;
_button.onClick.listen(changeColorFunc);
}
}
其中x-fancy-optionstring是元素的名称.
注意:我将构造函数更改为inserted()方法,这是一种生命周期方法.