我正在尝试让加载屏幕在 Polymer 中工作，如以下要点所示:https://gist.github.com/SlicedSilver/f2e93a5995f84d9cd512
这个想法非常简单:入口点是一个轻量级 HTML 文件，用于呈现加载屏幕，其主体包含一个 onload 回调，一旦呈现该轻量级页面，该回调就会通过 DOM 加载 Polymer 应用程序。
它在桌面浏览器上运行得很好。在移动浏览器上，filestoload.html 永远不会被加载(但也不会抛出任何错误)，因此加载屏幕只是停留在那里，应用程序永远不会加载。完整代码如下，但要特别注意这一行:
tag.setAttribute('onload', 'polymerLoader.insertPolymerApplication()');
该 onload 事件永远不会触发，也不会抛出错误。我尝试通过 DOM 和适当的事件处理程序来捕获它，但没有成功。我什至尝试将其完全从 JS 手中夺走，作为健全性检查，将链接添加到 HTML 文件，如下所示:
<link rel="import" href="/filestoload.html" onload="polymerLoader.insertPolymerApplication()" >
相同的结果 - 在桌面上显示应用程序，但仅在移动设备上显示加载屏幕。我没有什么想法。有什么帮助吗？
...
这是轻量级入口点(index.html)
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, minimum-scale=1, initial-scale=1, user-scalable=yes">
<link rel="shortcut icon" type="image/png" href="/assets/images/favicon.ico"/>
<title>GreenMaven</title>
<meta name="description" content="greenmaven description">
<script src="assets/js/polymerAppLoader.js"></script>
<style type="text/css">
.loading {
position: fixed;
top: 50%;
left: 50%;
/* bring your own prefixes */
transform: translate(-50%, -50%);
z-index: -500;
display: block;
}
</style>
</head>
<body onload="polymerLoader.loadPolymerApplication()">
<div id="loader" class="loading">
<img src="assets/images/gears.svg" />
</div>
</body>
</html>这是加载 Polymer 应用程序其余部分的 JS:
'use strict';
/* global polymerLoader */
/*jshint unused:false*/
/*jshint -W079*/
// This is the normal conditional loader for the Web components Polyfill
if ('registerElement' in document && 'createShadowRoot' in HTMLElement.prototype && 'import' in document.createElement('link') && 'content' in document.createElement('template')) {
// We're using a browser with native WC support!
} else {
// Add web components polyfill...
document.write('<script src="bower_components/webcomponentsjs/webcomponents.lite.js"><\/script>');
}
var polymerLoader = (function() {
// Function for creating a link element and inserting it into the <head> of the html document
function addLinkTag(elementType, address, shim, loadTrigger) {
var tag = document.createElement('link');
tag.rel = elementType;
tag.href = address;
if (shim) {
// add the shim-shadowdom attribute
tag.setAttribute('shim-shadowdom', '');
}
if (loadTrigger) {
// This file needs to be loaded before inserting the Polymer Application
// when finished loading it will call the polymerLoader.insertPolymerApplication() function
tag.setAttribute('onload', 'polymerLoader.insertPolymerApplication()');
expectedCalls++;
}
document.getElementsByTagName('head')[0].appendChild(tag);
}
var pgApploaded = false;
function loadPolymerApplication() {
// Only insert once.
if (!pgApploaded) {
addLinkTag('import', 'filestoload.html', false, true);
pgApploaded = true;
}
}
// Counter variable for insertPolymerApplication() calls
var callCount = 0;
var expectedCalls = 0;
function insertPolymerApplication() {
callCount++;
// Only when callCount >= expectedCalls
// The application is only inserted after all required files have loaded
// for the application to work.
if (callCount >= expectedCalls) {
// here is the html that is inserted when everything is loaded.
document.querySelector('body').innerHTML += '<template is="auto-binding" id="app"><polymer-app id="main-app"></polymer-app></template>';
document.getElementById('loader').style.display = 'none';
}
}
return {
insertPolymerApplication: function() {
insertPolymerApplication();
},
loadPolymerApplication: function() {
loadPolymerApplication();
}
};
})(document);最后，这是 filestoload.html 文件，其中包含通常在 Polymer index.html 中找到的链接和脚本:
<!doctype html>
<!-- Here is where you put the scripts required by the page, that would normally be -->
<!-- included in the index.html page, you can still use grunt/gulp build functions on these -->
<!-- will be replaced with elements/elements.vulcanized.html -->
<link rel="manifest" href="/manifest.json">
<link rel="import" href="/src/greenmaven-app/greenmaven-app.html">
<link rel="stylesheet" href="assets/css/main.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
<!-- endreplace-->
<!-- build:js scripts/app.js -->
<script src="properties_base/farmhacker-properties.js"></script>
<!-- endbuild-->
<!-- build:js scripts/thirdparty.js -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
<script>
$(function() {
$('a[href*="#"]:not([href="#"])').click(function() {
if (location.pathname.replace(/^\//,'') == this.pathname.replace(/^\//,'') && location.hostname == this.hostname) {
var target = $(this.hash);
target = target.length ? target : $('[name=' + this.hash.slice(1) +']');
if (target.length) {
$('html, body').animate({
scrollTop: target.offset().top - $('#navbar').height()
}, 1000);
return false;
}
}
});
});
</script>
<!-- endbuild-->最佳答案
事实证明这是 Polymer 构建中的某种错误，可能与另一个错误有关，在该错误中运行 polymer build 导致应用程序从 Bower 组件中抛出一堆 404 错误。
当我对服务器进行原始部署(无需构建/硫化)时，桌面和移动设备上的一切都运行良好，并且没有错误。
关于javascript - 让加载屏幕与 Polymer 配合使用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42358957/