刷新页面后，我想保留绘制的boxes和路径。
我正在使用 mxgraph https://jgraph.github.io/mxgraph/docs/manual.html
问题：完成绘图后，如果我刷新页面刷新，则应保留相同的内容<通过将工程图数据存储到localStorage中来实现strong>工程图。
注意：：我想从绘制的json object中提取canvas，并在刷新页面时从object重新构造它。
下面的视频演示了如何绘制： https://drive.google.com/file/d/1McTMz3e8I_quOcLGt2CtaQhqif3R31qs/view
https://jgraph.github.io/mxgraph/javascript/examples/editors/images/<!--
Copyright (c) 2006-2013, JGraph Ltd
Dynamic toolbar example for mxGraph. This example demonstrates changing the
state of the toolbar at runtime.
-->
<html>
<head>
<title>Toolbar example for mxGraph</title>
<!-- Sets the basepath for the library if not in same directory -->
<script type="text/javascript">
mxBasePath = 'https://jgraph.github.io/mxgraph/javascript/src';
</script>
<!-- Loads and initializes the library -->
<script type="text/javascript" src="https://jgraph.github.io/mxgraph/javascript/src/js/mxClient.js"></script>
<!-- Example code -->
<script type="text/javascript">
// Program starts here. Creates a sample graph in the
// DOM node with the specified ID. This function is invoked
// from the onLoad event handler of the document (see below).
function main()
{
// Checks if browser is supported
if (!mxClient.isBrowserSupported())
{
// Displays an error message if the browser is
// not supported.
mxUtils.error('Browser is not supported!', 200, false);
}
else
{
// Defines an icon for creating new connections in the connection handler.
// This will automatically disable the highlighting of the source vertex.
mxConnectionHandler.prototype.connectImage = new mxImage('images/connector.gif', 16, 16);
// Creates the div for the toolbar
var tbContainer = document.createElement('div');
tbContainer.style.position = 'absolute';
tbContainer.style.overflow = 'hidden';
tbContainer.style.padding = '2px';
tbContainer.style.left = '0px';
tbContainer.style.top = '0px';
tbContainer.style.width = '24px';
tbContainer.style.bottom = '0px';
document.body.appendChild(tbContainer);
// Creates new toolbar without event processing
var toolbar = new mxToolbar(tbContainer);
toolbar.enabled = false
// Creates the div for the graph
var container = document.createElement('div');
container.style.position = 'absolute';
container.style.overflow = 'hidden';
container.style.left = '24px';
container.style.top = '0px';
container.style.right = '0px';
container.style.bottom = '0px';
container.style.background = 'url("editors/images/grid.gif")';
document.body.appendChild(container);
// Workaround for Internet Explorer ignoring certain styles
if (mxClient.IS_QUIRKS)
{
document.body.style.overflow = 'hidden';
new mxDivResizer(tbContainer);
new mxDivResizer(container);
}
// Creates the model and the graph inside the container
// using the fastest rendering available on the browser
var model = new mxGraphModel();
var graph = new mxGraph(container, model);
// Enables new connections in the graph
graph.setConnectable(true);
graph.setMultigraph(false);
// Stops editing on enter or escape keypress
var keyHandler = new mxKeyHandler(graph);
var rubberband = new mxRubberband(graph);
var addVertex = function(icon, w, h, style)
{
var vertex = new mxCell(null, new mxGeometry(0, 0, w, h), style);
vertex.setVertex(true);
var img = addToolbarItem(graph, toolbar, vertex, icon);
img.enabled = true;
graph.getSelectionModel().addListener(mxEvent.CHANGE, function()
{
var tmp = graph.isSelectionEmpty();
mxUtils.setOpacity(img, (tmp) ? 100 : 20);
img.enabled = tmp;
});
};
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/rectangle.gif', 100, 40, '');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/rounded.gif', 100, 40, 'shape=rounded');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/ellipse.gif', 40, 40, 'shape=ellipse');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/rhombus.gif', 40, 40, 'shape=rhombus');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/triangle.gif', 40, 40, 'shape=triangle');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/cylinder.gif', 40, 40, 'shape=cylinder');
addVertex('https://jgraph.github.io/mxgraph/javascript/examples/editors/images/actor.gif', 30, 40, 'shape=actor');
}
}
function addToolbarItem(graph, toolbar, prototype, image)
{
// Function that is executed when the image is dropped on
// the graph. The cell argument points to the cell under
// the mousepointer if there is one.
var funct = function(graph, evt, cell, x, y)
{
graph.stopEditing(false);
var vertex = graph.getModel().cloneCell(prototype);
vertex.geometry.x = x;
vertex.geometry.y = y;
graph.addCell(vertex);
graph.setSelectionCell(vertex);
}
// Creates the image which is used as the drag icon (preview)
var img = toolbar.addMode(null, image, function(evt, cell)
{
var pt = this.graph.getPointForEvent(evt);
funct(graph, evt, cell, pt.x, pt.y);
});
// Disables dragging if element is disabled. This is a workaround
// for wrong event order in IE. Following is a dummy listener that
// is invoked as the last listener in IE.
mxEvent.addListener(img, 'mousedown', function(evt)
{
// do nothing
});
// This listener is always called first before any other listener
// in all browsers.
mxEvent.addListener(img, 'mousedown', function(evt)
{
if (img.enabled == false)
{
mxEvent.consume(evt);
}
});
mxUtils.makeDraggable(img, graph, funct);
return img;
}
</script>
</head>
<!-- Calls the main function after the page has loaded. Container is dynamically created. -->
<body onload="main();" >
</body>
</html>
答案 0 :(得分：4)
这使用mxgraph的XML编码。您会在mxGraph的one of the examples中看到此代码。虽然它不是json，但是很容易变成json，并且可以根据需要进行编辑或保存。现在，它按照您的要求存储在localStorage中。
在主函数的末尾（最后一次调用addVertex之后）添加以下行：
// read state on load
if(window.localStorage.graphState){
var doc = mxUtils.parseXml(window.localStorage.graphState);
var dec = new mxCodec(doc);
dec.decode(doc.documentElement, graph.getModel());
}
// save state on change
graph.getModel().addListener('change',function(){
var codec = new mxCodec();
window.localStorage.graphState = codec.encode(
graph.getModel()
).outerHTML;
});
更新2：切换到我自己的自定义html2json和json2html实现，以使答案完全独立
如果确实需要适当的JSON对象，则可以从xml转换为json，然后再转换回json。在下面您可以看到我对json对象进行了字符串化和解析，但这仅是将其保存在localStorage中所需要的。
首先添加这两个函数，以从html / xml转换为json，然后从json转换回html / xml：
function html2json(html){
if(html.nodeType==3){
return {
"tagName":"#text",
"content":html.textContent
}
}
var element = {
"tagName":html.tagName
};
if(html.getAttributeNames().length>0){
element.attributes = html.getAttributeNames().reduce(
function(acc,at){acc[at]=html.getAttribute(at); return acc;},
{}
);
}
if(html.childNodes.length>0){
element.children = Array.from(html.childNodes)
.filter(
function(el){
return el.nodeType!=3
||el.textContent.trim().length>0
})
.map(function(el){return html2json(el);});
}
return element;
}
function json2html(json){
var xmlDoc = document.implementation.createDocument(null, json.tagName);
var addAttributes = function(jsonNode, node){
if(jsonNode.attributes){
Object.keys(jsonNode.attributes).map(
function(name){
node.setAttribute(name,jsonNode.attributes[name]);
}
);
}
}
var addChildren = function(jsonNode,node){
if(jsonNode.children){
jsonNode.children.map(
function(jsonChildNode){
json2htmlNode(jsonChildNode,node);
}
);
}
}
var json2htmlNode = function(jsonNode,parent){
if(jsonNode.tagName=="#text"){
return xmlDoc.createTextNode(jsonNode.content);
}
var node = xmlDoc.createElement(jsonNode.tagName);
addAttributes(jsonNode,node);
addChildren(jsonNode,node);
parent.appendChild(node);
}
addAttributes(json,xmlDoc.firstElementChild);
addChildren(json,xmlDoc.firstElementChild);
return xmlDoc;
}
然后像这样从上面更改我的JavaScript代码片段，以将xml转换为json并返回：
// read state on load
if(window.localStorage.graphState){
var doc = json2html(JSON.parse(localStorage.graphState));
var dec = new mxCodec(doc);
dec.decode(doc.documentElement, graph.getModel());
}
// save state on change
graph.getModel().addListener('change',function(){
var codec = new mxCodec();
window.localStorage.graphState = JSON.stringify(html2json(codec.encode(
graph.getModel()
)));
});