FabricJS - 从JSON加载画布时出错 [英] FabricJS - Error when loading Canvas from JSON

问题描述

我使用的自定义对象从 fabric.Image 扩展到我的画布，如此答案。当我从服务器检索json字符串时，我试图将其加载到画布时出现奇怪的错误：

I'm using a custom object extended from fabric.Image in my canvas, as suggested in this answer. When I retrieve the json string from the server, I get odd errors when attempting to load it to the canvas:

var canvas = new fabric.Canvsd();

function loadCanvas(resp) {
  // response object contains a data field
  // that's essentialy a JSON string
  var json = JSON.parse(resp.data);
  canvas.loadFromDatalessJSON(json);
}

我得到一个奇怪的打印输出到控制台：未定义的调用方法'setupState'（fabric.min.js：1118）。我尝试用 canvas.loadFromJSON（json）替换调用，而是得到一个含糊的 SyntaxError：Unexpected token o 错误。当我在建议的链接线程中使用常规 fabric.Image 之前，此代码工作正常。我恐怕这可能是我失去了当我扩展favric的Image类与附加数据。

I get an odd printout to the console: Cannot call method 'setupState' of undefined (fabric.min.js: 1118). I tried replacing the call with canvas.loadFromJSON(json), and instead got a vague SyntaxError: Unexpected token o error. When I used a regular fabric.Image before the change suggested in the linked thread, this code worked fine. I fear this might be something I'm missing when I extended favric's Image class with aditional data. Thoughts?

推荐答案

搜索后，我看到一个类似线程在fabricjs google组中。原来我弄错了三件事：

After some search I saw a similar thread in the fabricjs google group. Turned out I messing up 3 things:

1. 我失去了一个 fromObject（）


2. 我使用 loadFromDatalessJSON（）当我使用了另一个自定义对象我应该一直使用 loadFromJSON（）。


3. 我使用 JSON.parse（json），然后将它传递到 loadFromJSON（）函数，该函数需要一个json字符串并在内部处理解析。 li>
   

1. I was missing a fromObject() callback definition in a different location for another custom object I made (I had a couple).
2. I was using loadFromDatalessJSON() when I should have been using simply loadFromJSON().
3. I was parsing the json string into an actual JSON using JSON.parse(json) before passing it into the loadFromJSON() function, which expected a json string and handled the parsing internally.

Derp。

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