[GitHub] [incubator-echarts] luruxi commented on issue #9383: echarts渲染不出来报错

[GitBox <gi...@apache.org>]

luruxi commented on issue #9383: echarts渲染不出来报错
URL: https://github.com/apache/incubator-echarts/issues/9383#issuecomment-494314107
 
 
   > I have solved this problem in my project.
   > 
   > When I debuged my project, it would sometimes log the errors like this:
   > ![image](https://user-images.githubusercontent.com/17041261/54177227-7ba5ee80-44cc-11e9-9aaa-f8e26799ec00.png)
   > 
   > From the errors tips, it significantly show that this error appeared when execute this code:
   > 
   > ```
   > this.ctx.dpr = this.dpr
   > ```
   > 
   > in `Layer.js` 、`Painter.js`、`zrender.js` etc.
   > 
   > So I detect the Layer.js file, in `node_modules\zrender\lib\Layer.js` , I saw this code in a function named 'initContext':
   > 
   > ```
   > initContext: function () {
   >     this.ctx = this.dom.getContext('2d');
   >     this.ctx.dpr = this.dpr;
   >   },
   > ```
   > 
   > I modified this function to the code below:
   > 
   > ```
   > initContext: function () {
   >     this.ctx = this.dom.getContext('2d');
   >     try {
   >       this.ctx.dpr = this.dpr;
   >     } catch (e) {
   >       setTimeout(() => {
   >         location.reload()
   >       }, 500)
   >     }
   >   },
   > ```
   > 
   > And the bug resolved.
   > 
   > I think this is a iOS bug happened occasionally, when the Layer.js or other Javascript library execute the command like `this.ctx = this.dom.getContext('2d');`，the lib find `this.dom` is not found, `this.dom` here represent the HTMLCanvasElement. It exactly is a canvas element in most time, when the iOS javascript engines display correctly, but sometimes it would not, it was not found instead. So `this.ctx` is `null`, so it will throw error when execute `this.ctx.dpr = this.dpr;`.
   
   Thank you. I'll try

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