Unhandled Exception: Null check operator used on a null value

[gtuceturan]

I have 4 pages I use 3 EChart graphs When ı click button and I rebuild that chart on which page it is.
But when page skip chart to different chart there is a blank page and I get error message Null check operator used on a null value
How can show Is there any way controlller editing in diffrent function from onLoad? Because when skip another graph never go onload function in Echart widget

Thank you for helping

[LIN Chen]

I suggest you to try this one: https://github.com/entronad/graphic