Open SharePoint Online documents with custom application

Question

I'm currently developing an Add-In for SharePoint Online. This Add-In should add a new content-type in SharePoint and create some custom open and edit actions. When someone opens a document with that content-type, SharePoint should redirect the user to another application, passing the item id along. How do I achieve this? All the tutorials online state that I have to put an .ascx file on the server, which cannot be done in SharePoint Online...

Does someone have a clue? Can someone give me any direction?

Thanks!

Answer 1

For those coming by later, you can use the FileHandler options in Office365: https://msdn.microsoft.com/en-us/office/office365/howto/using-cross-suite-apps

This works fine if this issue is fixed.