How to implement File Save/Download feature in Teams Mobile Extention/App?

Hi, 

I have checked the solution you provided. Permissions in the Manifest File have already been given. But when I checked this same solution check clicking on a element it just opened that Image but did not download to the IOS files/gallery or Download folder of my IOS device. It's Just opening on a new page from the Teams app. 

Can you give me an update regrading this? 

Thank you.