How can I let users upload file via mobile phone?

How can I let users to upload file via mobile phone.

I use a iframe and embed my form into my website.

I read past forums on your support site.

There's two way:

1. upload field 

2. filepicker

which is the better way?

I used filepicker to test in my android phone.

but when I upload my file . The pages just refesh and nothing happened...

Could you tell me how to make "upload file via mobile phone" work well.

Thank you

Best regard, 

Cheng Hsuan

File picker is the recommend one. Can you please share the link to your page where this form is embedded so we can test?