I do not aggree with Nicolas, because the filebrowser do it right and my example, too.
The implementation app.start is a little tricky.
I see in the photo app a canvas shortly blinking.
This code does not help either:
file.root r$: f$=r$+"/cartman.png"
cats$ = "android.intent.category.DEFAULT"
app.start "android.intent.action.VIEW", f$ ,,, "image/*",cats$,, HEX("04000000") %FLAG_ACTIVITY_CLEAR_TOP
Until now BASIC! have in the main task a waiting problem in context to Android outside intents.
In early spring I invested a lot of time to fix this. But with no success
So I used a differend and tested solution to work arround this behavior and also ableing to receive data.
I designed the Interface for given JAVA code examples, because if you find an example it is mostly written in JAVA. I hope it is more flexible for the future and not so cryptic.