See here.
I didn't bother to read any background information on SAF, because I am an idiot.
Idiot comes from the Greek (ἰδιώτης) and actually means "private person", not "expert." That's all. But you're certainly an expert when it comes to App Inventor. 
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13 posts were split to a new topic: When I pick an image using picker, I get READ_MEDIA_IMAGES has been denied
Dear @Anke, nice to read that. Me too, I've studied ancient greek and latin more than 50 years ago at the classic lyceum (as we call that type of school here in Italy), before discovering the charm of physics... 
German language has many similarities with ancient greek and latin: so I loved to study it (German) but the problem has been the short time remaining to do that after a "long" working day and an eveving to dedicate to the kids....maybe next life.... 
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