答案 0 :(得分：0)
No, once access is denied you cannot ask again. The only way to get access is for the user to enter settings and enable it themselves.
One alternative to this that I have seen is to display a message like ...
To enable us to blah blah blah we need access to your photos. Is that OK to ask? "YES" "Not Now"
Then if they tap yes you can ask for photo access and they will probably give you access.
If they press Not Now then you don't ask them but next time you can display your initial request again.
This means you only actually ask for access when they are probably going to grant access anyway.