java - How can I automatically delete a file referenced by a SQLite Database item when this item gets deleted from the database (in Android)? -


context

i'm creating sqlite database manipulated content provider in android.

question

let's have following sqlite table:

_id          _data ------------------------  0       /path/to/file/0  1       /path/to/file/1

where _id primary key , _data url file in local file system.

what have in order automatically delete file referenced _data column when correspondent row deleted?

p.s.: know sqlite has specific features accomplish this, i'm programming android, means of these features not available.

observations

i taking @ system mediaprovider.java class source , noticed trigger:

db.execsql("create trigger if not exists thumbnails_cleanup delete on thumbnails " +                 "begin " +                     "select _delete_file(old._data);" +                 "end");

which apparently deletes file referenced thumbnails._data when thumbnail item deleted.

i tried create similar trigger in application, didn't work. ideas why?


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