i have seen this question
Why Warning:Unable to find optional library: org.apache.http.legacy occurs?
and few more but the problem is not solved , i was using target 23 and i didn't want to , so now when i go back to target 21 i receive this error :
Warning:Unable to find optional library: org.apache.http.legacy
yes i have the optional.json file , yes i have try'd to put the apache in my lib folder but this error still occurs i am stuck on this for far to long .