The Dundee striker has been linked with Leeds United, Aston Villa, Queens Park Rangers, Derby County and Bolton Wanderers.
Hartley, though, has made it clear that he wants to retain the services of the 24-year-old striker for the 2016-17 campaign.
"We have had a lot of interest, but no concrete offers," Hartley told BBC Sport about Hemmings and Greg Stewart. ”They are two players we want to keep."
The Evening Telegraph reported back in April that Leeds United, Aston Villa, Queen Park Rangers, Derby County, Bolton Wanderers, Barnsley, Burton Albion, Sheffield United and Preston North End have all shown interest in Hemmings.
A recent report in The Evening Telegraph claims that Dundee will not sell the striker cheaply.
It has been reported that the Englishman does not have a clause in his contract which allows him to leave the Scottish Premiership side for a set fee.
Hartley scored 25 goals in 42 games for Dundee last season and was one of the best strikers in the Scottish Premiership.
Dundee finished eighth in the 2015-16 Scottish Premiership campaign.