My ringneck doesn't eat food outside his cage!!

I found a ringneck parrot 6 months ago as his feathers were cut by someone he couldn't fly well at that time....also his beak is a but black from bottom and he has a full ring so we assume that he is quite old parrot

Now he comes to my finger,climbs the curtains but he is not still trained enough....whenever I try to give him any treat outside his cage he never eats that and is always in hurry to either fly on the curtain or his cage ,so he never sits on me comfortably ....

Yup only except night when he likes to be pet on his head .....

So I need help about how can I ensure him more ....I tried every method but all in vain as he only eats inside his cage.....please help me....!!!!