If in the sonata forms of the better-known masters a lot of fascinating things happen within themes themselves, in the sonata forms of guitarist composers from the early 19th century many of the more dramatic things really take place in their transitions. Matiegka's no exception. His modulating transition is substantially longer and more substantial than his opening theme.
Transitions were where 19th century guitarists liked to show off, econdary dominant patterns to prepare us for a the new key, launches into a flourish of rising scale passagework that is predictable yet satisfying. One of my music professors might have dubbed this "trite, but delightfully trite". Crucially, Matiegka saves his repetitious sequencing for a space where he's got rhythmic momentum in his favor and he embellishes just enough on the second pass to keep things racing forward. He also further cements that we've moved to A major by indulging in some ornamentation by way of submediant harmony borrowed from the parallel minor of the A major arrival point.
It is from this material, by and large, Matiegka draws a few of his ideas for the development, but we'll get to that in time. Next, theme 2.