The app itself is a great start and really does help looking for Hanja. A couple of things I noticed
1. The app shouldn’t start with a predetermined search as the Home Screen. Maybe a an example search at the bottom would be better but it makes the back bottom look useless
2. Try adding throttle searching where after an initial hangeul part is written, it searches and returns based of what is currently in the search bar (like Google does)
3. (This is more personal/educative) as someone who has studied both Japanese and Mandarin, I think you have a good blend of Sino/Japa-Korean mixture in the search as well as plain hanja! Just add more because the pool seems pretty small for the generic words such as 이귝 (Which would be 離陸ー ririku in Japanese, I lyuk in Korean) or 창백 (蒼白 — cāng bâi in Mandarin, chang baeg in Korean)
Overall it’s definitely a great app and look for to using it!