I want to make nft marketplace with solana in android. There are many examples connecting solana wallet(ex. solflare, phantom ...) in web client. But i don't know how to connect wallet in android dapp.
It doesn't look like you can currently, it is something the mobile wallets need to implement an integration for first, it seems.
I/we had the same question, see these:
Suggestion: If you had a particular mobile wallet you wanted to use, like Phantom which provides a Web Browser feature, you could use that to load marketplaces that have wallet adapter functionality, which can potentially hook into the native app Wallet flows e.g. Metaplex + Phantom, which I've been able to connect dev wallets to.