I was searching for my Android App and saw some websites have listed my app but they have also provided link to download APK. It worries me. Is it possible to stop these thugs extracting APK and uploading on their websites?
The simple answer is nom, you can’t prevent. The Android ecosystem, unlike Apple’s ecosystem, is open. Anyone can get APK of your app and upload anywhere they wish. As long as they don’t mess with the APK i.e, reverse engineer it and exploit it you should be fine.
Don’t upload APK on Google Play or publish it anywhere. Problem solved 
To prevent people from extracting the APK from your Android app, you can use techniques like code obfuscation, proguard, or R8 to make the app’s code harder to reverse-engineer. Additionally, you can implement Secure API calls, use app signing with key management, and consider integrating tamper detection methods. Enforcing code integrity checks can also help protect your app.