Answers for "could not open proj generic class cache for build file 'c:\users\hp\studioprojects\first_flutter1\android\app\build.gradle' (c:\users\hp\.gradle\caches\6.7\scripts\67g05d481bu1uh5e789exjgwh)."

could not open proj generic class cache for build file 'c:\users\hp\studioprojects\first_flutter1\android\app\build.gradle' (c:\users\hp\.gradle\caches\6.7\scripts\67g05d481bu1uh5e789exjgwh).

check with jdk version, JDK 16 may causing the issue. You can try to install lower version. I have tried with 11 and 8 jdk and its working. And then rebuild your app.
version 11 worked good for me