Error : Ambiguous method call. Both findViewById (int) in AppCompactActivity and Activity

If you recently updated your project to API, Try doing

File -> Invalidate Caches / Restart

then

File -> Sync Project with Gradle Files

this resolve for me.

Upgrade to appcompat 27 solved this for me

You have

import android.support.v7.app.AppCompatActivity
import android.app.Activity

both in your code. Remove import android.app.Activity as I can see, it's not required for you.

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