public class BaseActivity extends AppCompatActivity { @Override public void onBackPressed() { super.onBackPressed(); // Perform necessary actions to go back to the previous activity } }In this example, we have created a BaseActivity class that extends the AppCompatActivity class. The onBackPressed method has been overridden to perform the necessary actions to go back to the previous activity. Package/Library: It is difficult to determine the specific package or library that BaseActivity belongs to without additional context. However, it is possible that this class belongs to an Android app development package or library.