MainActivity.java

public class MainActivity extends AppCompatActivity { 
  ...
  Button postsButton;
  
  ...
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      ...
      postsButton = (Button) findViewById(R.id.posts_button);
      postsButton.setVisibility(View.GONE);
      ...
      loginButton.setReadPermissions(Arrays.asList("public_profile",
                "email",
                "user_location",
                "user_birthday",
                "user_friends",
                "user_posts"));
      ...
  }