我有一个TabLayout Activity，它包含3个片段，每个片段都有按钮。我尝试从该Activity的其中一个片段中获取按钮，但在空对象引用上收到错误“尝试调用虚拟方法'void android.widget.Button.setText（java.lang.CharSequence）'”。如何从TabLayout片段中获取按钮，并在单击时将其分配给change Activity？
我的TabLayout类：

public class SecondPage extends AppCompatActivity {

    TabLayout tl;
    ViewPager2 vp2;
    PagerAdapter pa;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second_page);

        tl = findViewById(R.id.tab_layout_spage);
        vp2 = findViewById(R.id.view_pager_spage);
        pa = new PagerAdapter(this);
        vp2.setAdapter(pa);
        //there I try to get Button via Button b = findViewById(R.id.fbtn); and get an error
        //fbtn is in the fragment Basic

        tl.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                vp2.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });
    }
}

我的片段类：

public class Basic extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_basic, container, false);
    }

}