如何确保在活动中从静态方法new Instance创建片段

public class MyFragment extends Fragment {
    private static MyFragment instance;

    private MyFragment() {
        // 私有构造函数
    }

    public static MyFragment newInstance() {
        if (instance == null) {
            instance = new MyFragment();
        }
        return instance;
    }

    public static MyFragment getInstance() {
        return instance;
    }
}

// 在活动中使用片段
MyFragment fragment = MyFragment.getInstance();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.add(R.id.fragment_container, fragment);
transaction.commit();