使用序列化将数据发送到多个片段

Question

我是新来的，所以请多多包涵。我正在尝试使用 POJO 中的序列化方法将一些数据从 MainActivity 发送到多个片段。在 MainActivity 我打开一个新片段（FragOne）并且我能够获取数据，但是当我从 FragOne 打开一个新片段（FragTwo）时，应用程序崩溃并出现 NullPointerException。我搜索了如何使用序列化 POJO 将数据发送到多个片段，但没有结果。所以，如果有人能帮我解决这个问题，我将不胜感激。谢谢。

public class FragTwo extends Fragment{

    TextView name, position;

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

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        name = (TextView)view.findViewById(R.id.name);
        position = (TextView)view.findViewById(R.id.pos);

        Spa spa = (Spa)getArguments().getSerializable("spa");


        name.setText(spa.getName());
        position.setText(spa.getPosition());
    }
}

public class FragOne extends Fragment{

    TextView name, position;
    Button btn;

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

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        name = (TextView)view.findViewById(R.id.name);
        position = (TextView)view.findViewById(R.id.pos);
        btn = (Button)view.findViewById(R.id.change);

        Spa spa = (Spa)getArguments().getSerializable("spa");

        name.setText(spa.getName());
        position.setText(spa.getPosition());

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragTwo two = new FragTwo();
                ((MainActivity)getActivity()).replaceFragment(two);
            }
        });
    }
}

public class MainActivity extends AppCompatActivity {



    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

    public void replaceFragment(Fragment fragment){
        FragmentTransaction t = getSupportFragmentManager().beginTransaction();
        t.replace(R.id.frame, fragment).addToBackStack(null);
        t.commit();
    }

    public void SerializeMethod(View view){

        Spa spa = new Spa();
        spa.setName("Ricky");
        spa.setPosition("Android Dev");
        Bundle mBundle = new Bundle();
        mBundle.putSerializable("spa", spa);
        FragOne one = new FragOne();
        one.setArguments(mBundle);
        replaceFragment(one);
    }


}

public class Spa implements Serializable{

   private String name, position;

    public String getPosition() {
        return position;
    }

    public void setPosition(String position) {
        this.position = position;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Answer 1

从片段一切换到片段二时必须设置参数

btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Bundle mBundle = new Bundle();
            mBundle.putSerializable("spa", spa);
            FragTwo two = new FragTwo();
            two.setArguments(mBundle);
            ((MainActivity)getActivity()).replaceFragment(two);
        }
    });