为什么我可以将数据从我的活动到片段得到数据？

Question

我有一个主动脉，它发送登录信息，例如名称，日期，电子邮件至第二次。从该第二个动作中，我试图将这些信息添加到第二个标签中的称为ProfileFragment的片段中。我一直在遇到一个错误，说：

java.lang.nullpointerexception：尝试在null对象引用中调用虚拟方法'java.lang.string android.os.os.getstring（java.lang.string）'。

以下是我的主动行动中处理“ datePicker对话框”按钮的方法，以及将数据放入捆绑并将其发送到二极序的提交按钮。这里没有问题。

@Override
    public void onClick(View v) {
        //When the date button is clicked, display a calendar dialog
        if (v.getId() == R.id.dateButton) {
            final Calendar cal = Calendar.getInstance();
            mYear = cal.get(Calendar.YEAR);
            mMonth = cal.get(Calendar.MONTH);
            mDay = cal.get(Calendar.DAY_OF_MONTH);
            DatePickerDialog datePickerDialog = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {

                @Override
                public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {

                    dateText.setText(dayOfMonth + "-" + (monthOfYear + 1) + "-" + year);

                }
            }, mYear, mMonth, mDay);
            datePickerDialog.show();
        }
        //When submit button is clicked. Validate form data and go to next activity
        if (v.getId() == R.id.submitButton) {
            //Create intent for ProfileActivity
            Intent SecondActivity = new Intent(MainActivity.this, SecondActivity.class);
            //Create a new bundle
            Bundle bundle = new Bundle();

            //Convert all input data to strings
            String stringName = name.getText().toString();
            String stringEmail = email.getText().toString();
            String stringUserName = userName.getText().toString();
            String stringDate = dateText.getText().toString();
            String stringDescription = description.getText().toString();
            String stringOccupation = occupation.getText().toString();

            try {   //If age/name/email/username is invalid or under 18 then return
                if ( !validateEmail() || !checkAge(convertDate(stringDate)) || !validateName() || !validateUserName() || !validateDescription() || !validateOccupation()) {
                    validateEmail();
                    validateName();
                    validateUserName();
                    validateDescription();
                    validateOccupation();
                    checkAge(convertDate(stringDate));
                    return;
                    //If age/name/username/email is valid then bundle data to send to ProfileActivity
                } else {
                    //get users age
                    int age = getAge(convertDate(stringDate));
                    //add data to bundle
                    bundle.putString("name", stringName);
                    bundle.putString("email", stringEmail);
                    bundle.putString("date", stringDate);
                    bundle.putString("userName", stringUserName);
                    bundle.putString("description",stringDescription);
                    bundle.putString("occupation",stringOccupation);
                    bundle.putInt("age", age);
                    //Start activity
                    SecondActivity.putExtras(bundle);
                    startActivity(SecondActivity);
                }
            } catch (ParseException e) {
                e.printStackTrace();
            }

        }
    }

这是我的第二次

public class SecondActivity extends AppCompatActivity {
private TabLayout tabLayout;
private ViewPager2 viewPager2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        tabLayout = findViewById(R.id.tablayout);
        viewPager2 = findViewById(R.id.viewpager2);

        viewPager2.setAdapter(createAdapter());

        //create profilefragment
        ProfileFragment profileFragment = new ProfileFragment();

        //get bundle

            Bundle bundle = getIntent().getExtras();
            if(bundle != null) {
            String stringDate = bundle.getString("date");
            String stringName = bundle.getString("name");
            String stringEmail = bundle.getString("email");
            String stringUserName = bundle.getString("userName");
            String stringDescription = bundle.getString("description");
            String stringOccupation = bundle.getString("occupation");
            int userAge = bundle.getInt("age");

            //set arguments
            profileFragment.setArguments(bundle);
        }
    }

    private VpAdapter createAdapter(){
        VpAdapter adapter = new VpAdapter(this);
        return adapter;
    }
}

class VpAdapter extends FragmentStateAdapter {
    public VpAdapter(FragmentActivity fa){
        super(fa);
    }
    private static int NUM_ITEMS = 1;
    @Override
    public Fragment createFragment(int position){
        Fragment fragment = null;

        switch(position){
            case 0:
                fragment = new ProfileFragment();
                break;
        }
        return fragment;
    }
    @Override
    public int getItemCount() {
        return NUM_ITEMS;
    }
}

，这是我的个人资料fragment

public class ProfileFragment extends Fragment {
    TextView welcome;
    TextView name;
    TextView age;
    TextView description;
    TextView occupation;

public ProfileFragment() {
        // Required empty public constructor
    }

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.fragment_profile, container, false);

        //Receive data from secondActivity through getArguments

        String mStringDate = getArguments().getString("date");
        String mStringName = getArguments().getString("name");
        String mStringEmail = getArguments().getString("email");
        String mStringUserName = getArguments().getString("userName");
        String mStringDescription = getArguments().getString("description");
        String mStringOccupation = getArguments().getString("occupation");
        int mUserAge = getArguments().getInt("age");

        welcome = v.findViewById(R.id.welcome);
        name = v.findViewById(R.id.user_name);
        age = v.findViewById(R.id.age);
        description = v.findViewById(R.id.description);
        occupation = v.findViewById(R.id.occupation);


        //set username in welcome message.
        welcome.setText("Welcome " + mStringUserName);

        //set username, age, description, and job into the profile fields
        name.append(mStringUserName);
        age.append(String.valueOf(mUserAge));
        description.append(mStringDescription);
        occupation.append(mStringOccupation);

        // Inflate the layout for this fragment
        return v;
    }

我的错误指向以下“字符串mstringdate = getArguments（）。getString（“ date”）;”;在哪里获得空对象引用。有人可以帮我吗？

Answer 1

仅与ViewModel一起使用一个活动