java - 如何在 fragment 中放置或替换列表

Question

我制作了一个测验应用程序，我在其中使用 Fragment 和 ViewPager 显示我的问题。 Question 取自 SQLite，这里我很困惑:如果我有 10 个问题，那么我必须使用 10 个 fragment 。如何使用 1 个 Fragment 容纳所有问题？

有这方面的想法吗？

主要 Activity :

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private int mFragmentIndex = 0;
    private ViewPager viewPager;
    private Button back, next;

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


        viewPager = findViewById(R.id.view_pager);
        setupViewPager(viewPager);

        back = findViewById(R.id.buttonBack);
        next = findViewById(R.id.buttonNext);
        back.setOnClickListener(this);
        next.setOnClickListener(this);
    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFrag(new Question1(), "Question1");
        adapter.addFrag(new Question2(), "Question2");
        adapter.addFrag(new Question3(), "Question3");
        viewPager.setOffscreenPageLimit(adapter.getCount());
        viewPager.setAdapter(adapter);
    }

    @Override
    public void onClick(View view) {
        if (view == back) {
            mfragmentIndex--;
            viewPager.setCurrentItem(mFragmentIndex);
        } else if(view == next) {
            mfragmentIndex++;
            viewPager.setCurrentItem(mFragmentIndex);
        }
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitle = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }
        public void addFrag(Fragment fragment,String title){
            mFragmentList.add(fragment);
            mFragmentTitle.add(title);
        }

        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            return super.getPageTitle(position);
        }
    }
}

我的 fragment ，问题 1:

public class Question1 extends Fragment {
    private List<Question> questionsList;
    private Question currentQuestion;

    private TextView txtQuestion, tvNoOfQs;
    private RadioButton rbtnA, rbtnB, rbtnC, rbtnD;

    private int obtainedScore = 0;
    private int questionId = 0;

    private int answeredQsNo = 0;

    ArrayList<String> myAnsList;

    public Question1() {
        // Required empty public constructor
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        final DBAdapter dbAdapter = new DBAdapter(getContext());
        questionsList = dbAdapter.getAllQuestions();
        currentQuestion = questionsList.get(questionId);

        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_question1, container, false);
        final RadioGroup grp = (RadioGroup)view.findViewById(R.id.radioGroup1);
        tvNoOfQs = (TextView)view.findViewById(R.id.tvNumberOfQuestions);
        txtQuestion = (TextView)view.findViewById(R.id.tvQuestion);
        rbtnA = (RadioButton)view.findViewById(R.id.radio0);
        rbtnB = (RadioButton)view.findViewById(R.id.radio1);
        rbtnC = (RadioButton)view.findViewById(R.id.radio2);
        rbtnD = (RadioButton)view.findViewById(R.id.radio3);
        setPertanyaan();

        myAnsList = new ArrayList<String>();
        return view;
    }

    private void setPertanyaan() {
        rbtnA.setChecked(false);
        rbtnB.setChecked(false);
        rbtnC.setChecked(false);
        rbtnD.setChecked(false);

        answeredQsNo = questionId+1;
        tvNoOfQs.setText(+answeredQsNo+"/"+questionsList.size());

        txtQuestion.setText(currentQuestion.getQUESTION());
        rbtnA.setText(currentQuestion.getOptionA());
        rbtnB.setText(currentQuestion.getOptionB());
        rbtnC.setText(currentQuestion.getOptionC());
        rbtnD.setText(currentQuestion.getOptionD());

        questionId++;
    }
}

Answer 1

我建议使用 Fragment 的参数来传递问题 ID。您已经对 Question 进行了抽象——看起来这里唯一真正改变的是问题 ID。

例如，您只有一个 QuestionFragment，它负责显示任何给定的 Question:

public class QuestionFragment extends Fragment {
    private static final String ARG_QUESTION_ID = "question_id";

    public static QuestionFragment newInstance(String questionId) {
        final QuestionFragment fragment = new QuestionFragment();
        final Bundle args = new Bundle();
        args.putString(ARG_QUESTION_ID, questionId);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(
            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        final String questionId = getArguments().getString(questionId);
        final DBAdapter dbAdapter = new DBAdapter(getContext());
        questionsList = dbAdapter.getAllQuestions();
        currentQuestion = questionsList.get(questionId);

        // ...

        return view;
    }
}

然后，在设置您的 ViewPager 时，只需在创建它时为每个实例提供问题 ID:

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFrag(QuestionFragment.newInstance(0), "Question1"));
    adapter.addFrag(QuestionFragment.newInstance(1), "Question2"));
    adapter.addFrag(QuestionFragment.newInstance(2), "Question3"));
    viewPager.setOffscreenPageLimit(adapter.getCount());
    viewPager.setAdapter(adapter);
}