SectionsPagerAdapter 和 FragmentPagerAdapter

Question

首先让我尝试重现我的问题/问题。

我的活动是一个带有 3 个选项卡的 TabbedActivity，由一个 SectionPageAdapter 和一个 FragmentPageAdapter 完成。

用户在这 3 个选项卡上输入数据。只需滑动用户就可以更改选项卡。用户填写完所有数据后，他必须点击一个 FloatingActionButton 来保存数据。

现在有我的问题，我不知道我是否可以使用填充的数据访问这 3 个片段？ 我可以使用填充的数据加载所有 3 个片段，读取数据并保存它，还是我必须在更改页面之前处理 PageChangeListenEvent 并保存数据？

代码：

 public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {

        return TravelInfoActivity.PlaceholderFragment.newInstance(position + 1);
    }

    @Override
    public int getCount() {
        return maxTabs;
    }

}


 public static class PlaceholderFragment extends Fragment {

    private static final String ARG_FRAGMENT_ID = "fragment_id";
    private static int REQUEST_CODE_PLACE = 1;
    private View currentRootView;
    private View currentClickedView;

    @SuppressLint("UseSparseArrays")
    private HashMap<Integer, View> hMap = new HashMap<>();


    public PlaceholderFragment() {
    }

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static TravelInfoActivity.PlaceholderFragment newInstance(int sectionNumber) {
        TravelInfoActivity.PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        int fragmentLayout;
        switch (sectionNumber) {
            case 1:
                fragmentLayout = R.layout.fragment_accommodation;
                break;
            case 2:
                fragmentLayout = R.layout.fragment_visited_places;
                break;
            case 3:
                fragmentLayout = R.layout.fragment_additional_info;
                break;
            default:
                fragmentLayout = R.layout.fragment_accommodation;
        }
        args.putInt(ARG_FRAGMENT_ID, fragmentLayout);
        fragment.setArguments(args);
        return fragment;
    }
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        final View rootView = inflater.inflate(getArguments().getInt(ARG_FRAGMENT_ID), container, false);
        currentRootView = rootView;
        switch (getArguments().getInt(ARG_FRAGMENT_ID)) {
            // switch handling here, not relevant
         }
 return rootView;
    }

Answer 1

伙计们，我做到了让我的大脑焕然一新；）

只需将 Fragment 中的实例保存到数组中，以后就可以使用它。 我在 SectionPageAdapter 中制作了这个并覆盖了方法 instantiateItem()。

public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

    private SparseArray<Fragment> registeredFragments = new SparseArray<>();

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


    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Fragment fragment = (Fragment) super.instantiateItem(container, position);
        Integer fragmentId = fragment.getArguments().getInt("fragment_id");
        registeredFragments.put(fragmentToPageMap.get(fragmentId), fragment);

        return  fragment;
    }

    public Fragment getRegisteredFragment(int position) {
        return registeredFragments.get(position);
    }

    public boolean registeredFragmentExists(int position) {
        if(registeredFragments.size() >= position) {
            if(registeredFragments.get(position) != null) {
                return true;
            }
        }
        return false;
    }


    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
       return TravelInfoActivity.PlaceholderFragment.newInstance(position);
    }

    @Override
    public int getCount() {
        return maxTabs;
    }

}

稍后您可以访问片段 roo​​tView

mSectionsPagerAdapter.getRegisteredFragment(position);
fragment.getActivity().findViewById(id);