即使使用 childFragmentManager 和 FragmentStatePagerAdapter 从后台返回后 ViewPager 为空

Question

我有一个视图寻呼机，当我第一次用它打开片段时它工作正常。从返回堆栈返回此片段后，我有一个空屏幕。我正在为 FragmentStatePagerAdapter 使用 ChildFragmentManager，但它仍然不起作用。通过每次在 onResume 中设置新的适配器找到临时解决方案，但在我看来这个解决方案不是解决此问题的最佳方法。请你帮助我，告诉我我做错了什么。这是我的代码：

public class RecentReviewsCollapsedContainerFragment extends AbstractFragmentView
    implements RecentReviewsCollapsedContract.View {

@BindView(R.id.recent_reviews_view_pager)
ViewPager mRecentReviewsViewPager;

@BindView(R.id.server_connection_button_try_again)
Button mTryAgainButton;

RecentReviewsViewPagerAdapter mViewPagerAdapter;
RecentReviewsCollapsedContract.Presenter mPresenter;
List<Review> mReviews;

public RecentReviewsCollapsedContainerFragment() {}


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

    return inflater.inflate(R.layout.fragment_recent_reviews_collapsed_container, container, false);
}

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

    ButterKnife.bind(this, view);

    mPresenter = new RecentReviewsCollapsedPresenter(this);
    mPresenter.loadReviews();

    setUpViewPager();
}

@Override
public void onResume() {
    super.onResume();

    if ( mViewPagerAdapter != null ) {
        cleanChildFragments(getChildFragmentManager());
        mViewPagerAdapter = new RecentReviewsViewPagerAdapter(getChildFragmentManager(), mReviews);
        mRecentReviewsViewPager.setAdapter(mViewPagerAdapter);
    }
}

@Override
public void startProgress() {
    showProgress();
}

@Override
public void stopProgress() {
    hideProgress();
}

@Override
public void showConnectionErrorMessage() {
    showServerConnectionError();
}

@Override
public void showNoItems() {
    showNoItems();
}

@Override
public void setReviewsList(List<Review> reviews) {
    if ( mViewPagerAdapter == null ) {
        mViewPagerAdapter = new RecentReviewsViewPagerAdapter(getChildFragmentManager(), reviews);
        mRecentReviewsViewPager.setAdapter(mViewPagerAdapter);
        mReviews = reviews;
        return;
    }
    mReviews = reviews;
    mViewPagerAdapter.setData(reviews);
}

private void setUpViewPager() {

    mRecentReviewsViewPager.setPageMargin(getResources()
                    .getDimensionPixelOffset(R.dimen.viewpager_margin));
}

private void cleanChildFragments(FragmentManager childFragmentManager) {
    List<Fragment> childFragments = childFragmentManager.getFragments();
    if (childFragments != null && !childFragments.isEmpty()) {
        FragmentTransaction ft = childFragmentManager.beginTransaction();
        for (Fragment fragment : childFragments) {
            ft.remove(fragment);
        }
        ft.commit();
    }
}

}

public class RecentReviewsViewPagerAdapter extends FragmentStatePagerAdapter {
private List<Review> mReviews;

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

public RecentReviewsViewPagerAdapter(FragmentManager fm, List<Review> reviews) {
    super(fm);

    mReviews = reviews;
}

@Override
public Fragment getItem(int position) {
    RecentReviewCollapsedItemFragment reviewItem = new RecentReviewsViewPagerAdapter.RecentReviewCollapsedItemFragment();
    reviewItem.setReview(mReviews.get(position));

    return reviewItem;
}

@Override
public int getItemPosition(Object object) {
    return POSITION_NONE;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    super.destroyItem(container, position, object);
}

@Override
public int getCount() {
    return mReviews.size();
}

public void setData(List<Review> reviews) {
    mReviews = reviews;
    notifyDataSetChanged();
}

public static class RecentReviewCollapsedItemFragment extends Fragment {
    private Review mReview;

    @BindView(R.id.recent_reviews_item_scroll_view)
    ObservableScrollView scrollView;

    @BindView(R.id.recent_reviews_collapsed_item_text_view_date)
    TextView mDateTextView;

    @BindView(R.id.recent_reviews_collapsed_item_rating_bar_dealer)
    RatingBar mDealerRating;

    @BindView(R.id.recent_reviews_collapsed_item_rating_bar_user)
    RatingBar mEmployeeRatingBar;

    @BindView(R.id.recent_reviews_collapsed_item_text_view_title)
    TextView mTitle;

    @BindView(R.id.recent_reviews_collapsed_item_text_view_review_author_name)
    TextView mAuthorNameTextView;

    @BindView(R.id.recent_reviews_collpsed_item_image_view_verified)
    ImageView mVerifiedCustomerImageView;

    @BindView(R.id.recent_reviews_collapsed_item_text_view_verified_customer)
    TextView mVerifiedCustomerTextView;

    @BindView(R.id.recent_reviews_collapsed_item_text_view_review_content)
    TextView mReviewContentTextView;

    @BindView(R.id.recent_review_collapsed_item_ratingbar_customer_service)
    RatingBar mCustomerServiceRatingBar;

    @BindView(R.id.recent_review_collapsed_item_ratingbar_quality_of_work)
    RatingBar mQualityOfWorkRatingBar;

    @BindView(R.id.recent_review_collapsed_item_ratingbar_friendliness)
    RatingBar mFriendlinessRatingBar;

    @BindView(R.id.recent_review_collapsed_item_ratingbar_pricing)
    RatingBar mPricingRatingBar;

    @BindView(R.id.recent_review_collapsed_item_text_view_recommend_dealer_value)
    TextView mRecommendDealerValueTextView;


    public RecentReviewCollapsedItemFragment() {}


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


        return inflater.inflate(R.layout.fragment_recent_review_collapsed_item, container, false);
    }

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

        ButterKnife.bind(this, view);

        bindData();

        setOnClickListener(scrollView);
        setOnClickListener(mDateTextView);
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    public void setReview(Review review) {
        mReview = review;
    }

    private void bindData() {
        mDateTextView.setText(mReview.getDate());
        mDealerRating.setRating((int) mReview.getRating());
        mEmployeeRatingBar.setRating((int) mReview.getEmployeeRating());
        mTitle.setText(String.format("\"%s\"", mReview.getTitle()));
        mAuthorNameTextView.setText(String.format("- %s", mReview.getReviewUserName()));
        setVerifiedCustomer();
        mReviewContentTextView.setText(mReview.getReviewBody());
        mCustomerServiceRatingBar.setRating(mReview.getCustomerServiceRating());
        mQualityOfWorkRatingBar.setRating(mReview.getQualityRating());
        mFriendlinessRatingBar.setRating(mReview.getFriendlinessRating());
        mPricingRatingBar.setRating(mReview.getPricingRating());
        setRecommendDealer();
    }

    private void setVerifiedCustomer() {
        if ( mReview.isVerifiedCustomer() ) {
            mVerifiedCustomerTextView.setVisibility(View.VISIBLE);
            mVerifiedCustomerImageView.setVisibility(View.VISIBLE);
            return;
        }
        mVerifiedCustomerTextView.setVisibility(View.INVISIBLE);
        mVerifiedCustomerImageView.setVisibility(View.INVISIBLE);
    }

    private void setRecommendDealer() {
        if ( mReview.isRecommendDealer() ) {
            mRecommendDealerValueTextView.setText(getActivity().getString(R.string.yes));
            return;
        }
        mRecommendDealerValueTextView.setText(getActivity().getString(R.string.no));
    }

    private void setOnClickListener(View view) {
        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FullReviewFragment fragment = new FullReviewFragment();
                fragment.setReview(mReview);
                ((ViewContainer) getActivity()).showFragment(fragment, true);
            }
        });
    }
}

Answer 1

您似乎没有在重启时重新连接适配器

if ( mViewPagerAdapter == null ) {
    mViewPagerAdapter = new RecentReviewsViewPagerAdapter(getChildFragmentManager(), reviews);
    mRecentReviewsViewPager.setAdapter(mViewPagerAdapter); // <<<<
    mReviews = reviews;
    return;
}
mReviews = reviews;
mViewPagerAdapter.setData(reviews);

只要 mRecentReviewsViewPager 没有适配器，就必须调用此行

即使使用 childFragmentManager 和 FragmentStatePagerAdapter 从后台返回后 ViewPager 为空

ViewPager is empty after returning from back stak even with using of childFragmentManager and FragmentStatePagerAdapter

android-viewpager

fragmentmanager