Nested Fragment with backstack Resume

问题

In my application there are several fragments in an activity and I am maintaining a backStack for these fragment. Everything is okay, but there is a nested fragment among them. When I put it into backStack and again resume in by pressing back button, the fragment looks overllaping previous content (child fragment). This is the normal view:

This is the screenshot of overlapping view (when I resume the fragment):

You can get the difference as the second one's text is more deep (that means child fragment is overlapping)

How can I avoid that? This the code for my nested fragment:

public class CompetitiveProgramming extends SherlockProgressFragment implements
        OnChapterSelectListener, OnSubChapterSelectListener {

    View mContentView;
    static public List<Chapter> chapterList = new ArrayList<Chapter>();
    private ProcessTask processTask = null;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        mContentView = inflater.inflate(
                R.layout.competitive_programming_exercise, container, false);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setContentShown(false);
        setContentView(mContentView);
        processTask = new ProcessTask();
        processTask.execute();
    }


    protected class ProcessTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... params) {
            // background task
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            if (mContentView.findViewById(R.id.fragment_container) != null) {
                getChildFragmentManager().beginTransaction()
                        .add(R.id.fragment_container, new ChaptersListFragment()).commit();
            } else {
                transaction.add(R.id.category_fragment, new ChaptersListFragment());
                transaction.add(R.id.sub_category_fragment, new SubChaptersListFragment());
                transaction.add(R.id.sub_sub_category_fragment,
                        new SubSubChaptersListFragment());
            }
            transaction.commit();
            setContentShown(true);
        }

    }

    static protected class Chapter {
        String chapterTitle;
        List<SubChapter> subchapterList;

        public Chapter(String chapterTitle, List<SubChapter> subchapterList) {
            this.chapterTitle = chapterTitle;
            this.subchapterList = subchapterList;
        }

    }

    @Override
    public void onChapterSelected(int position) {
        SubChaptersListFragment subChaptersListFrag = (SubChaptersListFragment) getChildFragmentManager()
                .findFragmentById(R.id.sub_category_fragment);
        if (subChaptersListFrag != null) {
            subChaptersListFrag.updateList(position);
        } else {
            SubChaptersListFragment subChapterFragment = new SubChaptersListFragment();
            Bundle args = new Bundle();
            args.putInt(SubChaptersListFragment.CHAPTER_POSITION, position);
            subChapterFragment.setArguments(args);
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            transaction.replace(R.id.fragment_container, subChapterFragment);
//          transaction.addToBackStack(null);
            transaction.commit();
        }
    }

    @Override
    public void onSubChapterSelected(int prev, int position) {
        SubSubChaptersListFragment subSubChaptersListFrag = (SubSubChaptersListFragment) getChildFragmentManager()
                .findFragmentById(R.id.sub_sub_category_fragment);
        if (subSubChaptersListFrag != null) {
            subSubChaptersListFrag.updateList(prev, position);
        } else {
            SubSubChaptersListFragment subSubChapterFragment = new SubSubChaptersListFragment();
            Bundle args = new Bundle();
            args.putIntArray(SubSubChaptersListFragment.POSITIONS, new int[]{prev, position});
            subSubChapterFragment.setArguments(args);
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            transaction.replace(R.id.fragment_container, subSubChapterFragment);
//          transaction.addToBackStack(null);
            transaction.commit();           
        }
    }

    @Override
    public void onStop() {
        super.onStop();
        if (processTask != null && processTask.getStatus() != AsyncTask.Status.FINISHED) {
            processTask.cancel(true);
        }
    }

}

回答1:

Kirill Kulakov is right. replace instead of add should be used. I edited the code:

public class CompetitiveProgramming extends SherlockProgressFragment implements
        OnChapterSelectListener, OnSubChapterSelectListener {

    View mContentView;
    static public List<Chapter> chapterList = new ArrayList<Chapter>();
    private ProcessTask processTask = null;
    Fragment chapterFragment = null;
    Fragment subChapterFragment = null;
    Fragment subSubChapterFragment = null;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        mContentView = inflater.inflate(
                R.layout.competitive_programming_exercise, container, false);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setContentShown(false);
        setContentView(mContentView);
        processTask = new ProcessTask();
        processTask.execute();
    }


    protected class ProcessTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... params) {
            // background task
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            FragmentTransaction transaction = getChildFragmentManager()
            .beginTransaction();
            chapterFragment = new ChaptersListFragment();
            if (mContentView.findViewById(R.id.fragment_container) != null) {
                transaction.replace(R.id.fragment_container, chapterFragment);
            } else {
                subChapterFragment = new SubChaptersListFragment();
                subSubChapterFragment = new SubSubChaptersListFragment();
                transaction.replace(R.id.category_fragment, chapterFragment);
                transaction.replace(R.id.sub_category_fragment, subChapterFragment);
                transaction.replace(R.id.sub_sub_category_fragment, subSubChapterFragment);
            }
            transaction.commit();
            setContentShown(true);
        }

    }

    static protected class Chapter {
        String chapterTitle;
        List<SubChapter> subchapterList;

        public Chapter(String chapterTitle, List<SubChapter> subchapterList) {
            this.chapterTitle = chapterTitle;
            this.subchapterList = subchapterList;
        }

    }

    @Override
    public void onChapterSelected(int position) {
        SubChaptersListFragment subChaptersListFrag = (SubChaptersListFragment) getChildFragmentManager()
                .findFragmentById(R.id.sub_category_fragment);
        if (subChaptersListFrag != null) {
            subChaptersListFrag.updateList(position);
        } else {
            SubChaptersListFragment subChapterFragment = new SubChaptersListFragment();
            Bundle args = new Bundle();
            args.putInt(SubChaptersListFragment.CHAPTER_POSITION, position);
            subChapterFragment.setArguments(args);
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            transaction.replace(R.id.fragment_container, subChapterFragment);
//          transaction.addToBackStack(null);
            transaction.commit();
        }
    }

    @Override
    public void onSubChapterSelected(int prev, int position) {
        SubSubChaptersListFragment subSubChaptersListFrag = (SubSubChaptersListFragment) getChildFragmentManager()
                .findFragmentById(R.id.sub_sub_category_fragment);
        if (subSubChaptersListFrag != null) {
            subSubChaptersListFrag.updateList(prev, position);
        } else {
            SubSubChaptersListFragment subSubChapterFragment = new SubSubChaptersListFragment();
            Bundle args = new Bundle();
            args.putIntArray(SubSubChaptersListFragment.POSITIONS, new int[]{prev, position});
            subSubChapterFragment.setArguments(args);
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            transaction.replace(R.id.fragment_container, subSubChapterFragment);
//          transaction.addToBackStack(null);
            transaction.commit();           
        }
    }

    @Override
    public void onStop() {
        super.onStop();
        if (processTask != null && processTask.getStatus() != AsyncTask.Status.FINISHED) {
            processTask.cancel(true);
        }
    }

}

Hope this would help!

回答2:

You probably are adding the fragment in your onResume(), which is not what you want as each time you are resumed new fragment is added. Just fix your code's logic

来源：https://stackoverflow.com/questions/18322020/nested-fragment-with-backstack-resume