嵌套 Fragment 和返回栈的恢复问题

Question

在我的应用程序中，一个活动中有几个片段，并且我正在为这些片段维护一个后退堆栈(backStack)。一切都很好，但其中有一个嵌套片段。当我将它放入backStack中并通过按返回按钮再次恢复时，该片段看起来会重叠之前的内容(子片段)。

这是正常视图： 这是重叠视图的截图(当我恢复片段时)： 你可以看到第二个视图的文本更深(这意味着子片段重叠)。

我该如何避免这种情况？以下是我的嵌套片段的代码：

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);
        }
    }

}

- Kaidul

---

猜测这可能与transaction.add()有关，尽可能使用replace。 - Kirill Kulakov

我到处都用了 replace :( - Kaidul

Answer 1

Kirill Kulakov是正确的。应该使用replace而不是add。我编辑了代码：

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);
        }
    }

}

希望这可以帮助你！

- Kaidul

---

您的 ProcessTask 在后台中没有执行任何操作，因此将其放在 AsyncTask 中没有任何意义。 - Nickmccomb

Answer 2

你可能是在onResume()中添加了片段，这不是你想要的，因为每次恢复时都会添加新的片段。只需修复代码逻辑即可。

- Marcin Orlowski

---

您好，感谢您的回答！这是我提出的问题，A--C给了我一个非常好的解决方案，可以在backStack中添加片段。我已经按照它的方法进行了操作，请看一下并给我一些您所建议的示例代码。 :) - Kaidul