9

当我更改活动中的片段时，我想更改片段活动（abs）的菜单项的可见性。这些片段是 SherlockListFragments。

我要显示/隐藏的菜单项是我在创建菜单时创建的微调器：

public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    MenuInflater inflater = getSupportMenuInflater();

    IcsSpinner herbSortSpinner = new IcsSpinner(this, null, R.attr.actionDropDownStyle);
    SpinnerAdapter herbSortSpinnerAdapter = ArrayAdapter.createFromResource(this, R.array.herb_sort_elements, android.R.layout.simple_spinner_dropdown_item);
    herbSortSpinner.setAdapter(herbSortSpinnerAdapter);
    herbSortSpinner.setOnItemSelectedListener(this);
    herbSortSpinner.setId(HERB_SPINNER_ID);
    menu.add(R.string.menu_sort).setActionView(herbSortSpinner).setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);

    IcsSpinner noteSortSpinner = new IcsSpinner(this,  null, R.attr.actionDropDownStyle);
    SpinnerAdapter noteSortSpinnerAdapter = ArrayAdapter.createFromResource(this, R.array.note_sort_elements, android.R.layout.simple_spinner_dropdown_item);
    noteSortSpinner.setAdapter(noteSortSpinnerAdapter);
    noteSortSpinner.setOnItemSelectedListener(this);
    noteSortSpinner.setId(NOTE_SPINNER_ID);
    menu.add(R.string.menu_sort).setActionView(noteSortSpinner).setVisible(false).setEnabled(false).setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);

    inflater.inflate(R.menu.activity_lexicon, menu);
    menuHolder.setMenu(menu);
    return true;
}

我切换片段的逻辑是：

public boolean onNavigationItemSelected(int position, long itemId) {

    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    switch(position) {
    case 0:
        List<Herb> herbList = findHerbsByIntent(getHerbLocale());
        HerbListFragment herbListFragment = new HerbListFragment();
        herbListFragment.setListAdapter(new HerbListAdapter(this, getHerbLocale(), herbList));
        fragmentTransaction.replace(R.id.fragment_container, herbListFragment, HERB_LIST_FRAGMENT_TAG);
        //menuHolder.showHerbsSpinner();
        break;
    case 1:
        SymptomListFragment symptomListFragment = new SymptomListFragment();
        symptomListFragment.setListAdapter(new SymptomListAdapter(this, getDefaultSymptomLocale()));
        fragmentTransaction.replace(R.id.fragment_container, symptomListFragment, SYMPTOM_LIST_FRAGMENT_TAG);
        //menuHolder.showHerbsSpinner();
        break;
    case 2:
        NoteRepository noteRepository = new NoteRepository(this);
        List<Note> notes = noteRepository.getNoticables(ReferedType.HERB);
        NoteListFragment noteListFragment = new NoteListFragment();
        noteListFragment.setListAdapter(new NoteListAdapter(this, getHerbLocale(), notes));
        fragmentTransaction.replace(R.id.fragment_container, noteListFragment, NOTE_LIST_FRAGMENT_TAG);
        //menuHolder.showNotesSpinner();
        break;
    case 3:
        FavoriteRepository favoriteRepository = new FavoriteRepository(this);
        Set<Integer> favoriteHerbs = favoriteRepository.getFavorables(ReferedType.HERB);
        List<Herb> favoriteHerbList = herbRepository.getHerbsByIds(favoriteHerbs, getHerbLocale());
        FavoriteHerbListFragment favoriteHerbListFragment = new FavoriteHerbListFragment();
        favoriteHerbListFragment.setListAdapter(new HerbListAdapter(this, getHerbLocale(), favoriteHerbList));
        fragmentTransaction.replace(R.id.fragment_container, favoriteHerbListFragment, HERB_LIST_FRAGMENT_TAG);
        //menuHolder.showHerbsSpinner();
        break;
    }
    fragmentTransaction.commit();

    return true;
}

我的第一个想法是将菜单对象保存在一个持有者类中，并在我切换片段时在那里操作它（在上面的每个案例语句中）。

static class MenuHolder {

    private Menu mMenu;

    void setMenu(Menu menu) {
        mMenu = menu;
    }

    void showNotesSpinner() {
        if (mMenu != null) {
            mMenu.findItem(HERB_SPINNER_ID).setVisible(false).setEnabled(false);
            mMenu.findItem(NOTE_SPINNER_ID).setVisible(true).setEnabled(true);
        }
    }

    void showHerbsSpinner() {
        if (mMenu != null) {
            mMenu.findItem(NOTE_SPINNER_ID).setVisible(false).setEnabled(false);            
            mMenu.findItem(HERB_SPINNER_ID).setVisible(true).setEnabled(true);
        }
    }
}

我的问题是没有给定 ID 的菜单项是活动本地常量。我在这里得到一个NPE。有人知道我该如何解决吗？有没有更好的方法来更改切换片段的菜单？

最好的问候卡斯滕

4

2 回答 2

21

Is there a better way to change the menu on switching fragments?

May be yes :).

The doc :

Report that this fragment would like to participate in populating the options menu by receiving a call to onCreateOptionsMenu(Menu, MenuInflater) and related methods.

Prepare the Screen's standard options menu to be displayed. This is called right before the menu is shown, every time it is shown. You can use this method to efficiently enable/disable items or otherwise dynamically modify the contents.

Then, in this method, try to find your menu items by ID, and make them visible/unvisible, enabled/disabled, like this :

@Override
public void onPrepareOptionsMenu(Menu menu) {    
    menu.findItem(HERB_SPINNER_ID).setVisible(false).setEnabled(false);
}

Read More

于 2014-03-21T08:14:45.320 回答
1

就我而言，我有 2 个片段具有不同的菜单项。

在我的 MainActivity 上：

FragmentA fragmentA = new FragmentA();
fragmentA.setTargetFragment(fragmentA, 0);
FragmentB fragmentB = new FragmentB();
fragmentB.setTargetFragment(fragmentB, 1);

并且 FragmentA 和 FragmentB 具有：

@Override
public void onHiddenChanged(boolean hidden) {
    super.onHiddenChanged(hidden);
    if(hidden) {
        getTargetFragment().setMenuVisibility(false);
    }else{
        getTargetFragment().setMenuVisibility(true);
    }
}

这将使片段 A 的菜单在 B 离开时可见。如果它从 B 回到 A，则可以看到 A 的旧菜单。

参考：这里

于 2017-05-07T05:44:26.533 回答