Question

我在按钮中单击一个片段（联系人），然后单击“更改选项卡布局选项卡”，然后附加一个详细信息片段（“联系方式”）。 >

public class TabPager extends FragmentStatePagerAdapter {

    private final SparseArray<WeakReference<Fragment>> instantiatedFragments = new SparseArray<>();

    int tabCount;
    SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();
    private String[] tabTitles = new String[]{"tab1", "tab2", "tab3", "tab4"};
    private Fragment primary;


    public CallTabPager(FragmentManager fm, int tabCount) {
        super(fm);
        //Initializing tab count
        this.tabCount = tabCount;
    }


    //Overriding method getItem
    @Override
    public Fragment getItem(int position) {
        //Returning the current tabs
        switch (position) {
            case 0:
                Fragment1 tab1 = new Fragment1 ();
                return tab1;
            case 1:
                Fragment2 tab2 = new Fragment2();
                return tab2;
            case 2:
                Fragment3 tab3 = new Fragment3 ();
                return tab3;
            case 3:

                Fragmen4 tab4= new Fragmen4 ();
                return tab4;

            default:
                return null;
        }
    }


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

    @Override
    public Object instantiateItem(final ViewGroup container, final int position) {
        final Fragment fragment = (Fragment) super.instantiateItem(container, position);
        instantiatedFragments.put(position, new WeakReference<>(fragment));
        registeredFragments.put(position, fragment);
        return fragment;
    }

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

    @Nullable
    public Fragment getFragment(final int position) {
        final WeakReference<Fragment> wr = instantiatedFragments.get(position);
        if (wr != null) {
            return wr.get();
        } else {
            return null;
        }
    }


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

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        super.setPrimaryItem(container, position, object);
        primary = (Fragment) object;
    }

    public Fragment getPrimaryFragment() {
        return primary;
    }

    public void setUserVisibleHint(boolean isVisible) {
        if (primary != null) {
            primary.setUserVisibleHint(isVisible);
        }
    }
}

在Fragment类中，我使用此Tabpager将标签栏设置为viewpager

公共类CallDataFragment扩展了Fragment实现TabLayout.OnTabSelectedListener，OnBackPressListener {

CallTabPager adapter;
private TabLayout tabLayout;
private ViewPager viewPager;


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


    View vw = inflater.inflate(R.layout.activity_contacts_main, container, false);


    tabLayout = vw.findViewById(R.id.tabLayout);





    tabLayout.addTab(tabLayout.newTab().setText("tab1"));
    tabLayout.addTab(tabLayout.newTab().setText("tab2"));
    tabLayout.addTab(tabLayout.newTab().setText("tab3"));
    tabLayout.addTab(tabLayout.newTab().setText("tab4"));
    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);

    viewPager = (ViewPager) vw.findViewById(R.id.pager);


    adapter = new CallTabPager(getChildFragmentManager(), tabLayout.getTabCount());
    viewPager.setOffscreenPageLimit(4);

    viewPager.setAdapter(adapter);


    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));
    return vw;
}


@SuppressLint("LongLogTag")
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    SharedPreferences pref = getActivity().getApplicationContext().getSharedPreferences("MyPref", 0);
    SharedPreferences.Editor editor = pref.edit();
    editor.putString("key_name", "alls"); // Storing string
    editor.apply();

}

@Override
public void onTabSelected(TabLayout.Tab tab) {
    viewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(TabLayout.Tab tab) {
}

@Override
public void onTabReselected(TabLayout.Tab tab) {

}

@Override
public boolean onBackPressed() {

    OnBackPressListener currentFragment = (OnBackPressListener) adapter.getRegisteredFragment(viewPager.getCurrentItem());
    if (currentFragment != null) {
        return currentFragment.onBackPressed();
    }

    return false;
}

}

Answer 1

我要在可见的新片段中创建一个静态实例，并创建一种方法来将新的可见片段替换为较旧的片段。

    public class FragmentVisible extends Fragment{

    public static FragmentVisible instance;

     public static synchronized FragmentVisible getInstance() {
            return instance;
        }

public class Tab2 extends Fragment implements TabLayout.OnTabSelectedListener, OnBackPressListener {

        @Override
        public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View view = inflater.inflate(R.layout.layout_visible, container, false);
        instance = this;
        return view;

    }

    public void ChangeUI() {
            OlderFragemnt OlderFragemnt = new OlderFragemnt ();
            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.replace(R.id.root_view, OlderFragemnt);
            fragmentTransaction.commit();
        }

    }

当选项卡更改时，我检查碎片可见时的片段可见性，即调用方法ChangeUI（）

public class TabFragment extends Fragment{

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

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser)
        {
           Log.d("MyFragment", "Fragment is visible.");
           FragmentVisible.getInstance().ChangeUI(); 
        }
        else
        {
            Log.d("MyFragment", "Fragment is not visible.");
        }
    }
}

感谢您的帮助。

选项卡布局选项卡更改不显示主片段

1 个答案: