viewpager 中的 tablayout 问题答案

【问题标题】：Issue with tablayout in viewpagerviewpager 中的 tablayout 问题
【发布时间】：2016-10-26 05:06:12
【问题描述】：

我在每个选项卡片段中使用动态列表视图制作动态选项卡。问题是当我在两个连续选项卡之间切换时，会显示前一个选项卡的 xml，但是当我单击非连续选项卡时它工作正常。不知道问题出在哪里所以附上我的fragment类和HomeActivity`在这里输入代码。

public class HomeActivity2 extends AppCompatActivity   {

    public ViewPagerAdapter adapter;
    private Toolbar toolbar;



    private TabLayout tabLayout;
    private NonSwipeableViewPager viewPager;
    public ArrayList<String> mappingOfCategoryWithIndex = new ArrayList<>();
    public ArrayList<MenuItem> allMenuItemsList = new ArrayList<MenuItem>();
    ArrayList<MenuItemCategory> allMenuItemCategoryList = new ArrayList<MenuItemCategory>();

    //Getters
    public NonSwipeableViewPager getViewPager() {
        return viewPager;
    }
    public ArrayList<String> getMappingOfCategoryWithIndex() {
        return mappingOfCategoryWithIndex;
    }
    public ArrayList<MenuItem> getAllMenuItemsList() {
        return allMenuItemsList;
    }
    public TabLayout getTabLayout() {
        return tabLayout;
    }
    public ArrayList<MenuItemCategory> getAllMenuItemCategoryList() {return allMenuItemCategoryList;}

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_home2);


        findViewById(R.id.tabs).bringToFront();
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
// Getting All Menu Items



        GetAllMenuItems menuItemsReader = null;
        try {
            menuItemsReader = new GetAllMenuItems();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        allMenuItemsList = menuItemsReader.getMenuItemsList();

// Getting All Categories

        GetAllMenuItemCategories menuItemsCategoriesReader = null;
        try {
            menuItemsCategoriesReader = new GetAllMenuItemCategories();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        allMenuItemCategoryList = menuItemsCategoriesReader.getCategoryList();




//        toolbar = (Toolbar) findViewById(R.id.toolbar);
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);


        viewPager = (NonSwipeableViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);



        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {

                //THIS!!
                if (viewPager != null) {
                    viewPager.setCurrentItem(tab.getPosition());

                }
            }

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

            }

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

            }
        });

        tabLayout.setupWithViewPager(viewPager);
        setupTabIcons();

    }

    private void setupTabIcons() {



        for (int i=0; i<allMenuItemCategoryList.size() ; i++){
            TextView tab = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
            tab.setText(allMenuItemCategoryList.get(i).Menu_Item_Category_Name);
            mappingOfCategoryWithIndex.add(i, allMenuItemCategoryList.get(i).Menu_Item_Category_Name) ;
            tabLayout.getTabAt(i).setCustomView(tab);
        }

//        int j = 0;
//        for (int i=0; i<allMenuItemCategoryList.size() ; i++){
//            TextView tab = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
//            if(i%2==0){
//                tab.setText(allMenuItemCategoryList.get(j).Menu_Item_Category_Name);
//                j++;
//            }
//            else{
//                tab.setText("");
//
//            }
//            mappingOfCategoryWithIndex.add(i, allMenuItemCategoryList.get(i).Menu_Item_Category_Name) ;
//            tabLayout.getTabAt(i).setCustomView(tab);
//
//
//
////            tab.setCompoundDrawablesWithIntrinsicBounds(0, drawable.ic_launcher, 0, 0);
//
//
//
//        }
    }

    private void setupViewPager(ViewPager viewPager) {
        adapter = new ViewPagerAdapter(getSupportFragmentManager());

        for (int i=0 ; i<allMenuItemCategoryList.size() ; i++) {
                adapter.addFrag(new TabCategory(), allMenuItemCategoryList.get(i).Menu_Item_Category_Name);
        }


//        int j=0;
//        for (int i=0 ; i<allMenuItemCategoryList.size()*2 ; i++) {
//            if (i % 2 == 0) {
//                adapter.addFrag(new TabCategory(), allMenuItemCategoryList.get(j).Menu_Item_Category_Name);
//                j++;
//            }
//            else{
//                adapter.addFrag(new dummyClass(), "");
//            }
//        }

        viewPager.setAdapter(adapter);

    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

//        private final List<String> tabPositionCategory = new ArrayList<>();


        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

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

        public void addFrag(Fragment fragment, String title ) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);

        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}

public class TabCategory extends Fragment{

    private TextView nameOfItem;


    HomeActivity2 activity;
    public HomeActivity2.ViewPagerAdapter adapter;

    private TabLayout tabLayout;
    LinearLayout container1;

    public ArrayList<String> mappingOfCategoryWithIndex = new ArrayList<>();

    public ArrayList<MenuItem> allMenuItemsList1 = new ArrayList<MenuItem>();
    public ArrayList<MenuItemCategory> allCategoryList1 = new ArrayList<MenuItemCategory>();

    private NonSwipeableViewPager viewPager;

    private String selectedCategory;
    private int selectedCategoryId;

    private ArrayList<MenuItem> menuItemsOfSelectedCategory = new ArrayList<>();

    View rootView;

    public TabCategory() {



    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        activity = (HomeActivity2) getActivity();
        allMenuItemsList1 = activity.getAllMenuItemsList();

        mappingOfCategoryWithIndex =activity.getMappingOfCategoryWithIndex();

        tabLayout  = activity.getTabLayout();

        viewPager = activity.getViewPager();

        viewPager.clearOnPageChangeListeners();
        adapter = activity.adapter;

        tabLayout.setupWithViewPager(viewPager);


    }

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

        // Inflate the layout for this fragment
        rootView = inflater.inflate(R.layout.tab_category, container, false);



        menuItemsOfSelectedCategory.removeAll(menuItemsOfSelectedCategory);

        menuItemsOfSelectedCategory.clear();
        activity = (HomeActivity2) getActivity();
        allMenuItemsList1 = activity.getAllMenuItemsList();

        mappingOfCategoryWithIndex =activity.getMappingOfCategoryWithIndex();

        tabLayout  = activity.getTabLayout();

        viewPager = activity.getViewPager();

        adapter = activity.adapter;


        allCategoryList1 = activity.getAllMenuItemCategoryList();
        int tab_position=tabLayout.getSelectedTabPosition();

        selectedCategory = adapter.getPageTitle(tab_position).toString();
        System.out.println("Tab Category: " + selectedCategory );



        for (int i = 0 ; i<allMenuItemsList1.size();i++){
            if(allMenuItemsList1.get(i).getCategoryName().equals(selectedCategory)){
                menuItemsOfSelectedCategory.add(allMenuItemsList1.get(i));
            }
        }


        System.out.println("Size of Category Items: " + menuItemsOfSelectedCategory.size() );






        nameOfItem = (TextView) rootView.findViewById(R.id.nameofitem);

        System.out.println("Menu Size:"+ allMenuItemsList1.size());

        return rootView;

    }


    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);


        LayoutInflater layoutInflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        container1 = (LinearLayout) rootView.findViewById(R.id.container1);
        container1.removeAllViews();
        for (int i =0 ; i<menuItemsOfSelectedCategory.size();i++) {
            final View addView = layoutInflater.inflate(R.layout.menu_item, null);
            nameOfItem = (TextView) addView.findViewById(R.id.nameofitem);
            nameOfItem.setText(menuItemsOfSelectedCategory.get(i).getName());

            container1.addView(addView);
        }


    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        // not cleaning up.

        menuItemsOfSelectedCategory.removeAll(menuItemsOfSelectedCategory);

        menuItemsOfSelectedCategory.clear();
        container1.removeAllViews();
        container1.invalidate();
        System.out.println("destroyed!!!");
    }


}`

提前致谢。

【问题讨论】：

请添加完整的代码，以便我们重现问题。考虑MCVE question model。
需要注意的是，当一个ViewPager页面被选中时，被选中的页面和每边一个页面被加载（加载页面的数量可以使用setOffscreenPageLimit增加，最小为1 . 这就是为什么当您选择非连续页面时一切正常，因为所有计算都是从头开始使用此页面完成的，而当您选择相邻页面时，当前页面以及相邻页面执行相同的代码。
那么如何改正呢？ setOffscreenPageLimit 为 0？
@MohanadMohie 我想你已经发现了问题，因为当我设置 setOffscreenPageLimit(2) 时，会显示 2 个连续的上一页和下一页。这个问题有什么解决办法吗？我只想显示被选中的那个片段。
setOffscreenPageLimit 的最小值可以为0，增加这个值并不能解决你的问题，因为你的问题是你用当前ViewPager的位置初始化Fragment，所以当Frag1被选中时（ position = 0)，ViewPager 加载 Frag2，但仍带有 position = 0。我必须在回家后的几个小时内检查问题出在哪里。

标签： android android-fragments tabs android-viewpager android-tablayout

【解决方案1】：

所以，我放了一些模拟数据进行测试，这是一个工作示例（我修改了你的代码，它仍然需要一些增强但它可以工作）。

HomeActivity2.java：

public class HomeActivity2 extends AppCompatActivity   {

    public ViewPagerAdapter adapter;
    private Toolbar toolbar;

    private TabLayout tabLayout;
    private ViewPager viewPager;
    private ArrayList<String> mappingOfCategoryWithIndex = new ArrayList<>();
    private ArrayList<MenuItem> allMenuItemsList = new ArrayList<MenuItem>();
    private ArrayList<MenuItemCategory> allMenuItemCategoryList = new ArrayList<MenuItemCategory>();

    //Getters
    public ViewPager getViewPager() {
        return viewPager;
    }
    public ArrayList<String> getMappingOfCategoryWithIndex() {
        return mappingOfCategoryWithIndex;
    }
    public ArrayList<MenuItem> getAllMenuItemsList() {
        return allMenuItemsList;
    }
    public TabLayout getTabLayout() {
        return tabLayout;
    }
    public ArrayList<MenuItemCategory> getAllMenuItemCategoryList() {
        return allMenuItemCategoryList;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_home2);


        findViewById(R.id.tabs).bringToFront();
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        allMenuItemsList = new ArrayList<>();
        allMenuItemsList.add(new MenuItem("Item 1", "Category 1"));
        allMenuItemsList.add(new MenuItem("Item 2", "Category 1"));
        allMenuItemsList.add(new MenuItem("Item 3", "Category 2"));
        allMenuItemsList.add(new MenuItem("Item 4", "Category 3"));
        allMenuItemsList.add(new MenuItem("Item 5", "Category 3"));

        allMenuItemCategoryList = new ArrayList<>();
        allMenuItemCategoryList.add(new MenuItemCategory("Category 1"));
        allMenuItemCategoryList.add(new MenuItemCategory("Category 2"));
        allMenuItemCategoryList.add(new MenuItemCategory("Category 3"));


        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);


        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);

        tabLayout.setupWithViewPager(viewPager);
        setupTabIcons();

    }

    private void setupTabIcons() {

        for (int i=0; i<allMenuItemCategoryList.size() ; i++){
            TextView tab = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
            tab.setText(allMenuItemCategoryList.get(i).Menu_Item_Category_Name);
            mappingOfCategoryWithIndex.add(i, allMenuItemCategoryList.get(i).Menu_Item_Category_Name) ;
            tabLayout.getTabAt(i).setCustomView(tab);
        }
    }

    private void setupViewPager(ViewPager viewPager) {
        adapter = new ViewPagerAdapter(getSupportFragmentManager());

        for (int i=0 ; i<allMenuItemCategoryList.size() ; i++) {
            String category = allMenuItemCategoryList.get(i).Menu_Item_Category_Name;
            adapter.addFrag(TabCategory.getTabCategoryFragment(category), category);
        }

        viewPager.setAdapter(adapter);

    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

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

        public void addFrag(Fragment fragment, String title ) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);

        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}

TabCategory.java：

public class TabCategory extends Fragment {

    private static final String KEY_CATEGORY = "category";
    private TextView nameOfItem;
    private HomeActivity2 activity;
    private LinearLayout container1;

    public ArrayList<String> mappingOfCategoryWithIndex = new ArrayList<>();

    public ArrayList<MenuItem> allMenuItemsList1 = new ArrayList<MenuItem>();

    private String selectedCategory;

    private ArrayList<MenuItem> menuItemsOfSelectedCategory = new ArrayList<>();

    private View rootView;

    public TabCategory() {

    }

    public static TabCategory getTabCategoryFragment(String selectedCategory) {
        TabCategory tabCategory = new TabCategory();
        Bundle args = new Bundle();
        args.putString(KEY_CATEGORY, selectedCategory);
        tabCategory.setArguments(args);
        return tabCategory;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        selectedCategory = getArguments().getString(KEY_CATEGORY);


        activity = (HomeActivity2) getActivity();

        allMenuItemsList1 = activity.getAllMenuItemsList();

        mappingOfCategoryWithIndex = activity.getMappingOfCategoryWithIndex();


    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView = inflater.inflate(R.layout.tab_category, container, false);
        container1 = (LinearLayout) rootView.findViewById(R.id.container1);
        return rootView;

    }


    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        LayoutInflater layoutInflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        container1.removeAllViews();
        menuItemsOfSelectedCategory.clear();

        for (int i = 0; i < allMenuItemsList1.size(); i++) {
            if (allMenuItemsList1.get(i).getCategoryName().equals(selectedCategory)) {
                menuItemsOfSelectedCategory.add(allMenuItemsList1.get(i));
            }
        }

        for (int i = 0; i < menuItemsOfSelectedCategory.size(); i++) {
            final View addView = layoutInflater.inflate(R.layout.menu_item, null);
            nameOfItem = (TextView) addView.findViewById(R.id.nameofitem);
            nameOfItem.setText(menuItemsOfSelectedCategory.get(i).getName());

            container1.addView(addView);
        }

    }


}

【讨论】：