Использование макета вкладки в архитектуре MVVM с библиотекой привязки данных

Ответ 1

MainActivity -

public class MainActivity extends Activity 
{
    @Override
    protected void onCreate(@Nullable final Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        App.get(this).component().inject(this);
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setHandler(this);
        binding.setManager(getSupportFragmentManager());
    }

    @BindingAdapter({"bind:handler"})
    public static void bindViewPagerAdapter(final ViewPager view, final MainActivity activity)
    {
        final MainActionsAdapter adapter = new MainActionsAdapter(view.getContext(), activity.getSupportFragmentManager());
        view.setAdapter(adapter);
    }

    @BindingAdapter({"bind:pager"})
    public static void bindViewPagerTabs(final TabLayout view, final ViewPager pagerView)
    {
        view.setupWithViewPager(pagerView, true);
    }

}

xml -

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:fresco="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <import type="android.view.View" />

        <variable
            name="handler"
            type="com.ui.main.MainActivity" />

        <variable
            name="manager"
            type="android.support.v4.app.FragmentManager" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:animateLayoutChanges="true"
            app:title="@string/app_name"
            app:titleMarginStart="8dp" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:pager="@{(pager)}">
        </android.support.design.widget.TabLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:handler="@{handler}" />

    </LinearLayout>

</layout>

Адаптер -

public class MainSectionsAdapter extends FragmentPagerAdapter
{
    private static final int CONTACTS = 0;
    private static final int CALLS = 1;
    private static final int CHATS = 2;

    private static final int[] TABS = new int[]{CONTACTS, CALLS, CHATS};

    private Context mContext;

    public MainSectionsAdapter(final Context context, final FragmentManager fm)
    {
        super(fm);
        mContext = context.getApplicationContext();
    }

    @Override
    public Fragment getItem(int position)
    {
        switch (TABS[position])
        {
            case CONTACTS:
                return ContactsFragment.newInstance();
            case CALLS:
                return CallsFragment.newInstance();
            case CHATS:
                return ChatsFragment.newInstance();
        }
        return null;
    }

    @Override
    public int getCount()
    {
        return TABS.length;
    }

    @Override
    public CharSequence getPageTitle(int position)
    {
        switch (TABS[position])
        {
            case CONTACTS:
                return mContext.getResources().getString(R.string.contacts);
            case CALLS:
                return mContext.getResources().getString(R.string.calls);
            case CHATS:
                return mContext.getResources().getString(R.string.chats);
        }
        return null;
    }
}

Ответ 2

Я не уверен, что это недавно появилось недавно, но с версией поддержки Android 27.1.1 вам даже не нужен специальный адаптер привязки данных, вы можете просто использовать:

<android.support.design.widget.TabLayout
                android:id="@+id/tl_1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:setupWithViewPager="@{some_fragment_viewpager}"
                app:tabSelectedTextColor="@android:color/white"
                app:tabTextColor="@color/v5_grey_55"
                />


        <android.support.v4.view.ViewPager
            android:id="@+id/some_fragment_viewpager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:addOnPageChangeListener="@{vm.pageChangeListener}"
            app:setAdapter="@{vm.pageAdapter}"
            app:setCurrentItem="@{vm.pageChangeListener.currentPosition}"
            />

Обратите внимание, что переменная viewPager в app:setupWithViewPager="@{some_fragment_viewpager}" указывает на android:id="@+id/some_fragment_viewpager". Вот как делается ссылка на ViewPager (как по волшебству я знаю)!

ViewModel

public class SomeViewModel {
  public ViewPager.OnPageChangeListener pageChangeListener;
  public SomeFragmentPagerAdapter pagerAdapter;
  // ...
}

FragmentPagerAdapter

public classs SomeFragmentPagerAdapter extends FragmentPagerAdapter {
  public Boolean currentPosition;
}

Ответ 3

Вот мое решение для setUpWithViewpager с помощью databinding:

public class BindingUtil
{
    @BindingAdapter({ "setUpWithViewpager" })
    public static void setUpWithViewpager(final TabLayout tabLayout, ViewPager viewPager)
    {
        viewPager.addOnAdapterChangeListener(new ViewPager.OnAdapterChangeListener()
        {
            @Override
            public void onAdapterChanged(@NonNull ViewPager viewPager, @Nullable PagerAdapter oldAdapter, @Nullable PagerAdapter newAdapter)
            {
                if (oldAdapter == null && (newAdapter == null || newAdapter.getCount() == 0))
                {
                    // this function will helpful when 
                    // we don't create viewpager immediately 
                    // when view created (this mean we create
                    // will pager after a period time)
                    return;
                }
                tabLayout.setupWithViewPager(viewPager);
            }
        });
    }
}

XML

<android.support.design.widget.TabLayout
     ... 
     app:setUpWithViewpager="@{ viewPager }"
/>

<android.support.v4.view.ViewPager
     ...
     android:id="@+id/viewPager"
     app:adapter="@{viewModel.pagerAdapter}"
/>

ViewModel

public class MainViewModel extends BaseObservable
{

    @Bindable
    public PagerAdapter getPagerAdapter()
    {
        return adapter;
    }

    private void createViewPagerAdapter()
    {
        ...
        notifyPropertyChanged(BR.pagerAdapter);
    }
}

полный демо-проект здесь

Надеюсь, что это поможет