Collapsing/Expanding view coordinated with Sliding RecyclerView

Question

I am trying to achieve the following affect (also see image below):

• the app opens with a view (map) partially visible and the RecyclerView at a default anchor point (center image)
• user scrolls the RecyclerView up, the map collapses and the list continues scrolling (right image)
• user scrolls the RecyclerView down, the map expands to a maximum point (note the list should not slide completely off screen but to some anchored point) (left image)

Answer 1

To create this we need 1 Activity and 3 Fragments.

The Activity will host a TabLayout and a ViewPager like so:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" />

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

Since we only need to do the sliding behavior for the 1st Fragment the first Fragment gets an XML layout like so:

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="400dp"
        android:orientation="vertical"
        android:fitsSystemWindows="true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsingToolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <com.google.android.gms.maps.MapView
                android:id="@+id/mapView"
                app:layout_collapseMode="parallax"
                android:layout_height="400dp"
                android:layout_width="match_parent" />

        </android.support.design.widget.CollapsingToolbarLayout>

    </android.support.design.widget.AppBarLayout>

    <FrameLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>


</android.support.design.widget.CoordinatorLayout>

You can make the other Fragments however you like I just created fake data and a simple RecyclerView in the other Fragments.

Then call these views in your Activity and Fragment like so:

Activity

public class MainActivity extends AppCompatActivity {

    private TabLayout mTabLayout;
    private ViewPager mViewPager;
    private SampleViewPagerAdapter mViewPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.another_activity);

        mTabLayout = (TabLayout) findViewById(R.id.sliding_tabs);
        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        mViewPagerAdapter = new SampleViewPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mViewPagerAdapter);
        mTabLayout.setupWithViewPager(mViewPager);
    }

}

ViewPager Adapter

public class SampleViewPagerAdapter extends FragmentPagerAdapter {

    public SampleViewPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return new MapFragment();
            case 1:
                return new ScrollFragment();
            case 2:
                return new ScrollFragment();
            default:
                return new ScrollFragment();
        }
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        String[] tabNames = {"Stops", "Planner", "Alerts"};
        return tabNames[position];
    }

}

Map Fragment with Sliding RecyclerView

public class MapFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.activity_main, null);

        initCollapsingToolbar(root);
        // Initialize map
        initFragment();
        return root;
    }

    private void initCollapsingToolbar(View root) {
        CollapsingToolbarLayout collapsingToolbarLayout =
            (CollapsingToolbarLayout) root.findViewById(R.id.collapsingToolbar);
        collapsingToolbarLayout.setContentScrimColor(getResources().getColor(R.color.cyan_500));
    }

    private void initFragment() {
        FakeDataFragment fragment = new FakeDataFragment();
        getChildFragmentManager().beginTransaction()
                .replace(R.id.content, scrollFragment)
                .commit();
    }

}

You should get something like this then:

Setting the position:

You can programmatically collapse the toolbar (CollapsingToolbarLayout) using the following code:

public void collapseToolbar(){
    CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) mFrameLayout.getLayoutParams();
    AppBarLayout.ScrollingViewBehavior behavior = (AppBarLayout.ScrollingViewBehavior) params.getBehavior();
    if (behavior != null) {
        behavior.onNestedFling(rootLayout, appbarLayout, null, 0, 10000, true);
    }
}

This means when the User first sees the map the map is partially collapsed to your Default State.