Don't collapse Toolbar when RecyclerView fits the screen

Question

I\'ve made an app using Android Design Library, with a Toolbar and TabLayout.
Actually 2 tabs are present, both with 2 RecyclerView, that automati

Answer 1

I took a slightly different approach to solve this.

I created a custom AppBarBehavior that disables its self based on cells.

public class CustomAppBarBehavior extends AppBarLayout.Behavior {

    private RecyclerView recyclerView;
    private boolean enabled;

    public CustomAppBarBehavior() {
    }

    public CustomAppBarBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        updatedEnabled();
        return enabled && super.onInterceptTouchEvent(parent, child, ev);
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes) {
        return enabled && super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        return enabled && super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    private void updatedEnabled() {
        enabled = false;
        if(recyclerView != null) {
            RecyclerView.Adapter adapter = recyclerView.getAdapter();
            if (adapter != null) {
                int count = adapter.getItemCount();
                RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                if (layoutManager != null) {
                    int lastItem = 0;
                    if (layoutManager instanceof LinearLayoutManager) {
                        LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
                        lastItem = Math.abs(linearLayoutManager.findLastCompletelyVisibleItemPosition());
                    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
                        StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
                        int[] lastItems = staggeredGridLayoutManager.findLastCompletelyVisibleItemPositions(new int[staggeredGridLayoutManager.getSpanCount()]);
                        lastItem = Math.abs(lastItems[lastItems.length - 1]);
                    }
                    enabled = lastItem < count - 1;
                }
            }
        }
    }

    public void setRecyclerView(RecyclerView recyclerView) {
        this.recyclerView = recyclerView;
    }
}

Then set the custom behavior on the app bar layout

appBarBehavior = new CustomAppBarBehavior();
CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
appBarLayoutParams.setBehavior(appBarBehavior);
appBarLayout.setLayoutParams(appBarLayoutParams);

Last on page change of the view pager updated the RecyclerView on the behavior

private ViewPager.OnPageChangeListener pageChangeListener = new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { }

        @Override
        public void onPageSelected(final int position) {             
            appBarLayout.setExpanded(true, true);
            appBarLayout.post(new Runnable() {
                @Override
                public void run() {
                    appBarBehavior.setRecyclerView(childFragments.get(position).getRecyclerView());
                }
            });
        }

        @Override
        public void onPageScrollStateChanged(int state) { }
    };

This should work with changing datasets.

Answer 2

You can check if the last item in RecyclerView is visible. If it's not then turn off scrolling programmatically using this method:

            //turn off scrolling
            AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
            toolbarLayoutParams.setScrollFlags(0);
            mToolbar.setLayoutParams(toolbarLayoutParams);

            CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
            appBarLayoutParams.setBehavior(null);
            appBarLayout.setLayoutParams(appBarLayoutParams);

Answer 3

Just remove scroll from

app:layout_scrollFlags="scroll|enterAlways"

So it should be

app:layout_scrollFlags="enterAlways"

Answer 4

I guess it's the best solution. You need to define your custom AppBarLayout behavior:

class CustomScrollingViewBehavior : AppBarLayout.Behavior {

    constructor() : super()
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)

    var shouldScroll = true

    override fun onStartNestedScroll(coordinatorLayout: CoordinatorLayout, child: AppBarLayout, directTargetChild: View, target: View, axes: Int, type: Int): Boolean {
        return shouldScroll && when (target) {
            is NestedScrollView, is ScrollView, is RecyclerView -> {
                return target.canScrollVertically(1) || target.canScrollVertically(-1)
            }
            else -> super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, axes, type)
        }
    }
}

And then you just need to use it in your layout as attribute of AppBarLayout:

...

 <com.google.android.material.appbar.AppBarLayout
            android:id="@+id/appbar"
            android:layout_width="match_parent"
            android:layout_height="56dp"
            app:layout_behavior=".CustomScrollingViewBehavior">

...

That's it.

Note: custom behavior also supports fully disabling of the scrolling - you just need to set shouldScroll flag to false

customScrollingViewBehavior.shouldScroll = false

Answer 5

//turn off scrolling
AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
toolbarLayoutParams.setScrollFlags(0);
mToolbar.setLayoutParams(toolbarLayoutParams);

Answer 6

Final Solution (thanks Michał Z.)

Methods to turn off/on Toolbar scrolling:

public void turnOffToolbarScrolling() {
    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.appbar_layout);

    //turn off scrolling
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(0);
    mToolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    appBarLayoutParams.setBehavior(null);
    appBarLayout.setLayoutParams(appBarLayoutParams);
}

public void turnOnToolbarScrolling() {
    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.appbar_layout);

    //turn on scrolling
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
    mToolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    appBarLayoutParams.setBehavior(new AppBarLayout.Behavior());
    appBarLayout.setLayoutParams(appBarLayoutParams);
}

Find out if last item of RecyclerView is visible in my Fragment.
If yes, disable scrolling:

public void updateToolbarBehaviour(){
    if (mLayoutManager.findLastCompletelyVisibleItemPosition() == items.size()-1) {
        ((MainActivity) getActivity()).turnOffToolbarScrolling();
    } else {
        ((MainActivity)getActivity()).turnOnToolbarScrolling();
    }
}