Odtnhj

I've made an app using Android Design Library, with a Toolbar and TabLayout.
Actually 2 tabs are present, both with 2 RecyclerView, that automatically collapse the Toolbar when scrolled.

My question is: can I disable Toolbar collapsing when RecyclerView has few items and completely fits the screen (like in TAB 2)?

I've seen a lot of examples like CheeseSquare, made by a Google employee where the issue is still present: even if the RecyclerView has just 1 item, the toolbar keeps hiding on scroll.

I think I can just find out if the first item of the RecyclerView is visible on screen and if yes disable toolbar collapsing. The former is easy to implement, what about the latter?

This is my layout:

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

 <android.support.design.widget.AppBarLayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:fitsSystemWindows="true"
 android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

 <android.support.v7.widget.Toolbar
 android:id="@+id/toolbar"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 app:layout_scrollFlags="scroll|enterAlwaysCollapsed"
 android:background="?attr/colorPrimary"
 app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
 app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

 <android.support.design.widget.TabLayout
 android:id="@+id/tab_layout"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:background="@color/glucosio_pink"
 app:tabSelectedTextColor="@android:color/white"
 app:tabIndicatorColor="@color/glucosio_accent"
 app:tabTextColor="#80ffffff"/>
 </android.support.design.widget.AppBarLayout>

 <android.support.v4.view.ViewPager
 android:id="@+id/pager"
 app:layout_behavior="@string/appbar_scrolling_view_behavior"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <android.support.design.widget.FloatingActionButton
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:id="@+id/main_fab"
 android:layout_margin="16dp"
 android:onClick="onFabClicked"
 app:backgroundTint="@color/glucosio_accent"
 android:src="@drawable/ic_add_black_24dp"
 android:layout_gravity="bottom|right"
 />
 </android.support.design.widget.CoordinatorLayout>

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() 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();
 

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);

RecyclerView now (since version 23.2) supports wrap_content. Just use wrap_content as the height.

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.