Constrain max size of RecyclerView - android

I'm putting together a screen with 3 controls stacked vertically. Specifically, a RecyclerView sandwiched between two TextView. I have two situations I am trying to address.
When few items are displayed in the RecyclerView the 3 items should be packed towards the top of the screen with blank space BELOW them.
When many items are displayed in the RecyclerView the full screen will be used with the last TextView along the bottom of the screen and scrolling in the center RecyclerView.
I'm struggling to get the position of the last TextView correct as it either gets pushed off the screen or buried behind the RecyclerView if there are many items in the RecyclerView. What I need is a way to tell the RecyclerView to wrap contents, but stop growing when it starts to push the TextView off of the screen.
Below is my layout, any suggestions?
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/topItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toTopOf="#+id/middleItem"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_chainStyle="packed" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/middleItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scrollbars="none"
app:layout_constraintBottom_toTopOf="#+id/bottomItem"
app:layout_constraintTop_toBottomOf="#+id/topItem" />
<TextView
android:id="#+id/bottomItem"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal|top"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toBottomOf="#+id/middleItem" />
</androidx.constraintlayout.widget.ConstraintLayout>

Try the following:
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/topItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is the top item."
app:layout_constraintBottom_toTopOf="#+id/middleItem"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0"
app:layout_constraintVertical_chainStyle="packed" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/middleItem"
android:layout_width="0dp"
android:layout_height="0dp"
android:scrollbars="none"
app:layout_constrainedHeight="true"
app:layout_constraintBottom_toTopOf="#+id/bottomItem"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/topItem"
tools:itemCount="3" />
<TextView
android:id="#+id/bottomItem"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:gravity="center_horizontal|top"
android:text="This is the bottom item."
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/middleItem" />
</androidx.constraintlayout.widget.ConstraintLayout>
With three items in the RecyclerView:
With 50 items in the RecyclerView:
The key changes are:
Added app:layout_constraintVertical_bias="0.0" to the top TextView to position the chain always at the top;
Added app:layout_constrainedHeight="true" to the RecyclerView to make sure views don't go off-screen;
Changed match_parent to 0dp and set the horizontal constraints for direct children of the ConstraintLayout.
Changed the RecyclerView's height to '0dp'.
Update: Although the above works, it is a little overdone. As noted in the comments, the same effect can be accomplished by simply setting the height of the RecyclerView to 0dp.
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/topItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is the top item."
app:layout_constraintBottom_toTopOf="#+id/middleItem"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_chainStyle="packed" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/middleItem"
android:layout_width="0dp"
android:layout_height="0dp"
android:scrollbars="none"
app:layout_constraintBottom_toTopOf="#+id/bottomItem"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/topItem"
tools:itemCount="3" />
<TextView
android:id="#+id/bottomItem"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:gravity="center_horizontal|top"
android:text="This is the bottom item."
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/middleItem" />
</androidx.constraintlayout.widget.ConstraintLayout>

Related

Bottom item cut in reyclerview in android

Hey I am working in constraint layout with recylerview. My bottom item is cut in the screen. I read this stack overflow post. I don't want to use relative layout or linear layout. Can someone guide me how to fix this in constraint layout.
abc.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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">
<androidx.appcompat.widget.SearchView
android:id="#+id/searchView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="16dp"
app:closeIcon="#drawable/ic_cancel"
app:layout_constraintBottom_toTopOf="#+id/exploreScroll"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_chainStyle="packed"
app:layout_constraintVertical_bias="0.0" />
<HorizontalScrollView
android:id="#+id/exploreScroll"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:scrollbars="none"
app:layout_constraintBottom_toTopOf="#+id/exploreList"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/searchView">
<com.google.android.material.chip.ChipGroup
android:id="#+id/exploreChips"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:chipSpacingHorizontal="10dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:singleLine="true"
app:singleSelection="true" />
</HorizontalScrollView>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/exploreList"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="20dp"
android:paddingTop="10dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/exploreScroll" />
</androidx.constraintlayout.widget.ConstraintLayout>
My view cut from
UPDATE
#Zain after your suggestion i tried in my xml any my HorizontalScrollView is going behind my RV. I am adding my blueprint and you can see clearly that, HorizontalScrollView is going behind. After removing app:layout_constraintBottom_toTopOf="#+id/exploreList" from the HorizontalScrollView.
2nd suggestion try
Disclaimer Using a wrap_content height with vertical RecyclerView
can have impact on performance in terms of recycling views; specially
if the height is going to change frequently. Check this article
for more illustration.
So, the first step is to designate the RecyclerView height or to constraint it; from the constraints you want it to expand to the bottom; so use 0dp for that. But in order to make the minimum height to wrap content of the RecyclerView (in case that the items don't exceed the screen height); you can set the default height constraint to wrap with app:layout_constraintHeight_default="wrap" constraint.
Then remove app:layout_constraintBottom_toTopOf="#+id/exploreList" from the HorizontalScrollView, this actually made the bottom item of the RV hide (your main issue); because it is an over-constraint; the HorizontalScrollView tends to push the RV to the bottom while the RV tends to push the HorizontalScrollView to the top.
This will solve the main issue; but when the items are fully accommodated by the screen (no scrolling in the RV), then it will be biased in the middle; to fix this use the bias with app:layout_constraintVertical_bias="0.0" to be biased to the top.
Adding this in place into the layout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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">
<androidx.appcompat.widget.SearchView
android:id="#+id/searchView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="16dp"
app:closeIcon="#drawable/ic_cancel"
app:layout_constraintBottom_toTopOf="#+id/exploreScroll"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0"
app:layout_constraintVertical_chainStyle="packed" />
<HorizontalScrollView
android:id="#+id/exploreScroll"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:scrollbars="none"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/searchView">
<com.google.android.material.chip.ChipGroup
android:id="#+id/exploreChips"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:chipSpacingHorizontal="10dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:singleLine="true"
app:singleSelection="true" />
</HorizontalScrollView>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/exploreList"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginBottom="20dp"
android:paddingTop="10dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHeight_default="wrap"
app:layout_constraintVertical_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/exploreScroll" />
</androidx.constraintlayout.widget.ConstraintLayout>

Constraintlayout Vertical Bias not working in two views Android

I am using constraint layout with a vertical bias to fill view in recycler view. I successfully did that.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/white">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recylerview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingStart="10dp"
android:paddingEnd="10dp"
android:paddingBottom="10dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0" />
</androidx.constraintlayout.widget.ConstraintLayout>
My recyclerview items showing me in reverse order because I want to make chat application. So I added reverseLayout and stackFromEnd true. So it look like this.
If my item is single my ui convert into like this by above xml code
Now I want to add edittext and button in bottom. Its not working vertical bias. Does any one know how to fix. Any suggestion to what can i use
Expected Output
Scenerio 1
Scenerio 2
Actual Output
I tried this code
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/white">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingStart=10dp"
android:paddingEnd="10dp"
android:paddingBottom="10dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintBottom_toTopOf="#+id/inputContainer"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0" />
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/inputContainer"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="20dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/crecyclerView">
<EditText
android:id="#+id/editTextContainer"
android:layout_width="200dp"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="#+id/button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/editTextContainer"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
UPDATE
After adding #MartinMarconcini answer it fixed my Scenario 2. I want to fix as Scenario 1 as well.
The idea is that your RV will handle its own item size and space by itself. You don't need to worry about this.
The Remainder of the space, will be used by ConstraintLayout.
So you need to pin the RV and the "Bottom Container" together. This would by default cause the CL to try to pull and balance layouts, so you have to tell the bottom container to be biased at the bottom.
In pseudo-XML:
<ConstraintLayout>
<RecyclerView
width=0dp
height=0dp
start/end = parent
TopToTop=parent
BottomToTopOf=BottomContainer
>
<BottomContainer>
width=0dp
height=wrap_content
TopToBottomOf=RecyclerView
BottomToBottomOf=parent
start/end = parent>
</ConstraintLayout>
Now this needs one more thing, because the RV would take all the space, you want to ensure the BottomContainer has more information about where it wants to be placed.
So you add:
app:layout_constraintVertical_bias="1.0"
to the Bottom Container.
This means, vertically, as "bottom" as you can. (0.0 would be the opposite).
The end result is:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recylerview"
android:layout_width="0dp"
android:layout_height="0dp"
android:paddingStart="10dp"
android:paddingEnd="10dp"
android:paddingBottom="10dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:listitem="#android:layout/simple_list_item_2" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="0dp"
app:layout_constraintVertical_bias="1.0"
android:layout_height="wrap_content"
android:id="#+id/bottomContainer"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="#id/recylerview"
app:layout_constraintBottom_toBottomOf="parent">
<EditText
android:id="#+id/editTextContainer"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="#+id/button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/editTextContainer"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
Which looks like this:
UPDATE
If you add both
app:stackFromEnd="true"
app:reverseLayout="true"
It works the same way, except the item "0" is at the bottom, and the "last" item is at the top. Adding another item would add it at the top but the BottomContainer has no participation (or influence) over this:

Android Studio - Why does my recycler-view get stuck without letting me scrolling to its bottom?

Description
I am using a recycler view that has more items inside than screen´s height, so to see them we should scroll down. The problem is that I can only scroll some dps down (like 10 or 20 dps).
What do I need?
I need to scroll to it´s bottom in order to see all recycler´s views.
My design is private so I am going to show you a graphic:
The blue box is my recycler view. It has ten views loaded, but we can only see two and a half. I can slide so that I can see "Daddy Yankee" full name, but not more than that.
My fragment XML code (in which I have my recycler)
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
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:contentDescription="#string/ayuda">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/constraint_bar"
android:layout_width="match_parent"
android:layout_height="50dp"
android:elevation="2dp"
android:contentDescription="#string/ayuda"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:background="#8d6e63"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<ImageButton
android:id="#+id/imgbt_back"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:contentDescription="#string/ayuda"
android:background="?selectableItemBackgroundBorderless"
android:src="#drawable/icon_back_negro"
android:tint="#ffffff"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/txt_lobby"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="15dp"
android:contentDescription="#string/ayuda"
android:text="Lobby"
android:textColor="#ffffff"
android:textSize="15.5sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#+id/imgbt_back"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:id="#+id/txt_names"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginTop="20dp"
android:text="(10) names"
android:fontFamily="#font/arimo"
android:textColor="#000000"
android:textSize="16sp"
app:layout_constraintTop_toBottomOf="#id/constraint_bar"
app:layout_constraintLeft_toLeftOf="parent"
android:contentDescription="#string/ayuda"/>
<View
android:id="#+id/view_barra0"
android:layout_width="match_parent"
android:layout_height="1.5dp"
android:layout_marginTop="5dp"
android:background="#eeeeee"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toBottomOf="#id/txt_names"
android:contentDescription="#string/ayuda"/>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler_names"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="#id/view_barra0"
app:layout_constraintLeft_toLeftOf="parent"
android:contentDescription="#string/ayuda"/>
</androidx.constraintlayout.widget.ConstraintLayout>
What can I do to slide my recycler to the bottom to be able to see all the other views?
Add this constraint on your id/recycler_names:
app:layout_constraintBottom_toBottomOf="parent"
and then set layout_height to 0dp (match constraint).

ContraintLayout: Optional top view

I want to make the following design using ConstraintLayout. The screen should be devided into a top section (50% of screen), and a bottom section (50% of screen). The top section should be able to hide according to some application logic, making the bottom section use the remaining blank space on top.
My layout is as follows:
<ImageView
android:id="#+id/imageView"
android:layout_width="0dp"
android:layout_height="0dp"
android:visibility="visible"
app:layout_constraintBottom_toTopOf="#+id/guideline"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0"
app:srcCompat="#android:drawable/ic_input_add" />
<android.support.constraint.Guideline
android:id="#+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.5" />
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/imageView" />
Comparison image showing on the left side how the layout looks with both sections visible. On the right side the top section is gone but the bottom RecyclerView does not stretch to use the top space. I added padding to the ImageView and RecyclerView to better illustrate the relationship between the views.
You can set equal vertical weights for both views in the chain so each occupies 50% of the space. If you set the top view's visibility to GONE in code or in XML, the bottom view will fill the remaining space.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
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">
<ImageView
android:id="#+id/imageView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="#+id/recyclerView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#android:drawable/ic_input_add"
app:layout_constraintVertical_weight="1" />
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/imageView"
app:layout_constraintVertical_weight="1" />
</android.support.constraint.ConstraintLayout>

ConstraintLayout: Create a button that fills space after a RecyclerView

I have a horizontal RecyclerView inside a ConstraintLayout. I want to place a button at the end of the RecyclerView. When the recycler is empty, the button should expand to all available space. When items are added to the recycler, the button should squeeze down to a minimum.
There are some new additions to ConstraintLayout 1.1.0, like layout_constraintWidth_min, but I don't get it working. Is it supposed to work the way I intend?
Here are the relevant attributes, not including height:
<android.support.v7.widget.RecyclerView
android:id="#+id/horizontal_recycler"
android:layout_width="wrap_content"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toStartOf="#+id/add">
</android.support.v7.widget.RecyclerView>
and
<Button
android:id="#+id/add"
android:layout_width="0dp"
app:layout_constraintWidth_min="80dp"
app:layout_constraintStart_toEndOf="#+id/horizontal_recycler"
app:layout_constraintEnd_toEndOf="parent">
</Button>
So here is my solution.
<android.support.constraint.ConstraintLayout
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.v7.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="wrap_content"
android:layout_height="200dp"
android:layout_marginEnd="80dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/button"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="ADD"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/recyclerView"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
Please note that in order to keep the recyclerView from squishing the button the margin end on the recycler should equal the button with plus any padding and margin you see fit to have.

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