I'm using the latest Nav Component (2.2.0-alpha01) in my project, and am presented with an issue I can't seem to resolve.
I have a splash animation - nothing serious, a custom background stretching to the whole screen, and a logo in the very middle, using ConstraintLayout. During the initial sync, I animate a custom animated VectorDrawable (let's call it #drawable/logo_animated), which uses the common #drawable/logo as a source, and applies animations to its groups.
To time the animation right, I created the following helper function:
fun ImageView.setRepeatingAnimatedVector(
#DrawableRes animationRes: Int,
delayMs: Long = 0,
startDelayMs: Long = 0,
shouldRunOptional: () -> Boolean = { false },
optionalRunnable: () -> Unit = {}
) {
val anim = AnimatedVectorDrawableCompat.create(context, animationRes)?.apply {
registerAnimationCallback(object : Animatable2Compat.AnimationCallback() {
override fun onAnimationEnd(drawable: Drawable?) {
this#setRepeatingAnimatedVector.postDelayed({ if (shouldRunOptional()) optionalRunnable() else start() }, delayMs)
}
})
}
setImageDrawable(anim)
postDelayed({ anim?.start() }, startDelayMs)
}
It takes an AnimatedVectorDrawable as an input, and applies it to the ImageView. Upon finishing the animation cycle, a check in the form of a lambda (shouldRunOptional) is ran. If it returns true, the optionalRunnable lambda is launched, otherwise it repeats the animation.
With this, I can wait for the ViewModel to finish syncing, and then await the end of the animation to move between fragments without any weirdness. The animation itself is short (~900ms), so at most the user will be delayed by a second.
I also use a custom NavigationManager composition for navigation. The Manager itself is an interface (INavigationManager) of generic calls (such as splashToLanding() or openDetail(id: UUID)) that gets injected into ViewModels, with an extra interface taking care of the NavComponent specific bits:
IFragmentNavigator.kt
interface IFragmentNavigator {
val command: SingleLiveEvent<NavigationCommand>
var splashLandingExtras: Navigator.Extras?
fun setSplashLandingTransition(extras: Navigator.Extras) {
splashLandingExtras = extras
}
fun back() {
navigate(NavigationCommand.Back)
}
fun navigate(direction: NavDirections) {
navigate(NavigationCommand.To(direction))
}
fun navigate(navCommand: NavigationCommand) {
command.postValue(navCommand)
}
}
The implementation just takes care of property initializations, and then later on used in the following manner:
class FragmentNavigationManager:
INavigationManager, IFragmentNavigator by FragmentNavigator() { [...] }
The command property of this interface is then later used in the Fragments, via Observers:
open val navigationObserver = Observer<NavigationCommand> {
when(it) {
is NavigationCommand.To -> findNavController().navigate(it.directions)
is NavigationCommand.Back -> findNavController().popBackStack()
is NavigationCommand.BackTo -> findNavController().popBackStack(it.destinationId, false)
is NavigationCommand.ToRoot -> TODO()
}
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
navigator.command.observe(this, navigationObserver)
}
The Directions instance created in the FragmentNavigationManager is used by the NavController directly. I made sure to add the FragmentNavigator's Extras field to the actual navigation call:
override fun splashToLanding() {
navigate(
NavigationCommand.To(
SplashFragmentDirections.actionSplashFragmentToLandingFragment(),
null, null, splashLandingExtras
)
)
}
And of course in the SplashFragment, I assign the appropriate view to the transition name for splashLandingExtras:
navigator.splashLandingExtras = FragmentNavigatorExtras(binding.logo to "logo")
In the LandingFragment's onCreate method, I do set up enter and exit animations:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
TransitionInflater.from(context).inflateTransition(android.R.transition.move).let {transition ->
sharedElementEnterTransition = transition
sharedElementReturnTransition = transition
}
}
The layouts are the following:
splash.xml
<layout 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">
<data>
<variable
name="viewModel"
type="com.felcana.app.viewmodel.SplashViewModel" />
</data>
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<include layout="#layout/background" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<ImageView
android:id="#+id/logo"
style="?attr/logoStyle"
android:transitionName="logo"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</layout>
landing.xml
<?xml version="1.0" encoding="utf-8"?>
<layout 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">
<data>
<variable
name="viewModel"
type="com.my.app.viewmodel.LandingViewModel" />
</data>
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<include layout="#layout/background" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<ImageView
android:id="#+id/logo"
style="?attr/logoStyle"
android:layout_marginBottom="24dp"
android:transitionName="logo"
app:layout_constraintBottom_toTopOf="#id/button_register"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<com.google.android.material.button.MaterialButton
android:id="#+id/button_register"
style="?attr/flatWhiteButtonStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginEnd="24dp"
android:layout_marginBottom="8dp"
android:onClick="#{() -> viewModel.goToRegister()}"
android:text="#string/button_register"
app:layout_constraintBottom_toTopOf="#id/button_login"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<com.google.android.material.button.MaterialButton
android:id="#+id/button_login"
style="?attr/borderlessWhiteButtonStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="24dp"
android:onClick="#{() -> viewModel.goToLogin()}"
android:text="#string/button_login"
app:layout_constraintBottom_toTopOf="#id/disclaimer"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<TextView
android:id="#+id/disclaimer"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginEnd="24dp"
android:layout_marginBottom="32dp"
android:maxLines="2"
android:textAlignment="center"
android:textColor="#color/app_white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
tools:text="#tools:sample/lorem/random" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</layout>
For some reason, the animation does not play at all - the ImageView just jumps without any sort of transition to the new position.
What's going wrong here? According to the documentation, this should be working. I did try going back to more stable versions of the NavComponent library, to no avail.
Have you tried postponing the enter transition inside LandingFragment::onViewCreated and manually setting the transition name to the view?
Something like this:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
// Pause the enter transition
postponeEnterTransition()
// Manually apply the transitionName
logo.transitionName = "logo"
// Resume the transition
startPostponedEnterTransition()
super.onViewCreated(view, savedInstanceState)
}
Related
everyone. I have a BottomnNavigationsBar and a FrameLayout inside my activity_main.xml file. In the frame I display a ViewPager within a Fragment. The navigation contains 3 elements. If I click on one, the clicked status does not change. The respective fragment is displayed correctly, but the icon does not change in color and size.
What am I doing wrong or what do I have to change?
Here is my MainActivity:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
viewBinding = ActivityMainBinding.inflate(layoutInflater)
setContentView(viewBinding.root)
setFragementTo(HomeFragment.newInstance("",""))
viewBinding.bottomNavigationView.setOnItemSelectedListener{
when(it.itemId)
{
R.id.home ->{
setFragementTo(HomeFragment.newInstance("",""))
}
R.id.neu ->{
setFragementTo(NewFragment.newInstance("",""))
}
R.id.settings ->{
setFragementTo(FilterFragment.newInstance("",""))
}
}
false
}
}
private fun setFragementTo(fragment: Fragment) {
supportFragmentManager.beginTransaction().replace(R.id.myFrameInMain,fragment).commit()
}
activity_main.xml:
<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"
tools:context=".MainActivity">
<FrameLayout
android:id="#+id/myFrameInMain"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="#+id/bottomNavigationView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"></FrameLayout>
<com.google.android.material.bottomnavigation.BottomNavigationView
android:background="#drawable/bottom_nav_style"
app:itemRippleColor="#color/white"
app:itemTextColor="#color/item_bottom_nav"
app:itemIconTint="#color/item_bottom_nav"
android:id="#+id/bottomNavigationView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="#menu/bottom_nav"/>
</androidx.constraintlayout.widget.ConstraintLayout>
Here I click on the middle icon in the navigation. The fragment appears correctly, but the icon in the navigation does not
And here the filter icon:
I think I got it. I had to change the parameter from false to true in the setOnItemSelectedListener method
I have a problem:
I have a TextView whose content is constantly changing via LiveData. This looks all right when the animation isn't executing, but when the MotionLayout starts executing, my text gets blocked a little bit.
And the constraints of my TextView and Button are packed.
activity:
class ErrorActivity : AppCompatActivity() {
private val mViewModel by viewModels<ErrorViewModel>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
DataBindingUtil.setContentView<ActivityErrorBinding>(this, R.layout.activity_error).apply {
lifecycleOwner = this#ErrorActivity
viewModel = mViewModel
}
}
fun startStopAnim(v: View) {
mViewModel.anim()
}
}
activity layout:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:binding="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="viewModel"
type="com.test.test.ErrorViewModel" />
</data>
<androidx.constraintlayout.motion.widget.MotionLayout
android:id="#+id/layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutDescription="#xml/scene"
binding:anim="#{viewModel.mAnim}">
<TextView
android:id="#+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{#string/test(viewModel.mCountDown)}"
android:textSize="32sp"
app:layout_constraintEnd_toStartOf="#+id/btn"
app:layout_constraintHorizontal_chainStyle="packed"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="#string/test" />
<Button
android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Test"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/tv"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/anim"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="startStopAnim"
android:text="startOrStop"
android:textAllCaps="false"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.motion.widget.MotionLayout>
</layout>
viewModel:
class ErrorViewModel : ViewModel() {
private val _countDown: MutableLiveData<String> = MutableLiveData()
val mCountDown: LiveData<String> = _countDown
private val _anim: MutableLiveData<Boolean> = MutableLiveData()
val mAnim: LiveData<Boolean> = _anim
private var count = 0
private var state = false
init {
viewModelScope.launch(Dispatchers.IO) {
while (true) {
delay(1000)
_countDown.postValue(count++.toString())
}
}
}
fun anim() {
state = !state
_anim.value = state
}
}
#BindingAdapter("anim")
fun anim(layout: MotionLayout, play: Boolean?) {
play?.let {
if (it) {
layout.transitionToEnd()
} else {
layout.transitionToStart()
}
}
}
motionScene:
For simplicity, Scene has only one duration
<?xml version="1.0" encoding="utf-8"?>
<MotionScene xmlns:app="http://schemas.android.com/apk/res-auto">
<Transition
app:constraintSetEnd="#+id/end"
app:constraintSetStart="#+id/start"
app:duration="2000" />
</MotionScene>
gif
As you can see in the gif, when there is no click, everything works fine for the numbers, but when I click the button, a 2 second animation starts, during which time my text doesn't display properly.
Of course, this is just a demo example. In a real scene, not only the text is not displayed completely, but even the TextView And ImageView are misplaced, and once the animation is executed, it cannot be recovered.
Can someone help me...
Actually in a real scene, the parent layout (B) of the problematic TextView (A) would perform a displacement animation. As long as this animation is executed once, the constraint relationship of TextView A will definitely have problems and cannot be restored (onResume can be restored after onPause is currently found)
By design during animation MotionLayout does not honor requestLayout.
Because in the majority of applications it is not needed and would have a significant impact on performance.
To enable it in the transition add
<Transition ... motion:layoutDuringTransition="honorRequest" \>
I write a code for a simple dice roll app but there is a problem in updating the image of an image view that bound with a binding adapter
I can't extend BaseObservable class because I already extended the ViewModel class. I need that for keeping data after the status changed. Also, I can't observe the live data inside my binding adapter because the function is static
do you know any other way?
This is my xml code
<?xml version="1.0" encoding="utf-8"?>
<layout
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">
<data>
<variable
name="viewModel"
type="com.example.diceroller.MainActivityViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ImageView
android:id="#+id/imgDice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:imageRes="#{viewModel.drawableResource}" />
<Button
android:id="#+id/btnRoll"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="32dp"
android:text="Roll the dice"
android:onClick="#{() -> viewModel.onRollButtonClicked()}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
and this is my kotlin code
class MainActivityViewModel : ViewModel() , Observable {
#Bindable
var drawableResource : MutableLiveData<Int> = MutableLiveData<Int>()
init {
drawableResource.value = R.drawable.dice_1
}
fun onRollButtonClicked(){
drawableResource.value = when(Random.nextInt(1,7)){
1 -> R.drawable.dice_1
2 -> R.drawable.dice_2
3 -> R.drawable.dice_3
4 -> R.drawable.dice_4
5 -> R.drawable.dice_5
else -> R.drawable.dice_6
}
}
override fun addOnPropertyChangedCallback(callback: Observable.OnPropertyChangedCallback?) {
}
override fun removeOnPropertyChangedCallback(callback:
Observable.OnPropertyChangedCallback?) {
}
}
#BindingAdapter("android:imageRes")
fun loadImage(view : View , imageRes : Int){
(view as ImageView).setImageResource(imageRes)
}
I've written the test, testing if the recycler view is displayed (id: comments_view), but it always fails and I've no idea why. When I'm checking for layout (id: cm), the test passes.
I have the following fragment code:
<layout 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">
<data>
<variable
name="post"
type="com.example.kotlinpostapi.apiObjects.Post" />
<variable
name="comments"
type="java.util.List" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".views.MainActivity"
android:id="#+id/cm">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/comments_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
The test code (I'm navigating to the fragment from another one):
#RunWith(AndroidJUnit4::class)
class CommentsListTest{
#get: Rule
val activityScenario = ActivityScenarioRule(MainActivity::class.java)
#Test
fun testCommentsAreDisplayed() {
onView(withId(R.id.posts_view)).perform(actionOnItemAtPosition<PostAdapter.PostsViewHolder>(0, MyMatchers.clickChildView(R.id.show_comments_button)))
//it fails
onView(withId(R.id.comments_view)).check(matches(isDisplayed()))
//it passes
onView(withId(R.id.cm)).check(matches(isDisplayed()))
}
}
How is it possible, and how can I test my recycler view?
The height of the RecyclerView is set to wrap_content and if the element is not visible at least 90% the test fails.
What you could do is to check one of the RecyclerView children.
I firstly declare the following method:
fun nthChildOf(parentMatcher: Matcher<View?>, childPosition: Int): Matcher<View?>? {
return object : TypeSafeMatcher<View>() {
override fun describeTo(description: Description) {
description.appendText("with $childPosition child view of type parentMatcher")
}
override fun matchesSafely(view: View): Boolean {
if (view.parent !is ViewGroup) {
return parentMatcher.matches(view.parent)
}
val group = view.parent as ViewGroup
return parentMatcher.matches(view.parent) && group.getChildAt(childPosition) == view
}
}
}
with this you can check whether its first child is displayed:
onView(nthChildOf(withId(R.id.comments_view), 0)).check(matches(isDisplayed()))
And to check one element of its children (recyclerview_element_id for example):
onView(allOf(
withId(R.id.recyclerview_element_id),
isDescendantOfA(
nthChildOf(withId(R.id.comments_view), 0))
)).check(matches(isDisplayed()))
Another thing you could try if your RecyclerView expands to the available space of the screen is to change the layout of the RecyclerView to have all the constraints set and with and height to 0dp:
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/comments_view"
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_toTopOf="parent" />
I have it this way and doing:
onView(withId(R.id.myRecyclerviewId)).check(matches(isDisplayed()))
works for me.
I have a BottomSheet which houses a product detail card. The problem is, when I click on the + or - button on the product detail while the bottom sheet is in it's Expanded state, it jumps down.
When it is down and I click on the buttons it doesn't jump, it only happens when it is in it's Expanded (completely up) state
I have attached a GIF to show what is exactly happening
Here is the code
scan_sheet.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"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/bottom_sheet"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:animateLayoutChanges="false"
android:background="#drawable/bottom_sheet_dialog_fragment"
android:orientation="vertical"
app:behavior_hideable="true"
app:behavior_peekHeight="100dp"
app:layout_behavior="studio.monotype.storedemo.BottomSheetBehavior">
<include
layout="#layout/hero_item"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="32dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<View
android:id="#+id/divider_view"
android:layout_width="match_parent"
android:layout_height="4dp"
android:layout_marginStart="24dp"
android:layout_marginTop="44dp"
android:layout_marginEnd="24dp"
android:background="#color/colorPrimary"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/hero_item" />
<include
layout="#layout/related_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="24dp"
android:layout_marginBottom="16dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toBottomOf="#+id/divider_view"
tools:layout_editor_absoluteX="0dp" />
</androidx.constraintlayout.widget.ConstraintLayout>
ScanActivity.kt (simplified to show only what is essential)
class ScanActivity : AppCompatActivity() {
private lateinit var bottomSheet: BottomSheetBehavior<*>
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scan)
setupBottomSheet()
showSheet()
}
private fun setupBottomSheet() {
bottomSheet = BottomSheetBehavior.from(bottom_sheet)
bottomSheet.isHideable = true
bottomSheet.skipCollapsed= true
bottomSheet.isDraggable = true
bottomSheet.state = BottomSheetBehavior.STATE_HIDDEN
bottomSheet.addBottomSheetCallback(object : BottomSheetBehavior.BottomSheetCallback {
override fun onSlide(bottomSheet: View, slideOffset: Float) {
}
#SuppressLint("SwitchIntDef")
override fun onStateChanged(sheet: View, newState: Int) {
when (newState) {
BottomSheetBehavior.STATE_HIDDEN -> {
codeScanner.startPreview()
}
}
}
})
plus_btn.setOnClickListener {
var qty= qty_tv.text.toString().toInt()
qty++
qty_tv.text =qty.toString()
}
minus_btn.setOnClickListener {
var qty= qty_tv.text.toString().toInt()
if(qty!=0)
{
qty--
}
qty_tv.text =qty.toString()
}
}
private fun showSheet() {
bottomSheet.state = BottomSheetBehavior.STATE_EXPANDED
}
}
it seems that google engineer gave correct answer
Seems like something is going on because you are setting
android:layout_gravity="bottom" on the view with the
BottomSheetBehavior. You should remove that line.
It helped on my case
Looks to me like that could be a bug in the BottomSheetBehavior? Seems like the height of the sheet isn't getting saved or restored correctly. After the button is pressed, a layout happens again which changes the height. Could you file a bug at https://issuetracker.google.com/issues/new?component=439535