Develop Reference

RecycleView doesn't Scroll

been scowering the internet on this seems to happen a lot for a lot of reasons but I can't solve mine. I can't scroll my RecyclerView and I completly don't know why.
My recyclerView is included in another layout (activity_class.xml)
Here is my layout code:
content_home_screen.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView 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/recyclerview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFF"
tools:context="com.example.schoolteacher.ClassActivity"
tools:showIn="#layout/activity_class">
</androidx.recyclerview.widget.RecyclerView>
activity_class.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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="com.example.schoolteacher.ClassActivity">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.ActionBar"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#FFFFFF"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:title="#string/classes"/>
</com.google.android.material.appbar.AppBarLayout>
<include layout="#layout/content_home_screen" />
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_marginEnd="#dimen/fab_margin"
android:layout_marginBottom="70dp"
android:src="#drawable/ic_add_fab"
android:theme="#style/Theme.AppCompat"
app:backgroundTint="#color/colorPrimary" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="?android:attr/windowBackground"
app:menu="#menu/bottombar_menu" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
Any ideas, because I tried almost everything.

Add this to the content_home_screen layout
android:scrollbars="vertical"

How do I hide Material Bottom App Bar when Coordinator Layout's child fragment is scrolled?

I wonder why app:hideOnScroll="true" is not working in my case, when I want my BottomAppBar to be hidden when scrolling.
I want to achieve something like this: Hide bottom app bar on scroll
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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/main_coordinator"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay"
app:elevation="0dp">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/colorBackgroundPrimary"
android:theme="#style/customtoolbar"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:titleTextColor="#color/colorTextPrimary" />
</com.google.android.material.appbar.AppBarLayout>
<include layout="#layout/content_main" />
<com.google.android.material.bottomappbar.BottomAppBar
android:id="#+id/bar"
style="#style/Widget.MaterialComponents.BottomAppBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:backgroundTint="#color/colorBtn"
app:hideOnScroll="true"
app:layout_scrollFlags="scroll|enterAlways"
app:navigationIcon="#drawable/baseline_menu_24"/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:backgroundTint="#color/colorPrimaryDark"
android:src="#drawable/baseline_add_24"
app:layout_anchor="#id/bar" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
content_main.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:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/colorBackgroundPrimary"
android:backgroundTint="#color/colorBackgroundPrimary"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:showIn="#layout/activity_main">
<FrameLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginStart="16dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="16dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
</FrameLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

root element of content_main.xml should be NestedScrollView or RecyclerView if you want to enable hideOnScroll

SwipeRefreshLayout overlaps BottomAppbar

I feel like I've tried everything to resolve this but I can't figure out how to have a Coordinatorlayout containing an bottom app bar and a constraintlayout that contains a swipe refreshlayout without the refresh layout overlapping the bottom app bar.
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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:animateLayoutChanges="true"
android:background="#color/colorWhite"
tools:context=".departures.DeparturesActivity">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true"
android:background="#color/colorWhite"
tools:context=".departures.DeparturesActivity">
<RelativeLayout-with-some-stuff-in-it/>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
android:id="#+id/departures_swiperefresh_layout"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintTop_toTopOf="parent"
tools:layout_editor_absoluteX="0dp">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/departures_list"
android:layout_width="match_parent"
android:layout_height="0dp"
android:paddingLeft="#dimen/md_keylines"
android:paddingTop="#dimen/md_keylines"
android:paddingRight="#dimen/md_keylines"
android:paddingBottom="#dimen/md_keylines" />
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/departures_fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:backgroundTint="#color/colorAccent"
app:layout_anchor="#id/bottomAppBar"
app:srcCompat="#drawable/ic_add"
app:tint="#color/colorWhite" />
<com.google.android.material.bottomappbar.BottomAppBar
android:id="#+id/bottomAppBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
app:backgroundTint="#color/colorPrimary"
app:fabAlignmentMode="end"
app:fabCradleMargin="4dp"
app:fabCradleRoundedCornerRadius="16dp"
app:fabCradleVerticalOffset="4dp"
app:popupTheme="#style/ThemeOverlay.MaterialComponents.Light"
app:theme="#style/ThemeOverlay.MaterialComponents.Dark.ActionBar" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
The SwipeRefreshLayout will overlap the bottom app bar and I cant quite figure out why.
Part of the problem is the fact that the UI designer seems to indicate that the constraintlayout expands way below the coordinatorLayout.
This is due of the padding added here to push the layout below the actionbar.
<?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"
tools:context=".departures.DeparturesPresenter">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:layout_constraintTop_toTopOf="parent">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
</com.google.android.material.appbar.AppBarLayout>
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:id="#+id/contentFrame"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="?android:attr/actionBarSize" />
</androidx.constraintlayout.widget.ConstraintLayout>

How can i put the element RecyclerView under the element Toolbar in the Android Layout file?

Hey i want in my android app that the recyclerlistview and the floatingActionButton not cut the toolbar. Here is my Layout:
<android.support.design.widget.CoordinatorLayout
android:id="#+id/main_content"
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">
<include
layout="#layout/toolbar_task_layout">
</include>
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView_task"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
app:layout_anchor="#id/recyclerView_task">
</android.support.v7.widget.RecyclerView>
<android.support.design.widget.FloatingActionButton
android:id="#+id/floatingActionButton_task_openDialog_"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
android:layout_margin="16dp"
android:src="#drawable/ic_add_black_36dp"
app:layout_anchor="#id/recyclerView_task"
android:clickable="true"
app:fabSize="normal"
app:layout_anchorGravity="bottom|right|end"/>
</android.support.design.widget.CoordinatorLayout>
Here you can see the problem:
Update:
Here is the toolbar layout
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar 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="wrap_content"
android:id="#+id/toolbar_task"
android:layout_alignParentTop="true"
android:background="?attr/colorPrimary"
android:elevation="6dp"
android:minHeight="?attr/actionBarSize"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="0 items selected"
android:id="#+id/counter_task"
android:textSize="18dp"
android:textColor="#ffffff"
android:textStyle="bold" />
</RelativeLayout>
</android.support.v7.widget.Toolbar>

Try replacing your <include layout="#layout/toolbar_task_layout"></include>
with this:
<include layout="#layout/toolbar_task_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
EDIT: I assume you also want your FAB to be on the bottom right since this is the norm, try setting android:layout_alignParentBottom="true" and android:layout_alignParentRight="true" in your FAB and make the RecyclerViews height match_parent

try this make your toolbar android:layout_height to android:layout_height="?attr/actionBarSize"
<android.support.v7.widget.Toolbar
android:id="#+id/ac_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="exitUntilCollapsed"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" >

Use below code:
<android.support.design.widget.CoordinatorLayout
android:id="#+id/main_content"
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">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<include layout="#layout/toolbar_task_layout"/>
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView_task"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="0dp"
app:layout_anchor="#id/recyclerView_task"
android:layout_below="#+id/toolbar_task"/>
</RelativeLayout>
<android.support.design.widget.FloatingActionButton
android:id="#+id/floatingActionButton_task_openDialog_"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
android:layout_margin="16dp"
android:src="#mipmap/ic_launcher"
app:layout_anchor="#id/recyclerView_task"
android:clickable="true"
app:fabSize="normal"
app:layout_anchorGravity="bottom|right|end"/></android.support.design.widget.CoordinatorLayout>
I hope this will help.....

Android button permanently on bottom

I have the following Xml code where I want to display the content of a fragment into FrameLayount but I don't know how to keep my button always on bottom.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_lista_preguntas"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.ingenierovagabundo.encuestafacil.GUI.ListaPreguntasActivity">
<!-- Toolbar -->
<android.support.v7.widget.Toolbar xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/appbar_nueva_pregunta"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:elevation="4dp"
android:minHeight="?attr/actionBarSize"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="#+id/contenedor_Pregunta"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</FrameLayout>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
android:layout_marginBottom="16dp"
android:layout_marginRight="16dp"
android:text="#string/npa_button_guardar"/>

you can use RelativeLayout insted of LinearLayout as below:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_lista_preguntas"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.ingenierovagabundo.encuestafacil.GUI.ListaPreguntasActivity">
<!-- Toolbar -->
<android.support.v7.widget.Toolbar xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/appbar_nueva_pregunta"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:elevation="4dp"
android:minHeight="?attr/actionBarSize"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="#+id/contenedor_Pregunta"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/btn"
android:layout_below="#+id/appbar_nueva_pregunta">
</FrameLayout>
<Button
android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="false"
android:layout_marginBottom="16dp"
android:layout_marginRight="16dp"
android:text="#string/npa_button_guardar" />

You could add android:layout_weight="1" to your FrameLayout. This will expand the FrameLayout to fill any remaining space in the parent view. Which should result the Button to be at the bottom.
So your resulting FrameLayout will be,
<FrameLayout
android:id="#+id/contenedor_Pregunta"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1">
</FrameLayout>
For more on layout_weight follow the link
https://developer.android.com/guide/topics/ui/layout/linear.html#Weight

You use a LinearLayout as container, then the elements follow each other.
If you want to keep your button always on bottom, use a RelativeLayout with
android:layout_alignParentBottom="true".
You also need to close your container! ;)

Use this Code in activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
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:fitsSystemWindows="true">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay"/>
</android.support.design.widget.AppBarLayout>
<include layout="#layout/content_main" />
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/fab_margin"
app:backgroundTint="#color/colorOrange"
app:srcCompat="#android:drawable/ic_menu_share"
tools:ignore="VectorDrawableCompat" />
</android.support.design.widget.CoordinatorLayout>
And in content_main.xml, use this Code.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:showIn="#layout/app_bar_main">
<FrameLayout
android:id="#+id/frame_container"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>