Develop Reference

How to keep the floatingActionButton fixed at is original position when scrolling the recyclerview

I need help to keep the fab shown in pics at a fixed position when scrolling up or down i cant find anything on google as most search results return information on hiding the fab when scrolling
Here is my xml
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/accent"> <android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/accent"
>
<android.support.v7.widget.RecyclerView
android:id="#+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:dividerHeight="1dp"
/>
</android.support.constraint.ConstraintLayout>
<android.support.design.widget.FloatingActionButton
android:id="#+id/addmorefab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_marginBottom="#dimen/fab_marginBottom"
android:layout_marginRight="#dimen/fab_marginRight"
android:clickable="true"
app:backgroundTint="#color/primary"
app:srcCompat="#drawable/ic_action_new"
app:layout_anchor="#id/listView"
app:layout_anchorGravity="bottom|right|end"
/></android.support.constraint.ConstraintLayout>
I even tried to make two constraint layouts it didnt work
I also tried using recyclerView.setNestedScrollingEnabled(false);
It worked but it was limiting the scrolling of the recyclerview.
On the second picture i want the fab to remain fixed where it is not scrolling

You can use this view if you want your bright button to remain fixed while scrolling through the recycler.
I used Android X libraries and you can use lower version libraries.
<?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">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:dividerHeight="1dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/addmorefab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="18dp"
android:layout_marginBottom="18dp"
android:clickable="true"
app:backgroundTint="#color/colorPrimary"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:srcCompat="#android:drawable/ic_input_add" />
</androidx.constraintlayout.widget.ConstraintLayout>

Any reason why the distance between buttons do not match in design view and on device at Android Studio?

Here is the code I am using at the layout file. I am using Material components as theme style. Here I used both material component button and button, but I think they are both converted to material button due to my theming style:
<?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=".MainActivity">
<Button
android:id="#+id/createAccountBtn"
android:layout_width="238dp"
android:layout_height="wrap_content"
android:layout_marginStart="86dp"
android:layout_marginTop="35dp"
android:layout_marginEnd="87dp"
android:layout_marginBottom="318dp"
android:text="#string/create_account"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/signInBtn" />
<Button
android:id="#+id/signInBtn"
android:layout_width="237dp"
android:layout_height="wrap_content"
android:layout_marginStart="89dp"
android:layout_marginTop="282dp"
android:layout_marginEnd="85dp"
android:layout_marginBottom="14dp"
android:text="#string/common_signin_button_text"
app:layout_constraintBottom_toTopOf="#+id/createAccountBtn"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

The emmulator model and the model for which you designed the app might be different !
Please check that and revert back .

Apparently I need to use match_parent and wrap_content properties for layout_width and layout_height. One can see this documentation for its use with ConstraintLayout here: https://developer.android.com/training/multiscreen/screensizes
But I would suggest using LinearLayout as ConstraintLayout in my case behaved still badly because I had to define margin properties in exact dps which may not align with a certain screen size. I am adding the LinearLayout solution below which worked as I expected in portrait and landscape mode as well:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:gravity="center"
android:orientation="vertical"
android:padding="16dp"
tools:context=".MainActivity">
<Button
android:id="#+id/createAccountBtn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/create_account" />
<Button
android:id="#+id/signInBtn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/common_signin_button_text"/>
</LinearLayout>

How to get a whole screen in an activity to scroll when a scrollable recyclerView imakes up only half of the phone screen

I want my whole screen to scroll but only my recycler will scroll at the moment. This occurs despite all elements being placed in a linear layout inside a Scroll View.
Any ideas where the error is? Here's the relevant code.
<?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=".NoodleDetailActivity">
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
android:id="#+id/noodleImage"
android:layout_width="match_parent"
android:layout_height="200dp"
android:adjustViewBounds="false"
android:scaleType="centerCrop"
app:srcCompat="#mipmap/ic_launcher" />
<TextView
android:id="#+id/description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#drawable/border_bottom"
android:fontFamily="sans-serif-smallcaps"
android:hapticFeedbackEnabled="false"
android:padding="30dp"
android:text="TextView"
android:textSize="18sp" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/extras_recycler"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="0dp"
android:background="#F2F2F2"
android:padding="0dp" />
</LinearLayout>
</ScrollView>
</androidx.constraintlayout.widget.ConstraintLayout>
This is what it looks visually.
demo appearance

Found out: it seems best practice is to set the recyclerView to be the whole layout and make it contain multiple view types.
I won't be using a nested scroll view.

Android studio Java - Bottom Sheet view over maps

new to android programming , java , I'm trying to create a "simple.." BottomSheet that have to appear when I click on one of my location. Actually I've been able to create my map and load my point data. I have my map in a fragment..
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<fragment
android:id="#+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
/>
</RelativeLayout>
I then created my BottomSheet looking at online tutorial.
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinaCoordinatorLayout 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.chargesplit.android.activities.MainActivity">
<android.support.v4.widget.NestedScrollView
android:id="#+id/nestedScrollView"
android:layout_width="match_parent"
android:layout_height="300dp"
android:background="#android:color/holo_green_light"
android:clipToPadding="true"
app:behavior_hideable="true"
app:behavior_peekHeight="0dp"
app:layout_behavior="#string/bottom_sheet_behavior">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ciao"
android:textColor="#android:color/white"
android:textSize="24sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:text="ciao2"
android:textColor="#android:color/white" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinaCoordinatorLayout>
Finally, inside my Main Activity, I managed to reference my bottom sheet, but probably due to inexperience I'm every time getting error on this line:
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
-> View nestedScrollView = (View) findViewById(R.id.nestedScrollView);
mBottomSheetBehaviour = BottomSheetBehavior.from(nestedScrollView);
I'm always get this error and I'm probably missing a piece here... could someone try to drive me in te right direction to understanding what's wrong?
java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference

This error happens because your activity is unable to locate your bottom sheet view, why that? because your bottom sheet view isn't included in the activity_main.xml layout.
In other words, Your MainActivity.java can only look at activity_main.xml, but it still has no idea about the other xml file of your bottom sheet.
To solve this: replace your code in activity_main layout with
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinaCoordinatorLayout
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.chargesplit.android.activities.MainActivity">
<fragment
android:id="#+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"/>
<android.support.v4.widget.NestedScrollView
android:id="#+id/nestedScrollView"
android:layout_width="match_parent"
android:layout_height="300dp"
android:background="#android:color/holo_green_light"
android:clipToPadding="true"
app:behavior_hideable="true"
app:behavior_peekHeight="0dp"
app:layout_behavior="#string/bottom_sheet_behavior">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ciao"
android:textColor="#android:color/white"
android:textSize="24sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:text="ciao2"
android:textColor="#android:color/white" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinaCoordinatorLayout>
Caveat: To make your layouts look neat, you can separate your bottom sheet view into a separate layout, so you can put your <android.support.v4.widget.NestedScrollView> into say bottom_sheet.xml, and then reference it from the activity_main.xml with
<include layout="#layout/bottom_sheet" />
Wish that helps you out.. Should you need further help, please let me know

noob Q: layout_below not placing my button below my textView

Very new so please excuse misuse of terms.
I'm following an Android development course to build a basic app. I created a text view and then a button. The button should sit below the text view after using android:layout_below="#id/rollResult" but instead the button overlaps the text.
Adding and removing that line from my code has no effect on the botton's layout position. Changing this line android:layout_centerHorizontal="true" from true to false and back also has no effect.
Code:
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.example.diceout.MainActivity"
tools:showIn="#layout/activity_main"
tools:layout_editor_absoluteY="81dp"
tools:layout_editor_absoluteX="0dp">
<TextView
android:id="#+id/rollResult"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="The play App"
/>
<Button
android:id="#+id/rollButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/rollResult"
android:layout_centerHorizontal="true"
android:onClick="rollDice"
android:text="Roll" />
Any help is much appreciated.

Change your ConstraintLayout to RelativeLayout