recyclerview inside nestedscrollview loading slow

Question

I have recyclerview inside my nestedscrollview, when my recyclerview loads, I have no problem with scrolling, its very smooth but its loading very slow at first (its not about my data or networking) slow line is recyclerview.adapter = MyAdapter()

when I move the recyclerview out of nestedscrollview (first child of root element) its really fast. here is my xml

with this xml it blocks the ui for 3-4 seconds and loads it but if I place my recyclerview outside of nestedscrollview it loads in milliseconds, unnoticable.

I need the recyclerview in my nestedscrollview.

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:tools="http://schemas.android.com/tools" 
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:focusableInTouchMode="true"
        android:background="#f7f7f7"
        android:orientation="vertical">
        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:titleTextAppearance="@style/ToolbarExpandedTextAppearance"
            app:layout_collapseMode="pin"
            android:background="@color/colorPrimary">
            <ImageButton
                android:layout_width="?attr/actionBarSize"
                android:layout_height="?attr/actionBarSize"
                android:id="@+id/right_button"
                android:src="@drawable/ic_top_question"
                android:layout_gravity="end|top"
                android:contentDescription="@string/placeholder_right_button"
                android:background="?attr/selectableItemBackground"/>
        </androidx.appcompat.widget.Toolbar>

        <androidx.core.widget.NestedScrollView
            android:id="@+id/nestedScrollView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fillViewport="true"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            android:orientation="vertical">

            <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:orientation="vertical"
                android:layout_height="match_parent">

                <androidx.constraintlayout.widget.ConstraintLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:background="@color/colorPrimary" android:id="@+id/constraintLayout">

                    <TextView
                        android:text="Give £8, Get £8"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:textColor="@color/white"
                        android:textSize="@dimen/field_header_title_text"
                        android:fontFamily="@font/apercu_medium"
                        android:id="@+id/textView2" android:layout_marginTop="8dp"
                        android:layout_marginStart="16dp"
                        app:layout_constraintStart_toStartOf="parent"
                        app:layout_constraintTop_toTopOf="parent"/>
                    <TextView
                        android:text="Give your friends £8 with your code and get £8 for every friend that uses it!"
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:fontFamily="@font/apercu"
                        android:textSize="@dimen/discover_message_text_size"
                        android:textColor="@color/text_white"
                        android:lineSpacingExtra="10dp"
                        android:id="@+id/textView3" android:layout_marginTop="16dp"
                        app:layout_constraintTop_toBottomOf="@+id/textView2"
                        app:layout_constraintStart_toStartOf="parent" app:layout_constraintEnd_toEndOf="parent"
                        android:layout_marginEnd="32dp" android:layout_marginStart="16dp"/>
                    <LinearLayout
                        android:orientation="horizontal"
                        android:layout_width="0dp"
                        android:layout_height="80dp"
                        app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="8dp"
                        app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="8dp"
                        android:layout_marginTop="24dp" app:layout_constraintTop_toBottomOf="@+id/textView3"
                        android:id="@+id/linearLayout" android:layout_marginBottom="8dp"
                        app:layout_constraintBottom_toBottomOf="parent">
                        <LinearLayout
                            android:orientation="vertical"
                            android:layout_width="0dp"
                            android:layout_weight="1"
                            android:layout_height="match_parent"
                            android:gravity="center"
                            android:layout_margin="8dp"
                            android:background="@drawable/white_radius">
                            <TextView
                                android:layout_width="match_parent"
                                android:fontFamily="@font/apercu_bold"
                                android:textColor="@color/warm_grey"
                                android:layout_height="wrap_content"
                                android:gravity="center"
                                android:textSize="24sp"
                                android:id="@+id/txt_pending_invites"/>
                            <TextView
                                android:text="Pending invites"
                                android:layout_width="match_parent"
                                android:fontFamily="@font/apercu"
                                android:lineSpacingExtra="10dp"
                                android:textColor="@color/greyish"
                                android:layout_height="wrap_content" android:id="@+id/textsView5"
                                android:gravity="center"/>
                        </LinearLayout>

                        <LinearLayout
                            android:orientation="vertical"
                            android:layout_width="0dp"
                            android:layout_weight="1"
                            android:gravity="center"
                            android:layout_margin="8dp"
                            android:layout_height="match_parent"
                            android:background="@drawable/white_radius">
                            <TextView
                                android:layout_width="match_parent"
                                android:fontFamily="@font/apercu_bold"
                                android:textColor="@color/warm_grey"
                                android:layout_height="wrap_content"
                                android:gravity="center"
                                android:textSize="24sp"
                                android:id="@+id/txt_earned"/>
                            <TextView
                                android:text="Total earned to date"
                                android:layout_width="match_parent"
                                android:fontFamily="@font/apercu"
                                android:lineSpacingExtra="10dp"
                                android:textColor="@color/greyish"
                                android:layout_height="wrap_content" android:id="@+id/textView5"
                                android:gravity="center"/>
                        </LinearLayout>

                    </LinearLayout>

                </androidx.constraintlayout.widget.ConstraintLayout>

                <androidx.constraintlayout.widget.ConstraintLayout
                        android:layout_width="match_parent"
                        android:layout_height="100dp"
                        tools:layout_editor_absoluteX="16dp" android:layout_marginTop="8dp"
                        app:layout_constraintTop_toBottomOf="@+id/constraintLayout"
                        android:id="@+id/constraintLayout3">

                    <androidx.constraintlayout.widget.ConstraintLayout
                            android:layout_width="0dp"
                            android:background="@drawable/edittextround"
                            android:layout_height="50dp" app:layout_constraintBottom_toBottomOf="parent"
                            android:layout_marginBottom="8dp" app:layout_constraintStart_toStartOf="parent"
                            android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="parent"
                            app:layout_constraintEnd_toEndOf="parent" android:layout_marginStart="15dp"
                            android:layout_marginEnd="15dp" android:id="@+id/constraintLayout2">
                        <TextView
                            android:id="@+id/txt_promo_code"
                            android:layout_width="0dp"
                            android:layout_height="wrap_content"
                            android:maxLines="1"
                            android:textSize="16sp"
                            android:text=""
                            android:textColor="@color/evergreen"
                            android:background="@android:color/transparent" android:layout_marginBottom="8dp"
                            app:layout_constraintBottom_toBottomOf="parent" android:layout_marginTop="8dp"
                            app:layout_constraintTop_toTopOf="parent"
                            app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="20dp"
                            app:layout_constraintEnd_toStartOf="@+id/invite_button"/>
                        <Button
                            android:text="Share"
                            android:layout_width="wrap_content"
                            android:background="@drawable/form_button_radius"
                            android:textAppearance="@style/BottomButtonAppearance"
                            android:layout_height="32dp"
                            android:id="@+id/invite_button"
                            app:layout_constraintEnd_toEndOf="parent"
                            android:layout_marginEnd="8dp" android:layout_marginBottom="0dp"
                            app:layout_constraintBottom_toBottomOf="parent" android:layout_marginTop="0dp"
                            app:layout_constraintTop_toTopOf="parent"/>

                    </androidx.constraintlayout.widget.ConstraintLayout>

                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:background="?android:colorBackground"
                        android:includeFontPadding="false"
                        android:paddingLeft="5dp"
                        android:paddingRight="5dp"
                        android:textSize="13sp"
                        android:text="Share Code"
                        android:textColor="@color/warm_grey"
                        android:fontFamily="@font/apercu"
                        android:textAppearance="@android:style/TextAppearance.Medium"
                        app:layout_constraintEnd_toEndOf="@+id/constraintLayout2"
                        app:layout_constraintStart_toStartOf="@+id/constraintLayout2"
                        app:layout_constraintHorizontal_bias="0.05" android:layout_marginTop="8dp"
                        app:layout_constraintTop_toTopOf="@+id/constraintLayout2"
                        app:layout_constraintBottom_toTopOf="@+id/constraintLayout2"/>

                </androidx.constraintlayout.widget.ConstraintLayout>

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textSize="18sp"
                    android:textColor="@color/black"
                    android:letterSpacing="-0.01"
                    android:lineSpacingExtra="4sp"
                    android:text="Invite your contacts"
                    app:layout_constraintTop_toBottomOf="@+id/constraintLayout3"
                    android:layout_marginStart="16dp" app:layout_constraintStart_toStartOf="parent"
                    android:id="@+id/textView" android:layout_marginTop="12dp"/>

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textSize="16sp"
                    android:textColor="@color/warm_grey"
                    android:lineSpacingExtra="10sp"
                    android:visibility="gone"
                    android:text="Send your friends and family a link and you both get rewarded when they sign up."
                    android:layout_marginTop="12dp"
                    app:layout_constraintTop_toBottomOf="@+id/textView" android:id="@+id/txt_invite"
                    android:layout_marginStart="16dp" app:layout_constraintStart_toStartOf="parent"/>

                <androidx.constraintlayout.widget.ConstraintLayout
                    android:layout_width="match_parent"
                    android:layout_height="220dp"
                    android:background="@drawable/white_radius"
                    app:layout_constraintTop_toBottomOf="@+id/txt_invite"
                    app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="16dp"
                    app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="16dp"
                    android:id="@+id/permission_layout">
                    <Button
                        android:text="Give Access"
                        android:layout_width="0dp"
                        android:background="@drawable/form_button_radius"
                        android:textAppearance="@style/BottomButtonAppearance"
                        android:layout_height="48dp"
                        android:id="@+id/btn_give_access"
                        app:layout_constraintEnd_toEndOf="parent"
                        android:layout_marginEnd="16dp"
                        android:layout_marginStart="16dp"
                        app:layout_constraintStart_toStartOf="parent"
                        app:layout_constraintTop_toBottomOf="@+id/textView6" android:layout_marginTop="16dp"/>
                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:textSize="13sp"
                        android:textColor="@color/warm_grey"
                        android:lineSpacingExtra="7sp"
                        android:gravity="center_horizontal"
                        android:text="@string/to_send_your_friends_and_family_a_referral_link_please_give_us_access_to_your_contacts"
                        tools:layout_editor_absoluteX="0dp"
                        android:layout_marginTop="16dp" app:layout_constraintTop_toBottomOf="@+id/imageView2"
                        android:id="@+id/textView6"/>
                    <ImageView
                        android:layout_width="60dp"
                        android:layout_height="60dp" app:srcCompat="@drawable/icon_person"
                        android:id="@+id/imageView2" android:layout_marginTop="20dp"
                        app:layout_constraintTop_toTopOf="parent" app:layout_constraintEnd_toEndOf="parent"
                        android:layout_marginEnd="8dp" app:layout_constraintStart_toStartOf="parent"
                        android:layout_marginStart="8dp"/>
                </androidx.constraintlayout.widget.ConstraintLayout>


                <androidx.recyclerview.widget.RecyclerView
                    android:id="@+id/contact_recycler"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    tools:listitem="@layout/item_contact"
                    tools:layout_editor_absoluteX="0dp" android:layout_marginTop="16dp"
                    app:layout_constraintTop_toBottomOf="@+id/permission_layout"/>

                <ProgressBar android:layout_width="wrap_content" android:layout_height="wrap_content"
                    app:layout_constraintTop_toBottomOf="@+id/permission_layout"
                    android:indeterminate="true"
                    android:indeterminateTintMode="src_atop"
                    android:indeterminateTint="@color/colorPrimary"
                    android:visibility="gone"
                    app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="8dp"
                    app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="17dp"
                    android:progressTint="@color/warm_grey" android:layout_marginTop="24dp"
                    android:id="@+id/progress_bar"/>

            </androidx.constraintlayout.widget.ConstraintLayout>

        </androidx.core.widget.NestedScrollView>

    </LinearLayout>
<layout>

Code for adapter

internal class ContactAdapter(context: Context, private val mProductList:   ArrayList<ContactModel>) : RecyclerView.Adapter<ContactAdapter.MyViewHolder>() {
    private val inflater: LayoutInflater;
    private val key: String? = null;

    init {
        inflater = LayoutInflater.from(context);
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = inflater.inflate(R.layout.item_contact, parent, false);
        return MyViewHolder(view);
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int){
        val selectedProduct = mProductList[position];
        holder.setData(selectedProduct);

    }

    override fun getItemCount(): Int {
        return mProductList.size;
    }

    internal inner class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
        fun setData(selectedProduct: ContactModel)
        {
            itemView.txt_name.text = selectedProduct.name;
            itemView.txt_number.text = selectedProduct.number;
        }

        override fun onClick(v: View)
        {

        }
    }
}

Answer 1

I solved the problem using coordinatorlayout/collapsingtoolbar.

Answer 2

This is a common problem, the problem when using recycler view inside a nested scroll view this cause the recycler view height not defined so if you have 1000 item to be displayed in this recycler view (recycler view inside nested scroll view) the onCreateViewHolder() method in recycler adapter will be called 1000 times because the hight of this recycler isn't determined.
So to overcome this issue you have to use

recyclerview.setNestedScrollingEnabled(false);

this will solve your issue
Also, it's better to define a certain height for recycler view when it is placed inside a nested scroll view.