Develop Reference

How to make Button on top of Surfaceview in android

I am creating a QR code scanner and facing an issue where my button is blurr because of surface view overlay. i want my button on top of surface-view. any way of doing it?
my layout
<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/main"
android:layout_width="match_parent"
android:layout_height="match_parent">
<SurfaceView
android:id="#+id/overlay"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="#+id/preview_view"
app:layout_constraintEnd_toEndOf="#id/preview_view"
app:layout_constraintStart_toStartOf="#id/preview_view"
app:layout_constraintTop_toTopOf="#id/preview_view" >
</SurfaceView>
<androidx.camera.view.PreviewView
android:id="#+id/preview_view"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" >
</androidx.camera.view.PreviewView>
<ImageButton
android:id="#+id/imageButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="100dp"
android:layout_marginTop="50dp"
android:translationZ="200dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#android:drawable/ic_menu_manage" />
</androidx.constraintlayout.widget.ConstraintLayout>

Wrap the overlay in separate layout, e.g. ConstraintLayout. Below a working code of mine:
<?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.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:background="#color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<FrameLayout
android:id="#+id/scanViewContainer"
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" />
</androidx.constraintlayout.widget.ConstraintLayout>
<ImageButton
android:id="#+id/scannerCloseBtn"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_marginTop="24dp"
android:layout_marginEnd="24dp"
android:background="#color/transparent"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="#android:drawable/ic_menu_close_clear_cancel"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="#+id/scannerFlashIcon"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_marginStart="24dp"
android:layout_marginTop="24dp"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="#drawable/ic_flash"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<android.widget.Button
android:id="#+id/scannerFlashOffButton"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_marginStart="12dp"
android:layout_marginTop="24dp"
android:background="#color/transparent"
android:text="#string/flash_off"
android:textAllCaps="false"
android:textColor="#color/white"
app:layout_constraintStart_toEndOf="#+id/scannerFlashIcon"
app:layout_constraintTop_toTopOf="parent" />
<android.widget.Button
android:id="#+id/scannerFlashOnButton"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_marginStart="1dp"
android:layout_marginTop="24dp"
android:background="#color/transparent"
android:text="#string/flash_on"
android:textAllCaps="false"
android:textColor="#color/white"
app:layout_constraintStart_toEndOf="#+id/scannerFlashOffButton"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

Issue adding "app:layout_behavior" in Constraint layout for collapsing toolbar

I am facing one issue since past few days. Below is the issue details.
I need to hide the top layout while scrolling the recyclerview, for that I am using "app:layout_behavior" in Coordinator layout with Collapisng toolbar.But after adding "app:layout_behavior="#string/appbar_scrolling_view_behavior" in Coordinator layout a blank space is coming at the top of the "com.customviewtext.customviews.recyclerviews.TrayRecyclerView". That recyclerview should start from the top of the 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:tools="http://schemas.android.com/tools">
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
>
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/constraint_scroll"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
>
<com.customviewtext.customviews.recyclerviews.TrayRecyclerView
android:id="#+id/main_home_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
android:visibility="visible"
android:orientation="vertical"
android:paddingBottom="#dimen/page_margin_bottom"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
/>
<ImageView
android:id="#+id/l3_menu_back"
android:layout_width="#dimen/dimens_30dp"
android:layout_height="#dimen/dimens_30dp"
android:layout_marginStart="#dimen/l3_back_icon_margin"
android:layout_marginTop="#dimen/l2_menu_margin_top"
android:contentDescription="#string/no_go_back"
android:paddingTop="#dimen/dimens_5dp"
android:paddingBottom="#dimen/dimens_5dp"
android:visibility="gone"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/back_arrow" />
<com.customviewtext.fab.custom.CustomFabButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_gravity="bottom|start"
android:layout_marginEnd="#dimen/dimens_10dp"
android:layout_marginBottom="#dimen/dimens_86dp"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<pl.droidsonroids.gif.GifImageView
android:id="#+id/gifFLoat"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_marginEnd="#dimen/dp_10"
android:layout_marginBottom="#dimen/dp_100"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<ImageView
android:id="#+id/static_image"
android:layout_width="wrap_content"
android:background="#color/white"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_marginEnd="#dimen/dp_10"
android:layout_marginBottom="#dimen/dp_100"
android:contentDescription="#string/background_image_for_card_view"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<ViewStub
android:id="#+id/cast_minicontroller"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginStart="#dimen/dimens_8dp"
android:layout_marginEnd="#dimen/dimens_8dp"
android:layout_marginBottom="#dimen/minicontroller_bottom"
android:layout="#layout/cast_mini_controller_fragment"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/rl_home_cast"
android:layout_width="#dimen/home_cast_button_size"
android:layout_height="#dimen/home_cast_button_size"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_marginEnd="#dimen/dimens_15dp"
android:layout_marginBottom="#dimen/home_cast_button_bottom_margin"
android:background="#drawable/ic_home_cast_bg_new"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent "
app:layout_constraintEnd_toEndOf="parent">
<androidx.mediarouter.app.MediaRouteButton
android:id="#+id/pt_home_cast_icon"
android:layout_width="#dimen/home_cast_button_size"
android:layout_height="#dimen/home_cast_button_size"
android:layout_centerInParent="true"
android:backgroundTint="#color/white_color"
android:icon="#drawable/common_full_open_on_phone"
android:mediaRouteTypes="user"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<FrameLayout
android:id="#+id/home_fragment_level_two_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<ImageView
android:id="#+id/close_fab"
android:layout_width="#dimen/dimens_floating_close_icon"
android:layout_height="#dimen/dimens_25dp"
android:layout_gravity="bottom|end"
android:layout_marginEnd="#dimen/dimens_10dp"
android:layout_marginBottom="#dimen/dp_120"
android:src="#drawable/close_floating_button"
android:visibility="gone" />
</FrameLayout>
<ViewStub
android:id="#+id/page_loader"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout="#layout/layout_skeleton"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ViewStub
android:id="#+id/api_error_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout="#layout/api_error"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ViewStub
android:id="#+id/connection_error"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout="#layout/connection_error"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/my_appbar_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#drawable/home_top_menu"
android:animateLayoutChanges="true"
android:fitsSystemWindows="true"
>
<com.google.android.material.appbar.CollapsingToolbarLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:toolbarId="#+id/toolbar">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/top_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_collapseMode="pin"
app:layout_scrollFlags="scroll|enterAlways|enterAlwaysCollapsed"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/recyclerview_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="5dp"
android:orientation="horizontal"
android:visibility="visible"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<ImageView
android:id="#+id/click"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="#string/app_name"
android:foregroundGravity="center"
android:scaleType="fitXY"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/sony_liv_logo" />
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/subscribe_renew_upgrade_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintStart_toEndOf="#+id/click"
app:layout_constraintTop_toTopOf="parent">
<FrameLayout
android:id="#+id/frameLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/subscribe_button_frame_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="#dimen/dimens_5dp"
android:paddingTop="#dimen/dimens_2dp"
android:paddingEnd="#dimen/dimens_2dp"
tools:ignore="RtlSymmetry">
<ImageView
android:id="#+id/subscribe"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="#string/subscribe"
android:foregroundGravity="center"
android:scaleType="fitXY"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/subscribe_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:padding="#dimen/dimens_5dp"
android:textColor="#color/white"
android:textSize="#dimen/l2_menu_text"
app:layout_constraintLeft_toLeftOf="#+id/right_icon"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:ignore="RtlSymmetry"
tools:text="hello" />
<ImageView
android:id="#+id/right_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="#string/right_arrow_icon"
android:foregroundGravity="center"
android:paddingStart="#dimen/dimens_2dp"
android:paddingEnd="#dimen/dimens_5dp"
android:scaleType="fitXY"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#id/subscribe_title"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</FrameLayout>
<View
android:id="#+id/divider_line"
android:layout_width="#dimen/dimen_1dp"
android:layout_height="0dp"
android:layout_marginStart="#dimen/dimens_2dp"
android:background="#color/dark_grey"
android:scaleType="fitXY"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="#+id/frameLayout"
app:layout_constraintStart_toEndOf="#+id/frameLayout"
app:layout_constraintTop_toTopOf="#+id/frameLayout">
</View>
</androidx.constraintlayout.widget.ConstraintLayout>
<ImageView
android:id="#+id/search_more_icon"
android:layout_width="#dimen/dimens_25dp"
android:layout_height="#dimen/dimens_25dp"
android:layout_marginEnd="#dimen/dimens_10dp"
android:foregroundGravity="center"
android:padding="#dimen/dp_2"
android:scaleType="fitXY"
android:visibility="invisible"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.9"
app:layout_constraintStart_toEndOf="#id/subscribe_renew_upgrade_layout"
app:layout_constraintTop_toTopOf="#id/click"
app:srcCompat="#drawable/ic_search_white" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler_view_l2_menu"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:foregroundGravity="center"
android:visibility="gone"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="#id/click"
app:layout_constraintTop_toBottomOf="#+id/click" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
</com.google.android.material.appbar.CollapsingToolbarLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler_view_l2_menu_navigation_fix"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginStart="#dimen/dimens_18dp"
android:layout_marginTop="5dp"
android:layout_gravity="bottom"/>
<!-- app:tabGravity="fill"
app:tabMode="scrollable"-->
</com.google.android.material.appbar.AppBarLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
<data>
<import type="android.view.View" />
<variable
name="sampleData"
type="com.customviewtext.viewmodel.home.SampleViewModel" />
</data>
</layout>
Any help would be appreciated.

Recycler view cannot be at the bottom?

I'm trying to add a horizantal recyclerview at the bottom in linearlayout but it always starts from top of linearlayout , here is my code
<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<androidx.fragment.app.FragmentContainerView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/fragment_container_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.cardview.widget.CardView
android:id="#+id/cardView"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
android:layout_marginRight="16dp"
android:background="#color/white"
android:divider="#android:color/transparent"
android:elevation="100dp"
android:foreground="?android:attr/selectableItemBackground"
android:orientation="vertical"
app:cardBackgroundColor="#android:color/white"
app:cardCornerRadius="6dp"
app:cardElevation="66dp"
app:cardPreventCornerOverlap="false"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.076"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<ImageView
android:id="#+id/menu_image_view"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_gravity="center_vertical"
android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/menu_icon" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:layoutDirection="ltr"
android:orientation="horizontal"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="#+id/frameLayout2"
app:layout_constraintStart_toEndOf="#+id/menu_image_view"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:id="#+id/medfast_linear_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:gravity="center"
android:layoutDirection="ltr"
android:orientation="horizontal"
android:visibility="visible">
<com.plus.medfast.customViews.views.CustomRegularTextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:gravity="center"
android:text="#string/be_healthy" />
</LinearLayout>
<LinearLayout
android:id="#+id/zinc_linear_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:gravity="center"
android:layoutDirection="ltr"
android:orientation="horizontal"
android:visibility="gone">
<ImageView
android:layout_width="match_parent"
android:layout_height="30dp"
android:layout_weight="1.3"
android:src="#drawable/medfast_word_only" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="3dp"
android:layout_marginRight="-2dp"
android:layout_weight="1.7"
android:gravity="center">
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:src="#drawable/ic_deal" />
</LinearLayout>
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:src="#drawable/zinc" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1.9">
<FrameLayout
android:id="#+id/frameLayout2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_weight="1.1"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/medfast_ads_image_view"
android:layout_width="40dp"
android:layout_height="50dp"
android:layout_gravity="left"
android:src="#drawable/ic_logo"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/medfast_ads_text_view"
android:layout_width="15dp"
android:layout_height="15dp"
android:layout_gravity="top|end"
android:layout_marginTop="24dp"
android:background="#drawable/circle_view_white_solid"
android:gravity="center"
android:text="10"
android:textColor="#color/white"
android:textSize="10dp"
app:layout_constraintBottom_toTopOf="#+id/medfast_ads_image_view"
app:layout_constraintEnd_toEndOf="#+id/medfast_ads_image_view"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</FrameLayout>
<FrameLayout
android:id="#+id/frameLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_weight="1.3"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/normal_ads_image_view"
android:layout_width="30dp"
android:layout_height="40dp"
android:layout_gravity="left"
android:src="#drawable/ic_notification"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/normal_ads_text_view"
android:layout_width="15dp"
android:layout_height="15dp"
android:layout_gravity="top|end"
android:layout_marginTop="16dp"
android:background="#drawable/circle_view_white_solid"
android:gravity="center"
android:text="10"
android:textColor="#color/white"
android:textSize="10dp"
app:layout_constraintBottom_toTopOf="#+id/normal_ads_image_view"
app:layout_constraintEnd_toEndOf="#+id/normal_ads_image_view"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</FrameLayout>
</LinearLayout>
</LinearLayout>
</androidx.cardview.widget.CardView>
<ProgressBar
android:id="#+id/progressBar"
style="?android:attr/progressBarStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<LinearLayout
android:layout_width="match_parent"
android:gravity="bottom"
android:layout_height="wrap_content"
app:layout_constraintBottom_toTopOf="#+id/focused_service_name_text_view"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/services_recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clipToPadding="false" />
</LinearLayout>
<com.plus.medfast.customViews.views.CustomBoldTextView
android:id="#+id/focused_service_name_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:gravity="center"
android:textColor="#color/colorPrimary"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<com.google.android.material.navigation.NavigationView
android:id="#+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="#layout/nav_header_maps_navigation_drawer"
app:menu="#menu/core_activity_navigation_drawer" />
</androidx.drawerlayout.widget.DrawerLayout>
but the result as shown bellow, i need the recyclerview be in bottom because i wan't to translate Y axis of the view to up

Everything in my xml is well written.
after adding marginTop=20 to the recycler view item it works 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"
android:id="#+id/root_view"
android:layout_width="90dp"
android:layout_height="90dp"
android:layout_marginTop="20dp"
android:layout_marginBottom="20dp"
android:gravity="center"
android:orientation="vertical">
<LinearLayout
android:layout_width="80dp"
android:layout_height="80dp"
android:background="#drawable/circle_view_red"
android:gravity="center"
android:orientation="vertical">
<ImageView
android:id="#+id/service_image_view"
android:layout_width="50dp"
android:layout_height="50dp"
android:padding="5dp" />
<com.plus.medfast.customViews.views.CustomBoldTextView
android:id="#+id/service_name_text_view"
android:layout_width="60dp"
android:layout_height="match_parent"
android:layout_marginTop="-5dp"
android:gravity="center"
android:text="Test"
android:textColor="#color/white"
android:textSize="10dp"
android:visibility="visible" />
</LinearLayout>
</LinearLayout>

Image not appear in Collapsing Toolbar

When first launch activity, the image not appear, but when u scroll, the image appear. I really confuse about this problem, please help. Is it because I'm using ConstraintLayout instead RecyclerView or LinearLayout?
Below is the XML code i use
<?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"
tools:context=".InsideActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/collapsing_toolbar_appbarlayout"
android:layout_width="match_parent"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
android:layout_height="200dp"
android:fitsSystemWindows="true">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:contentScrim="#android:color/transparent"
android:fitsSystemWindows="true"
>
<ImageView
android:id="#+id/collapsing_toolbar_image_view"//this where i add image to toolbar
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
app:layout_collapseMode="parallax"/>
<android.support.v7.widget.Toolbar //this where the toolbar asign
android:id="#+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView //Im using to this, to make it scrollable
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.CardView 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"
app:cardCornerRadius="4dp">
<com.facebook.shimmer.ShimmerFrameLayout // this to make shimmer effect when loading
android:id="#+id/shimmer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
app:shimmer_clip_to_children="true"
app:shimmer_direction="left_to_right"
app:shimmer_shape="linear"
android:layout_alignParentLeft="true">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<include layout="#layout/placeholder_inside_item"></include>
</LinearLayout>
</com.facebook.shimmer.ShimmerFrameLayout>
<android.support.constraint.ConstraintLayout 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">
<ImageView
android:id="#+id/image_penulis"
android:layout_width="60dp"
android:layout_height="57dp"
android:layout_marginLeft="24dp"
android:layout_marginStart="24dp"
android:layout_marginTop="18dp"
android:src="#mipmap/ic_launcher_round"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/text_judul" />
<TextView
android:id="#+id/text_penulis"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="24dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
android:textSize="14sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/image_penulis"
app:layout_constraintTop_toBottomOf="#+id/text_judul"
app:layout_constraintVertical_bias="0.0" />
<TextView
android:id="#+id/text_tanggal_tulis"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="TextView"
android:textAppearance="#style/TextAppearance.AppCompat.Small"
android:textSize="12sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toEndOf="#+id/image_penulis"
app:layout_constraintTop_toBottomOf="#+id/text_penulis"
app:layout_constraintVertical_bias="0.0" />
<ImageView
android:id="#+id/image_thumbnail"
android:layout_width="0dp"
android:layout_height="200dp"
android:scaleType="fitXY"
app:layout_constraintBottom_toTopOf="#+id/text_judul"
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"
android:visibility="invisible"/>
<TextView
android:id="#+id/text_judul"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="24dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="24dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/image_thumbnail" />
<TextView
android:id="#+id/text_isi_berita"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="8dp"
android:layout_marginStart="16dp"
android:layout_marginTop="24dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
android:textSize="14sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/image_penulis" />
<Button
android:id="#+id/btn_comment"
android:layout_width="200dp"
android:layout_height="30dp"
android:layout_marginBottom="24dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="24dp"
android:background="#drawable/rounded_corner_button"
android:text="COMMENT"
android:textColor="#android:color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.51"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/text_isi_berita"
app:layout_constraintVertical_bias="0.0" />
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>
Below is the code in main activity :
Toolbar toolbar = (Toolbar)findViewById(R.id.collapsing_toolbar);
setSupportActionBar(toolbar);
ActionBar actionBar = getSupportActionBar();
if(actionBar!=null)
{
// Display home menu item.
actionBar.setDisplayHomeAsUpEnabled(true);
}
CollapsingToolbarLayout collapsingToolbarLayout = (CollapsingToolbarLayout)findViewById(R.id.collapsing_toolbar_layout);
collapsingToolbarLayout.setTitle("");
ImageView collapsingToolbarImageView = (ImageView)findViewById(R.id.collapsing_toolbar_image_view);
collapsingToolbarImageView.setImageResource(R.drawable.food);
I have followed all the solutions which could solve my problem, but the fact its not. Please help

Try this
<?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:id="#+id/collapsing_toolbar_appbarlayout"
android:layout_width="match_parent"
android:layout_height="200dp"
android:fitsSystemWindows="true"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="#android:color/transparent"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<ImageView
android:id="#+id/collapsing_toolbar_image_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
android:src="#drawable/kid"
app:layout_collapseMode="parallax" />
<android.support.v7.widget.Toolbar
android:id="#+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin" />
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<android.support.v7.widget.CardView 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"
app:cardCornerRadius="4dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<com.facebook.shimmer.ShimmerFrameLayout
android:id="#+id/shimmer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
app:shimmer_clip_to_children="true"
app:shimmer_direction="left_to_right"
app:shimmer_shape="linear">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<include layout="#layout/placeholder_inside_item"></include>
</LinearLayout>
</com.facebook.shimmer.ShimmerFrameLayout>
<android.support.constraint.ConstraintLayout 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">
<ImageView
android:id="#+id/image_penulis"
android:layout_width="60dp"
android:layout_height="57dp"
android:layout_marginLeft="24dp"
android:layout_marginStart="24dp"
android:layout_marginTop="18dp"
android:src="#mipmap/ic_launcher_round"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/text_judul" />
<TextView
android:id="#+id/text_penulis"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="24dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
android:textSize="14sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/image_penulis"
app:layout_constraintTop_toBottomOf="#+id/text_judul"
app:layout_constraintVertical_bias="0.0" />
<TextView
android:id="#+id/text_tanggal_tulis"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="TextView"
android:textAppearance="#style/TextAppearance.AppCompat.Small"
android:textSize="12sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toEndOf="#+id/image_penulis"
app:layout_constraintTop_toBottomOf="#+id/text_penulis"
app:layout_constraintVertical_bias="0.0" />
<ImageView
android:id="#+id/image_thumbnail"
android:layout_width="0dp"
android:layout_height="200dp"
android:scaleType="fitXY"
android:visibility="invisible"
app:layout_constraintBottom_toTopOf="#+id/text_judul"
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" />
<TextView
android:id="#+id/text_judul"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="24dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="24dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/image_thumbnail" />
<TextView
android:id="#+id/text_isi_berita"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="8dp"
android:layout_marginStart="16dp"
android:layout_marginTop="24dp"
android:text="TextView"
android:textAppearance="#android:style/TextAppearance.Medium"
android:textSize="14sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/image_penulis" />
<Button
android:id="#+id/btn_comment"
android:layout_width="200dp"
android:layout_height="30dp"
android:layout_marginBottom="24dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="24dp"
android:background="#drawable/rounded_corner_button"
android:text="COMMENT"
android:textColor="#android:color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.51"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/text_isi_berita"
app:layout_constraintVertical_bias="0.0" />
</android.support.constraint.ConstraintLayout>
</LinearLayout>
</android.support.v7.widget.CardView>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>

Put the Floating action button on Top always

I have Mainactivity, one Fragment and BlogRecycleadapter to populate the Fragment with Blog post.
Inside Mainactivity, I have Floating action Button. But When I run the app It hides beneath the items of blogRecycleadapter.
How can I make Floating action button always on Top??
My mainactivity layout is
<?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"
tools:context=".Main2Activity">
<android.support.v7.widget.Toolbar
android:id="#+id/main_toolbar"
app:titleTextAppearance="#style/Toolbar.TitleText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Light"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"></android.support.v7.widget.Toolbar>
<android.support.design.widget.BottomNavigationView
android:id="#+id/mainBottomNav"
android:background="#color/colorblog"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:menu="#menu/bottom_menu"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/add_post_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:clickable="true"
android:layout_gravity="bottom|end"
android:focusable="true"
android:visibility="visible"
app:elevation="6dp"
app:layout_constraintBottom_toTopOf="#+id/mainBottomNav"
app:layout_constraintEnd_toEndOf="parent"
app:srcCompat="#mipmap/action_add" />
<FrameLayout
android:id="#+id/main_container"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="#+id/mainBottomNav"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/main_toolbar"
app:layout_constraintVertical_bias="1.0">
</FrameLayout>
</android.support.constraint.ConstraintLayout>
and my fragment layout is ,
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".HomeFragment">
<!-- TODO: Update blank fragment layout -->
<android.support.v7.widget.RecyclerView
android:id="#+id/blog_list_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
and my blogRecycleadapter class is
<?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="wrap_content">
<android.support.v7.widget.CardView
android:id="#+id/main_blog_post"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:padding="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/blog_like_btn"
android:layout_width="32dp"
android:layout_height="32dp"
android:layout_marginBottom="8dp"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/blog_desc"
app:srcCompat="#mipmap/action_like_gray" />
<de.hdodenhof.circleimageview.CircleImageView
android:id="#+id/blog_user_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:src="#drawable/profile_placeholder"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/blog_user_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:text="Username"
android:textStyle="bold"
app:layout_constraintStart_toEndOf="#+id/blog_user_image"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/blog_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
android:text="Blog Post Date"
app:layout_constraintStart_toEndOf="#+id/blog_user_image"
app:layout_constraintTop_toBottomOf="#+id/blog_user_name" />
<ImageView
android:id="#+id/blog_image"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:scaleType="centerCrop"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/blog_user_image"
app:srcCompat="#drawable/image_placeholder" />
<TextView
android:id="#+id/blog_desc"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="16dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="Lorem ipsum dolor sit amet, soluta regione urbanitas vis in, qui elit populo ut. "
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/blog_image" />
<TextView
android:id="#+id/blog_like_count"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="0 Likes"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#+id/blog_like_btn"
app:layout_constraintTop_toBottomOf="#+id/blog_desc" />
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>
</android.support.constraint.ConstraintLayout>

Try This for you mainactivity layout:
<?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">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<android.support.v7.widget.Toolbar
android:id="#+id/main_toolbar"
app:titleTextAppearance="#style/TextAppearance.AppCompat.Light.SearchResult.Title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="#+id/main_container"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</FrameLayout>
<android.support.design.widget.BottomNavigationView
android:id="#+id/mainBottomNav"
android:background="#color/list_background"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:menu="#menu/bottom_menu"
android:layout_alignParentBottom="true"/>
</RelativeLayout>
<android.support.design.widget.FloatingActionButton
android:id="#+id/add_post_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="?attr/actionBarSize"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:clickable="true"
android:layout_gravity="bottom|end"
android:focusable="true"
android:visibility="visible"
app:elevation="6dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:srcCompat="#mipmap/ic_launcher" />
</android.support.constraint.ConstraintLayout>
Hope this helps.

Try like this (inversed the position of FramLayout and FloatingActionButton):
<?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"
tools:context=".Main2Activity">
<android.support.v7.widget.Toolbar
android:id="#+id/main_toolbar"
app:titleTextAppearance="#style/Toolbar.TitleText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Light"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"></android.support.v7.widget.Toolbar>
<android.support.design.widget.BottomNavigationView
android:id="#+id/mainBottomNav"
android:background="#color/colorblog"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:menu="#menu/bottom_menu"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<FrameLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"></FrameLayout>
<FrameLayout
android:id="#+id/main_container"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="#+id/mainBottomNav"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/main_toolbar"
app:layout_constraintVertical_bias="1.0">
</FrameLayout>
<android.support.design.widget.FloatingActionButton
android:id="#+id/add_post_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:clickable="true"
android:layout_gravity="bottom|end"
android:focusable="true"
android:visibility="visible"
app:elevation="6dp"
app:layout_constraintBottom_toTopOf="#+id/mainBottomNav"
app:layout_constraintEnd_toEndOf="parent"
app:srcCompat="#mipmap/action_add" />
</android.support.constraint.ConstraintLayout>

You can increase elevation until it gets visible over bottom navigation.
Give elevation greater than 8dp and try.
<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:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.Toolbar
android:id="#+id/main_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Light" />
<android.support.design.widget.BottomNavigationView
android:id="#+id/mainBottomNav"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
app:menu="#menu/bottom_bar_menu" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/add_post_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/mainBottomNav"
android:layout_alignParentRight="true"
android:layout_marginRight="20dp"
android:clickable="true"
android:focusable="true"
android:visibility="visible"
app:elevation="10dp" />
<FrameLayout
android:id="#+id/main_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#+id/mainBottomNav"
android:layout_below="#+id/main_toolbar">
</FrameLayout>
</RelativeLayout>
just load your fragment in main container.. hope this works