Fading the whole layout as scrolled up in collapsing bar layout android

Question

Below is the code of my coordinator layout. It works well.

 <android.support.design.widget.CoordinatorLayout 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"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="#f4f4f4"
            app:expandedTitleMarginEnd="16dp"
            app:expandedTitleMarginStart="48dp"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent">

                <ImageView
                    android:id="@+id/header"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:background="@drawable/echo3"
                    android:fitsSystemWindows="true"
                    android:scaleType="centerCrop" />

                <RelativeLayout
                    android:layout_width="match_parent"
                    android:layout_height="40dp"
                    android:layout_alignParentBottom="true"
                    android:background="#fff">

                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_centerInParent="true"
                        android:text="Private Albums"
                        android:textColor="#000"
                        android:textSize="22sp"
                        android:textStyle="bold" />
                </RelativeLayout>

            </RelativeLayout>

            <android.support.v7.widget.Toolbar
                android:id="@+id/anim_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="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@+id/anim_toolbar"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <include layout="@layout/content_profile" />


        <!--<fragment-->
        <!--android:id="@+id/detail"-->
        <!--android:name="<package>.<fragment_name>"-->
        <!--android:layout_width="match_parent"-->
        <!--android:layout_height="match_parent" />-->

    </android.support.v4.widget.NestedScrollView>

</android.support.design.widget.CoordinatorLayout>

But I want to fade the whole relative layout as I scroll up it should started fading(Mean whole collapse bar layout). It do fade out at a specific point but I want it to fade out as I scroll up. Thanks, Any help is appreciated.

Answer 1

You can reduce the alpha of the RelativeLayout as you scroll up by hooking up an AppBarLayout.OnOffsetChangedListener to the AppBarLayout. Below is the code I used in my app.

appBar = (AppBarLayout) findViewById(R.id.app_bar_layout);
appBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
        @Override
        public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {

            relativeLayoutToFadeOut.setAlpha(1.0f - Math.abs(verticalOffset / (float)
                    appBarLayout.getTotalScrollRange()));


        }
    });