android – CollapsingToolbarLayout and hide toolbar while scrolling-ThrowExceptions

Exception or error:

I am trying to create some combined layout using CoordinatorLayout and also CollapsingToolbarLayout.

In the first state, when we on the most top page, and didn’t scrolled yet, I want the toolbar to expend as shown below (yes, i did it):

enter image description here

In the second state, when starting to scroll down, the image and toolbar should disappear, as shown below (only tab will show):

enter image description here

And in the last state once I am at some point in the list (but not the top of the list) I want to start scrolling up, once I start scrolling up I want the toolbar (and not the expended one with the image) to start whowing, as shown below (if didn’t reaches the top of the list, the image will not show, only the toolbar):

enter image description here

I was able to achive the the first state, but the other 2 state are problematic,
once toolbar is implemented inside CollapsingToolbarLayout, the flexability of what I can do with it outside of CollapsingToolbarLayout component is not clear.
I can’t make the toolbar hide, if I do so, then it will only be shown once I reaches the top.

Anyways, my current XML (showing below) is in state where the first picture is implemented, but once I start scrolling down, the toolbar stay at the top and do not hide. Note: I must tell the toolbar to stay “pin” because if I didn’t then the information inside the toolbar disappear, and only an empty toolbar will show (that’s for another post, but it still interesting to know why this happen?).

here is my current xml:

    <android.support.design.widget.CoordinatorLayout
    android:id="@+id/benefit_coordinator_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_material_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/main.collapsing"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            >

            <include
                android:id="@+id/toolbar_search_container"
                layout="@layout/search_box"
                android:layout_height="192dp"
                android:layout_width="match_parent"
                app:layout_collapseMode="parallax"

                />

            <include
                android:id="@+id/toolbar_benefit"
                layout="@layout/toolbar_main"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:contentScrim="?attr/colorPrimary"

                />

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

        <android.support.design.widget.TabLayout
            android:id="@+id/benefit_tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/primaryColor"
            app:tabIndicatorColor="@color/accentColor"
            app:tabSelectedTextColor="@android:color/white"
            app:tabTextColor="@android:color/black"
            app:tabIndicatorHeight="4dp" />

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

    <android.support.v4.view.ViewPager
        android:id="@+id/benefit_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
    <include
        layout="@layout/floating_btn_benefits"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        />
</android.support.design.widget.CoordinatorLayou
How to solve:

I have fixed the issue, just to clerify, I wanted my Toolbar to be able to expand with a paralex image once it reaches the top, but I also wanted the toolbar to disappear if scrolling down, and show itself again (without the paralex image) once I scroll up. the paralex image effect should only displayed if I reaches the top.

So basically the solution is, change the component CollapsingToolbarLayout with the following attribute:

app:layout_scrollFlags="scroll|enterAlways|enterAlwaysCollapsed"

and also change toolbar component with the following attribute

android:minHeight="?attr/actionBarSize"

regarding my paralex effect image (which is my toolbar_search_container) I shouldn’t add any layout_scrollFlags to it.

So why is it working?
To understand it, you need to know what is enterAlwaysCollapsed,
The enterAlwaysCollapsed effects views that added the minHeight attribute. this means, every child of CollapsingToolbarLayout which have minHeight will be effected by this attribute.
So my toolbar will be effected.

enterAlwaysCollapsed attribute definition in simple words:

Assuming enterAlways is declared and you have specified a minHeight, you can also specify enterAlwaysCollapsed. When this setting is used, your view will only appear at this minimum height. Only when scrolling reaches to the top will the view expand to its full height…”

Well, isn’t this exactly what we want? (do not answer this retorical question 😉 )

One more thing to add, the parallax component (toolbar_search_container) is depends on the toolbar to expand, and because the toolbar will expand only when it reaches the top, then this is all just working great!

The new code is :

<android.support.design.widget.CoordinatorLayout
    android:id="@+id/benefit_coordinator_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_material_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/main.collapsing"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways|enterAlwaysCollapsed"
            >

            <include
                android:id="@+id/toolbar_search_container"
                layout="@layout/search_box"
                android:layout_height="192dp"
                android:layout_width="match_parent"
                app:layout_collapseMode="parallax"
                />

            <include
                android:id="@+id/toolbar_benefit"
                layout="@layout/toolbar_main"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:minHeight="?attr/actionBarSize"
                app:contentScrim="?attr/colorPrimary"
                app:layout_collapseMode="pin"
                android:fitsSystemWindows="true"
                />

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

        <android.support.design.widget.TabLayout
            android:id="@+id/benefit_tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/primaryColor"
            app:tabIndicatorColor="@color/accentColor"
            app:tabSelectedTextColor="@android:color/white"
            app:tabTextColor="@android:color/black"
            app:tabIndicatorHeight="4dp" />

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

    <android.support.v4.view.ViewPager
        android:id="@+id/benefit_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
    <include
        layout="@layout/floating_btn_benefits"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        />
</android.support.design.widget.CoordinatorLayout>

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