title: android - collapsing toolbar with tablayout set background
body: <p>My app contains a collapsing toolbar with a tabview. The tabs have an own background color, my <code>@color/colorPrimary</code> and the collapsing toolbar has a set background image. Now I would like to 'merge' them: the tablayout should be transparent, so the background image reaches from the toolbar down including the tabs. Like it is not divided by the background anymore.
  I set up the layout and tried to make the tabs transparent, but like this the image won't continue.</p>
  
  <p>My XML file:</p>
  
  <pre><code> &lt;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"
      tools:context="com.example.te.e6.MainActivity"&gt;
  
      &lt;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/AppTheme.AppBarOverlay"&gt;
  
          &lt;android.support.design.widget.CollapsingToolbarLayout
              android:id="@+id/colbar"
              android:layout_width="match_parent"
              android:layout_height="175dp"
              app:expandedTitleGravity="center|bottom"
              android:fitsSystemWindows="true"
              app:contentScrim="?attr/colorPrimary"
              app:layout_scrollFlags="scroll|exitUntilCollapsed"&gt;
  
              &lt;ImageView
                  android:id="@+id/backg"
                  android:layout_width="match_parent"
                  android:layout_height="match_parent"
                  android:fitsSystemWindows="true"
                  android:scaleType="centerCrop"
                  android:src="@drawable/materialbackground"
                  app:layout_collapseMode="parallax" /&gt;
  
              &lt;android.support.v7.widget.Toolbar
                  android:id="@+id/toolbar"
                  android:layout_width="match_parent"
                  android:layout_height="?attr/actionBarSize"
                  app:expandedTitleGravity="center|bottom"
                  app:layout_collapseMode="pin"
                  app:popupTheme="@style/AppTheme.PopupOverlay"/&gt;
  
          &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;
  
          &lt;android.support.design.widget.TabLayout
              android:id="@+id/tabs"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:background="@android:color/transparent"
              app:layout_anchor="@id/appBar"
              app:layout_anchorGravity="bottom"&gt;
  
              &lt;android.support.design.widget.TabItem
                  android:id="@+id/tabItem"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="A" /&gt;
  
              &lt;android.support.design.widget.TabItem
                  android:id="@+id/tabItem2"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="B" /&gt;
  
              &lt;android.support.design.widget.TabItem
                  android:id="@+id/tabItem3"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="C" /&gt;
  
          &lt;/android.support.design.widget.TabLayout&gt;
  
      &lt;/android.support.design.widget.AppBarLayout&gt;
  
      &lt;android.support.v4.view.ViewPager
          android:id="@+id/viewpager"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          app:layout_behavior="@string/appbar_scrolling_view_behavior" /&gt;
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>