title: What is layout_collapseParallaxMultiplier used in CollapsingToolbarLayout?
body: <p>What is <code>layout_collapseParallaxMultiplier</code> used in <code>CollapsingToolbarLayout</code> ?</p>
  
  <p>I have seen the <a href="https://developer.android.com/reference/android/support/design/R.attr.html#layout_collapseParallaxMultiplier" rel="noreferrer">android developer doc</a>, but I didn't understand.</p>
  
  <p>please explain this parameter &amp; it's effect when it used with <code>layout_collapseMode</code> with example.</p>
  
  <p>Below is a simple example of xml.</p>
  
  <pre><code>&lt;android.support.design.widget.CollapsingToolbarLayout ... &gt;
  &lt;ImageView
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:fitsSystemWindows="true"
          android:src="@drawable/random_pattern"
          android:scaleType="fitXY"
          app:layout_collapseMode="parallax"
          app:layout_collapseParallaxMultiplier="0.75"/&gt;
   &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;
  </code></pre>