How can achieve Gmail like pinch zoom and header scrolling

How can achieve pinch zoom behavior like gmail app? . I've put header container in ScrollView followed by webview. Seems It's very complex behavior.

Here is without zoom.

When we pinch Webview upper container scrolled up as per zoom:

So far here is my initials:

<?xml version="1.0" encoding="utf-8"?>
  <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/white">

    <RelativeLayout
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:background="@color/white"
       android:fitsSystemWindows="true">


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

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="@color/white">

        </android.support.v7.widget.Toolbar>
    </android.support.design.widget.AppBarLayout>


    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/appbar">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <FrameLayout
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:background="@color/colorPrimary"></FrameLayout>

            <WebView
                android:id="@+id/webView"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/white"
                android:scrollbars="none" />
        </LinearLayout>


    </ScrollView>


  </RelativeLayout>


</FrameLayout>

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