title: Change size textview in fragment view pager from button in activity
body: <p>In my app I have a activity.
  My activity </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent" &gt;
  
      &lt;RelativeLayout
          android:id="@+id/Rlayout_top"
          android:layout_width="match_parent"
          android:layout_height="50dp"
          android:background="#ffffff"
          android:paddingBottom="5dp"
          android:paddingLeft="5dp"
          android:paddingRight="5dp"
          android:paddingTop="5dp" &gt;
          &lt;Button
              android:id="@+id/btnUp"
              android:layout_width="40dp"
              android:layout_height="40dp"
              android:layout_alignParentBottom="true"
              android:layout_marginRight="4dp"
              android:layout_toRightOf="@+id/layout_btn_back"
              android:background="@drawable/custom_btup" /&gt;
  
          &lt;Button
              android:id="@+id/btnDown"
              android:layout_width="40dp"
              android:layout_height="40dp"
              android:layout_alignParentBottom="true"
              android:layout_toRightOf="@+id/btnUp"
              android:background="@drawable/custom_btdown" /&gt;
      &lt;/RelativeLayout&gt;
  
      &lt;android.support.v4.view.ViewPager
          android:id="@+id/view_pager"
          android:layout_width="match_parent"
          android:layout_height="fill_parent"
          android:layout_below="@+id/Rlayout_top" &gt;
      &lt;/android.support.v4.view.ViewPager&gt;
  
  &lt;/RelativeLayout&gt;</code></pre>
  </div>
  </div>
  
  And in my fragment view Pager I have a scroll view, in scroll view I have a few pictures and text.
  Now I want when click button in activity I can change size of textview in scroll view
  How i do?I was looking for a solution and found some reviews say should use the interface, but I still do not get it
  Please help me!
  Thank all</p>