ScrollView onclick set the visibility to be Visible

I have got this Scroll View in my android app and what I am trying to do is set its visibility to be gone. When you click on this button with an id clickme it should change the visibility of the scroll view and set it to be Visible. However when I trying to do this I am getting the error sayign "Unfortunately, ExampleApp has stopped". Basically crashes. this is my code for the button;

<Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/lastmonth"

                android:id="@+id/lastmonth"
                android:layout_marginLeft="40dp"
                android:paddingLeft="40dp"
                android:textSize="14sp" />

            <Button

this is the code for the scroll view

<ScrollView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/scrollview"
            android:layout_gravity="center_horizontal"
            android:layout_marginLeft="30dp"
            android:layout_marginRight="30dp"
            android:layout_marginTop="5dp">

<LinearLayout
                android:orientation="vertical"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:id="@+id/scrollvisibility">

<LinearLayout
                    android:orientation="horizontal"
                    android:layout_width="fill_parent"
                    android:layout_height="fill_parent">

<TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="@string/exampletext"
                        android:id="@+id/textView10"
                        android:textColor="#ff010101"
                        android:textSize="14sp" />

</LinearLayout>

  </LinearLayout>
        </ScrollView>

this is the code that I have got in my activity;

final View v = null;

 v.findViewById(R.id.scrollvisibility).setVisibility(View.GONE);


v.findViewById(R.id.lastMonthButton).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.i("Testing","Button Clicked");
            //v.findViewById(R.id.scrollvisibility).setVisibility(View.VISIBLE);
        }
    });