error: Error parsing XML: unbound prefix after adding ScrollView

Question

After adding scrollview to my xml file i am getting error at 4th line. I have tried moving xmlns:android="http://schemas.android.com/apk/res/android" but still getting the same error.

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ScrollView01"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

<RelativeLayout
android:id="@+id/RelativeLayout01"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.easy.convert.MainActivity" >

<ImageButton
    android:id="@+id/btnbitsbytes"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="25dp"
    android:background="#00000000"
    android:gravity="center"
    android:src="@drawable/btnbitsbytes" />

<ImageButton
    android:id="@+id/btnmassweight"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/btnbitsbytes"
    android:layout_below="@+id/btnbitsbytes"
    android:layout_marginTop="14dp"
    android:background="#00000000"
    android:src="@drawable/btnmassweight" />

<ImageButton
    android:id="@+id/ButtonConvert"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/btnmassweight"
    android:layout_below="@+id/btnmassweight"
    android:layout_marginTop="14dp"
    android:background="#00000000"
    android:src="@drawable/btnlength" />

<ImageButton
    android:id="@+id/imageButton3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/ButtonConvert"
    android:layout_below="@+id/ButtonConvert"
    android:layout_marginTop="14dp"
    android:background="#00000000"
    android:src="@drawable/btntemperature" />

<ImageButton
    android:id="@+id/imageButton4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/imageButton3"
    android:layout_below="@+id/imageButton3"
    android:layout_marginTop="15dp"
    android:background="#00000000"
    android:src="@drawable/btndistance" />

<ImageButton
    android:id="@+id/imageButton5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/imageButton4"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="22dp"
    android:background="#00000000"
    android:src="@drawable/btnaboutus" />

</RelativeLayout>
</ScrollView>

Answer 1

Remove xmlns:android="http://schemas.android.com/apk/res/android" for RelativeLayout. That is need only for the root element ie ScrollView

<RelativeLayout
android:id="@+id/RelativeLayout01"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
>

Remove this

tools:context="com.easy.convert.MainActivity"

or add xmlns:tools="http://schemas.android.com/tools"

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/ScrollView01"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent" 
 tools:context="com.easy.convert.MainActivity">

Edit:

xmlns:android="http://schemas.android.com/apk/res/android

is the xml name space for android.

 xmlns:tools="http://schemas.android.com/tools"

http://schemas.android.com/tools is the namespace uri and the prefix is tools. You can find a list of tools attribute @

http://tools.android.com/tech-docs/tools-attributes