frequent issues arising in android view, Error parsing XML: unbound prefix

I have frequent problem in android view, Error parsing XML: unbound prefix on Line 2.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:orientation="vertical" android:id="@+id/myScrollLayout" 
android:layout_width="fill_parent"  android:layout_height="wrap_content">
    <TextView android:layout_height="wrap_content" android:layout_width="fill_parent" 
    android:text="Family" android:id="@+id/Family" 
    android:textSize="16px" android:padding="5px" 
    android:textStyle="bold" android:gravity="center_horizontal">
    </TextView>

    <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent" android:layout_height="wrap_content"
        android:orientation="vertical" android:scrollbars="vertical">
        <LinearLayout android:orientation="vertical" android:id="@+id/myMainLayout" 
        android:layout_width="fill_parent"  android:layout_height="wrap_content">
        </LinearLayout>
    </ScrollView>

</LinearLayout>

A couple of reasons that this can happen:

1) You see this error with an incorrect namespace, or a typo in the attribute. Like 'xmlns' is wrong, it should be xmlns:android

2) First node needs to contain: xmlns:android="http://schemas.android.com/apk/res/android"

3) If you are integrating AdMob, check custom parameters like ads:adSize, you need

xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"

4) If you are using LinearLayout you might have to define tools:

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

I'm going to add a separate answer just because I don't see it here. It's not 100% what Pentium10 asked for, but I ended up here by searching for Error parsing XML: unbound prefix

Turns out I was using custom parameters for AdMob ads like ads:adSize, but I hadn't added

    xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"

to the layout. Once I added it it worked great.

I had this same problem.

Make sure that the prefix (android:[whatever]) is spelled correctly and written correctly. In the case of the line xmlns:android="http://schemas.android.com/apk/res/android" make sure that you have the full prefix xmlns:android and that it is spelled correctly. Same with any other prefixes - make sure they are spelled correctly and have android:[name]. This is what solved my problem.

As you mention, you need to specify the right namespace. You also see this error with an incorrect namespace.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns="http://schemas.android.com/apk/res/android"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:padding="10dip">

will not work.

Change:

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

to

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

The error message is referring to everything that starts "android:" as the XML does not know what the "android:" namespace is.

xmlns:android defines it.