Android XML layout: Error parsing XML: not well-formed (invalid token) - I did close my View tags

Question

I am getting this error on the Button view. From the many questions I saw on SO, it seems that this error arises when you don't close your views properly.

I think I have closed all the tags properly but still getting this error. Why is that?

<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"
    tools:context="${relativePackage}.${activityClass}" >

    <Button 
        android:layout_width="wrap_content"
        android:layout:height="wrap_content"
        android:text="@string/mainActivity_button1"
        android:onClick="startSecondActivity" />

</RelativeLayout>

Answer 1

There's an additional/typo : in an attribute name.

Replace

android:layout:height

with

android:layout_height

The error is not only about unclosed tags but XML syntax problems in general. In XML, you can have only one namespace prefix for an attribute, and namespace prefixes are separated from the name with :.