what does the "@+android:id/title" mean?
<p>In normal, we should use <code>@+id/</code> to define an id and use <code>@id</code> to reference an id. Today I found <code>@+android:id/title</code> in <code>apps/settings/res/layout/preferenc_progress.xml</code>.</p>

<p>How to understand it and how to use it? </p>
