android:id what is the plus sign for

Question

The document says \"@[+]id/myid\" as the definition for android:id, from the notation it indicates that the plus is optional. But nowhere can I find a definition of what the plu

Answer 1

The documentation says,

The plus-symbol (+) means that this is a new resource name that must be created and added to our resources (in the R.java file). There are a number of other ID resources that are offered by the Android framework. When referencing an Android resource ID, you do not need the plus-symbol, but must add the android package namespace, like so:

android:id="@android:id/empty"