From the Developer Guide:
android:id="@+id/my_button"
The at-symbol (@
) at the beginning of the string indicates that the XML parser should parse and expand the rest of the ID string and identify it as an ID resource. 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"