What does “@+id” mean?

Question

I\'ve read through much of the Android documentation and I\'ve yet to find any statement that says what an id value prefix of \"@+id\" means. I know what \"@string\" and variat

Answer 1

The at sign (@) is required when you're referring to any resource object from XML. It is followed by the resource type (id in this case).

The plus sign (+) before the resource type is needed only when you're defining a resource ID for the first time. When you compile the app, the SDK tools use the ID name to create a new resource ID in your project's gen/R.java file that refers to the UI element. With the resource ID declared once this way, other references to the ID do not need the plus sign. Using the plus sign is necessary only when specifying a new resource ID and not needed for concrete resources such as strings or layouts.