Vikas Patidar Vikas Patidar - 4 months ago 10
Android Question

Difference between "@id/" and "@+id/" in Android


What is the diffirence between the
@id/
and
@+id/
?


In
@+id/
the plus symbol + instructs to create a new resource name and add in to the
R.java
file but what about
@id/
? From the documentation of
ID
: 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/list"


But in the image below Eclipse doesn't suggest any kind of
@android:id/
.

Image showing the suggestion for the @/id and @+/id


Are
@id/
and
@android:id/
the same?

Answer

you refer to Android resources , which are already defined in Android system, with @android:id/.. while to access resources that you have defined/created in your project, you use @id/..

More Info

As per your clarifications in the chat, you said you have a problem like this :

If we use android:id="@id/layout_item_id" it doesn't work. Instead @+id/ works so what's the difference here? And that was my original question.

Well, it depends on the context, when you're using the XML attribute of android:id, then you're specifying a new id, and are instructing the parser (or call it the builder) to create a new entry in R.java, thus you have to include a + sign.

While in the other case, like android:layout_below="@id/myTextView" , you're referring to an id that has already been created, so parser links this to the already created id in R.java.

More Info Again

As you said in your chat, note that android:layout_below="@id/myTextView" won't recognize an element with id myTextViewif it is written after the element you're using it in.

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