Question

From the O’Reilly book “Android Application Development ” by Rick Rogers, John Lombardo, Zigurd Mednieks & Blake Meike, page 23:

 <TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    />

From page 44:

 <application android:icon="@drawable/icon2">

What is the meaning of the @ in each of the above fragments?

Answer 1

In this case:

android:layout_width="fill_parent"

the value for the attribute, android:layout_width, is specified directly inside the quotes, fill_parent. In the other case:

android:text="@string/hello"

the value for the attribute, android:text="@string/hello", is specified elsewhere. This is indicated by the @ at the beginning of the string. In this example it is @string/hello. The value is in a resource.

From the “Resource values” section in The AndroidManifest.xml File from the Android Developers site. Found from link in allclaws answer.

Resource values are expressed in the
following format,

@[package:]type:name

where the package name can be omitted
if the resource is in the same package
as the application, type is a type of
resource — such as “string” or
“drawable” — and name is the name that
identifies the specific resource.