Strings

This is another XML file that contains all text that your application uses. For example, names of buttons, labels, default text and all such strings go into this file. This is the best practice of separating concerns of various files, even if they are XML files. In other words, layout XML is responsible for layout out widgets, and strings XML is responsible for their textual content. The following file is used in this application:

HelloWorld/app/src/main/res/values/strings.xml 
<resources>
  <string name="app_name">HelloWorld</string>
  <string name="home_page">Home Page</string>
  <string name="next_page">Next Page</string>
  <string name="action_settings">Settings</string>
</resources>

Consider the following layout XML code:

HelloWorld/app/src/main/res/layout/activity_main.xml 
<LinearLayout
  xmlns:android            = "http://schemas.android.com/apk/res/android"
  android:orientation      = "vertical"
  android:layout_width     = "fill_parent"
  android:layout_height    = "fill_parent"
  android:weightSum        = "1"
  android:gravity          = "center">
  <TextView
    android:layout_width   = "wrap_content"
    android:layout_height  = "wrap_content"
    android:textAppearance = "?android:attr/textAppearanceLarge"
    android:text           = "Hello, your name:"
    android:layout_weight  = "0.07"
    android:textStyle      = "bold" />
  <EditText
    android:layout_width   = "216dp"
    android:layout_height  = "wrap_content"
    android:id             = "@+id/name" />
  <Button
    android:layout_width   = "wrap_content"
    android:layout_height  = "wrap_content"
    android:text           = "@string/next_page"
    android:id             = "@+id/next" />
</LinearLayout>

The attribute value @string/next_page, where string is the resource type and next_page is the resource name, represents the string “Next Page,” stored in the file: 
     /res/values/strings.xml
You can use this syntax in an XML resource any place where a value is expected that you provide in a resource.