What is the difference between specifying values in the attributes using ?attr: or using ?android:attr/
For example to apply the color of the text as if it were a deactivated control (soft gray)
Directly:
android:textColor="@android:color/secondary_text_dark" />
using? android: attr /:
android:textColor="?android:attr/textColorSecondaryNoDisable" />
Values extracted from themes.xml
The difference is where you get the values, in this case the attributes, in the case of using:
?android:attr
the attributes are obtained from the SDK
In the case of using:
?attr
The attributes are obtained by definition made in your application, for example in the file attrs.xml .
This is similar to obtaining other properties such as color, for example, in this case we obtain a color defined in our file colors.xml :
android:background="@color/black"
But we can get the color defined in the SDK by means of @android:
android:background="@android:color/black"
The difference is that ?attr are references to values that you have created while ?android:attr are ready values, incorporated and available on Android.