Resource IDs will be non-final in Android Gradle Plugin version 5.0, avoid using them in switch case statements

Question

Android Studio is now warning this breaking change is coming.

Resource IDs will be non-final in Android Gradle Plugin version 5.0, avoid using them in switch case statements

Is the only other option an if/else?

Answer 1

Have to use if/else per Google: http://tools.android.com/tips/non-constant-fields.

In a regular Android project, constants in the resource R class are declared like this: public static final int main=0x7f030004;

However, as of ADT 14, in a library project, they will be declared like this: public static int main=0x7f030004;

In other words, the constants are not final in a library project. The reason for this is simple: When multiple library projects are combined, the actual values of the fields (which must be unique) could collide. Before ADT 14, all fields were final, so as a result, all libraries had to have all their resources and associated Java code recompiled along with the main project whenever they were used. This was bad for performance, since it made builds very slow. It also prevented distributing library projects that didn't include the source code, limiting the usage scope of library projects.

The reason the fields are no longer final is that it means that the library jars can be compiled once and reused directly in other projects. As well as allowing distributing binary version of library projects (coming in r15), this makes for much faster builds.