Up vs. Back or in other terms hierarchy vs. chronology is one of the User Experience aspects touched upon in my post UML: Modelling User Interfaces Part 1 – Hierarchy and Navigation. The Android methodology for UI navigation has received some attention over the years and the largest change to date was brought in with the introduction of the Action Bar as part of Android 3.0+.

In the process of updating and refactoring an old Android project I unwittingly changed a Project configuration option (the “Is Library” option) that lead to my resource file being generated differently. E.g

Before

[java] public final class R { public static final class id { public static final int button1=0x7f090001; public static final int button2=0x7f090002; public static final int button3=0x7f090003; } } [/java]

After

[java] public final class R { public static final class id { public static int button1=0x7f090001; public static int button2=0x7f090002; public static int button3=0x7f090003; } } [/java]

A subtle change indeed but one that caused the following compiler error for each line

case expressions must be constant expressions