Question

I have a Library project set up and a project which depends on this library project – Everything compiles fine and I’ve had the Dependent project running fine however;

I’m have an intermittent problem however while using an Activity from the Library project.

My Library project can be “unchecked” as a library project and the “picker” Activity can be run in isolation. Running the Library project in it’s own right works fine with no problems.

When I use the Library project (and the “picker” Activity) from the dependent project it gives me either NullPointerExceptions (or historically DexOp) errors saying that the “picker” Activity can’t find it’s resources.

Can anybody tell me if they have experienced this before?

EDIT

Manually copying the layout.xml used by the Library project activity to the dependent project makes the project open the “picker” Activity correctly. Is this required?! Surely not? This further makes me wonder if there is a problem with merging/referencing the integer id’s from R.java in the Library project.

EDIT

I’m not sure if this is of any consequence, but one of my Library projects is a wrapper around a set of custom views used in different front end projects.

These custom views each have an Activity so that they can be tested in isolation.

One of these view’s has custom attributes, which while running in isolation work very well. However, it doesn’t seem like the dependent project correctly pull’s in the attributes and keep’s them in their original namespace, causing the imported layout’s to throw compilation errors:

[2012-05-16 12:07:28 - Project] D:\opt\workspace\CustomGlowList\res\layout\main.xml:14: error: No resource identifier found for attribute 'listId' in package 'com.company.library.glowlist'
[2012-05-16 12:07:28 - Project] D:\opt\workspace\CustomGlowList\res\layout\main.xml:14: error: No resource identifier found for attribute 'type' in package 'com.company.library.glowlist

EDIT

DexOp errors were solved by removing a duplicate file name which was present in the Dependent project. Not sure if the file name was the problem or the contents of the file.

EDIT

I’ve been unable to find a solution to this problem as of yet (although @yorkw’s answer certainly helps with the xml attributes! Thanks).

I have managed to make this problem intermittent however:

I have gone through each of the library projects and ensured they all had their own namespace (ie, com.company.library.component1, com.company.library.component2 etc). After a couple of clean’s (each project ordered with the correct precedence) this problem resolves itself, however does eventually come back when switching around library/not a library to test components.

Answer 1

The problem was being caused by the R files from each of the Library projects not correctly being built and referenced. The resource files are built and referenced directly from the calling project.

Each of the Libraries need to have unique package as defined in the AndroidManifest.xml. This leads to each of it’s resources being compiled in that unique namespace within the calling project alongside the Library jar which contains the class files.

The problem becomes intermittent when switching between a library and a runnable project because a clean and build needs to take place to regenerate these files as it isn’t done automagically when unclicking the Use as library checkbox, where as the jar (and java classes) don’t require as much coaxing for them to be correctly referenced as the library projects references them when acting as a Library.

This can lead to intermittent and also varying errors including missing references, DexOp and NullPointerExceptions depending on to what degree the R.java files have been mangled or partially built and what conflicts are taking places between packages.