Develop Reference

Is it possible to add a externally-maintained project library, without copying?

I'm working with Android Studio 0.5.8.
I have a Working project, and I want to reuse all its contents to make an almost identical app with only another name and different colors.
Basically I want to make a library from the original app and reuse it in various identical apps, but I don't want to copy & paste inside each new app, I want to maintain and develop only one codebase (the project library).
I have read and read, but I can'tt find any real solution.
I tried this in my settings.gradle:
include ':AppCopy1', ':..:LibraryProject'
It works, but I cant use any classes in AppCopy1.

This sounds like a good candidate for Product Flavors. The Gradle build system has support for maintaining a single codebase and building multiple apps from that codebase that only differ by a few files changes. See the configuration examples here: http://tools.android.com/tech-docs/new-build-system/user-guide#TOC-Build-Variants for details.

Manage code/build for Android app stores (Google/Amazon/etc)?

I have an Android app that's downloaded primarily from Android Market (now, Google Play). We made a few tweaks to the source and also submitted to the Amazon App Store to see what sort of traction it gets. I'm now looking for a sustainable way to develop from a common code base and yet build so that I can submit to either/both.
Amazon's store has some restrictions about available APIs, and hence I'd like to conditionally remove/modify features from that version. Since Java doesn't support traditional conditional compilation, and conditionally including files in Eclipse doesn't seem trivial (is it even possible?), I wanted to ask what others are doing to solve this.
Admittedly, I'm no Eclipse/Java expert so feel free to school me.
What I'm looking for in a solution:
Building/debugging using Eclipse.
Static code files, with environment/settings toggles to control what to build.
No duplicate code or conditional logic in code to pick code flow at runtime
Is this something you've solved for Android apps specifically, or for other Java/Eclipse based projects? Suggestions for where to begin?

It's quite easy to do in the newest versions of ADT (version 17), though I do find it makes compilation a bit longer:
Create a new Android project (proj-A)
Go to Project->Properties, select Android, and check "Is Library"
Move all your common code to proj-A, import all the necessary libraries
Create a new Android project for Google Play (proj-B)
Go to Project->Properties, select Android, and add Proj-A to the Library
Repeat #4&5 for the Amazon version
If you have some variables that should be set differently for each sub project (i.e. boolean GOOGLE_PLAY_VERSION to enable Google Play specific functions), you have to create another project to contain these values since you can't have projects that reference one-another in a circular fashion. You can solve this by adding the following steps:
Pull all of your sub-project specific variables into one or more Classes that just serves as container(s) for these variables
Create a "dummy" Java project (dummy)
Config proj-A to add a new Source link to the bin directory of dummy
Add the config Classes in each sub-project with project-specific changes
Profits!
Note that the variables in dummy should not be set as final, otherwise it will override sub-project's setting.
This may seem like quite a bit of up-front work, but has worked quite well for me as far as version control goes.
Edit:
Now with Google's move to Android Studio & Gradle, it may be better to move to that if you are starting a new project if you want to support multiple APKs, see Android dev site's Building Your Project with Gradle#Work with build variants. It definitely doesn't hurt to evaluate that option before deciding.

Unfortunately, it's sort of a convention in Android to change flow at runtime based on what would be in C/C++-land conditional compilation.
Our app has to maintain different behavior for different API levels, so we've created some application-level constants that are initialized statically based on API-level information available to us, and used throughout the code. This is the way that Google does things in their examples (for example, see the ActionBarCompat compatibility library, and in particular the factory method used here).
You could create an interface CustomBuild, and implement it in AmazonBuild and GooglePlayBuild, then use a static getBuild() method to switch functionality as necessary:
if(getBuild().shouldEnableFeatureX()){
doStuff();
} else {
doDifferentStuff();
}
Then all you've got to worry about switching between builds is a line or two of code in the factory along with maintaining which things you want enabled in which versions. Or you could include a different version of a static class CustomBuild for each build.
I'm going to second the suggestion of others above re: switching to something like Maven for building; it should make your life much easier once you have it set up.
I'm also going to say you should make the core of the app a library as suggested above, and have two different modules (one for amazon, one for play store) that depend on the library but each only contain the one custom factory file (or just a static class for each type of build that contains the same "should I do this thing?" methods... once you have the infrastructure it's just a matter of preference).

I haven't actually tried this yet, but it's something I've thought about.
How about using Eclipse's ability to link to files from a directory outside your workspace?
Start with one Eclipse project: for the sake of argument, say it's the Google Play version.
Now build a second project, beginning with asking Eclipse to link (not copy) the source files from your first project.
To develop the second project, add classes that subclass ones from the original project to realize your modifications. For resources, you can use some combination of includes, attribute overrides, and selectors.
Where it's not possible to subclass or extend, then obviously you'll have to just copy the original source file and hack on it. If you're really OCD about it, you can probably just maintain a patch set rather than a whole redundant set of files.
What do you think, will it work?

You may create manually two projects in Eclipse pointing to the same source folders but with different inclusion/exclusion filters and different target directories.
Then two Ant targets using properties to switch excluded files from javac fileset are enough to generate corresponding jar files.
The aim is to get a clean application for each target, without any code from the other one.
With features listed as pluggable behaviors in a property file or XML configuration, your runtime will adapt itself with the addition of menu entries.

Multiple Apps with a shared code base

Since it's popular to have both a free and a paid version in the android market of the same app, I had decided to do the same. Initially I just duplicated the complete codebase and adapted some code here and there (added ads, built in some limitations etc) since there was no option to do library projects at that time, but that left me with two projects that are horrific to manage fixes to bugs as I need to do those twice.
Since r14 we can use library projects with resources, so that would be a great solution to this particular problem as far as I can tell. Therefore I've read up on library projects and conciderations, and I'm curious to know what the minimum amount of files needed in the projects of the different versions are. My questions therefore are;
Could I have all of the code in the shared project, and have bare bone project with basically just a manifest?
If so, should I? is this the optimal way conceptually? (so apart from the fact that it depends on my code base)
How should I deal with library package naming, are there specific rules?
Are there tools about that can compare code from two different projects and perhaps merge them auto-magically or auto-manually, and which one is preferred?

If I understand your problem correctly, you want to create multiple Android apps that are similar to one another (i.e., have a lot of the same source code), but which are different in particular (minor) ways, and you want each of these apps to have a distinct package, so that it can be separately uploaded and distributed on an app store such as Google Play. A Project Library is an excellent facility for accomplishing those goals.
I'm assuming that the differences between your various versions are minor, involving things like resources and the app name and package, and a switch that turns on certain features for a paid version while leaving them off for a free version.
Even if that is not the case, by using polymorphism in the ways described below, your various apps could differ in significant ways and still share a common Project Library.
A Project Library can be defined in Eclipse in the same way as any Android project can be defined, but it is marked as a Project Library (by checking the "Is Library" box near the bottom of the Android page of the library's Project Properties dialog) and cannot be compiled and run on its own. Instead, it is intended to be included by reference in one or more other projects which are actual apps (by adding a reference to it on the Android page of each such app's Project Properties dialog). These apps will use the Project Library, and thus will share its code and capabilities.
Each such referencing app will have its own manifest file (where their respective, different packages can be declared), and they can also define their own classes (including classes derived from the Activity and/or Application classes of the Project Library), so that these classes can be specialized polymorphically for each app that uses the Project Library (e.g., by overriding methods or by providing definitions for methods that are defined as abstract within the Project Library's Activity- or Application-derived classes), although you can also use those Library classes without modification (provided that they are not abstract) by simply referencing them within the manifest file (e.g., in an activity or application tag) of each app that uses the Library, just as you would reference Activity or Application-derived classes defined within the app itself.
If you decided to use this approach, then you would put your main source files in a Project Library, and would create a separate project for each app you want to produce, each of which would reference the Project Library. The manifest file of the Project Library would be overridden by the manifest of whatever project is being created using that Library (actually, I think that the Project Library's own manifest is completely ignored, not just overridden, but nonetheless it is useful to create a manifest for the Library, so that you can manually template - copy and edit - the manifest of each project that uses it from the Library's own manifest).
I have used this approach to create multiple android apps that share some of the same capabilities, and it has worked very well for me.
Regarding package naming, any old package name will work for a library project, but of course it makes sense to use the same prefix for the Library Project's package as you use for your various individual (e.g., free vs. paid) apps that use it, with something like ".library" as the last part of the name, while the various apps could have endings like ".myappfree" and ".myapppaid". Naturally, you would want to use your reverse domain name convention for the library's package prefix to prevent conflicts, just as you would for a package name of a released app.
In Windows, a nice, open-source tool for comparing code bases is WinMerge:
http://winmerge.org/
If I were in your position, however, I would only use this tool to manually identify differences, and would not attempt to use it to automate the refactoring of your code into a Library Project. That would be best done under your own (manual) control.
Finally, as an alternative, you might consider using a single app that is free and that has your free app's capabilities by default, with an option to upgrade to your full app's capabilities (delivered within the same APK) via an in-app payment, rather than having separate free and paid apps. In-app payments have improved a great deal in the past several months (with the release of version 3 of IAB), and although there are still some glitches, they have become a more practical alternative to the free/full dichotomy than they were at first.

Yes, you can have a project that is basically just a manifest specifying app name, name space, icon etc, with all the actual code and 99% of the resources in the library project.
Yes, I think you should use this approach. It's very common to use library projects to deal with the Free/Paid app problem.
I've not had any problems with naming, though you should be careful with any resources in separate projects to avoid using the same names.
I'm not aware of any tools, and if it were me I'd want to do it manually to be sure I'm merging what needs merging and keeping separate what needs to be separate. you've one significant refactor to do, but once all the duplication is removed I'm sure it'll be much easier.

Including project within another project

I built an app and published it for purchase in the Android Market. Now what I would like to do is release another version of it that is free. Once you install it though its going to ask you for an activation code. I have built that program seperately. I was wondering if there was a way I could include my first app into the second one (like an include statement in C# and reference?) I dont want to have to update 2 projects every time I release an update.
UPDATE
Ok, ive managed to set my first application as a library. Then I went into the properties of my second application and added the library to it. The src folder for the first application showed up in the second one but Im seeing that the resources were not imported. Is there an easier way of doing this or do I have to manually copy over all my layouts, values and drawables as well?

Read this doc on managing projects. You should probably separate all the common functionality out into a common library project.

Android & Eclipse 2 different versions of the same app

Hello I am a beginning android developer using windows and the eclipse IDE to develop java android applications.I have published one game but there is a free version of the game and a paid version. The google market insists that the different versions must have different package names. So far i have been refactoring the package with 2 different names and changing the R resource file import each time i build the different versions. The code is 99% the same for both versions.Is there a better way?

You have various discussions on this topic here and there, but basically the solution is akin to duplicate the project.
For instance (not based on eclipse):
It is difficult to answer this, since we don't know what the difference is between the free and not-free versions of your app.
I'm going to assume that the differences could be handled by some sort of global free/not-free flag. By that, I mean that the same code would make up both versions of the app, and which portions are enabled or used would be dependent on some public static data member somewhere:
if (SomeClass.IS_PAID_APP) {
// add more stuff to menu, etc.
}
If you can organize your app that way, then you only need one code base.
Have it set to build your app one way (free or paid, your choice) and with the proper package in your manifest for that version of the app.
Then, add an Ant task that does the following:
Makes a tree copy of your project dir to a temporary location
Switch the copy of the manifest to the new package name via a
search-and-replace
Switch all import statements for your old package's edition of R to
the new package, again via search-and-replace, and again on the copy,
not your original
Change your IS_PAID_APP (or whatever) to the opposite value
(search-and-replace in the copy)
Executes an Ant build for the copy of the project
Copies the binaries from that build to the main project's bin/
directory under a distinct name (so it doesn't clobber your other copy
of the APK)
Deletes the tree copy made in step #1
If Java had a pre-processor, this would be somewhat simpler. However, the basic technique that I describe above has been used for a couple of decades now. It's clunky, but it works, and it means you only have one set of source code to deal with.
Note that the Ant <replace> task would handle your search-and-replace stuff nicely.

This is one of the failings of Android Market though I can see why they did it that way. It just wasn't designed for having Free and Paid versions of your app (they claim the 24hr return policy is what this is for, but that's instead used for piracy)-:
Anyways, simplest thing to do is to write an Ant build script (or whatever scripting language you use). Do a search replace of your package name through all the .xml and .java files. Then do the build of your app there. Refactoring your code is more pain than it's worth IMHO...