I'm developing a software layer that I would like to reuse several time for building my Android applications. Basically I want that, once installed, the software layer any other apps can use it (like a system library).
I was wondering what is the best solution for doing this, when I found that recently Android supports library projects (http://developer.android.com/guide/developing/projects/projects-eclipse.html#SettingUpLibraryProject).
So I decided to create my software layer as a library project, making the code it contains re-usable by the other applications I want to realize.
My software layer depends on a set of external jar, which are correctly located in the lib folder of the library project.
The problem is that when I create a new project referencing the library project I'm not able to see the classes defined into the external jars of the library project: i.e. it seems that they are not part of the classpath.
So when referring to a library project is possible to re-use only the source code defined there? If my library project have some other libraries I have to import these libraries also in the other ones (I want to avoid this!)?
I'm also interested to know if there are other ways for doing this, but searching around I haven't found other ways for realizing Android libraries/shared code.
Thanks.
Android library projects definitely incorporate any JARs you have in the library project's libs/ directory. However, if you are using Eclipse, you probably have to somehow manually add those to your build path of the host project (the one reusing the library).
Ok I finally figured out that for solving this is sufficient to add the jars to the host project build-path (no need to re-import them, you can just choose the path from the library project). However it is weird that they are not automatically exported in the host project classpath.
Related
I have started working on a project where I will need to share a bunch of Java classes across a bunch of apps. In Eclipse it was possible to create one project with all such classes and use it as a library in a workspace with all your dependent projects, but in Android Studio it doesn't seem possible to do so (At least not easily).
I have been reading a bunch of posts and a lot of them suggest setting up a library project, generating an aar file and then using that in my projects. But, as I understand it, this will make my library open-source (Am I right?), which I don't want. I am doing this for a client and I want the code base to be private.
Also, I know that a module can be imported into a new project. But this creates a COPY of the original module. This is not what I want at all. I don't wanna maintain multiple copies of the same classes, which completely defeats the purpose of 'code sharing'.
Is there any good way of achieving what I am looking for? Any help is appreciated.
You have a couple different options.
One option is to maintain your libraries as separate projects and compile them to an archive format, such as JAR or AAR; JAR files are for pure Java libraries, and AAR is for Android libraries (which contain code that accesses Android APIs and/or has Android resources). As was pointed out in the comments, AAR doesn't force you to publish your code to the world any more than JAR files would; it's just an archive file format whose files can be local to your machine or your organization.
With that archive file in hand, you can include it in other projects. If you're part of a multi-developer organization, you may find it convenient to use a repository manager to publish and maintain those libraries within your organization, and you can use Maven coordinate-style specs to include libraries in your projects, which you don't have to manually copy over to your development machine.
The disadvantage of this approach is that it makes it a little harder to make changes to those libraries: you need to load up the project, make changes, build an archive, and distribute the archive.
The other approach is to keep the library as a source module like you did in Eclipse. You observed that Android Studio will make a copy of the module if you import it via UI, but if you bypass the UI and modify the build scripts directly, you can do what you want, which is to use the module in-place and share a single copy among multiple projects. To do this, work in your settings.gradle file and add this:
include ':module_name'
project(':module_name').projectDir = new File(settingsDir, '../relative/path/to/module')
I would strongly encourage you to not use a pure relative path here; in this example, the path is anchored to the settingsDir variable supplied by Gradle, which is defined to be the directory where settings.gradle is found. If you use a pure relative path (i.e isn't anchored to anything), you're dependent on the working directory being the same in all environments where the build file is run (command line vs. Android Studio vs. CI server), which isn't a good thing to assume.
You need to think in the eclipse projects as Android Studio/IntelliJ Idea modules. Then, you can generate android (or java) libraries and then include them in your project.
To mark an Android Studio module as a library you can go to File -> Project Structure -> Facets and there click on Library Module
I was in same situation as you, and i founded an approach using git.
Steps to do, to have library:
Create project in Android Studio.
Create android library module in that project.
In that library module create git repository.
Add modulename.iml in .gitignore file
Use GitHub or Bitbucket for private cloud repository. and push your library to it.
Create new android library model in any project that you want.
Close Android Studio (not sure is that mandatory).
Using explorer go to your created module folder.
Remove all data in it, except modulename.iml.
Clone your library from "GitHub" into it.
That's all.
Now you are able to use library in multiple project whether you are at home or at work. Just after finishing you work not forget to push library changes. And after opening new one pull them.
I think you can automate this thing somehow.
The benefit is that you don't need to build any jar, or aar.
You can certainly create and use a library without making it open source or available to others.
First, you don't need to make it an aar unless it contains Resources.
If it's just plain classes, you can just make it a .jar file.
Either way, the easiest way to share these libraries (either aar or jar) is to set up your own repository. Nexus and Artifactory are the two most common repository managers.
You keep the library in its own project, and then publish it to your own, in-house repository.
Then, projects that need to use the library are configured (in gradle) to use the in-house repository, and get the library from it.
So I recently migrated to Android Studio from Eclipse. For the most part, it's better, but I haven't found a good way to maintain a shared codebase between multiple projects.
What I want to do is be able to share some code between several of my applications. Each application is in its own project. From what I've seen, most people add it as a library module in the application's project. The problem with that is the module is accessible from only one project. The other projects within which my other applications reside can't access the library.
It seems to me like there should be a mechanism for creating another library project and then allow each of the application projects to access that code. This worked in Eclipse, where I would create another project in my workspace, mark it as a library, and then have the other projects reference it. I would be able to change the code in the library and then all of the projects referencing it would automatically build with the updated code.
Is this something I could do in Android Studio?
Yes this is possible:
Create the project you would like to have as a shared library - we'll refer to it as sharedProject.
Now in the project that you want to use this library open settings.gradle and paste the following:
include '..:sharedProject:app'
Open your build.gradle and paste the following under the dependencies element:
compile project(':..:sharedProject:app')
You can use this technique for as many projects as you'd like to refer to your common codebase in sharedProject. Note that this assumes your project and your sharedProject directories are in a common workspace directory (which is almost always the case).
I want to create an Android jar library which has activities which use layouts that are all within the jar file.
I have been researching and trying different methods for the last few days and exhausted the related posts here. I have managed to get drawables and other raw assets to reside and be loaded from within the jar. However I have not been able to include valid resources which include the layouts. The official view is that it is not supported yet however I am sure it can be done.
I see that this is possible with .aar libraries when using Gradle but I am unsure if .aar libraries are compatible with older Android projects.
Could anyone shed some upto date info on this issue of resources/layouts in jar libraries and also the compatibility of .aar libraries.
Many thanks
I want to create an Android jar library which has activities which use layouts that are all within the jar file.
That is not possible, sorry. However, you are welcome to create an Android library project that serves this role, and that library project can ship a JAR instead of Java source code (see the Play Services SDK's library project for an example). The layouts would not be inside of the JAR file, though.
The official view is that it is not supported yet however I am sure it can be done.
I am sure that you are incorrect in your assessment.
I see that this is possible with .aar libraries when using Gradle but I am unsure if .aar libraries are compatible with older Android projects.
Project age has nothing really to do with it. If you are using Gradle, AAR files work. If you are not using Gradle, AAR files do not work.
I have seen this question, and have some more doubts regarding creating a jar file which I can distribute and can be used in any android applications.
What my requirement is
As I said, I want to build and distribute a closed source library. I
don't want the source code to be visible.
In that library I don't want to use any assets, layouts, resources
etc. But I want to use some android specific codes, like getting
android device id.
The most popular answer in the above linked SO question tells to create a regular java project and import android.jar in it. I tried to do that, but I don't know how to add android.jar to any java project. I would like to get some clarification on that too.
Moreover I would like to know if there are any other methods using android sdk itself (without using java project) create a closed source library jar file.
I think what I want is possible, since google analytics for android native apps seems to have done it. I am sure in the .jar file they distribute they are using android specific codes, since there seems no other way for them to get the device information to display in the analytics viewer.
EDIT : CAN SOMEONE CLARIFY THIS??
I think I have made some progress. This is what I have done
Created a regular android project (not library project, the "is
Library" checkmark is unchecked)
In the project I have coded out my logic. It uses some android
specific classes like SharedPreference, UUID, PackageManager. But
nothing related with assets, layouts also no class extending
Activity. Just a java class extending java.lang.object
Exported the project using Project->rightclick->export->Java->JAR
file. In the next screen I unchecked the checkbox near
AndroidManifest.xml. Set a destination directory to export and
clicked next thrice with keeping the default settings. Then I clicked
Finish, and got a lovely libMyLibraryName.jar at my desktop.
Then I created another android project, added this libMyLibraryName.jar to new project using project->rightclick->properties->java build path -> libraries->add external jar.
And I tried to use my class in the library, in my new project
MyLibraryClass objClass = new MyLibraryClass(this);
And I was able to compile and run successfully. I even sent the library to one of my co worker who was able to use the library in his on machine (Just making sure library project in my workspace wont influence the project using it).
Now I have 2 questions.
1) My first question is , what they meant by the term "true library" in the below given documentation ? Is it any non android java project which can be exported to a JAR file?
However, a library project differs from an standard Android
application project in that you cannot compile it directly to its own
.apk and run it on an Android device. Similarly, you cannot export
the library project to a self-contained JAR file, as you would do
for a true library. Instead, you must compile the library indirectly,
by referencing the library in the dependent application and building
that application.
Well this portion is taken from documentation under title "Library Projects".
2) My second question is, anything wrong with the way I have created the JAR file? Any possible pitfalls which might bite me back later? I would like to make sure I am not doing something terribly wrong, before using it in my important projects.
I might add that I didn't try the method of creating a JAVA project and importing android.jar. I am ready to try that one, if what I have done currently is wrong.
The android.jar will be located where you installed your Android SDK. Under the platforms directory there should be a number of other directories named android-<version>. The android.jar will be there. Choose the one specific to the minimum android version you are targeting.
Once you have that, copy it into your project. If you're using eclipse I think you can just cut and paste jars straight into your project, right click and add it to build path. If you're not using eclipse or any other IDE, you just need to ensure that the android.jar is on the classpath when building your jar file.
After that your newly built android library can be dropped into any Android project.
In answer to your additional questions:
What they mean by a true library is a jar file as opposed to an Android library project.
I don't think there's anything wrong with the way you created the jar file. I would have made it using the android.jar as I mentioned above but your way should also work. To verify this I would examine the jar contents and make sure all you have in there is .class files.
One of the newer functions of Android is the ability to create a Library Project.
This is great for unit testing and sharing common functionality across many apps you may be developing, but I seem to have stumbled upon a bug in their implementation.
When you have the following situation:
-LibraryProject contains LibraryProject/libs/folder/lib.jar in it's build path.
-ReferencingProject references LibraryProject.
From ReferencingProject you don't have access to anything inside lib.jar (Such as constant's used to communicate with methods in the Library Project).
A solution to this is to include "lib.jar" as an external library in the referencing project but this approach begins to negate the benefits you gain from having a self contained Library Project by creating multiple manually added references to resources which could move/change during the development of the library project (not to mention cause some pretty confusing errors).
Is there any way to expose an included libs classes to the referencing project without having to manually reference them as external jars?
As #Selvin says,
In the Library Project you can specify which libraries you want to mark as "exported" in the window brought up by using: Project properties => Java Build Path => Order and Export. From this example you would check libs/folder/lib.jar.
Clean and build the Library Project and the "exported" libraries are now included in the produced jar.
EDIT
This is a symptom of upgrading to ADT 17 - (Android Team: Perhaps put a few warnings on your release notes when an update breaks existing architectures?)
http://tools.android.com/recent/dealingwithdependenciesinandroidprojects
If you don't want to add the library to the "Order and Export" then placing local jar's in /libs/ base folder will automatically add it to "Android Dependencies" which are exported in the jar created from your shared library.
EDIT2
Recent ADT upgrade would have you also manually select "Android Dependencies" as "Exported" in your Java Build Path. Again, warning would be nice.