Develop Reference

What is the correct way to add an Android Library to an Android Project?

I am trying to add android-support-v7-appcompat to my newly created Android project.
Following the Support Library Setup Documentation (developer.android.com/tools/support-library/setup.html), section Adding libraries with resources, I have created an android-support-v7-appcompat project, before adding it as an Android dependency.
EDIT: Here are more details on the process I followed to add the library project as an Android Dependency to the main project:
In the Project Explorer, right-click your project and select Properties.
In the category panel on the left side of the dialog, select Android.
In the Library pane, click the Add button.
Select the library project and click OK.
However, even if the dependency is correctly recognized, Eclipse still sees the compatibility references, such as ActionBarActivity, as errors, forbidding me to build the project. (See picture here).
To solve this problem, I tried the solutions accepted by similar questions on SE, i.e. adding android-support-v7-appcompat to the Project's Build Path, which successfully silents the errors that prevented me to compile earlier.
However, now when building and deploying the project, I get an error: the app crashes at launch, and the Console displays an error message: Could not find android-support-v7-appcompat.apk! (See picture here).
To resume, with the first configuration I am not able to compile with Eclipse, while with the second configuration I can't launch the application.
Therefore, I have two questions:
First, how should I be adding a library to my project, so I can at the same time build my project and be able to use the library's additions in my code in Eclipse?
Secondly, I feel like I am missing theoretical knowledge on how Eclipse handles dependencies.
What is the difference between adding a library as Android dependency vs Java Dependency / vs adding the project or its jar to the Build path?

First, how should I be adding a library to my project, so I can at the same time build my project and be able to use the library's additions in my code in Eclipse?
Your first approach should be fine, which would indicate that there is some other problem. For example, there may be errors in the appcompat library project that are preventing it from being compiled. However, given the error from the second approach, either you are running the appcompat library (which will not work) or something else is more fundamentally broken in your project setup, where your app thinks that it is supposed to build android-support-v7-appcompat.apk, when there is no such APK.
What is the difference between adding a library as Android dependency vs Java Dependency / vs adding the project or its jar to the Build path?
Never manually modify the build path in Eclipse for an Android project. While that will satisfy the compiler, the contents of the JAR(s) will not be packaged into your APK for use at runtime, resulting in runtime crashes (e.g., VerifyError).
"Java dependency" is for pure Java source code. Not only do you not have the source code to appcompat from the SDK, but an Android library project includes Android resources (and, at least on Android Studio, also assets and an optional manifest file).
For Eclipse, library projects are attached via the approach you describe as the first approach in your question. For Eclipse, plain JARs are just dropped into libs/ in your project root, and those are automatically added to your compile-time and runtime classpaths.

How do I add a new library to android dependencies using eclipse adt?

I am trying to add external library to android dependancies using eclipse adt. I have a couple of libraries like pull to refresh etc in there. But everytime I add a new library jar file it shows outside of the android dependancies library folder. How do I make it such that it is coupled with the other libraries as a part of android dependancies library. Here's what I did so far:
Project> Properties> java build path > libraries> add jars ( also tried adding external jars), but it always showed my new jar file independantly, i want it to be a part of android dependancies). any clue?
Here's a screen shot, I would like to add it as a part of android dependencies:

I still do not get why that is important to you.
However, when you reference a library project: rightclick project->properties->Android->Add then the jar goes into Android Dependencies.
If you add the jar directly to your project under libs or using build path, then it goes under Android Private Libraries.
Both methods works but referencing a library project can have benefits if you want to alter the code of the library during development.

In my case I had the following in my project.properties file
target=android-18
proguard.config=proguard.cfg
android.library=false
android.library.reference.1=..\\com_facebook_android
android.library.reference.2=../actionbarsherlock
After I changed the last line to
android.library.reference.2=..\\actionbarsherlock
actionbarsherlock.jar appeared in the Android Dependancies and I could run my app without the java.lang.noclassdeffounderror exception

How can I use a project source code as a library for an another project?

I am a beginer in android.My client gave me a project source code(using native libraries) as a refference.Is there any possibilities to use these source code as library for my android project? If it is possible,how can I access methods of these library file? any one please help me..

Import the project into work space. Right click on the project in eclipse. Goto properties. Choose Android. Check if Is Library chexk box is ticked. If not tick the same. This is a library project now.
To refer the library project in your android project.
Right click on the project in eclipse. Goto properties. Choose Android. Click add. Browse the library project and add the same.
Clean and build.
For more information check the link
http://developer.android.com/tools/projects/projects-eclipse.html
Information regarding library project
http://developer.android.com/tools/projects/index.html

If the Android development tools build a project which uses a library project, it also builds the components of the library and adds them to the .apk file of the compiled application.
Therefore a library project can be considered to be a compile-time artifact. A Android library project can contain Java classes, Android components and resources. Only assets are not supported.
To create a library project, set the Mark this project as library flag in the Android project generation wizard.
To use such a library, select the generated project, right-click on it and select properties. On the Android tab add the library project to it.
The library project must declare all its components, e.g. activities, service, etc. via the AndroidManifest.xml file. The application which uses the library must also declare all the used components via the AndroidManifest.xml file.
Other projects can now use this library project. This can also be set via the properties of the corresponding project.

Please check this
To create a library project, set the Mark this project as library flag in the Android project generation wizard.
http://www.vogella.com/articles/AndroidLibraryProjects/article.html

How to add external libraries to my application in android

I have an application that I have to look at as a training exercise. It has used few external libraries such as SlidingMenu, ImageViewZoom and ActionbarSherlock.
I have downloaded and extracted those libraries but I have no idea how to add them to my existing project.

For those that are distributed as a simple JAR, do what Emil Adz indicates, and copy that JAR into your project's libs/ directory.
For those, like ActionBarSherlock, that are distribute as Android library projects, you will need to do a bit more work. In the case of Eclipse, you will need to import the library project into your workspace, then go into Project > Properties > Android for your application project and click the [Add] button to add the library project to the application project. For a command-line build, use android update lib-project to link the application and library project together.
You can read more about referencing an Android library project from Eclipse or the command line in the documentation.

You need to import those libraries as Android Project from existing source and mark them as "Is Library" by going into their properties.
Once you marked it as "Is Library" add it to your
project by going into Properties->Android->Library->Add (it will show the list of library you imported).

The Right Way:
What you need to do is to copy the external library (JAR file) to the /libs folder of your project.
That way those libraries will compile with your project and could be use on real device when you deploy your application.
Some times you will need to add a project to your workspace ( For example the Google Map library)
and then add the library reference using the properites -> Android window at the bottom.
You can get an idea of how it's done by reading the first 3 step of this Google Map API V2 guide I wrote. there I reference the android library project:
Google Map API V2 Guide
The Wrong Way:
any other way, like for example adding the files using the properties - > Java build path screen may result in a missing library when you run the project on a real device.

if they are jars the make a libs folder then paste the jar in it and then go to your project buildpath->configure build path->Add Jars-> ok and if it is a library project then go to your project Property->Android->Add(Your Lib Project)->Ok->Apply

How do I build my project with ANT when it depends on a non-library project with an Android library project dependency?

I'm trying to build my project using ANT. My project uses ActionbarSherlock, and Roboguice-Sherlock. ActionbarSherlock is an Android library project, but Roboguice-Sherlock is not. It's not even an Android project at all. See here:
https://github.com/rtyley/roboguice-sherlock
I can get ActionbarSherlock to build using ANT no problem, the problem lies with Roboguice-Sherlock. It's not an Android project, yet it has dependencies on Android and ActionbarSherlock, as well as Roboguice. When I try to build I get a ton of errors saying it can't find the Roboguice-Sherlock stuff.

If your project has the Roboguice .jar and the library project reference to ActionBarSherlock already configured you should be able to just drop it into your libs/ folder to have it automatically picked up.
I am working with Roberto to ensure that the .jar of his project gets uploaded to GitHub for non-Maven users to use.
For now, you can clone the project simply run mvn clean package to get a standalone .jar in the target/ folder which will enable you to do as I described above.

You need to add robiguice-sherlock as a .jar to your Android project. You can download it here (click Download (JAR)). Trying to build the source in Android will fail because it is not an Android project. Once it is in your directory, you need to open project properties and add the .jar to your build path.