Every Android developer uses Open Source libraries. Android has a large ecosystem of libraries that developers can freely use in their own apps, but before to choose to use a library, you should know some important points about the open source development. This sessions will introduce how to evaluate a library and how to get started the incredible experience to write an Open Source.

1. +GabrieleMariotti
@GabMarioPower
Can you work without open
source libraries?

2. Droidcon Torino - 9/10 April 2015
Gabriele Mariotti
Mobile Project Manager at Namirial S.p.A.
Android Developer
Community Lead at GDG Ancona

3. Droidcon Torino - 9/10 April 2015
How many of you have used open source
libraries in your projects?

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Can you work without them?
PicassoRetrofit
Universal-Image-LoaderCrouton
Ion
AndroidStaggeredGrid
Cupboard
OkHttp
EventBus
ListViewAnimations
SwipeListView
Dagger
ButterKnife
Otto
ShowCaseView
PhotoView
SmoothProgressBar
StickyListHeaders
TwoWayView
PagerSlidingTabStrip
GoogleProgressBar
Teleport
Cardslib
Material Dialogs

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Use an open source library
Can you work without them?
Write your custom code
Which are the alternatives?

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● Never choose the first library
● Read the licence
● Read the readme
● Pay attention to some points
Before using open source libraries

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Some important points:
● Licence
● Maintenance
● Support
● Documentation
● Quality code
Before using a open source libraries

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Open source != Free
● Open source doesn’t mean you're free to do anything you want with
the library
● you have to respect the license
What is open source?

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What do you know about
the types of licence ??

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Can I use it ???
● Check the licence under which the library is released
● Check if the licence is compatible with your project
● Pay attention to legal issues
Licence

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Strong copyleft
● GNU GPL
It is a reciprocal licence VIRAL licence.
Are you ready to release your product under GPL licence?
Licence

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Weak copyleft
● LGPL
● Mozilla Licence
Permissive
● Apache V2
● MIT
● BSD
Licence

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Telegram+ was removed from Google Play for:
Violation of the intellectual property and impersonation or deceptive behavior
“Telegram is open source.
What’s wrong with a third party app based on that source? ”
Type of licence Telegram
Telegram is licensed under the GPLv2+.
This means you’re free to do pretty much whatever you want with the source code, as long as you make
it available to anyone who asks (you can make it public accessible for everyone, or include a written
offer to make the source code available any user who requests it).
A recent history

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Who is the author of this library ??

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Who is maintaining the library ??
● a company ?
● a community ?
● a single developer ?
Maintenance

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Is this library still alive ??
● Check the last commits in the repository. If the last commit was 1
year ago likely the project has been abandoned (or it is complete
and doesn't require updates...).
● Check how often the project is updated (or was updated).
Maintenance

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Do not underestimate this point.
If you use a library which is no longer maintained, you could have
problems in the future.
Maintenance

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Can someone help me….?
● Evaluate what kind of support you can find using it.
● Popular libraries have a tag (and a lot of posts) on stackoverflow
● Popular libraries have a G+ community or a very good issues
section where to find a lot of comments and posts.
Support

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Is someone fixing the issues….?
● Check how many issues are open
● Check how many issues were closed
If you find 300 issues open and 1 issue closed is not a good evidence
Issues

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How can I use the library ??

21. Droidcon Torino - 9/10 April 2015
You can’t use a library without documentation!
Check if the library provides:
● Doc section
● Wiki section
● A good Readme file
Doc & Wiki

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Check if the library provides:
● demo sources
● examples
● a demo in Google Play
Often a demo is the best way to see the features and it capabilities
Demo & examples

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The existence of unit tests is a good indicator of a serious project
● Few libraries have unit tests
● Unit tests requires time
● Unit test are very very important
Unit tests

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Is it good?
● Spend a few hours to browse the code
● Check how it is written
● Check if the authors use comments, javadoc, clean code..
Code quality

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Integration...

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● Does this library provide a Gradle support ??
Do not hesitate to open an issue to ask the author to push an aar on
maven.
Central Maven or jcenter

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What is Travis CI?
Travis CI is a hosted continuos integration and deployment system.
Some libraries are beginning to have this integration.
Travis CI

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Are you ready for….??

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Are you ready for…??
What if a day...
PLEASE NOTE, THIS PROJECT IS NO
LONGER BEING MAINTAINED

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Are you ready for…??
What if a day...
DEPRECATED

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Are you ready to explain to your
customer that a part of the project is no
longer maintained?

32. Droidcon Torino - 9/10 April 2015
Use an open source library
Can you work without them?
Write your custom code
Which are the alternatives?

33. Droidcon Torino - 9/10 April 2015
Write your custom code:
● Do you really need this code?
● Don’t reinvent the wheel
● Can you obtain the same result in a short time?
● Is it so easy to build this code?
Before writing a custom code

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PRO:
● Own code
● Without licence or royalities costs
● You can easily add a new feature
Before writing a custom code

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CON:
● It can requires a lot of time
● It can requires an extra budget
Before writing a custom code

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Use an open source library
Can you work without them?
Write your custom code
It could be not so simple

37. Droidcon Torino - 9/10 April 2015
A different point of view:
on the other side

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An incredible experience
2 years ago I decided to share a library.
I could not expect this…..

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1. IDEA

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IDEA
● Collect your ideas
● Collect your code
● Collect your examples

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2. CODE

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CODE
Writing for others is different from writing for themselves
● Make abstractions
● Write comments
● Write javadoc
● Write in a clean way

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3. PUBLISH

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PUBLISH
Brace yourself…
● Post a blog
● Publish a demo in Google Play
● Try to share your project

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4. SURPRISED

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SURPRISED
OMG…
● Emails
● Pull requests
● Issues
● Messages

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FINAL STEP…..

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Are you ready for…??
Now I can understand why I can find...
DEPRECATED

49. +GabrieleMariotti
@GabMarioPower
Thank you!