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Android KTX or Anko

I'm a little confused about the advantages and disadvantages of using Android KTX vs Anko. Because both libraries are trying to achieve the same end goal, and the line between them it's getting a little bit blurry to the point, in some cases, the same functionality is available in both libraries.
I will be very thankful if you help me to clarify the mission of each one, and their use cases.
Thanks in advance!

Anko is a project JetBrains started while developing Kotlin and making it relevant for Android. I'd qualify it as an early production-ready showcase of Kotlin possibilities.
Anko is well known for Anko layouts, but also has some extensions for Android development in Anko Commons, and also a few other modules like SQLite.
However, Anko libraries have accumulated a significant number of methods updates after updates, which today make the library relatively heavyweight when you are limited to 65K methods per dex file (I prefer staying with a single one, for apk size and performance reasons).
Anko commons provides extensions for Android, so it's similar to Android KTX in a way, but it's not as well integrated and organized (packages and artifacts wise) as Android KTX which is now part of AndroidX, which is part of Android Jetpack. Making the libraries smaller, and more loosely coupled is part of the Android Jetpack / Android X philosophy BTW.
So Android KTX, is clearly the future, and I see no reason to not jump in the ship, or rather, not letting it jump in your Android projects.
Also, as you yourself pointed out, future Anko versions will deprecate (and probably finally remove) overlap with Android KTX, to provide only features that are not in AndroidX.
Includes a shameless plug:
Since you're talking about Anko, if Anko layouts got your attention, but you experienced struggles with them (especially when interacting with custom or third-party views), I'd recommend you to check out Views DSL in Splitties, which is more flexible than Anko layouts, and very lightweight. The other modules may also interest you. I started this project to leverage Kotlin features in my Android projects at work and at home.
You've not asked about it, but here's my take on Anko coroutines:
I find the bg { … } extension confusing. I prefer to use kotlinx.coroutines with the Android artifact, using launch, withContext, etc, along with Dispatchers.IO.
However, the Anko coroutines listeners (e.g. onClick that can suspend) are not a bad idea IMO.

Anko is a Kotlin library from JetBrains. It shares the goals with Android KTX of making your life as an Android developer easier and making your code more readable and pleasant to use. Android KTX and are Anko are similar but not quite the same.
Differences Between Anko and Android KTX
They have common goals but with different scopes in mind. The mission of KTX is to bring idiomatic APIs to Kotlin users. KTX does not intend to add new functionality to the existing Android APIs.
Anko has a wider scope, and this gives it the flexibility to innovate and create new features
Deciding When to Use Anko or Android KTX
Generally speaking, Anko and Android KTX cover different parts of the Android API, and there’s no reason you can’t use both in your project. Investigate each one individually and use either as much as you want in your projects!

What are the pros and cons of android data-binding?

Both of my colleague and I have experience in MVVM of Web App, while we are new to native android development. Now we have contrary opinions about android data-binding -- I'm a fan of it while he is not.
My Arguments:
Reduces boilerplate code which in turns brings
Less coupling
Stronger readability
Powerful, easy to implement custom attribute and custom view
Even faster than findViewById (details)
His Arguments:
The auto-generated .class increases app size.
Harder to debug
I've made some investigation but there are not many discussions about it. Now I want to collect the pros and cons of android data-binding.
Aspects of discussion include but are not limited to:
unit test
app size
performance
learning curve
readability
coupling

I will comment on your arguments first then I will state my opinion:
1.Remove boilerplate code - it will remove some it will just move some in the xml or it will require additional classes. So you have to be careful and balance the use of data binding.
2.Stronger readability - depends if you are a new developer then you may find it easy to learn it but if you previously worked on android you will need extra time to learn it.
3.Powerful - the code has more power, you can implement whatever you like in code. Think about it like this, everything you implement using data binding has a code equivalent (it might be longer and more code to write), but the revers is not valid.
4.Even faster than findViewById - comparing the speed between these two, in my opinion is useless, you will never notice the difference, if you see some difference, then one of the implementation is wrong.
5.Auto generated class - it's true it will increase the app size, but again only if you have tons of it it will matter. It's true that on the android dev web site they state that it's kind of bad to use libraries that create autogenerated code or annotations that will generate extra code.
6.Hard to debug - depends, like readability, of what you are used to, heck debugging is hard either way for some problems, and you will get better by debugging not by using a different library.
So this is pure my opinion, I've developed many apps using different libraries and different approaches, and they all had pros and cons, but what I've learn: balance everything, don't use tons of libraries, don't waste time implementing things that are implemented already and work well, don't "decouple everything", don't "couple" everything, don't use code only, don't try to "generate" everything.
I think it's quite wrong, and you can get a wrong idea, if you ask for 'pros & cons' about some library/implementation, because usually it won't be impartial, you will get a lot of pros from somebody who used the library in a specific way and it worked and others will give you cons because they used different and it didn't work.
So in conclusion, I think you should check what the library can do for you and what can't do for you and decide if it's good for your setup. In other words, you should decide if a library is good for you not other people ;).
Update - 8 August 2018
First of all I still stand with my initial conclusion, balance is the key in these kind of situations, but in my case, data-binding speed-up a little bit the development process and also improved it. Here are a few new points that you should all think about.
Testing the UI -- with data-binding it's much more easy to test the UI, but data-binding it's not enough for that, you also need a good architecture and using the Google suggested architecture will show the actual power of data-binding.
The most visible changes were provided for points 2 & 5 from my original answer. It kind of was easier to read the code after we decided to use data-binding, and the most important thing here is: we as a team decided that we will use data-binding and after that, we kind of expected to have most of the trivial and basic UI setup in the XML file.
For the debugging part, here's a little bit tricky, Android Studio has a lot to improve on the errors and autocomplete for the data-binding but the most common errors you'll get them after the first 2-3 occurrences. Also I've learned that a "clean project" form time to time, helps A LOT.
Another point that you'll have to take in consideration is the project configuration to use data-binding, right now AS (3.1) supports by default data-binding (just set a flag in graddle) for Java, but I had some issues with Kotlin, after a bit of search here on SO, I managed to fix everything.
As a second conclusion (from my original post), if you can and the project deadline/requirements/etc allows you to try data-binding, go for it it will worth (unless you do some really stupid stuff :)) ).

I am working on a huge Android project and the team has decided to phase out Data Binding library. Why? The primary reason is that it is exacerbating build time(10+ mins), by generating a lot of classes in the build process.

Even if i like danypata's answer i would like to add/edit some of his statements to android databinding.
1.Remove boilerplate code - As written in danypatas answer it removes some code and adds some code somewhere else like in layouts. That doesnt mean that the boilercode isnt reduced because usually it is reduced.
For example you may want to create a bindingadapter, which handles several custom arrayadapters for your spinner/recyclerview/listview/.. but requires only one simple adapter. You may want to use the adapter in your layout by using e.g.
app:myCoolAdaptersData="#{model.mydata}"
Now you can create your generic adapter and (re)use your bindingadapter in all your layouts instead of using for example:
ListView lv = findViewById(...);
CoolGenericAdapter<MyModel> coolAdapter = new CoolGenericAdapter<>(...);
lv.setAdapter(coolAdapter);
This is just one simple example which recudes the code alot in larger projects. Another sample to recude code is, that you bind your model to your layout. Updating field-values of your model usually updates your model aswell (if its at least a BaseObservable/ObservableField).
That means that you dont need to find all your views, update your views, update your models, ...
2.Stronger readability - The extra time spent for learning databinding doesnt really matter. Since the layouts are not really different except that you wrap them into a layout tag and put your namespaces there, it doesnt really differs from "regular" layouts. Using bindingadapters and accessing the model in the layout may take some time, but usually you can start beginning with the basics which are easy and beautiful to use aswell. Learning new stuff always takes time, but you will easy overhaul the time when using databinding after a while.
3.Powerful - Yes, its very powerful. Its easier to reuse existing code, reuse existing bindingadapters and may lead to more generated code but thats not always true. For example you may create multiple adapters within several classes instead of creating one bindingadapter, it may be hard to "optimize" it later. Optimizing the Bindingadapter means that it gets updated everywhere. Optimizing may decrease the "lines of code" since the boilerplace is reduced anyway.
I agree to 4. and 5.
6. Hard to Debug Since AS 3.0+ outputs useful hints like syntax issues in your layout (line number and file) its easy to debug databinding generated code. If you have problems finding the issue you may also want to check for errors in the generated code. Some librarys like dagger 2 or android architecture library may confuse you because the error lines doesnt match with the real "error". This is due generated code by other annotation processors. If you know that those annotation processors may get in trouble with databindings error outputs, you can easy fix that.
7. Unit Testing Its possible like if you dont use databinding by using executePendingBindings.
8. Readability Readability may be better without databinding. Since you put some business logic into your layout, some into your real code, it may lead to spaghetti-code. Another problem is that using lambdas in your layout may be very confused if the "layout-designer" doesnt know which param may be used.
Another very big problem is that bindingadapter can be everywhere. Using BindingAdapter annotation generates the code. That means that using this in your layout may lead to problems to find the proper code. If you want to update a bindingadapter you need to "find" it.
When should you use what? For larger projects it is a really good idea to use databinding together with the mvvm or mvp pattern. This is a really clean solution and very easy to extend. If you just want to create a small simple application you'r fine using MVC Pattern without databinding. If you have existing generic bindingadapters which can be used from other projects you may want to use databinding, because its easy to reuse this code.

Data binding, concept wise looks promising to me, but I do not like the implementation part.
I would appreciate a bit more simpler and direct approach to it.
Thus I feel lot more comfortable in keeping it old school.
Model classes, mutable objects, observers feel like too much to me, if some how the data variables used for binding are received as Objects that are mutable and observable directly in a class , then that would make the process lot more cleaner, simpler and concise.

Dagger and Butter Knife vs. Android Annotations

I am evaluating Dependency Injection (DI) frameworks for an Android app. The top contenders are: Dagger (with Butter Knife) and Android Annotations. I understand that Dagger and ButterKnife are from the same source- square and they complement each other. Here're are the key matrices that I am looking for:
Ease of use (our build is based on Gradle and we use Android Studio IDE)
Testing support (we use Robotium for functional testing and RoboLectric for unit testing)
Performance (DI frameworks use reflection, which one is faster?)

AndroidAnnotations
uses compile time annotation processing. It generates a sub class with an underscore apppended to the original name (MyActivity_ generated from MyActivity). So to have it work you always have to use the generated class for references instead of your original class.
It has a very rich feature set, see the list of available annotations.
Butterknife
uses also compile time annotation processing, but it generates finder classes which are used by a central class (ButterKnife). This means that you can use your original class for referencing, but you have to call the injection manually. A copy from the ButterKnife introduction:
#Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_activity);
ButterKnife.inject(this);
// TODO Use "injected" views...
}
The feature set is not so rich, ButterKnife supports view injection (AndroidAnnotations equivalent would be #ViewByIdand #ViewsById) and some event binding (for a complete list see the namespace directory here, just count the OnXXX event annotations).
Dagger
is a DI implementation for Android, similar to Guice. It also uses compile time annotation processing and generates object graphs which you use for manually injection. You distinguish between application object graph and scoped object graphs for injecting e.g. in activities. Here you see an Application.onCreate example:
#Override public void onCreate() {
super.onCreate();
objectGraph = ObjectGraph.create(getModules().toArray());
objectGraph.inject(this);
// use injected classes
}
I found it is harder to start with dagger, but this might be only my experience. However see some videos here for a better start: 1, 2
From the feature set point of view I would say that Dagger implements functionalities which could be compared to AndroidAnnotation's #EBean and #Bean functionality.
Summary
If you are comparing ease of use, testing support and performance I can't find much difference between using AndroidAnnotation and ButterKnife+Dagger. Differences are in the programming model (use classes with _ instead of using the original ones and call the injection manually) and in the feature set.
AndroidAnnotation gives you a full list of functionalities, but ties you to certain libraries. For example if you use it's rest api you have to use Spring Android. You also have annotations for features like OrmLite (#OrmLiteDao) regardless if you use OrmLite or not.
At the end it is a matter of taste, at least in my opinion.

Here is the Nice article in Dzone blog.
We to need to compare the features of each, such as :
Minimum Jars required
ActionBarSherlock compatibility
Injection for click listeners
POJO injection
Performance
Only Pojo Injection missing in butterknife! So looks like Butterknife is the winner!
Source

Google does ask specifically not to use dependency injection.
But by reading their request they seem to be referring more to the Guice and reflection based DI library's. Libraries such as android annotation use no reflection instead employing compile time generated code, while butterknife and dagger uses a small amount of reflection optimised for android but are supposedly slightly more powerful than android annotation. It really depends on the project and how much of a performance hit you are willing to take. In my opinion just using butterknife is sufficient to speed up code development by itself. If you need slightly more use android annotation and lastly if you are willing to take a slight performance hit due to reflection the best option without absolutely destroying performance with a powerhouse Guice based reflection use dagger + butterknife.

You should give a try at Toothpick.
Toothpick is (per the README):
pure java
fast, it doesn't use reflection but annotation processing
simple, flexible, extensible & powerful, robust & tested
thread safe
documented & Open Source
scope safe : it enforces leak free apps
test oriented : it makes tests easier
it works very well with Android or any other context based framework (such as web containers)
It can even be faster than Dagger 2 in most cases, and it's much simpler.
Note: Yes, I am one of the authors.

Use Android Annotations or Butterknife to ease your coding. But don't go for Roboguice! Roboguice forces your activies, fragments to extend to roboguice classes. Not fun, at all!
Dagger 2 is a much better option. You can use it along with Android Annotations if you'd like. I would just use Android Annotations for a simple app, but these days is good to work more with Dagger.

Seems like Google chooses dagger, as they are developing it jointly with Square, who created it.
Concerning Butterknife and Dagger themselves, there is the SO question difference-between-dagger-and-butterknife-android which clarifies how they complement each other.

The reddit-thread mentioned by #ChrLipp has someone who used all three on the same project, speaks highly of dagger+butterknife but also gives AndroidAnnotations its place:
For dependency injection, butterknife is used for Views, Dagger is
used for all objects and is highly recommended and Android Annotations
creates more of a framework for developing Android instead of
injecting objects into your classes so each library are quite
different from each other. Dagger is equivalent to Guice but is much
much faster. Dagger is more powerful then ButterKnife and Android
Annotations as it injects all objects rather than ButterKnife and
Android Annotations which only inject a certain set of objects.
Dagger can be a pain to setup and configure but is well worth it once
you have it done. But then again, because these are all quite
different from each other, it all depends on what your needs are for
the project.
Also, speaking of each one being quite different, in your project you
can use ButterKnife, Android Annotations and Dagger all in the same
project if you really want to. They each have the same idea but do
something different so you could use them all.

Eventually if you use one of the three, you'll have a hard time transitioning to Android's databinding. That's what's fastest if you need to consider performance:
https://developer.android.com/tools/data-binding/guide.html

Design Pattern in Android? [duplicate]

I'm working on an Android project and I would like to know any recommendations about what's a good architecture to build an android application.
I want to use dependency injection using Roboguice and I've been reading about MVVM pattern or MVC pattern (Android MVVM Design Pattern Examples).
Also I know that roboguice have a pretty cool Context-Based Event's raising and handling feature that could be very testable as the code is decoupled.
Any recommendations on a working design pattern? a testable and scalable architecture you have worked with or developed?

The Android platform provides a common set of design patterns, and with the limited hardware resources you get compared to Web-apps it is still often best to stick with using these directly in production code. There are other frameworks that sort of "wrap" the base platform; these are worth looking into if you have a specific purpose (or perhaps for prototyping/experimenting), but for the best level of support you are generally best sticking with the standard components.
This is a great resource when working on UI solutions: http://www.androidpatterns.com/
Specifically for DI: There is a Spring framework for Android, I've had a play with it and it looks quite promising. You've already mentioned Roboguice as another alternative to this. However, to avoid performance and library overhead, I still find the easiest approach is to write a simple reflection-based class that registers and injects dependencies within my own code. Similar to this approach, except I usually move the injection code into a separate singleton and reference it from there.
In my experience most of the third-party offerings are not yet mature enough to rely on right now, and don't really give you much on top of what the base platform provides. They are constantly progressing, however, so be sure to experiment with the big names from time-to-time.

Does it make sense to use Guice for Android

I'm debating using guice in an android project that is quite complex and has a lot of business logic. Guice seems like a good fit, but whenever I start reading deeper into it, it starts to look more complicated than it needs to be.
One thing I don't understand is: if Guice is so great and the best way to write java code, how come there is so little Android code that uses Guice... and why didn't Google use guice internally for Android?

Guice totally makes sense to be used and in fact is used in a whole bunch of applications. The extension RoboGuice adds some niceties for Android that makes it super productive to use.
In fact I can not imagine writing an Android app without it. Too painful.
Check out the links to apps using Roboguice on the website (e.g. Google Docs, OpenTable...). Also other apps like the Square app are known to use Guice directly.
It totally makes sense .. go do it!
Together with Robolectric it will also make your testing efforts easier.
PS: I am a committer on RoboGuice so I am partial ;-)
PPS - June 2013: Recent developments have given rise to other annotation/dependency injection based frameworks that do most of the work at build time and therefore avoid the performance hit of the runtime reflection (that is slow on Android) and are therefore more suitable for performance critical work - check out Dagger and AndroidAnnotations if you are interested in that.

Actually google discourages using Guice or RoboGuice in android applications due to memory overhead.
Source:
http://developer.android.com/training/articles/memory.html#DependencyInjection
5.11.2014 Edit:
There is a dedicated fast dependency injection library for android. I can see more and more people using it:
http://square.github.io/dagger/
13.04.2015 Edit:
Google released its own version of dagger, which does not use reflection in runtime:
http://google.github.io/dagger/

You know there is RoboGuice? It's Guice for Android.

The problem with demonstrating the strengths of a dependency injection framework is that it isn't possible to achieve it with a simple Hello World application. These frameworks show their value only in big systems with a lot of complexity. Also, they have a somehow steep learning curve.
Therefore it is quite normal that you can't find enough tutorials - open source projects that use Guice. This will be most often used in enterprise applications that do not get published.
As why Google doesn't use Guice, Guice doesn't fit everywhere. It adds a perfomance overhead and it doesn't make sense to use it in places, where it isn't needed.