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Is Xamarin perfect tool for a Camera Surveillance application? [closed]

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I am having experience in iOS application development in native platform and tools. I have a requirement to port an existing native application to Xamarin platform so that it is only a matter to maintain single code base for multiple platforms. My existing application has following features.
Api calls using AFNetworking Library.
Local caching of data using
Core Data, NSIncremental Store. Core Data migrations are implemented
to support versioning. Also complex mappings are done using many-many
relationship, one-many relationship etc.
Asynchronous and
synchronous network calls.
Listing items using table view controller
with Search Controller. Pagination is implemented in these view
controllers.
One of the views in the application is rendered using
Open GL.
Can all these features be perfectly ported to Xamarin. Does Xamarin provide apis for these features? Any help will be appreciated.

First of all, let me tell you that Xamarin is not about a single code base for all the three platforms, but you could share a good amount of code between the three platforms. But that will depend on each app.
To the best of my Knowledge AFNetworking has a partial support. This is repo for it: https://github.com/paulcbetts/AFNetworking-Xamarin . But if you plan to port your app to xamarin/ cross platform. I would recommnend using a C# variant, check if Modernhttpclient will help you?
Local data caches are very well supported
https://www.nuget.org/packages/SimpleStorage/
https://github.com/akavache/Akavache
Async progrmamming is one of the strengths of C#/xamarin.
https://developer.xamarin.com/guides/cross-platform/advanced/async_support_overview/
TableViewController and Pagination is supported
Hope it helps you to get started with porting your app.

If you aren't using any third party libraries you shouldn't have any problems porting this application to Xamarin.
Before you begin I would advise that you think about any functionality that you can wrap up in a core project and inherit in your iOS and Android projects so that you have the maximum amount of code re-use. Thinking ahead will save you a lot of time.
Also be cautious when using table and collection views. I've previously encountered a solution which was holding on to a lot of memory because the table view cells weren't being deallocated correctly.

Considering you are having experience in iOS application development in native platform and tools. there is going to be a huge learning curve.
Shifting from Android studio to Xamarin(VS2015) was a hectic job for me.
But maintaining the less code for multiple devices is really fun using Xamarin.
your first requirement is answered by this github link here
Asynchronous and synchronous network calls are easy to handle as I am using it in my project so that is not going to be the problem.
Happy Coding

When to use Dagger in android application? [closed]

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I know that Dagger is a dependency injection framework, but I have not still used it in my projects.
I am starting a new project and wondering if Dagger is suitable for it. As far as I understand, using of Dagger leads to a lot of boilerplate code and annotations.
So I am not sure if it is not an overkill for my relatively simple project.
A bit about the project. It is focused on image processing and main part of functionality is built around it. However, it will also probably have a simple backend for data storage.
In general, I would like to know some basic principles that I can use to choose using Dagger for a project or not.

Basic Understanding:
Suppose, you want to test your application that deals with Credit Card service. For testing purpose you must not want to Access a real RPCCreditCardService as it will need real transaction and other stuffs that you don't want to perform during development. In that case you must had to create a clone fake service that will mimic the same thing that real CreditCardService does but not transact anything. If you use the dependency injection framework you can define common tasks in a dependency and inject it in both fake and real service. It will minimize coding complexity as well as helps to make each module independent.
From the documentation:
By using dependency injection framework, each class is easy to test. You don't need a bunch of boilerplate just to swap the RpcCreditCardService out for a FakeCreditCardService.
Dependency injection isn't just for testing. It also makes it easy to create reusable, interchangeable modules. You can share the same AuthenticationModule across all of your apps. And you can run DevLoggingModule during development and ProdLoggingModule in production to get the right behavior in each situation.
Reference:
For more detailed understanding you can check this discussion.

QML on android - will C++ work for business logic? [closed]

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Doing some investigation on the feasibility of using QT/QML for an upcoming project. Client wants it initially on Windows and Mac desktops, with the possibility of iOS and Android down the road. They would like to know that what we build will move relatively easily. I'm not much of a desktop programmer, but what I see is that QML is designed to work with C++. As a result, it should be relatively easy to build an app that runs on Mac and Windows, and iOS will accept C++, so I can't see a lot of roadblocks there. But I'm confused about Android. I see folks talking about building an Android app using QML, but they seem to still be using java; I gather it uses the NDK in the background.
But if you write an application that has QML for the front and, and C++ for any guts not covered by QML, can it work on Android? Or do you need to rewrite the C++ piece in java? The app is not a simple one, so we are going to have to provide some logic outside of QML, at least, it sure looks that way. While we might save time and $$$ by using QT to not have to go native on the desktops and iOS, I see a problem with Android down the road.

But if you write an application that has QML for the front and, and C++ for any guts not covered by QML, can it work on Android? Or do you need to rewrite the C++ piece in java?
It really depends. You may need to go through the Java interface where the Android platform does not provide direct and public API for certain functionality. One example is low-level IO operations, like writing the serial port for usb-serial devices, but there is more to it.
In general, what Qt modules and third-party software based on Qt do is to use the QAndroidExtras add-on module introduced in Qt 5.2. This will allow easy backend integration into your C++ logic.
With that in mind, you could hide the Java implementation details in the background while you still maintain the C++ interface to QML. Therefore, it should just work that way.
Please see the following documentation to get the grasp of it:
Qt Android Extras
Here you can find one of those nice examples:
Qt Notifier - Demonstrates calling Java code from an Android application.

Why do iOS and Android force you to write the UI in the native App Programming language? [closed]

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:) When you write a iOS App, in order to use the UI like buttons. you have to write it in Objective-C. (Java on Android). I was wondering if anyone had any thoughts on the technical reasoning behind this. Why they might of done this. As you can write apps in C++ on iOS so I've never fully worked out why they didn't expose a way of making the UI in that. (Ignoring the fact that this is how they did it on the Mac).
Note: I know you can write apps in c++ for Android but the question is more why is the main UI i.e buttons etc forced to be written in a dynamic language for these platforms, why not expose access to it thorough C++ without having to write a crude wrapper or binding layer yourself.

I'm guessing that when the original framework engineers were working on their respective operating systems, cross-platform desires like UI support in a different language like C++ was at the bottom of their concerns. You'll have to realize that when deadlines loom, all of the features are prioritized only what is considered most important is made to work. Everything else is a consequence of that.
In the case of iOS, Objective-C is the language of choice for the OS that Apple uses. All of the MacOS app developers were writing in Objective-C so their developer based was in familiar territory.
In the case of Android, Java was already a popular language, with existing open source tooling and libraries (Eclipse IDE, Apache Harmony), so presumably they decided to use Java as the first class language for app development with apps running in a VM as a consequence. Alternatively the decision may have been VM first for the sandboxing of apps and Java was picked as the language for app developers. Or some other reason.
In either case any attempt to add in additional languages now that both are in the hands of customers means design decisions and trade offs along with a host of other questions like: how to add it in without breaking existing APIs, how to support it along with new features, how to test, etc. etc.
As you see more and more software, you'll realize that lots of stuff is just arbitrary or made sense at the moment of when it was designed.

iOS does expose a C API for drawing UI components; it's called Core Graphics.

Because the view itself is written in Objective-C, or Java, respectively. When in Rome, do as the Romans do.

Moving to Android from J2ME [closed]

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Coming from J2ME programming are there any similarities that would make it easy to adapt to Android API. Or is Android API completely different from the J2ME way of programming mobile apps.

Actually the Android API is much more powerful than the J2ME.
It is much easier to create an application for the Android.
Using the J2ME you are limited to simple forms due to the absent of swing-like libraries (though now there exists a library called LWUIT, avoiding the need to recreate from scratch a swing-like library).
In Android you will be able to create complex form very quickly, and software package for the android SDK is easy to install (while in J2ME you have to install the wireless development toolkit from sun, or install one of Nokia's, Samsung's or SonyEricsson's... it gets a bit confusing sometimes).
The things I had to change when switching from j2me to android were:
1/ The font and graphics class is easier to use on j2me. The API is more thorough on Android, but also more complicated.
2/ If you are used to the database storage of j2me (RecordStore), well you can forget it in Android. You will have to use a SQL-like databased, so be prepared to rethink your data model.

I've also found the path from Java ME to Android to be pretty simple. Here are a few things I've noticed:
There is ONE ui draw thread in Android. You have to be aware of the difference between calling postInvalidate and invalidate on Views to force them to update.
The actual bit-wise graphic manipulation is very similar. I was able to port large amounts of custom J2ME draw code by writing a few shims for drawRect and drawImage.
Android's UI library is much more extensive, much less useless, and much more complicated than Java ME's
Threadwise, you have to be much more careful about thread saftey with Android. In Java ME you can get away with not making methods synchronous or variables volatile most of the time. Not so in Android.
I will say, on the whole, that Android's UI library fails a critical test. I call this the "roll my own" test.
Your UI library fails this test if it takes me longer to complete a detailed task task (say, changing the background on one individual menu item) than it would take me two write my own Menu from scratch. Android fails the "roll your own" test by a factor of 3 or 4. In fact, if you look, the majority of the questions on this website are "How do I make the Android UI toolkit do my bidding?" questions.
Android is an amazing platform and it has been worth every frustrating moment I've sunk into it. It is, however, a young platform, and needs some serious work in times to come.

A good start would be to watch the Android architecture videos and look at some of the documentation.
http://www.youtube.com/view_play_list?p=586D322B5E2764CF
http://code.google.com/android/what-is-android.html
Google is very good about documenting. From what I've heard Android very very similar to J2ME in its goals. It may be slightly different in programming style and structure but if you have J2ME experience you should be more then ready to move on to Android.
Good Luck!!!

Well, you may not actually need to adapt.
There is a good chance that a J2ME stack will become available for Android before long since Android is not supposed to become as restrictive of third-party runtimes as the iPhone.
I know one guy who has been working on just that:
http://justanapplication.wordpress.com/
Now, of course, that doesn't mean you shouldn't have a look at the Android APIs and application lifecycle.