Develop Reference

Android application only in C++

Is it possible to make an Android application only in C++? I don't know Java. I've tried Visual Studio 2019 approach but I guess my computer isn't good enough for emulating Android phone.

You can write code for Android in C++, if you have the appropriate programming tools. You'll need a cross-compiler and linker for the appropriate architecture. These are readily available in Google's Native Development Kit:
https://developer.android.com/ndk/
I don't know if these tools can be used with Visual Studio -- I suspect it will be fiddly to set up.
The problem with programming in C or C++ for Android is that it's hard to integrate the application with the regular launcher and, even if you can do that, it's hard to provide a regular Android graphical user interface. Android simply does not provide a C API for the user interface.
I write/port a lot of command-line stuff for Android, so the lack of a graphical user interface doesn't bother me. However, most developers provide the user interface in Java and, if parts of the app needs to be in C or C++, it gets integrated with the app in the form of a native library.
Android Studio and similar tools know how to manage a project that has a mixture of C or C++ and Java code. Using well-established Android tools for developing complex, mixed-code apps like this is way simpler than trying to figure it all out yourself using a hodge-podge of tools from different places.

Xamarin.forms (or) xamarin.ios/xamarin.android (or) Native

We are developing an app in our organization where we have to implement charts,maps,GPS, If we Develop in Xamarin.ios/xamrin.android can developers able to share business logic of the app? since both android/ios projects will be in c#.

I'm doing exactly the same thing.
Do not use Xamarin Forms. It is not designed for nor capable of doing heavily customised UIs.
If you are going to require integration with Maps and also producing any kind of non-standard rendering or "User Controls" Xamarin.Forms is not going to work for you.
Go down the route of using a framework like MvvmCross to further abstract away the platforms and keep your core code / logic and user experience flow within the realms of a Core.Pcl type library.
Also I wouldn't try doing this on Windows 7 based bachines if you are doing this on Windows. Most of the components you will find yourself wanting to use will be targetting Profile259 and since Windows 7 doesn't support Windows Phone 8 you'll have all manner of oddities, even if you do the Profile259 hack.
Go with MvvmCross, Windows 8 and ignore Xamarin Forms.
I wrote a bit of it up on my blog.
Read this from Xmarin, they clearly state that Forms is for run of the mill business apps or for prototyping. It's not mature enough yet.

Yes, you can write your core app logic (services, data, domain, etc) in a PCL library that is shared by both your Android and iOS apps.

From my experience, you can build most apps in Xamarin Forms. The main hurdle is that doing anything not included in X.Forms requires that you write Custom Renderers. The thing is, writing custom renderers is much more straightforward if you have a solid grasp of vanilla Xamarin (Xamarin.iOS & Xamarin.Android).
What I think happens is that developers getting into Xamarin go directly to Xamarin.Forms and then become frustrated when they are unable to write custom renderers to accomplish some custom requirements.
So my recommendation is that if you have experience building apps using Xamarin.iOS and Xamarin.Android, Xamarin.Forms is awesome for getting an application developed rapidly for multiple platforms. Being able to use MVVM + XAML + Data Binding is a huge win.
If you are new to Xamarin or even mobile development, build the app using Xamarin.iOS and Xamarin.Android.

Is Visual Basic compatible with Android?

If something is written in VB is it compatible with android?
If so, can you give me some documentation?

No, you can not use programs written in visual basic on android. Android uses java. The closest you'll get is Mono For Android which currently doesn't support VB.NET.

EDIT: (7/12/2016): This is now supported via Xamarin
I assume you are talking about VB.NET, then Mono does not yet support it.
Currently Mono for Android does not support Visual Basic.
We are looking at adding support for Visual Basic on upcoming versions
of Mono for Android.
Technically, what needs to happen is the following: we need to provide
the Visual Basic helper library (part of Microsoft.VisualBasic.dll)
and compile it to work with the Mono for Android mscorlib.dll instead
of the standard Mono 2.0 mscorlib.dll
With the above it will be possible to use Microsoft's Visual Studio to
compile VB code that will run on Mono for Android. But we want to
support Mono's own Visual Basic compiler, but that will also require
the compiler to run using the Mono for Android mscorlib.dll. This is
not difficult, but requires time to get done and integrate into our
release process.
At this point there is no ETA on when the above will happen.
2: http://mono-android.net/FAQ
You could try however Basic4android if that suits your needs.

The closest you're probably going to get is VB.NET via MonoDroid, which according to their FAQ currently does not support Visual Basic. (But they do have it on their radar at least.)

VB is a Microsoft product. While there are some 'nix' implementations of .Net product like Mono, Android is unlikely to support .Net mainly due to liscencing.

MonoDroid VS Java in android development?

I know C# rather well and just love Visual Studio as IDE. :) Yet now I want to start developing for android...
I found out about MonoDroid and wanted to ask if it has any downsides to it that would make Java more preferable, or should I uninstall Eclipse and dive straight into MonoDroid?
If I understand right, MonoDroid deploys/compiles native android applications and does not need any additional .net-like framework or anything?
Are there any significant limitations to what I can do with MonoDroid? For example, having the app run in the background or using some external .net libraries for image editing, etc. ?

I've been worrying about the same thing - productivity in C# instead of playing with an unfamiliar language, vs developing how the OS developers intended it to be.
Its easy to list pros vs cons -
pros (of monodroid, for C# developers)
familiar dev environment, can develop using Visual Studio
C# instead of Java
Reusable code assets - you can use a lot of code in your iphone project or Windows phone 7 project using monotouch and the WP7 SDK.
cons -
debugging could be difficult, due to lack of api documentation from Google. Will have to depend solely on monodroid documentation.
there could be a lag when it comes to latest cutting edge features - safe to assume that the monodroid team will require some time to wrap around the latest android features every time there is a new OS release
availability of libraries - I am not sure how you can use the open source libraries that would have evolved around the android platform, that could cut down on development time

Much of the documentation available is in Java: so if you run into difficulties with phone behavior when using MonoDroid you won't really find that much help or debugging information so you may want to stick with Eclipse.

There's a lot more than just a set of wrappers running under davlick, truth to be told, there is much more of a horizontal relationship between MonoDroid and Android;
When did using the same language as the OS developers become a big issue? There's lots of C++ programmers wondering how to use BSD or SVR5 and many C programmers who want to know what the heck to do on Windows++...

If you will write in c# anyway you will be have to wrap it into a Java code, so what's the point ? Also you may head with a very difficult issues while trying to understand the APIs who written for Java programming...

Here are some points that you can mull over:
Android applications are predominately written with Java. The Android SDK itself is natively written in Java.
Working in Mono may not provide all the functionality available in the Java SDK.
If you are a C# Developer you wont be able to find, in Java, some of the (cool) features available in C# (like Property Delegates etc).
Code written in .NET can be re-used for other environments - this may save a lot time that would have been spent learning a new language/environment (like Objective C), and coding in it.
.NET extends the Android development stack with it's existing libraries and API's.
I think both are good for certain reason. It will be very hard to say which one is preferable for Android development - in the end that is up to you too decide.

Also note that any release build using monodroid adds an additional 4mb to the apk filesize and increases app startup time with a few seconds.
For simple apps this can mean a 500-800% increase in filesize - whic is pretty bad in my book.

Has anyone done or does anyone knows of a way to use Delphi/Prism to develop for the Android os?

Is it somehow possible to use the Delphi language (or Prism if absolutely necessary) to develop programs for the Android platform ?
Any starting point ?

There is Delphi for Android, a project by Lennie de Villiers.
Blog:
http://lenniedevilliers.blogspot.com/2010/09/delphi-for-android-sneak-preview-2.html
Screencast:
http://www.lenniedevilliers.net/preview/DAndroid_01.avi

Android applications are Java applications. There is a native SDK which should be use for particular needs and doesn't allow to build full applications, the application API is a Java API. Unless you have specific needs (i.e. portability), the best way to develop Android applications is using Java. IMHO using other tools that usually lag behind the main ones just to code with a different language is a waste of time.

No for the moment, but soon, check this link for more info about how develop android applications using the Object-Pascal language the Delphi-Prism programming language (wich is based on the Delphi language), with MonoDroid.
...and will soon be available from our
friends at Embarcadero, but it will
work with said release. So if you’re a
Delphi Prism customer, or just have a
fondness for Pascal syntax, keep an
eye out here – more info will be
available soon, including templates &
other support files.

You mean Object Pascal. I don't think it is currently possible. I don't think that crosscompiler exists...

There are couple of working examples in Lazarus How to create an LCL Android Application