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Website to android app approach

I'm a newbie android developer and we have a website that sells some stuff (using a payment gateway), you can also login on the site using credentials, facebook, or google+ login. Now we have a need for an android and iOS app. What is the best approach to port the site functionalities to Android or iOS app? What are the issues I need to consider when I choose one approach? What would be the best approach: native, hybrid (phonegap, xamarine etc.) or using wrapped (using webview as far as I know)? I'm especially interested in the user login part (because I want the user to be able to login to his account if it exists and if not to create it using the website API endpoint - this is how I imagine it), how to solve that when choosing between these approaches? Any suggestions (answers, comments, links, books) would be helpful.
Thanks

My sugestion is to do native, always can reach more performance in multi thread ,high concurrency transactions and heavy applications.
For android, you can build from source an application, and export the html/css content to the smartphone using android.webkit.WebView. Take a look:
https://developer.android.com/reference/android/webkit/WebView.html
I think is a excellent solution for your problem.

converting desktop web app to mobile app?

I am working on desktop based responsive web application where UI/front end will be in HTML/JS and back end point will be either servlets or struts/spring controllers.
My question is say after 3 years i want to have android mobile app , can
I continue to use my servlet as back end code and serves the response coming from android mobile app,
Mine understanding :- I will develop the native UI part(wherever it is required) using android SDK which then can communicate with existing servlets .
Then android app on mobile can render the html returned from my servlets or servlets can return the android specific views. so changes are required only whenever i need custom views(htmls or android specific views) for my mobile application. Is that right ?

after 3 years... can I continue to use my servlet as back end code and serves the response coming from android mobile app
We have no way of predicting the future with accuracy.
Then android app on mobile can render the html returned from my servlets
To render HTML in Android, you use WebView (or maybe a third-party library, though that is uncommon). WebView handles lots of stuff but not everything that a desktop browser does. How well that all works three years from now is unknown, and how well it works today with whatever your Web site does is unknown.
or servlets can return the android specific views
No.
so changes are required only whenever i need custom views(htmls or android specific views) for my mobile application
Can you get that to work? Possibly, but the details will depend a lot on what your existing Web site does and what sorts of client-side technologies it depends upon. For example, Android does not support Flash. There are also technical and security issues with interoperating between Java based UIs and WebView-based UIs, though this is a bit better in your case, as you are only hitting one server (I think).
All that being said, I would never write an Android app this way, and I would never recommend anyone else write an Android app this way. I would revise the Web server to have a proper Web service API, and I would write a native Android app that uses that Web service API, not using servlets returning HTML. The primary place where I would use WebView is when I had material that only exists in HTML, typically because I did not create the HTML in the first place (e.g., user-generated content).
Primarily mine question is can I continue to use existing servlets. I don't think its based on opinion. It should be either yes or no
Of course it is not "yes or no". We have no way of predicting the future, and we know almost nothing about the Web site. Your question collected two "too broad" close votes, and that is a reasonable assessment.

how to make website compatibility for mobiles as well as pc's

i searched on net for web apps compatibility on mobile and pc browser finally i decided.make 2 websites one is for mobile browser and other is for pc browser.how to find out requested is mobile or pc and how to redirect website for mobile or pc.
If there is any other way for compatibility.Please let me know and give your good suggestion for this
Thanks in advance

Well, actually you can do it in different ways. The best solution is some script which checks the UserAgent first. I kow, its not that save, 'cause its easy to change the agent but why should someone do it and with which benefit of it ;)
So this should be your solution. Also you can optimize the websites to the specfic target device/browser. For example, for devices like iPhone, Android or WinMob you ould use Javascript Frameworks to work withthe website content.
I made a little post on another question which could help you aswell: Is there an equivilent of jQTouch that covers iPhone, Android, WebOS and Blackberry OS?

This is not as simple as one may think.
First, determine if the web app is accessed from a mobile device is not easily done. What is a mobile device? Is iPad a mobile device? Should all devices with a resolution less than 1024*768 be handled as "mobile devices"?
Second, designing a web application to make it compatible for all different devices - which in turn can have many different browsers installed - is not a piece of cake.
But fortunately there are some solutions as well.
There is WURFL -
http://wurfl.sourceforge.net/ - which
is an open source alternative.
Device Atlas -
http://deviceatlas.com/ - a
commercial alternative.
Mobizoft C4M - http://mobizoft.com/ -
another commercial alternative with
both an API as well as some
prepackaged solutions.
Wordpress mobile pack - http://wordpress.org/extend/plugins/wordpress-mobile-pack/
Any of them can be used to switch a mobile device to a special mobile adapted site. They can also be used to build/adapt a mobile friendly site, depending on what you need.
When you have built an mobile friendly site you should first of all test it devices with different resolutions/os/browsers. Another useful site is http://mobiready.com where you can validate the site.
A final tip is to consider which devices to support. Only iPhone/Android? Maybe have a full version for these devices and a simpler version for all other devices. Depends what your requirements are.
Good luck!

Developing a mobile version of a site

I'm working on a large website project that makes heavy use of in-page graphing of data. To make the graphs interactive (the old paradigm was to post data to the server, have the server render the graph as a jpg, then send it back to the browser) we've started building the graphs in Java. It's a smooth system, but the website is still very much computer-dependent.
I'd like the site itself to work as a device-aware web application - switching layouts based on user agent strings to render a mobile-optimized version for cell phones and PDAs. But I'm concerned about the nebulous support for 3rd-party applets (Java, Flash, etc) when it comes to platforms like the iPhone.
So if you were building a web application that could be accessed either through a standard web browser or an iPhone/Blackberry/Palm device, what would you do to still display interactive graphs? Is there a workaround for using Java on the iPhone? Is there another platform we should pursue all together?

If you want to support more browsers, you may want to look at using Javascript to help decide what to do.
You could generate the graphs using the canvas element, and if the browsers doesn't support that element then you could use a Flash app, and if that doesn't work, have the graphs developed on the server and use the <img> tag and just refresh.
This third approach could also work if the browser doesn't have javascript enabled.
This way you can handle the various situations and get away from having to run Java in the browser.

The iPhone and Android browsers support HTML5 features such as "canvas", which you may want to look into. The browsers on BlackBerry phones are somewhat behind the times - they are finally releasing a WebKit-based browser for their upcoming 6.0 OS but all of the current in-market devices are quite limited in terms of browser capabilities. For those devices you're probably best off just using a static server-generated image.

I would use a JS charts library and gracefully downgrade to images when you detect an older browser.

Blackberry apps: Native or webapps?

I have read the Blackberry documentation and it is possible to push a notification from a webapp. I am planning to create a Blackberry application that compliments to our webapps. But I am still left in the middle whether to develop a webapp or native Blackberry app. I have also look at how a webapp runs on Blackberry browser and it looks smooth.
From your experience does the native app offer something that the webapp doesn't? Bonus question, is Facebook and Twitter app on Blackberry a native app or a webapp? If it is a webapp, is it possible to make a launcher for the application on Blackberry?
Thanks for your help.

Facebook and Twitter are on both types. The web apps are just a website formatted for a small screen so anything you do in say asp.net will show on a blackberry web app if you program it to. The native app just feels like part of my phone. You can save data on the phone so if your app is a relating to news or something that would be stored I can read it offline or slow connectivity (camping, rural areas, etc...). It can also interact with other feature that blackberry offers such as contacts, email, media player, etc...
If you would like to save anything for the user to view without pinging the internet a native app would be preferred.
It's possible to create a launcher but I haven't created one so I'm not sure of the details. I would assume it's just an app that opens the browser to your URL.
One more thing about a web app would be if your application stores users settings (twitter auth key, etc...) they would need to be stored on your server and not the users phone adding more expense and maintenance.
Good Luck.

Widget is not supported for device software less than 5 , you combine both of web and native development by using browser field ,but you need to consider that its Java Script support is poor

Let's not forget that the blackberry browser is really bad as well. I don't know any BB users who would want to use a web application because of that.
When it comes to native apps, you have some choice however and you are not restricted to java (depending on which OS version you want to target). In addition to the mentioned Java, you can use Widget (link for resources) that behaves like a native app, but can be accessed like a web app.

I was just at innoTech and they had a whole session on this topic. But instead of recaping it let me just post the funny video they showed at the end which sums it all up.
Mobile Dev Rap Battle: Native Code vs. Web Apps