Develop Reference

Multiple Language Support Android APP

I am very new for developing the multi-language oriented Android APP. This is the first time i am going to support my app in multi-support language app. I need some clarification for developing the multi-language support app. Already i have some ideas before initiate the development.
Single APK with Localization like will make the multiple String.xml and include it in inside of the app and based the member selection of language its automatically invokes and works.
All language strings values will retain in app server (back-end) and will raise the Rest-API request and get those values and change it inside of the entire app (all screens) if member click and change the language inside of the app.
Main concern is if anything needs to change in future then Idea2 is best way. We will just change in back-end side it will be appeared in client side. But if we are going Idea1 and wants to change then we need to put the new build only.
Which one is best approach and recommended way to develop?

You will need to create different String.xml depending the languages you want to target as JDenais says, in my app i have the following
for example the first arab string consist in the same as Strings.xml but with all in arab, now, you only need to call one string in your xml files and it will just select where to grab depending on the phone language. Or in default the language from where the app was downloaded by google play, in fact, they are all the same strings.xml , so you dont need to specify which one you want to pull the translated text from, just replicate your main strings.xml in your other strings.xml and then the phone will decide where to pull the data.
Also please read the official doc on how to accomplish this https://developer.android.com/training/basics/supporting-devices/languages
Also please check the language ISO Codes here
What is the list of supported languages/locales on Android?

All your texts should be packaged in the APK in different String.xml files. Forget about receiving texts from a backend. It would be a lot of extra work for limited gain and with added risks of failure.
The framework takes care of selecting the appropriate string.xml file and offers support for needed use cases like plurals.

right click the values folder and choose new-> values resource file -> locale -> choose the language you want and name it strings.
copy the strings from the original string file to the new file and change them to the new language just the strings
make sure that the view xml files have their text set as "#string/the_name of the string" not hard coded

Using strings from #android:string

I am a bit noob in Android and recently I found out that I can use the predefined string that Android provides as #android:string/cancel or #android:string/ok. At first I thought it was a good idea to use them because is a way to reuse code, but now I am not so sure about that.
What if somebody with a device configured with a language that I don't support install my app?
I assume that the app will use a default language, probably english, but those string from #android:string will get translated to the user's language, so he will end up with a mix of languages.
It this true? What do you think about use #android:string?
Thanks!
EDIT: Apparently my question hasn't been understood properly. I am NOT asking about how to support different languages. My question is about the convenience of use strings defined on #string:android, if it is correct to use them or can be lead to undesirable situation like a mix up of languages in the same application.

To ensure that your strings are appearing properly on devices configured with different languages, you'll want to create different values directories for different languages. For example, your default string values would be kept under values/strings.xml and French string values would be kept under values-fr/strings.xml.
The Android Developer website gives you plenty of information for supporting different languages in your application. http://developer.android.com/training/basics/supporting-devices/languages.html

The android: values (strings, icons, themes, etc.) will differ between devices and Android versions. If you want to use them, it's safest to copy them into your project. So for strings, you wouldn't have to worry about partial translation.

In the ressource folder of your app (res), ther is a folder "values" in it, and in this folder is the string ressource xml (strings.xml).
Usually, your app selects the strings from this file.
But you can add other value folders like this: Just create a new folder and name it "values-countryCode", for example "values-ch" for Switzerland ;)
Your app automaticly chooses the right string ressource, depending on your device's langague settings. If the langague of your device isn't available, it just takes the sting ressource of the default "values" folder.
A list if the country-codes is here.
Further information can be found here.
Hope I helped, and this is what you're looking for!

Change set of strings based on app purpose

I'm building an Android app that can be used for two different purposes, say biking and running. I would like to load the sport-specific keywords given a user's preference. They could be defined in different files, like strings_biking.xml and strings_running.xml .
How can I implement this as efficient/elegant as possible? I've taken a look at locales, styles, themes and lots of other topics in the Android documentation, but nothing seems to fit well enough.

AFAIK it does not support such distinguish as per category. strings.xml are used for localization only. For your purpose, you can define some prefix/suffix to the string name. While using them in activity, create string runtime by applying that prefix/suffix and string name for biking or running or any other condition.
May be this link can help for dynamic creation of string.

ANDROID: What is the main idea behind of using strings.xml?

Someone please explain what is the main idea of using strings.xml?
I think it would be useful for multi-language support but how can we organise it for that?
Do I need it if I don't want to use multi-language support in my android application?

The idea is that it represents a single location for various strings, so your code isn't peppered with string literals. In addition to that, you gain the ability to easily localize. Organization of files for localization is covered here:
http://developer.android.com/guide/topics/resources/localization.html#creating-alternatives
Do you need it if you're not localizing? No. But it may make things easier in the long run, and I would recommend using it just for that reason.

Hard-coding strings is Bad.
Parameterizing strings (e.g. with strings.xml) is Good.
Being able to internationalize your strings (with language and/or locale-specific versions of strings.xml) is even Better :)
PS:
To make use of internationalization, just create resource subdirectories. Google will give you plenty of references/examples. Herre's one:
http://developer.android.com/guide/topics/resources/localization.html
* res/values/strings.xml
Contains English text for all the strings that the application
uses, including text for a string named title.
* res/values-fr/strings.xml
Contain French text for all the strings, including title.
* res/values-ja/strings.xml
Contain Japanese text for all the strings...
And yes, you should absolutely get in the habit of using strings.xml (and colors.xml and dimens.xml etc etc) even if you don't plan on internationalizing immediately.
IMHO....

Defining Strings in res/values/string.xml?

What's the point of defining strings in xml at the res/values/string.xml directory? Is it more efficient than just defining the strings as constants within your classes? (e.g. Database table creation scripts, etc..)
Is it a matter of organization or is there some benefit in how Android handles these objects in memory?

So you can easily translate them into different languages.
So they're nicely organized and you have them all in one place.

You can easily translate your app if you use strings.xml. Just create a new folder with suffix like values-cs and put the xml with czech strings in it and the whole app will be translated to czech if you have set czech localization in your phone.

applications access them/compute them faster than normal strings
localization
The hello string is defined in the res/values/strings.xml file. This is the recommended practice for inserting strings to your application, because it makes the localization of your application to other languages graceful, without need to hard-code changes to the layout file.
language (computer) translation
For me the first point is the deal breaker, anything to make your app faster. (this is assumed from the countless hours of creating my own applications and being told using string.xml is best from an optimization point of view, plus, especially in a long listview, it does seem to load faster for me (droid A855) )