Interview Questions.

Question 1. What Is Scripting Layer For Android (sl4a) For?

Answer :

SL4A makes it possible to quick prototype packages for Android on the tool itself the usage of excessive-degree scripting languages. These scripts have access to many of the APIs available to full-fledged Android packages, but with a greatly simplified interface. 

Question 2. Why Sl4a? Android Programs Are Easy Enough To Write.?

Answer :

That's very true. Android's improvement surroundings does make existence quite smooth. But, you're tied to a laptop to do your paintings. SL4A helps you to strive out an concept now, inside the state of affairs in which you need it, quick.

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Question 3. How Does Sl4a Work?

Answer :

SL4A provides Android facades which make APIs available via JSON RPC calls. Only the components of Android's APIs which has been wrapped by using facades are to be had to interpreters.

Question four. Does Sl4a Compile The Supported Languages To Dex Bytecode Or Is There An Additional Layer Of Interpretation?

Answer :

It relies upon at the language a piece. BeanShell is run in the JVM and has an additional layer of interpretation. Lua, Python, and Perl are clearly the C variations jogging natively.

All interaction with Android is over RPC channels. Still, the RPC API is compiled to dex so there may be no additional interpretation in Java (apart from mirrored image).

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Question 5. What About Performance?

Answer :

With appreciate to the interpreters SL4A provides, Lua and Python are both cross compiled C binaries that run in their own manner. CPython is substantially greater performant than Jython (mainly considering the fact that Android does no longer currently support JIT).

As for the Android facades, the API is by and large centered on making it easier to write down scripts than at the performance of those scripts. That said, bear in mind the adage "measure first, then optimize." SL4A is ready fast development after all.

If you have got performance concerns in your utility, it's probably higher to apply the usual Android SDK (or NDK) where you will have more manage over the machine.

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Question 6. Are Scripts First-elegance Apps From The Point Of View Of The System?

Answer :

Yes, on the whole. You can invoke arbitrary intents and there are also plans to help broadcast receiver scripts. That is, you could write an app that consumes pictures and indicates up inside the list of apps while the user presses Share in the Camera app.

It is not presently possible to write a script so as to exit with a end result (e.G. Every other Android hobby begins your activity for end result).

Question 7. Is This A Complete Api Bridge, Or Are There Restrictions?

Answer :

BeanShell, JRuby, and Rhino essentially come up with a complete API bridge (you can invoke Java calls without delay). See the documentation for the ones interpreters for education on how to perform this. Cross compiled languages like Lua are extra restricted. They only have get right of entry to to the APIs exposed via the RPC layer. 

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Question eight. What Do I Do With All These Barcodes?

Answer :

Barcodes are a easy manner to get right of entry to a web link on your phone (e.G. To down load SL4A). 

Question 9. Where Are The Sample Scripts And Other Interpreters?

Answer :

As of launch zero.8 alpha, interpreters and sample scripts are disbursed one at a time. Please study InstallingInterpreters for guidelines on a way to upload them.

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Question 10. Can I Run Scripts As Root?

Answer :

If you have a rooted phone, you will be interested by doing so. At the moment, SL4A does now not support this at once. 

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Question eleven. How Do I Install Sl4a?

Answer :

Enable "Unknown Sources" below Application settings.
Install Barcode Scanner.
Scan the barcode on the home web page to down load the APK.
Tap on the downloaded APK to install SL4A.
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Question 12. Can I Use Sl4a To Write A Real Android Application Or Embed Sl4a Scripts In My Application?

Answer :

Yes! You can embed your script in a (often) stand by myself APK.

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Question thirteen. Will Sl4a Work On An Android Emulator?

Answer :

Yes. Use adb set up sl4a_rnn.Apk to put in it to the emulator.

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Question 14. Will Sl4a Work On My Android Device That's Not Built On Arm (e.G. X86)?

Answer :

Yes and no. All go compiled interpreters are compiled for ARM. Java primarily based interpreters like JRuby, BeanShell, and Rhino will work.

Question 15. Can I Run An Sl4a Script From My Application?

Answer :

Yes. See IntentBuilders.Java.

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Question 16. My Script Stops Working When The Screen Turns Off! Wtf?

Answer :

Your cellphone turns the display screen off, among different matters, whilst it is going to sleep. If an utility would not request that it hold running while the telephone is asleep, it's going to stop walking until the cellphone wakes up once more (i.E. You switch the display screen returned on). Requesting that the tool continue to be on while your application is walking is called a wake lock.

SL4A offers APIs for obtaining and liberating wake locks. It is important to observe that wake locks notably impact battery lifestyles. You should continually launch a wake lock as quickly as feasible.

Instead of the usage of a wake lock, you can also allow the "Stay unsleeping" device putting. From your house display faucet Menu, Applications, Development, and take a look at Stay wakeful. With that enabled, your smartphone will by no means sleep at the same time as charging. This does have an effect on the quantity of time it takes to price your phone, however.

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Question 17. Can I Use Sl4a For Ui Automation?

Answer :

No. For protection reasons, it's far handiest viable for the shell user to inject UI activities into arbitrary applications. See UI/Application Excersier in the Android documentation.

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Question 18. What Usage Information Does Sl4a Collect?

Answer :

If you permit "Usage Tracking", the application will collect anonymous usage information thru Google Analytics.

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Question 19. Where's Javascript?

Answer :

JavaScript is implemented the usage of the Mozilla Rhino project and V8. Look for "Rhino" in the interpreter downloads. Or, write an HTML script to apply V8.

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Question 20. Where's Php?

Answer :

There is a PHP interpreter, that's a separate mission. The PHP installer and interpreter may be located there.

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Question 21. What's Logcat?

Answer :

Logcat is a rotating log of messages that Android produces. It's a totally useful tool for programmers to work out what exactly is going on if a person reports and blunders. It's a requirement in our Issues reporting to connect a logcat anyplace possible. 

Question 22. Sl4a Won't Install Interpreters On An Emulator?

Answer :

In truth, SL4A works excellent on emulators, having been to a big diploma developed on them. But these interpreters require a chunk of room, and the default AVD length for a sdcard is on 16Mb. This is inadequate. I could allocate not less than 128Mb, and actually typically set mine to 512Mb. Bear in mind that it is unusual to get an Android device with much less than 2Gb nowadays.

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