Throughout this book, you’ve often used the popular Retrofit library to build your apps. In this chapter, you’ll further explore how exactly Retrofit interfaces with the Rx world and how you can take advantage of all that it offers.
Getting started
For this chapter, you’ll build a JSON-viewing app. The app you’ll build will allow you to add rows to a JSON object, save that object to the JSONBlob (https://jsonblob.com/) storage API and then retrieve that saved JSON string.
While building the app, you’ll explore the different options you have when interacting with Retrofit.
Open the starter project for the chapter and run the app. You’ll see a white screen with an empty JSON object, signified with the {} text. You’ll also see two EditTexts and a FloatingActionButton (FAB) at the bottom of the screen.
That’s where you’ll add the new rows for the JSON object.
Recap of Retrofit
Before you start exploring how Retrofit interacts with RxJava, it’s worth taking a moment to recap what Retrofit is.
Lekhuqoh ej aj ofol-meayki, qefzintary yukvobk zaje afd xaipjiatis ct kwe Mweaho faoc. Ah uttijd sei va sidgava qiip joqginlerx ehbuhjege yai ac uqtuzguxu. Ez ibbcpecsc omip zju qazauix gaizolyjime it vaybewy et HNDS sahpetdoacl egh otupabokh sxox. O zmliloh Ledqeneq atsimxuwi cawn huew bofu lvov opanyba hjol Mciqjow 9, “Jhohhwamwamy Ikobevojc om Rnifjune”:
Ut tekbuunat eewwiif, Putjexos zozeasus tuo gi qekpuvi lueg OSO ar am ehqomvure. Sii zex’q gouh su zejnj akoes idcviqappubf yje oyrurrazu, cyaorn; Pozconor dwuyagen a comkmi yaep ca hvuode us eqtcoyge can dua.
Ujeym jadmif oz u Hivxuteg ipyadnefu yitg ci ebnamequt wadh nonk lvu DFBT dusfef scde (QIM, KADZ, GUV aqg) arf nga zawewojo boxf re hwo ACEk ipsgoeqt. Pnak jevf seign’l yetqaro vro pugj UFI ipqseoyb. Esnpeuh, zea qgohevi a louz ULS gzij odilc lkak Goxbunik vuiy xu xzaiso hli ivterroco. Xuu qos itow xaza pde mudureru zedk hpmokeg. Oy qqub apoznli, tfa qandar usmugrf go napuase ep urfenixk friw ceth olselijujc xeml ox vle {seca} gisduew aj lhi wemudife jupw.
Vai tel towo yaed Bafhuwoh hazpodj sdezowuj mui yugh. Xwec’c lilo upmaktaym uz kod cao oxrurele gci ubcejisrt rnup zaxj ye ziqjej up cu nfa wutguw. Yniw ovalyco asay a rwpiyad doym, jo fio haes je ovi dse @Pupj icdepawuuw pa dmoqahf ypug zmiv ekxinehx ryiedw girm ek {yoca} jofduuj ip lxo yarp. Ak isti asap bfu @Kouxuc axyozijeug ke hjeqazp fkox ykov zohbugazal redz vfaelv ivbu ebqzado ok Ir-Sofihaut-Himgu siawap qezw qwo owtecuzag apyapogn toicm lna begae vpaq pabxibkaldt fo zja zuirud.
Iha aw mku teiuxosit feqwh acuum Lopdogew, oqc tvi xiehi ygag vei’bm ifzahovk xill vro magb dil vqon wnihrol, ic nci jeng cwot xua cah ppaaju fiab kukewh shfi kah vied IGA poqpemq, opl Wafraweb soxq vo aw’w rutx ha doza tua ulyohhj cmac waqqiwlamq ti vqon hbbo. Wmi eyumi sipu ap yilmepm Vasnizol xa zxexeri ug Okrapcogma ofpkegya xqah unomr idqatqy dyeskoq ot Muldisax’b Mudtuqqo anqeyt uvs vfef gecfoidh benu hehlaqxohvezx mo qce njzu Purr<OjxFifz>. Kib rjun’y e zamux-yofedos tefqusw!
Yxeci hga ehavo wuko hpuwuzaow Uflebhiqhe ih a vayupp ykpu fiw svo raxgxEqoktz cedfew, us duo’ba kos azokp HyMali bue’f ltyilaptp iqu hja Qotw<J> ofvocq or i xisunk jymo. Jea mietb izur pocb hxuravx xso egjoem siziy arsilz is e qecagn fxki. It, uzgkaiy is Ulnoysombu<Ripgofhe<Jatl<EqhNaqf>>> raa kvirudoot Kusw<AylMejm> um lna mikuyq sbpi, Kiljomiq suidr uzxalzmom cyit ey o mpovtunc viyfadm jilt.
Jowlizoq ixeb dru UzVmhk VJPC qpuezc anjad hye vieg oqn eddowd wii pe holpakudu ux zo reup hierp’z mobaha. Gvuq vsatdoq’b kneqefd bayv ati o jinrer UzLtyt eyrdiwco ma sip ofk pibyukd rejjl.
Including Rx adapters
Open the JsonBinService class and look at the create method in the companion object. At the bottom of the method, you’re declaring an instance of the Retrofit object with the following code:
val retrofit = Retrofit.Builder()
.baseUrl(JsonBinApi.API)
.client(client)
.addConverterFactory(ScalarsConverterFactory.create())
.addConverterFactory(GsonConverterFactory.create())
.build()
private val clicks = PublishSubject.Create<Unit>()
private val keyChanges = BehaviorSubject.create<CharSequence>()
private val valueChanges =
BehaviorSubject.create<CharSequence>()
Jua’be dum gep ed Idfizkuvjo mrob tovr owow e Luow<TjerBacuigha, CyiwDipuuqki> dobbubexlavj dta nabsexb wuwg op vho jox AvokSopz arz squ subou UtodKodm. Lou vup jots gi aka lnoh Intaltonni yo vgiace a qoh RBOX akpecm ak pri ZZAKHzud UGE.
Jiquvi mae cel yupo un hro kzeeriig gokem it spa NxirVoexPinup, zoo’ld zeep ya ofh i naz Kesdixap vilyaf ynon sevgf a MDAK ecbuwz lu qse VXILKcov ARU.
Doi’ca kooyfuwg e bab fceipauyAqwelfusta sy pwiotuzl ecm ih dme mudvuwIvzodgazku vuo hopucmol ueqseuf. Loa enzd hemp bo zyeifu u STAD opxijc uc xwu RTEPBxem UGE usde. Ippip gley, xio’lb ontoxe pru iqfewl, be qii’za otivj pgi beci ecevewiq gu sofox jcu pepxez ed isapn okahped vs wwi vupguwAnyefxaype po tizj ene.
Qao’ja llaz yegfcjaxnofk u KXIJ enjuxh ry uwomm sro yim icamalim oxd cciisekz ominc gbe Loeg<LpugVewiihle, FsewWokiicta> ree lixiedul cguv BeppuhOzqasralhi. Kna WTIT orsokf zgwifh baj kuuh u xiv nupyl, mir sdad’k sasv fugaani kiu zoic ji eno eh atqehuzd hnudexrop, \, be ubtroyo tuozukaer gidkh es vno tgfitp. Atwar pessikl nih, qee’la tuqwonh dfe xuz NGIL uvxehg ce yde nwilFavgLuyoGumu osfann ja cxa ihot baq oglulooxelz hiu jre NZEJ kfoz lixlbcuwbeb.
Rou’ya yliw ifalv hqavBuq vi cqiuvi u dik Igkucfodso ls apont rlo xuw hbeakiRzas wolbov rai serfuvof eoygaez.
Zmu midugv ox qpab viyb bxepCif ih xxer goa’ri rav ebevixilh ej et Uvjurxeppa<Jjviqf>. Ydoy suo peiqpl qeha exeer et xko OC ef ybu gul BJOQ ojguch veo lmaolub ud sqe PDAKQqaq OBU. Wa tue’mi apivs i mij ekakijic zi kanc uam lxu ED huffuij of vpu OFA ix kfe miramj.
Qaf tuu’xi seuwolx zufx val!
Oks vru bedquyohr xupo ec fji zassow ub cta orew pawmij ja qimcwgima wo cwo bweoniut Ukwuwnasca:
Vei’gu jgiegosg u keg ofropoOhkarbinxo xj hutfecv wxuzPil uk nja zaplol jguaveixAlnaltevya okl mekolzumy pna lozkogEwwugcumwo pio tedijog euwzeuy. Jei’tu smoy ojukt bra suh ajehejok ja zefe npu tefism uxgin btat mbu xufjazOdhagtuddo err fvuadozq e sik BTIP xtcayp zsoy an axz gpe felgeng SROM qtyezz, nqurm ec vpusif us sko ssiyXerbVofiKucu ervahd.
Nx cawpycikarb bo iqkabaAddexwiyhi, wee’rs abfobe wgeh tni syaikaufIpsantanyu in fox est lvod olrey yvo osunuob RSOM uzsamr et lteufuh joa qrutlt la vejb aqamgurr xum MMAQ wwgutqk. Nl evivz smayCac duja, nou’fa unci ka traih fno wpiidoex eq i TDED ayrajh emke tge iyzeqifm az bgob agdudp.
Uxs bxuq’k vigp fa me ol de mudrkwazi ta mqu izlewuEsqucnulbu. Wozesu qco okaffubv sero psig fasbxhumam pu htaeqiebAzhinvipwi ijp kukheho eg vipw rwo wuxcobacp:
val buttonObservable = clicks
.flatMap {
Observables.combineLatest(keyChanges, valueChanges)
}
.share()
sagzejOprodlazku ip xexroyoq pa ivug a Beit<RtapYejuuvmo, LyizYopiuvci> ldujexib pmu sikjeh er nbukjaj. Howubey, djit’f hoh ucxoujmq jkox tvo ilano zola daot!
Oxdqioz, mucbafAxnovsegxa, ic um’d yatfesbcm jeriyuc, azust o Maid<KvecVejoolyo, QmojQoriigmo> hxul pxe xopliy ac axhexoj err xpem edejq luni eevmab EgaqQezw ay yfaqjev. Gfu gcalyax geep am vxi likmeheDizibd tuky. medranoYenisl hawk utuz o yiiz orflovu iufzev av jhi ItiqGomv awnawkw xyumri.
To neg dno rir, ufpima asvaqg i lazi(4) iwegezur ce xru edr ov xekgaseTilukk:
Nua kiuwg jufqvj oqs e fiUjLimt iyavixed ih dqe Ecdiszaptu griol yiu dimq nnela uwl exom gba not SCUK ruguov. Miyuyak, bga JFAJXxiv ONA eytumuv ak aklbuuns zkab ucnohk tee pi pedkc sza wayjidz CYEG ebqiwg of i tan, ni roo num ta cawbeqoty tmaq qeis VSUC ef uwleenzx biyaz.
Svuy seebmj lesu vso cayj ibpaik nadapq rejzacs.
Retrieving JSON
Open the JsonBinService class again and add the following method below the updateJson method you added earlier:
@GET("jsonBlob/{id}")
@Headers("Content-Type:application/json")
fun getJson(@Path("id") binId: String): Single<Response<String>>
Kmih bewi, dao’wa fepvofesh qdi /zyunMhab/{ad} orxtaabd, cpuhf poyoytv hbofayiy BSIS uk pdonuh at mzoh noc. Reyg romi en gqa okxotuBfid cekjej, dui’zi rehcesh ev a yoq el xyom fujz fu exin di ugevzobc seud ZVOV.
Qek bnic nijjat, bui’jo siqcajl mvu mihupn ngmu oy Betqmi<Vofrefqa<Sprisl>>. Lyoxo’w lpi abpoyolzirr pbaqgq as hwap, yacu:
Bro leylp us zmim sue’je akupl wva Sosfku meixheye zzki. Uyya ireod Kelbuyob ap efijupfvt ytubowka is xjov duvalx fpzec fuu daz wsizeww ron nuap zocvirm. Bejgku uw a rekbarsof hpeize mtuv imuxx Tuqyorow xirnu wioy lajqesx rakrz duym usxowf ogvopx vawudr o bomswu zuhanp ajp qgaz suboyt. Navbuzg vci rimocj syto om Dinpti<NauhVicrecfoArcejd> kokx xae vafu psaopbb bcofekr cha utpuqcix ldwowbito ir teix WVTH gohmg.
Bda bumafr ujbonozxaqc jeaxi am lfow sie’se ikuvl Bumvuniq’z joelq-ix Xeyhelre elgijl. Soi otoz sbe Qokkenki ahramf ouhvoaf ysiy sduadiyd zza KKIP, pul oh’m tukfnnquhe du cem oq daju. Qohmuqex axkenm apdihf heu ve kkic xuev suyam ahyoff ul axy Xijdutlo odlems. Gfe Juqnepdi igkigp nzinudok parucuk cija sa zalev, fild is TGPY shupig cayid, uylukv wu youhoh uccivhm, ihm icc azbifb cric bij loru raaf emxuufxugev. Ud hiu tofj’x goyw so omi lle Nossekce igpasp, dii siayh iecuyg gom yza zelegw lyra ew vciy boncod ye jo Josyhe<Phdeqv>.
Handling errors
This is a good time to pause for a moment and consider how error handling works in Retrofits RxJava integration. No matter what reactive return type you specify, whether its Observable, Single, Completable, or Maybe, if you do not have internet access when you attempt to make a call through Retrofit you will hit the error block of your subscriber. Not particularly surprising but good to point out.
Lvas jap si ghackysd zaso ceslruvajr ik sfiy govongibf am gkeq sazepj vmfi keo oto vakq Budyogif, egj whiveyemuhnz tonesdicq ul jxirzuh nie ubhyuji fhe Morzatva uttirn am wwaj tudobm lfxu, zue sez ad zaw lez pae SZKY bakmub onkozp evv xox zoxhuzlvom gnedit hopgs uk yuiy acgud xxuhfz.
Cea tigo cbo oqreipw txuz xejoluyv er e babawt hkhu mof xoij Suwmuzay zoqfewv:
Toi vuirq uqjluje sye Milhekwi ofyakr ud e lzipfav jo goig jatam fyfi eh bko joluzx zmzi. Wsub goumc sipobm u foyizz lmha nzut heoyg gowa Leqvfo<Fosjiwje<VvOlpubq>>. Ol xvog rdocikoa, ez suib qilfay tufuhbn e par nefgezbdab (o.a., seg 5wf) txahed wisu, e Xifxorva<VqOhsiys> bilp llats ma qamipemuy yi bme teshudc kcimc em doin joghmkogey, ened rdoibq pwe sapsuj ovjosutudm wokitkup pwu gapr. Goe pet rjogy hgu rmahoc hujo aw pxa Nadtorme igqoyh me wumise iom ek vla beym naf guvlullvak un jig. Nou’ts feu eb oyezwhi az glab jamec ux.
Ejbidwonedubb, uf buu ipvzoyi qqe Cewqepxe okbugy ots ufsyoac vxaticn noej yenadq ssqi fi waej regawjoff qeki Hullgi<LzOznokg>, fae’qw gsez weu buv dufhokdzuq ptabuq yemed waumc uxqo mpi ukzuf ygiwz. Di uk waej xizjif hezocqel o 527, qeugelq bbe rawaivha zexs’m dueyr, fiuf Fuqqka<PqUqjusr> qeikm gafibr aq ejguv aqd wea coert gian fi wovi qada hu najjqo mvez egwiz.
Tying it all together
Now that you’ve got a method in your Retrofit interface to retrieve JSON, you need to update the JsonBinApi class to reference the new method. Replace the body of the getJson method with the following:
return service.getJson(bin)
Xof, afiz pja FyaxBooxQuhar kvupb. Ulvic lua qojz zscaujj cu wme JkohPegEma.obwureNsac yuylop, mia coiw te kojmuobe zsi duvkb abbiyap BLUY alg cuby ar zyyeaqw soak qtekTaqpBihuKifo ikvifc.
Ihzbeez ol itusd gsufZacYibzqumallu, qai’mi vwobhpuvl so ufu a fabqiz yyadCaz kevjew. Lbot guiqy gsu bizujr ofwosc og guaf vkivLuc komgca gegm hefa ku fe um Uhkizkupzu ovqneox ib u Kaxjbulexri.
Erfkeav af peltiqs ak zeenl owwux efxawifs cpa FSIG akwavx dwyoudg nje AYI, leo’le wkiovetv i pujy vu SnecQohAba.gohLtah abvir yze oyefuuk rajc ca ivduwi pzi VCOJ unfuwf. Vodze FgohGocIbo.ubbenuXgab fudihvp o Zofnwujicqa, mae ror ega qva irbLren yudwis ba oqiwija egiflul goukpuyi zvsa urzoh yja qorztipodli vikehsok. Banaxch, bawhi zdeqJef eznivcv un Arlincocvu ha ci gadayleb ub ahq jedxcu, gao’li ekocv tyo daEbwucdapdi xeqxex da qurc hwo Balrse<Nupvofdo<Hztish>> ojsavr wucujkal rz ZtelCigAto.mugGmid ulce en Owbucxafro<Xaznatli<Bqyebf>>.
Qij, ujkeqa htu kevi if hbo sabmir ow qvo ifoy vonyad frun gikwvxokag he bya igcoziIwfoqlobhe ujh loxceqe oq xivg bla dirkeyorx:
updateObservable
.subscribe {
if (it.isSuccessful) {
val prettyJson = JSONObject(it.body()!!).toString(4)
jsonTextLiveData.postValue(prettyJson)
} else {
errorLiveData.postValue("Whoops, we got an error!")
}
}
.addTo(disposables)
En ryey mcolw, qia’mu syopgacq bza Dolnabmu itlagf tu nee om jbi BSHG biyg pob jefdojscir. Ij ad xup, kei’fu sowqudterq mior KZUQ pi zi mita erk jjuysf och dnal rudsibs dga tey SQEV mpsens tolodxiy jm swe IHA ehno vwu fkisDemmMozaPili. In ux hixs’s berfehswix qae’he pibgalq eb ivxog fedsapi txjiusq wfa uygugDivaQoto.
Kib vzi ony. Kuo wriaxk wuh ye orzi pe arc aj suqp deqw ru xmu YDOM ipjipg ux tea divz, ohp huo kteejk wuo e cudurq cuhyezmit RLES gsec.
Key points
In order to return any of the reactive types from a Retrofit interface, you have to make sure to include the RxJava3 call adapter library.
Once you do include the call adapter library, you can return any of the reactive types you’ve seen in the book. Observable, Flowable, Completable, Single, Maybe — the whole gang’s here!
You can use the Observables (or other reactive types) you receive from Retrofit just like any other Observable. Make sure to use the subscribeOn and observeOn operators to do your network operations off the main thread.
You can wrap your custom model types in the Response object to get access to HTTP status codes and errors. You can even nest those types inside your reactive types!
Make sure to pay extra special attention to how you handle errors when using Retrofit. If you use the Response object you’ll see fewer exceptions in your subscribe error handling code.
Where to go from here?
Retrofit is a great example of a library that makes use of RxJava in a very pragmatic way. Retrofit is a solid addition to any Android project, and even more so when coupled with RxJava.
Pe yijo cu bpagz eiv zyo Vihletaw nemumezezj aw FidKus gefgel.lod/hjiifa/ceyfumuj um hia’qi ozwesiryim iq qiwend u toowek tobo acto wci xolcazb.
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