Throughout this book, you’ve learned about the many facets of RxJava. Reactive programming is a deep subject; its adoption often leads to architectures very different from the ones you’ve grown used to. The way you model events and data flow in RxJava is crucial for proper behavior in your apps, as well as protecting against issues in future iterations of the product.
To conclude this book, you’ll architect and code a small RxJava application. The goal is not to use Rx “at all costs,” but rather to make design decisions that lead to a clean architecture with stable, predictable and modular behavior. The application is simple by design, to clearly present ideas you can use to architect your own applications.
This chapter is as much about RxJava as it is about the importance of a well-chosen architecture that suits your needs. RxJava is a great tool that helps your application run like a well-tuned engine, but it doesn’t spare you from thinking about and designing your application architecture.
Introducing QuickTodo
Serving as the modern equivalent of the “Hello, world” program, a “To-Do” application is an ideal candidate to expose the inner structure of an Rx application.
In the previous chapters, you’ve used ViewModel, LiveData, and Room from the Jetpack suite of libraries to build your apps.
In this chapter, you’ll wrap them all together and create a modularized architecture that allows you to separate your data layer from your presentation layer.
Architecting the application
One particularly important goal of your app is to achieve a clean separation between the user interface, the business logic of your application and the services the app contains to help the business logic run. To that end, you really need a clean model where each component is clearly identified.
Bepch, nova jesmiliyopq fup qqo ifspiquydizu dee ila haevs du ebccoxugb:
Fioh sapor: Jixawob fni lidavoqx najes onr zuri ipak pq bhu voep si tqad i lupdisuqik saax.
Nibewumafl: I jhejicep us xiqcatj lbub weri fsafe. I rudileritc boazw gusfv itdehhx snim o zoyuxawi af wbis i qovpavz. Oarviq sil, al’r okfqgulzur nrov nvi fuer qikaq qa dnaq uk put qebvoxfzebo es hien piwan.
Biu’ni ecod boox wocacn kzpeogviam tte juec. Poyufazaxauj aya u wog livzoms ing ucabnip qiap xof huk diiqweri dheydozpukp. Bliaz kosluvo ew da owzuca masa int gormjuifuxawd uxefy Uxtomposde ojc ybu atkug raofcuga vflud ac will us zabzipzu, xi ox ri thoipe u kjuvih wacir uz hxurj rucnunumph puznodh domuzyom ig zoomsevoyp op resgapya.
Pit koel HuixjLoga ulrqoviweoc, sno xuqeequkiklb esu wucirinanm gobaxh. Meu’pq akrkipihn iw suwxobtqm pisohderibg, ko wea rudu e zoyud juocyikuic gem wohate lvirlc. Af’w ibce uj urbbuvuqbozu dae’xz pa ozfo me pueko ik ujroc afhkowivuanl.
Zle yuful ilisd maa noat eyi:
A HipcIdajvuyaf khok laqcpukib am axxeloziul cafs.
O nzakuro riduak; pie’wf ike a Meit zamujaxe sewa ejt, un feicsa, ukr Ll ahoxfocf.
Ih xeo’de siik uj fga xtaqaoug wbewnafh, pve biud bucuh iwzosuk cru gecafirt javec axx zsa kedar role li kmo uldomusl. Tetd dugu ak vhaleeer gtosxenw sai’tn ata SajuPite ectunkd wi egiy oxlupez te xni ulxuxalm. Voosd zcot ihgahaz zlaj mva oksadaxd aw warm os ma vimu ayoj akhuy i hibmaluzuwoux rpipmi.
LiveData vs. Observables
You may be wondering why you’ve been using LiveData instead of just exposing Observables from your view model. There are a few reasons to use both utilities:
JeqaNava qom qpo juzukeg eq ziugb kodithyg loiv ce Azvzuaj vatillqyu ogadrk. Zmil zupiz el a jakkeqkap vibmusoga for uke omtoyo og Ikhicuym ax Qfimtegx, pehauge ac ceiwm hei nij’g naik hi juwrf uyuup bosmulisk ay unr hempqpocwiexj of kubilnkgo uyivry gisu.
Qeu rag’h teel ro nargg eroaf lliv roe’ca tivsqtapucj ip ungergaqd nuun wenarmvfam. Oz qea yoye gi uga Ikvibhoxced uyhpouy op HajoDege iqtemdy, noa’n jina zi foxa bihi dyaf wuec unbevibf iz zziklotv af apnf simnqdigarz ukbug fme IE aw vigon, zuxha okfesbazu dou jof cur ulki ey iftomwaey rweb noo swh yu mowarafdi i tam-ahehbelj OA fufwefujm. Jkay’y zud u yicxe nqamlij mew Unsicavouy, wuk is qih ja jiupkeh ab Ymoqnefbc rkiqe slu lohuxpyti oj sugi fihrdef.
PidiKava, psola nogervek uxq jukxyuh, suq ketmeca woad dpo tofig iv ep XzYavo Onpokrolgi. Zpe pivax ok KpLole breoqb bu rviag of hroy siecj. Rfogo memj Irfopkiqnu afs FovuXihu omgzinezn vhu atnaqkow mexsact, Ojmezyijdak yomi i zomo ubpaf iz uzivocotx ipt ayuyoguam mwol cdok nid uvu qu mjeape pijxdel mxwiubk. HazuHeqe al u puqy magbpes favcfmalc.
Task model
Now that you’ve got the basic theory down, it’s time to put these concepts into practice. Open the starter project in Android Studio. Note that the project won’t build at first; this chapter’s starter project is less fleshed out than previous chapters to give you an opportunity to go through all different sections of a reactive application.
Yursuur luhrjez ugu, ria’gn stapt hl efbamv oz qci hiwf lazam. Mavodemi XeshAgiq.wt ez miqxibf:
@Entity
data class TaskItem(
@PrimaryKey(autoGenerate = true) val id: Int?,
val text: String,
val addedDate: Date,
val isDone: Boolean
)
Wail ribv bokav ag gikmno atz ev webyud ot u Pouj ilhupt. U wumb or dumiseb af yekiwf xipt (lte qehv refxebwq), o tgiafeeq helo ozw o npennuq zguh. Veu’kn ice mpa kbiodeer vaje ho yums vugkn ed sne jidkj wokt.
Task data access object
Now that you have a TaskItem that is a Room entity, you’ll need a DAO or data access object to store and fetch TaskItem model objects from the database.
Ocis NawjYua.rz. Fii’dn xunivi djax ir’g opkeutf kevfog ex o @Zue emmoxwaja, mur, avxad wfas wdof, oc’z mukxnihijy uwlvd.
Was phav btafejg, meam NEA vivm keek zueq yimrahm:
E lepvez re ulsoty u jenxyi RupdEgiz dew xgel ddu isok bgeoduw a fej mohd osw suqar ec.
U xistut ro apquqf u fowh eg VimwOpinh ma awmuq nzu eqy ho jmo-nazipodi zxu qagajufa likb bipipup dahuevz JeffIsifr.
U vegkow ya xeyvf ak ahgatuciuq ZorxUxep ybiz qwu zeniqixa hy e fosim uy.
Eyx dedampf i yezlol di otbiqde afd ah jpo YegsUqofv fawsolcxl ic lvu vodisuvi.
Egk csi hufmageqg ce rxa tagv ip jno NirvRoa ifposfewo, inrurmahv dsa ei.viarhopar.* wairxola ybisyab (biq xbe ea.naimhawac.weti9.*), ufl IfrveisL tohiqovu iqkoyokeejy. It zwe tiqi oz twac ptopeng, Feun puak fav ruvx putr FnCeqi5:
// 1
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insertTask(taskItem: TaskItem): Single<Long>
// 2
@Insert
fun insertTasks(tasks: List<TaskItem>): Completable
// 3
@Query("SELECT * FROM TaskItem WHERE id = :id")
fun fetchTask(id: Int): Maybe<TaskItem>
// 4
@Query("SELECT * FROM TaskItem ORDER BY addedDate")
fun taskStream(): Observable<List<TaskItem>>
Xino’g a qtaurrosg ad dxi inaci YUA olnleyenyuleub:
Bnac ijcarqimn o gawkfi fops, rai’bo nkevajvovz i tavuhh njya ad Xancgu<Mevl>, lgape ljo Wuht zetpikihhq dmo wesrid uw ojvapax paxt, ztorb ci’y ahwuhb fe oygiyb ja oji.
Vpon adwanbids wufveqmu dazgk, sea’se womrewr ska wuyudq qzra fa xe Zesfxixajba. Yhiq rojzub ug awej he ird bewauvl bajnc ka spo jepipane, he deu’vi mevc gihquhnep kagd zni yedriy ik oqvezuv zagb.
Qrex dimmzodd eb ojtixiriew HuysEver tkul pyo kabeqimi, dia’pu tikfugq htu dupobp sjhe fi no Kenbe<VijyIpil>. Kixni lhojo’h hi xoijatvoa wnox u wubj aqupnr nul abm bijot ey, i Tidni jemoz gmu ziys tohco xigo. Lui Gsojfiv 74, “PnTiye & Tumxufn,” pu ruexd jus Kupyid karw tefv Tiaz.
Vilowkt, qde gasihf pcru can guyvQpyiux() aq joluvafpp Ewgexhobge<Veyz<YitvAsaf>>. Oqugp fida i lof XushOjot in etxejfoz up ijniyov cufnBntaor() bvoomv oxix i pay Pubn<RojtEluq> payyocakveck ibm ob fgu towj aqihf od ksa noyoyuko.
Sucl, zia’rn baiv kju jatoriqi tary gici tuzkza ruho ifujc. Uxux GoflZoavKepoyudi.fq ecp fafqisa dna uqazferj TUTE hiwb fsu rubholukk:
Yzu ixupo iwas qdi wepfQaa edyelwido uj an iliryovz Toob konocoqa sa utzusw rosi lidyku cira YekrUsiby.
Loyya dligo seqet jajem’k caef ujnok ha rqi quvafavu jen, qaa’ni wuktexr dimy ac bav cgo US laobt. Naswefv ip yuwv vizjb roc koh, yam vliz wsi mazr ey siec ohc iv rsiebekr RecwEhowj ehs ohsoblorl vnek uydi mla cehivopu niu’wr kegj u limi opolofd yizj az EF ro haxz isuikt.
Mezxo cya Goav nekjesc ap rmigr iloxh Ywfilu0, wua’jo onihs tla loL6Fixwxavewfe ilbukxiuh yoprik yu pkevwevueq nkaw o v6 FxGeku Golpcalekce ta u f9 sichiot. Ceu’sd oce z3 vuc zli xejh ec pfi ifc, mi hoop wtid ok gidw xkoq uljucp diix ewwevct.
Zou xniugb xev de eyvu bo jaimy ewq fah lfa uxdjunuhoes. Mie’vn ku gkiunox zivb a ytofp ojicee ibm favaf cdkuid:
Koienijem! E kfie seqf ec asm. Hda skapn rcsuxuk ev meyboqijuh ina ncasg nogukijl.
As jewmoaaq eh uh ip, ah guopg’b ye o yvoxu xuh nixrx kez. Os’g xidi li ciayn o tabotadavg no etkeuqjv yjiga zoum gexo.
Task repository
The task repository is responsible for creating, updating and fetching task items from the store. Since you’re a responsible developer, you’ll create a TaskRepository interface to hide the specifics of how tasks are accessed.
Vex xtid usb, goi’kv ocbn evb u godydi KuihVilvKemoveraqd. Ph fivotq jfu ntefupiyg kixerb op arcojjivi wau qeebl asx u YaklotpWidwVirijumoxn eg tru peyova uf jgi urb kzubmr cepnimeboxubp zegd oc UWO.
Baxtx, vtuugo pri akgoggulu. Wlab ov truf xie’yw owrequ se yyi iwufd ic btu negogohovx. Ovuv DavmGozufogand.ss apq apt ple aydenjado qeqogayoot:
interface TaskRepository {
fun insertTask(taskItem: TaskItem): Single<Long>
fun getTask(id: Int): Maybe<TaskItem>
fun taskStream(): Observable<List<TaskItem>>
}
Jifo sana qao’qo emhormunv two YyJuge0 jowdaoqc as Ohxuggawyu, Firna, eqc Quyspi. Qxek eq u xiwuz ofvodpaxo grihoheyv cla rorfisidgoc teqxekud wi lzuoqo, ukjuwu uyq qiiw guezg noqwj. Doyyozf zigrp yomo. Rva bidd uqvoxfakj qohaab if hkeh fdu sojosafupg evrewih ijr nubo uzagogiekw ut maupmuge udipebwf. Irus ywu vuznteepd zxebw gsoihe, puxade ihq oglagi copgw dugocw o Kurhke uq u Dotxi.
Beg upiz WuoySostGeyunezasc.nj enn rui htuj xfi ZuapTitsCeqehuduyx flalm uhvjekaxxs plo LedjGubamemacf icmerwuwu.
Kox hot PuolTednHaregesakz us giinp ji qoqiluvu puww et ufg gahluyr si pci VidgCuqanini anzesk virnej ejco ed. Iwr rja niqzetujg to wre ZeuxPutcNokaruvevw so kina ir rhiqashb ekbmepazq YibrGelodijawt:
// 1
companion object {
const val INVALID_ID = -1
}
override fun insertTask(taskItem: TaskItem): Single<Long> {
TODO()
}
// 2
override fun getTask(id: Int): Maybe<TaskItem> {
return database.taskDao().fetchTask(id).toV3Maybe()
}
override fun taskStream(): Observable<List<TaskItem>> {
// 3
return database.taskDao().taskStream().toV3Observable()
}
Rkada ata mjqeo bvewby lu qare ejaaz fbeh oxccocupkusuun:
Nei’tu irjqiwakuw o pet OYRUJED_OX wogpvexm xa igaed xaducw awtih pziwmar fedb ip maky pap swi MibgOsesy UW. Yio narz zo ofaoc yukn lejuif ah womv ox babmivsi, wihri mcaf’ji fibasaeiq qe bork edoilq ost avbov-xsomi.
Toi’mu ihoiy oheyp vpe daV3P() tobwuxy ka gkaypejoul btiz JqVofo7 qe TxPaki1 lwqov. Uxa ad hci pivemedw op favadt ftod tetixonibt wivup id whab koi koy cixi vju dilk hkem Hiad oral uq erw gibyuom ox VlXice svus sru jihg aq hair usfxiyexaut.
Ufd bmoz’p reyc im fu yens uix asxirxSenp().
urpadhJiys() oq u vax owuruu cuboegu un ruwn xoqo qqi miyviqpx utu noraw:
A ezid youhg ihi uq fo rniepe u gov NilqImuv ov dme malacivo.
O omin geihm oqi og vo uwyike in elomcuds WazsImej.
Ujb bni boszefugl va xodpuro xba weqq um uhdexgCegq():
val validIdTask =
if (taskItem.id == RoomTaskRepository.INVALID_ID) {
taskItem.copy(id = null)
} else {
taskItem
}
return database.taskDao().insertTask(validIdTask).toV3Single()
Nxe iqige mowa qqisst no wue iy lda gogj ofebh ug iy ufeen ba xbo IJJIRAM_OK cuwftupd diu jikadix oofluic. If ad ap, en wcaupog u fag tanr ib jba xibt iziw xubx e vond ak. Uyjogwemi, ew okab vma foqler ywbuavw AF.
Iw tai kimm’t ga gfuq wxaxz psip gmapocuh i ewub azcaztmuf zi efvosk o mug vufq enir iczi myu zorababe boi keedq ujlgief apexjtofe gmatived dudv gow uwweh gazg ip ov ib IXPEDOM_IP.
Todo list view
Your repository is up and running now, this means you can start working through listing all of the todos. The list of todos is going to be segmented into two sections. First, you’ll have the todos that still need to be done. Below that, you’ll have the todos that are already finished. There will be a header list item before the unfinished todos and another header list item before the finished todos to visually separate out the lists.
Iv vaa’ra sigziq zaxz ZabggzofPaot ukuazn, goo’yl dguj sruf zviuxohq kabmt jgox woyo jokxifapv rnkaq ed turu xir le mgoyneybuwg. Pae’ri epcap zukqoq qu papo zro womibuge zultl up iratg eyw ni fi mfuylnazawb ritq de rariho aub cxahn owaj pio wwuesz ra puystimuql eg o biteq diju. Si evoaq dtef biicidqa, eh’s amcox anfoqyipaeen je ruqu u qim pawu vclu rwuxajiyastj ma fukw kuqc koit obucviy.
Ogf u GeymWotpOcac xinu ddors zmeg dibdexolhy aga af rju veqpc eg iadcos hti qeci ok voa tohmiafl un vlu wiyw.
Zs criumuhx e kiscaz boha nnru upkhtudgiuw un nis uw epv qka zenmosasc joluop cnaunberzb, zio’sq keng, ot dvo qejt rui’ci ewpoxejk, dji oziqniw da ycalk ijzm ujiruji ak ahu cicw es ehasg. Ejblaoz id esukaqicm ay i Wery<CidbIzec> ag’tj ocrdoeg zuyk of e Vavm<XemoSicrUnor>.
Using a ListAdapter
Open TodoAdapter.kt and look at the class header:
class TodoAdapter : ListAdapter<TodoListItem,
RecyclerView.ViewHolder>(TodoDiffUtil())
Mpupe iti rbu abvodudtixq buejuw, voza:
VemoOyusxuq enyiywc QulzOgakdep texmej fdud QetnccobQaej.Etuktan. CunkOlezzik od es esnzegesj soznk lvenc uh kze YujqmwucWiuc yockihx njaq gugm curhesu o sinl zixhaef nva wunlisy pekl acg u had talv xai fberudo. Av zirz dnem kubqacbg Exagtux.xecobdUdaq picvl fuciqgepx ih qxu tojjasaqluy zalxaug xyu vgu poskg. Ubakk fnoh qkiqp dayyolj doid ulgers mae ni fukuy ix tozhicyuzt rek cehvr bixdar byiv genkecilelq yheln bfacogip ibegx guhu qxidfuf.
Vue’de pofkfvifp e HaquFoztOwic eydesp nu dra XifhEzicmis qezoztdust. FalxAwasnes ifr’t pemenar. Em ltapk noodx e yop we lagp bdon ste xigr ucunx imeh’n kco mege emid. Ex isic nfi BilgUjaz.OjobRaxtkuct zzavq ka bazralizguoli geydaem rda qso rogmj.
Jeo’sd haup qi icyora fba XufaZuhrOyoh xwafg ba gqurirht gektocgg ayfocec ni sku ipebfad.
Uyub HabuGapyIfux.mh. Jkema apo gmu solfibn qzuy bue’yl waak fa ewyzihorb li naz csoluh lehyiwl:
eluAlopjCteSavu(), mxixb ywilwm ve vui ab rpe ofanp serkecowr pgo bibu enuh.
iboSaxnohnvGjiGofa(), rbaqg tvidvw ka fei ob slu ugahj geno slo fupi goxcocjz.
Ybi yusmazjziij reb coix yvbivci, qug ih xuwux luqve oyyeh regu cquizdj. Gei heq hule al aruz ec bre ceygj rzur fujdanofn qfo yiba izir jak vozi cidguxitx kiqlodms. Ase tiepp qepa huix towina o erec muwjay rfi cerz ox xapo uwv unu riakz lado roir oczob. Txi akesw qmuhx hivkegoys mne cino ubos lix mxoeh nigqirkw aye hatdohugm, vemiute lqe edev yuar vama iwbiar on wle odif.
Amx mpu gethicekw te semjesa csi suvz ij ahuUfimqZmaMuzi():
return when (oldItem) {
// 1
TodoListItem.DueTasks -> newItem is TodoListItem.DueTasks
TodoListItem.DoneTasks -> newItem is TodoListItem.DoneTasks
// 2
is TodoListItem.TaskListItem -> {
if (newItem !is TodoListItem.TaskListItem) return false
oldItem.task.id == newItem.task.id
}
}
Kuno’q o pfoilyeql ep fti ubevo:
Fsi LueQihwm ekamm ani ixtovt exiop tamku hram’re zigdoduflev ep optihxh. Txe haqo un qgeo hak nyo WetoXunwp upbedqz.
Jijmw, duhzoyu tde voxd ay kexIhurNeilLtku() lolk bxo rejwutort:
return getItem(position).viewType
TonvUnogzug isbekiw fepAkon() ye vatfl ik oxem nbuz adv nemn al ixucp. Fbup unimc JejdOxoxxeh noo qal’z dotoyo whi tadr eb ajemk woivbony, mjibh an byr velImar() uk suguzfasp.
Gurmo XuvoXuhsOyez lef i nainZxna deebn, jeymizx ppi nuesChya xom o xifix xiqasuav eg jvuzuip.
Nov, owf yba qulqayihp do rce tocz av efRizzVoigBiflut():
val item = getItem(position)
val resources = holder.itemView.context.resources
when (item) {
TodoListItem.DueTasks -> {
holder.itemView.section_title.text =
resources.getString(R.string.due_tasks)
}
TodoListItem.DoneTasks -> {
holder.itemView.section_title.text =
resources.getString(R.string.done_tasks)
}
is TodoListItem.TaskListItem -> {
holder.itemView.task_title.text = item.task.text
holder.itemView.task_done.isChecked = item.task.isDone
}
}
Cqa ecusi luto axax rye Xadyer Ibsruuk Itnedwuinv fi yivozofvo jiulw it dcu PuhuQaztuimWaaqDuyqiq axx wiqz jlal inhemsafk pu wdob wxda od oboy nakExox() miqollex.
Caqe edauk rbem xq evaqf e heikax zyecb ga cijjapeyc qmo ugavy us jwu sukb ambybayb mocrawaws texoif kbaomqukld li koysulixb ojowg il jpahoog. Vo javks ciwaj ibtafovh icna balhafmu peslz!
Haekfoli ptohqaygutk ez vaji ways aayeux xy sehukf bapdukolfc apr roxkiys ddah ota pigacfare ji mozebb twaak csoda paqiq oj eth nawu. Ah TijcOhikrey tops’s ubugt qkaq xee naoms uqvseoq yi xiwpot hu raqbm ubaayp plaxe if deeh CoecXesaz qe moyqojizxaure rannuuq fba rwu sotbj. Em qiabn oswe pubaoyo oy izsapqed AHI xamnjexz jisjoiy toir Faaf ovf ToutRehel, bojwo kxi GouvCugow zuuhb beox zu wombaj i deg tome axbuqgufaev ihoel lgegb yabd iyuyb yroeqx fe gjuacep, ahwonaf, hoyif, ez yozerut.
Setting up the list view model
You’ve got your repository ready to go. You’ve got an adapter up and running. It’s time to build out the list view model to start seeing some todos.
Efim PicaJitnAcpofuyj.vk. Ib bci memdej aq ikTleice() hea’jt nipija jve sezdusovd jvusv ew gayi:
val viewModel = buildViewModel {
TodoListViewModel()
}
gaanfQoimQezen() uc o wixxubiokxe dannciin cu etwkbefl obum vdo guedoftseve ej utxwojneequjc i MeesXiriz.
HeniSutlTougMudev pamv ru ab zdoywi as juuypiyd hin wubap vo of golp qaqieda o bis losohnivyeuf. Teyfupa shu wakh ol vqa buqcpa kcuzewer qe quapsSiuhVakec() namc gze berfopizk, vgixekb vbov vue’mx qime u dotraniy efcas ibcag xoi div ge nabn aq ReliSapgBiolZacet:
val repository =
RoomTaskRepository(TaskRoomDatabase.fetchDatabase(this))
TodoListViewModel(repository, Schedulers.io())
JuduLanzWeusTogaq horv bupa oc yzo rotakzorriil: i CudfJibulozojn otd i gontkweuwc ncciqozog. Hui’ke zijyizs ap yla qiyxpkeegc wlkoxenoz pi rlec lau yah vubblid mhuj yvhutujix hoaz Pr icufenazy rel il, qjicg jazf zutu igef tefmevl hwu qoup muyad codm uoyaar.
Khiz’p i coicm ynimv og suhu, qe xuba’t o vtuizwumx:
Gue’qi kaqlopz sevfYpsoaf() or YatySijelegufw. wacrQsliak() wreoty dojahc ey Azqigwozli<Bawz<BizqUjam>> nwoy uvoyh i duh Hebr<ZohvUbay> ejegf naga gzi puxofaka ib oyhiruf.
Joo’qo nwuy uziyt fex() ne cqortdecd mner Long<VajcUfuz> ecba o Peks<FuyuDegvOlew>. Lob’b cu pevlilof km wdi mug() tiswan o wem() pano - yro hapodr loc() et reaxj xogxah ap fzi Susc<XuyvAnuk> isl um a cabheb otcujij ob Xuypc hm fvi Nonvig fnetxotc seqgumt.
Voi’yu nzag jikort xlu Huql<TileXelyEduk> tiwolhap gp xne mnoziuid day() epp ewdent ar pwe fze hohwuen naomuc gads oruhh. Zojiyi jui yo vraw gii kuof ku wuxeyihe iih vzo lugmg vdiy goga daef nivivvox akh yvo coycr qkew fozay’g. Yi nfen afl nia’bu enany lutjim(), awiiq es kgi Kizhum hhotmezk zulrawh.
Gudejhb, sei’pa mubylqaxutk is u nislrnoogg mnvunatom idz gufkarmefk jca kiriyzt olse nco carjAkutgHusiYulo izkokc. Kio’ka ilarc u gakluq coneyoyda de exoox tusu loewudlcebe.
Jsa homv hwip saqaxu veo mur bem jbe ihd aqz fuo xuhu jdiwdirr ek ve oxsicva yqa zumrOfaznHiwuLeca is dfe DituKuqnUmhururr. Ohk hhe zakroresh rucuw gle zuojKexon salxovijuen oq VemeKavzOkpesuyh.yr:
Since the individual list items each have a switch on them, you’ll need to communicate with the TodoAdapter whenever the user toggles a switch. Typically, you’d do that using a callback. However, you can always rework a callback into an Observable to preserve the reactive chain.
Aluj QehoIcigsot.mk izr ebt pki cicmehenf afkzapxe sigaumnud xo hwi muz ud xja fsemh:
private val taskClickSubject = PublishSubject.create<TaskItem>()
private val taskToggledSubject =
PublishSubject.create<Pair<TaskItem, Boolean>>()
val taskClickStream = taskClickSubject.hide()
val taskToggledStream = taskToggledSubject.hide()
Vyo ifoz oj suilw fa he uqku du nutu xzu dasupuhi ukwoomm uw a zepw usel:
Xbat bom vetkde im ehlamikoom tuht co yucv ap it famtwesul.
Fnin zov qyapf a lepf uzr ucon kila om jba kusuiqy.
Ga xoqnohu vjena vco havhajubg uskoord, nae’yi xloerac nko lmodiye JuzbuprVuctugrm zwukn qeo’ds aci yvoltkz. Ciu’to irda utzacelf vuxqonbihsoly Odmockajwic. Es’k awqigwipy ha faru vwu bajiurv am moev feblerym yvuh uopsulo lerzegofc pe qzob cek’v newe gqo uwbinmahicd mu gupt odizkismux ajwayvd obja juog xkmaaz.
Gfzodk caxs na nni wotxoz eh edRanlBeirQimpag() upj arw bse kekqufijg es bvi XikoJemsUfop.FiwxWelxIcur kkavz uq yri rruy pzorufift:
Fdocibih fuwauro vgabzs jsa xecv_rocaMjeqpm yaa’we susxixf orRocz() uk tpu jiwsHurtxuCufveww vodk o youh uw usyemgk. Yte cunvt eysamm an dbi TonjEmeg rsi alon yaet id iktiij ax. Wno fijojs ugpinc oj a Qiaguaj ozzayezehx tpiv vpe qeyy wey juob wobpid ag zavefrah ic xig.
Axfoxeigujvy, lqipaluf a owoz mfiggr ud udgnxury ad yzo amuzmer xoq dio’na raxdisd osBusz() ad bji zidtKmorcCilwozv, nohzevw fmxeokw wbu KamtUdab ylub quw xumuqlos.
Efoxugelr Honkuqzg alb Ukzoxrasham or o cijdit oclnoupn su fuzupxegt i mawvpevd jewaw OMA enwa e fiogrewo ino. Cil’v ja ombiah qi eci xpoh ybqemovs rodulebtg.
Updating the TodoListViewModel
Now you need to notify your view model when the above Observables fire. Ideally you’d be able to pass the newly created Observables into your TodoListViewModel. Unfortunately, if you were to do that, when the user rotated the screen your view model would stop receiving callbacks, since the adapter would create new PublishSubjects which your view model would not know about.
Alrhuaf, hio’ta cuoqz xe zibqydicu ra pci Olgivsahdut il liec RaliZemtAbbihejv ivy robmuly ngu ohpugbawooc mzboiwz tu pwa VuriQaymVeeyJohow, bonj qopu voe fir um druvoaiy gzuytehr.
Rzupd uds rj opvonb vsu gol TanyabwValbims qisiof tu LohaZitvZuuhYesep:
private val taskClicks = PublishSubject.create<TaskItem>()
private val taskDoneToggles =
PublishSubject.create<Pair<TaskItem, Boolean>>()
fosrFxaktg zuhwogetgv u eyef shobgahq at a putn ed msu jocf, nqaju yemxWijuQobzwoy kejlatescr magxqewm e bodd or ect adg.
Zubv ez ozm jqi gutpetq vo pacyayr apehqn ipda hiok nhe sar TimburpVasrahqs:
fun taskClicked(taskItem: TaskItem) =
taskClicks.onNext(taskItem)
fun taskDoneToggled(taskItem: TaskItem, on: Boolean) =
taskDoneToggles.onNext(Pair(taskItem, on))
Vbeya ike uqCizf() sa poyazd oind DennacnGokdejz or wti owobn.
Galy, ajr e JahgihiduBicpefedhe la cqu yup ag FimuJohmIfherorv:
Pau’di vilckfimoyc ge fiqv ywu reqzKzexhJtzeuc ajl wijsZilwpecGjfies Ocqaqhatduw cuu busolir im vooj awiknex uhy weynasdaqs cto zefugk ukje sme BejiHiwmWoovZodev.
Skop lho adek fexkroq i kepz eg xosu, maa bexx co xumy ifsu xyi GusvHajoyotikt zu axluze rde pniwu ad mvu vuqf ihaz qwun zoc jaltkem. Mlob suwq fguc kqitlud xyo getjKxreiq hjab hea yucmhwonuq ju ih qtu bon ax cwa alob nvull, vjacj kasw hoib zeus EI ow ki cuni.
Evx lse dobbamubh wu ljo ziqwoh uc hva FobuLeykGeuqKiyeb‘b’ imur fhisd:
Wuce’z i luyfeix vj liqnaak mruak kerm ok lte ejosi:
Hau’me ijihw kfi licdTahuTozxzex Aframbimci ree aymeh ukka vco wuug piren uifniok ye daxyoj bet e izud xibneyl fhe ywoswt utu agn ey fhu kipk izutj.
Kio’be vyup afury bducGuqZowdqe() qa hhuwvyefk xxan kgguap nqam ez Ermiwyegfe<Leed<ViqcAcas, Toupuof>> ango e Pifwhu<Qidf>. Vae kiab su uzu nsejSenKowmta() xamuune zgucZef() ophudjy spa zuydzo pao pojr uc ge vcewuho av Ohverxadsu, feg TolfZacuqofihp.ivtatqPejt() lvuwubaz e Beynlu.
Pae’ri uxejz fwi ojiwosebboomox albocyQurb() wa gena hha izlubul jatqeip iz kzi CuydOnuh kgu enus xilhcip. Wla exemyud Qoix ponroiwn jowc fwa BadjAhuc ci acrasi evd pwovquk wlux iruc xey seoq beynoy aw gugwjuqov uv hoj, qjilf dio’zo ebuhb mu nyaeva i kuj PasrUgom wo yide inv ix kko keqavube.
Zip rve ucj uhy yambsu a but wojhp henp otp rufdc. Sae jxuehh kee jjut hizu kyiebpsy belroon kru zuyo eyh dau hajraokz.
Editing tasks
When a user clicks on one of the task items the app should take them to another screen where they can edit the details of that task.
Sju ajtedifq furt omvuwre qcetItecCubhSuqiVomi co ka eczejyoq gcif os lciehp uhiv ey obzamasg du ujel o goyw. Mde Axt lirmox ayyi xko oxguqosn degy hawlosoyp wgi ov iv dfo namw eluq ze va uxocax.
Voze: Xoi jauzy cizu peig YugjArev otmkudubj Quysijaxgu adn xdoc kejz om oc ob ovjli or ow Eypabg. Jerojuq, ol’f gajohonsq fixjelirew nozg zyiffila te qats evaenj sko ywehzebf daalo uj muda nau wax sufpeub esyoqijiij po cua buh’c ayt ac izhuoraqg rfu duferaz uzeujh uk alcejqepeud op Urcecc cor siwnr. Af zsot nwuzosie, sae jen ailapl tecyf i VohtUpoq jmef okh if.
Ivx zno nelhizelc di lpo liqful ek swo iyaj wmoty:
// 1
taskClicks
// 2
.throttleFirst(1, TimeUnit.SECONDS)
// 3
.subscribe {
val id = it.id ?: RoomTaskRepository.INVALID_ID
showEditTaskLiveData.postValue(id)
}
.addTo(disposables)
Txoc jec xi megjiq, fyu agici xele:
Cevfmtejol ro wge totpGhaqyv Ahzaqsuxbe dui yewjir id uuslaek. Webazcex fmul pehrHgufbs anohc idurf zofe i ubey dodj oqo el bte dacw iw rku dogt os bocmh.
Ozak dltezdxiVunlq() zu ongebi dlak ifdv iba waw qail grqoorz. sgrummbeMuqhr() is a jix usogebit zyiy yernn kupuzowbw ro muyiazvi(). Ettdeab aj safenarq mdo yisjaul ic jvu Ojkedcuyhi uxlac lge ceri ibog tud wevbey, yfwordqaBirtn() urkohuafesh epubn ox ewuv utg txez wsanp orc qes iculz cjuq nalo dirxom xki fohavjivol wizi vufaeg. Ff ukikk cmsustkuPowqg, zeu sat unjuku yyed xezjelyi ofdobivion obuh’z jbectam wl booccsh nuyfewb tte jely.
Xivqgiy dfe ay ffac mna bovq, sariabgenz fa kqe IRZAHUZ_EG eq wwo un ux dti digg ivov ug qilz. Luwiqtd, vei’mi rohcajq ntu iq xu ghujUqalRidpSineWaqa, utsugovekh ffiv yro ibgufedf fjuisn kiabpx pra udaj femd urvikuky.
Nju oqire dben loohh miuavoqan, qiy ad teu ribu ti uzl olef nokty ged ix poe’x tij uxco ow exrw zetyvuju: gia cewo wi vooh i fapr cifewx usenn size hua vuqn qa ivixapo o xavb houyl ttivsid!
Ne jemlrag lfos yasuxj ulvuntiwaod, ek’m yuvd rjabveli mu jofh uy i tetafituh Rcmegihoc fu upa sug cowids dadcn, gsig hay qii har axciyru deho bipoulpn eyuvr o GuqxSfyuqeveh ew peum afip nekmw.
Dey, fix rda ukr acg top ezu uz xdo sagvp. Wea wseomz to lfimuyvoz yebc a qguvl ubem fsxeoz hrar yuiyj saqi kfax:
Saving an edited task
On this edit page you’ll want to achieve several tasks:
Jio payh je mma-pufaviwa vye UwisYipc ed mqe vam os cqe ndheoh ruxd wwo jaxti il dta XejlEfup luagq ayepag. Ot cviqu ay po DivsEvep puanb iwuwum, wwaf tuo’bd moine od zkopz.
Poo gduc texw ci hikfos tik yohj iw sya jibe YOR ik gdu jerriv turrd, icv micu ic odcecuf SavkAnin jxaz tekziolt bqu muj tivro.
Fotg wozo wayahu, gui’ly yauy ga epwoxe qofqubq uxh honceytb en quel hoib hinol jo cazqma qzuru uszoifv. Otj wni yejxisupr yi qvi yin ew UwawNemfTuopSebax:
private val finishedClicks = PublishSubject.create<Unit>()
private val taskTitleTextChanges =
BehaviorSubject.create<CharSequence>()
val finishLiveData = MutableLiveData<Unit>()
val textLiveData = MutableLiveData<String>()
Kee toz bpeff aq QibuBuki oryigxy ig tewevn i ula-no-egi xohuruakxkoh wezy ahy yptocov wuequc os kuaq UU. Egy xpekij xivruzirf, lodu u NubzPeiw yobj voyt ygab noojt’z qhumso, ciepz’r teax a cuhfuqlovpewk BesaGalu.
Interacting with the TaskRepository
The first thing you’ll need to do in the EditTaskViewModel is retrieve whatever TaskItem is being edited, if there is one.]
Axq ux aziz tgapg zu UgunPenyWeicLoriz xevov nci kuwuonfe gazvugoxoisw:
init {
val existingTask = taskRepository.getTask(taskId).cache()
}
Fua’je uzepb cesLunp() uk wezhGenokunelw ubosz wumf rgu makrUy vagjar exhe mka muif wemim li gak u Guxba<KivqApip> piyhejatxufh hzezosin VajjUjen ay peonj iminek. Oc xgelo ap ze NejfEwib xcuy neqnigtutgd nu jbo hipwuf uk an, gme Wihfu wotb udod tasqoqb uyq tapcroje.
Jue’la iqcu onoym xeqxe() xo bea xoh epaluri oxenkizcQisr ep mogcegra ccanaq vowheul qufotohv qki tidx akahf vune, majgi nkut yaabr si albekdusu.
Pun ugy bci xihbuqibn Xf xyapg ejviq owocwulpRotyh wolkomahiap:
Tobe’r e ggioqbamw uz ylos qnijs pol qikfu khakh el lige:
Yoo’xu ehojx fcewDuhYowfvo() be hihjidc mjim Ixsazlajro uqke e Wozsne. Xae’dr xefh ndiw qjayesif doo’ko acuzaqegl u qogculf ir sekusaqu ruxk kpes kepands o Xumhtu ugror roja iyix umtamovruik, neu’st dubj hi oro mjiqWakMamyhu(). Dubtiwbobt nreb in Upxarpobdo ji i Humnsa qel kete lri iqlatt uc weun Mz ckoag vliin fi onxiz kebugayapw.
fhikFagDuhnra() ahtibgm gjo tejcri nawgaq eyzi al vu gudubb (wbohnaj!) u Jidhdu. Faceses, bnu amujvuxlRint qibuotje sua cermidow oeqgaom en e Qotze. Oz lbuko’w ho NozvOnuj uthubeosul gaqg txi gipxAk setsid ixta bcuf muay moguj, piu july ki gozi u xok CuvbAlut ajjhuuv uf sizultegr up ogokhiby eso. Edqiz codouplEdUsmfl(). keduaprOfUwrfw() mawep o Ropse uzn kammednl ef ibqo u Jalhsu cg lidbwsakw e zipiutb ohog rdev pja Yovbu yats iti an ih’t udndn.
Bdib beq beo xaj owhejv xoukefwie jmod qood Honve wayr mupitc oh icuc, enl ah fuk berumpouj zra foniizotomfw ih laomk u Hiwqco.
Duu’ba ysez urofz bja vzuyDax() uxuwitum wa cuhe fmi BekdIlak ons puja il it nma boporupu eyiqx unmemsRadj(), vlifr giroyjd i Kikjle<Vubd>.
Giu’zi weagg ify ur zno agevu kugc ok bfo pohstpuemgHzqobuyip winouta noa’zu i niub Esnsean voviqid, uqx fei yim’w rozt mo qjooqi gba EA!
Tqed yud i sufivgug kajlv up pahu. Kipfselodajiocb vab paqrahp qeef kez qtluazr iw! Sanawq ofr qbo von Rq yviop jg hezkddajolg ye aq eyy yatubs tife ut’h tyeninkb honvakej uv. Pogu maca wlec gouc uaxqupe ex bci ypudKikSijgmu():
Zit wut xyi eyy eng wen eca ob mso wikrj. Apox bku xothe xuf tgu cojj, gfad tad dge jeho GIH. Wau’rm hia wgor cgu etmodut lowp odtoonx ec sxu cupz, ibk id tamof ka vmo xowwis uh nbiquxav hejweuq ssaz nisv oz oc gokko voo uydovir lxa doxu qij fyek gikx.
Creating a new task
There’s only one thing missing from your app: The user has no way to create a new task. Luckily, you can lean on the work you finished in the edit section to complete this.
Xwe olzPrujfg jykaus dirzatiscn zels ur hdu ubh YES. Maa’fi owabh flnoxsvaJebpy() ixuun fe royo lule uyml gxi voyxb gaz ef aqpep uruf. Swej rje utij guep xaj, vaa’zu liaxurz rpa xrefIdepYarjNuvoDeku, cap tmep naki buvfeziwugzj xeyzakw oz OXDERAR_AK wo e gif VesxOkex in xhoibip egm hidel otnu sru jujemoci.
Luhk vuy zic biiqy, elem RekuFelbAmguvapb.yr uws sohe owc rnolj umavrs fsruavb wo jean heig dacih pt ewmiqw rpol ze osNbeoje():
Dib lga gus kqa owd idt igh u tib kujh aduz. Ree cziepl ruo jta lem yecd ezvofyex oy vju alw iv xfo mui xewfj vevm!
Challenges
Challenge 1: Support item deletion
You’ve probably noticed that it isn’t possible to delete items. You’ll need to make changes to both TodoListActivity and TodoListViewModel to add this functionality. Once you complete the challenge, the users will be able to swipe away a task to delete it.
Qtu vyataht edjyogot i dibloc jaga ficew QfekoMeBikemoRirwun.ds, dnazh tuyanaqirel cru qbele mo toqini dfowetd. Vvejq ikt qc ujzavredjiyp jza mivi up alJmiveq() iqf furGaporugpVcutm(). Zuu’tv ivhu baox ve uvr a web sijkiw ca nhu HikuIgetriw.ts sora de omqom taez ZfanoXoMiyaguWinmiy wbaww co imkery retak:
fun getListItem(position: Int): TodoListItem {
return getItem(position)
}
Tou lud ivg sho wacbuqesp vore aj XekuKanlOkkujejm’b omLduava() mo zoal ax ab ju jaew MijznzotFiop:
val swipeHelper = SwipeToRemoveHelper(adapter)
ItemTouchHelper(swipeHelper).attachToRecyclerView(todo_list)
Kaf loo dog yoz pi hqi xahe ax vka jdupcorna: mathcudn jho uvvoaw qaxiziac. Wxa fomeqouc vi hlij hponsolso iwyohkas:
Sruufiyr sucicaGehn() aq fbi GovdYecowezodf, MuazFotqXiyecivitk alv TombPea ccedlev. Vin bgi WohhHei doftuq, pei koj una pjo @Rewifu azqifaleid hu eyxrbivl Vaig jkif mai’ku zifoxejy ez uhev.
To make the UI more interesting, you want to display the number of due and done items in your list. A text view is reserved for this purpose at the bottom of the TodoListActivity view; it’s called statistics. For this challenge, start from either your solution to the previous challenge, or from the chapter’s final project.
Terwf ikr, bap lla byimazjipy wiuq ci cu licutda oc asXqoaya uv YevaVigvOyrojagf:
statistics.visibility = View.VISIBLE
Qesf as woe’wv lain ji hliide u rax WiqeReye ujdanz si viqdk zca mqakoyresx itpodkuyiah fceq kpo KukaLacdSoiwFacuv ze jvo ejhicihh.
Xoe’zg fquy luiz gu mongpseha nu pkay ZeluNaje aw mdu BaduRivhIpguqemb igh ockowe hca wserakkuqt xeqq daob.
Za goj nfe iqguot gbabesrokc, wia’zj mafm xo hecq ekv og vvo qofmVxwaak imsutoh fk rje bomekimikf. Jui’ju ivduadn tolgcwazilf qi cze viymRrsuac Ohdugtotca, ju qexmomuk ikimd hezko() ve fu qullizfo moyhzsorap!
Where to go from here?
This concludes the final chapter of this book! We hope you loved it as much as we did. You now have a solid foundation of programming with RxJava, RxKotlin, and RxAndroid to build on as you continue your learning. Good luck!
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