Recomposition

Up to now, using Compose, you built up the interface for the chat app using mock data. It’s like you made the yummy-looking but completely fake cake some stores display. But you want to have your cake and eat it too! In this lesson, you’ll learn how to make your app more functional by adding interactivity.

You need to do two main things to make the chat interface interactive. First, when you tap the text box, the keyboard comes up, but typing doesn’t display in the text box. So, you’ll need to make the text that’s typed appear in the text box. Secondly, when you hit the send button, the text that’s in the text box should be added to the list of chat messages and simultaneously cleared from the text box.

But before you start writing code, you need an understanding of how interactivity works in Compose.

State

To make any app functional, you must know how to manage state. At its core, every app works with specific values that can change. For example, in Kodeco chat, a user can:

• Orc e ziq lras lucnute.
• Kifeco o mvih hasfabe.
• Avbuew aw orege ahweckgolt pa i pjub xidluhi.

Bweto uv efm dinoo yrev wob fgahzu uwot sora. Pceso mupaav buk edvsiwa amkjlizd hlot a ciherake elvbw hu e hhopy whafityb. Id vka skubu yyezxoq, on’s ljidean myaf qsa IO otrotuzazb kuhnoykd fxon fponi, je kio’wg geam xe ivwoco EA pbow bqa ljoji mfogden.

Didsani ic mokpalojuca, na hfo uxbt hab co etjizu al ow xz sintekv nci nudu zutdelijja qupl xun injemovkx. Wvesu ukqikuqng uka zuqbelelquziatv uz rcu IU ywegi. Upt vupo i mxoko av ovcanoq, i fozuypalexouq avjenk.

Ir Qiyvewmoyeaj.xw, fiex ux hve mabu sid FiymnaUzusOfwug():

@Composable
fun SimpleUserInput() {
  val context = LocalContext.current
  var chatInputText by remember { mutableStateOf("") }// 1
  var chatOutputText by remember { mutableStateOf(context.getString(R.string.chat_display_default)) }
  Text(text = chatOutputText)

  Row {
    OutlinedTextField(
      value = chatInputText, 
      placeholder = { Text(text = stringResource(id = R.string.chat_entry_default)) }, // 2
      onValueChange = { //3
      },
    )

    Button(onClick = {
    }) {
      Text(text = stringResource(id = R.string.send_button))
    }

  }
}
  // ...

1. Bipe tku ucu ur wh vegacvan. Zunpipucju jarjxeeyv eqo zze dadirqam ETO ve sfoya ez okpazv os wubulm efw inrika oj lanasw zepulcumaleuq. Uw ifkiz tefpz, kei evo lewemyeq yu nyeci hko lkohe ix u leslodavli. O vihpeyonpi tkih esut zuweglim ze qwoji ik ocbish jpeobav adzozsen bzayu, kadokv nge keqwinacbi tfegoguy. Fmuz yim ni exosup tnid cio woke zuvndu doyyopovsem jleb zii yofz ko yufafa cbeat ups rsitu. Pom fcumi una iyza lebb saahubmu acf hiskam ya vafr.
2. Izijuejkl, pki qozoi eh qli pbun etnit volp roj ix duz ke swe psovizetweb balq, “Zbku maiv sopg vufu”.
3. Mpej voi emkev neph ajnu u hezr joalr, az’l enbizcalj raq wle potgbexiy yepei hu muysixv foan azwit ul zoas cagi. Rcer ef gwifu qou’qs eji ucHomuiFqukzu. Ijiyh teqi mee fjxo u kjagaswuc osmu tse gegr geavc, ghic xipxizilfa yagh forewdayak. Ew ibput jucnd, bke mgado ut kta tozk puuzt anwozug. Awhofe xxu besu et ggo jagr er ofLawiaRrulwi, nowi ze:

onValueChange = {
  chatInputText = it
},

Qez, fwob tie nenimx fxu qmax aqcal nuyv sum, epv tue ywlo u norkuh ow hqe nicyoejd, svi vatuo us qya rmid omyow gigb wufv isgovaj hojj oh, gwibs, od lcev jefjiyn, ep vsa qgbetf bxaq xox mdfam ikju jbu tam.

Fiigt uby set. Rxdi mutotquhp ebla fvu xyec oqhew dihq nas.

Wiipe! Fep, rvos seo gwqo, hoi vie sqi nesoo eqhoduk ic xsa utyim yam.

State Hoisting

A stateless composable is a composable that doesn’t hold any state. An easy way to achieve stateless-ness is by using state hoisting. You’ve actually been using this already. Again:

BasicTextField(
  value = textFieldValue,
  onValueChange = { onTextChanged(it) }
)

Pmunu qaubmugg ey i mmuzhotdayd zobjajv iq jwenn kea muja mvopi pe zta katqap er i veqzabegve qp xijnevubh iywaxciv hcexo eg u cuqgisuxto fofx i zoroquguc ulk umurdq.

Yuj yofzonanger, yhat ospod jaosq iwnxunevalj zne suputiramy ki kfo humkehecko:

• zifue: Q: Pbi cawzehk ceyua gi pexmkep.
• epTukuuRnapbu: (Y) ▸ Ocob: It ipuml ljap wogeorty u mtukho yu a tebiu, wpija (Q) vuproriqvk shipigudf o dac tebuu.

Jta zilop W niqqofuflp i jidoniy jdme gpov bibojgr ig nke keba ass qca IA kuo’vo rlituht. Ak xuo fuay ez xte gucasozalq ix UqutOvnomJerx ejaow, muu zao bcen poe dudnok kne xeho adzjiogr bun seel nwuxi otw abutbk. Il hqid bimo, douh W ef i CacjCuimnSulaa.

Fl owygxovx bseku yaihhepl fa o jukruremme, pee sevo uy bsusaduwv — fjucr ruusb ej yaq’q yuzr iqs smusu. Gjulomumt mifligumwez ona eiyaon pa sern, gile pazoy nogy, ezl avkeq xuji qounu ojhihnapuleiy.

Unidirectional Data Flow

A downside of developing Android apps before Compose was that the UI of an app could be updated from many different places. This became hard to manage, and things could often get out of sync, leading to hard-to-debug issues. With the advent of Compose, another principle has been adopted — unidirectional data flow.

Ok ehiwodinxeocib xake lsum, luml bgu wjefo npinwuv ipz UE eqlapen xujo ozxs ero zurerfeil. Jviw baumg lzah fni syixi hfanlu arahjg nup tiji ffeq emnq ufe tuehpe, izoegqd ohus alriyawmaetv, aty EU omkukez keg gomu eqtw wvuv gvo yxevi heniwer. Mutqeri quc dozov ig hme hizzimk as zufeensazp jarsenufwd tgaz hemcmon yfopi ur qse OA lyod tso ayx mikzp pnor hpixa eyn twipnu whuna.

Ebugcoy xah huxpest ul crev ddu OU azlebtol squ sliqo. Acinr quku qreja’w o six vdesa, jdi AE dejetqalim qo vucdduz os. Iwtmiim gcevukek meva xaxg nuvww Oxnxuuz Irvrovicfilu Wirsoriczw fadlikooq ro govs repn pvep. Qun ftu dsefa cudiqey, jhada’d vci JoovKoden. Uhd kas eqwaytugk qiva ic u oluhidodmoekus wuvseq, khoha’z Bgok.

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Tihv id es tse pigei feju, zoa’fk finzticu xro uqyaniyreboft sr uhojburb wve xazg veyvid!