Peb npaj koj qhov kev pom! Kev ua tau zoo nrog ONMA scout android app kev txhim kho yog lav.
Hu rau
Yog tias koj tsis tau ua ib daim ntawv thov Android ua ntej, tej zaum koj yuav ntshai me ntsis los ntawm tag nrho cov kauj ruam cuam tshuam. Yog koj yog ib tug pib, Koj tuaj yeem xav tias ntshai los ntawm Android Studio, uas yuav ua tau ib tug me ntsis complex siv. Nrog me ntsis kev xyaum, koj tuaj yeem ua tau yooj yim nrog Android Studio thiab nws ntau yam nta.
Thaum tsim mobile apps, Nws yog ib qho tseem ceeb uas yuav tau xav txog yam kev ua tau zoo uas koj cov khoom yuav xav tau. Koj tuaj yeem xaiv los ntawm haiv neeg lossis hybrid apps. Native apps yog optimized rau tej operating systems, thaum hybrid apps khiav hauv lub web browser. Cov apps hauv haiv neeg yog qhov nyuaj dua thiab xav tau cov lus programming cais. Hybride apps muaj cov kev xav tau zoo sib xws, tab sis pheej yig dua los txhim kho.
Tus txheej txheem ntawm kev tsim ib qho app yuav kim heev, tab sis nws tuaj yeem muaj txiaj ntsig yog tias nws ua tiav. Nws pib nrog kev npaj kom raug, kev sib sau ua ke, thiab prototypes. Lub app ua tiav tuaj yeem pab koj txhim kho koj txoj kev lag luam thiab koom nrog cov neeg siv khoom. Txhawm rau tsim kom muaj kev vam meej app, koj yuav tsum paub koj lub lag luam thiab dab tsi yuav ua rau lawv zoo siab.
Android yog qhov nrov mobile operating system. Nws muaj peev xwm tsim hybrid thiab haiv neeg apps rau Android. Native apps yog tsim tshwj xeeb rau Android thiab nkag mus rau kho vajtse. Yog tias koj xav tsim ib qho app rau lwm lub platform, koj yuav tsum tau rov code nws thiab tswj nws nyias. Koj tseem tuaj yeem siv hauv app yuav khoom kom tau nyiaj.
Yog tias koj tab tom npaj tsim ib qho app rau Android, nco ntsoov xaiv lub tuam txhab uas txhawb nqa cov txheej txheem. Cov tuam txhab xws li zeroseeven tsim studios muaj kev paub txog kev tsim cov apps ib txwm muaj thiab tuaj yeem pab koj kom koj lub app tawm hauv av. Lawv siv cov thev naus laus zis tshiab los tsim cov apps uas phim lawv cov neeg siv khoom’ hom, cov neeg tuaj saib, thiab xav tau.
Koj xav kawm yuav ua li cas los tsim Android apps nrog Kotlin programming lus. Tab sis ua ntej koj pib tsim cov apps hauv Kotlin, koj yuav tsum paub koj tus kheej nrog cov hauv paus ntawm Android programming. Tam sim no, ntau lub npe tsim thiab paub txog Android app developers siv Kotlin. Txawm li cas los, hom lus tshiab no muaj qee qhov tsis zoo.
Tus thawj constructor muaj nyob rau hauv cov chav kawm header. Qhov no tshem tawm qhov kev xav tau ntawm tus tsim khoom thib ob thiab tus neeg txais thiab cov neeg tsim khoom. Ntxiv thiab, koj tsis xav tau constructor parameter. Hloov chaw, koj tsuas yog yuav tsum tau sau ib kab ntawv hauv chav kawm nrog koj tus tsim thawj.
Yog tias koj tab tom nrhiav lwm txoj hauv kev rau Java, Tej zaum koj yuav xav mus saib Kotlin rau Android app creation. Nws yog ib qho niaj hnub, statically-typed programming lus uas khiav ntawm Java Virtual Machine (JVM). Kotlin tau txais kev txhawb nqa rau Android apps. Koj tsis tas yuav muaj kev paub dhau los hauv Java lossis Kotlin, txawm hais tias nws yog qhov zoo tshaj plaws rau cov uas muaj kev paub me ntsis hauv kev txhim kho daim ntawv thov.
Ib qho ntawm qhov txaus nyiam tshaj plaws ntawm Kotlin yog nws txoj kev yooj yim. Vim Kotlin yog li ntawd compact, Kotlin tuaj yeem txo qis ntawm tus lej ntawm boilerplate code uas cov neeg tsim khoom yuav tsum sau. Qhov no ua kom yooj yim rau tus tsim tawm txoj haujlwm thiab txo cov kev pheej hmoo ntawm kev ua yuam kev. Ntxiv rau, hom lus tsis siv kev txiav txim siab rau nws tus kheej. Boilerplate code ntau dhau ua rau muaj kab ntau ntxiv thiab nkim sijhawm.
Qhov laj thawj tseem ceeb vim li cas Java siv los tsim Android apps yog vim nws yooj yim kawm thiab muaj ntau yam muaj zog. Java yog ib hom lus programming nrov tshaj plaws thoob ntiaj teb thiab muaj lub tsev qiv ntawv nplua nuj ntawm cov peev txheej. Nws tuaj yeem txuag cov neeg tsim khoom ntau lub sijhawm los ntawm kev tshem tawm qhov xav tau los tshawb nrhiav cov ntaub ntawv tshwj xeeb. Txawm tias qhov no, nws tsis yog hom lus zoo tshaj plaws rau cov pib tshiab.
Pib, koj yuav tsum tsim ib qhov project hauv Android hauv Eclipse IDE. Thaum koj ua tau li ntawd, Koj tuaj yeem xaiv lub Android version thiab lub npe ntawm koj lub app, zoo li lub pob, chav kawm, thiab chaw ua haujlwm. Tom ntej no, koj yuav tsum tsim cov dej num. Cov haujlwm yog cov haujlwm sib txawv uas tus neeg siv tuaj yeem ua ntawm qhov screen. Thaum qhov no ua tiav, Eclipse IDE yuav qhib cov ntaub ntawv tsim nyog.
Lwm hom lus siv los tsim Android apps yog Python. Thaum Android tsis txhawb nqa Python kev txhim kho ib txwm, muaj cov tsev qiv ntawv qhib uas ua rau nws yooj yim los tsim ib qho Android app hauv Python. Kivy yog ib lub tsev qiv ntawv zoo li no, thiab nws txhawb kev txhim kho app sai. Txawm li cas los, yog tias koj tsis paub nrog Python, koj yuav tsis txaus siab rau tag nrho cov txiaj ntsig uas Python muab cov apps ib txwm muaj.
Java muaj ntau yam txiaj ntsig dhau C ++ thiab Python, tab sis nws kuj muaj nws downsides. Cov neeg uas xaiv Java rau Android txoj kev loj hlob zoo li yuav siv cov thev naus laus zis tsis tu ncua. Thaum Java yog hom lus nrov tshaj plaws los tsim cov apps, Kotlin kuj tau siv dav. Nws yog ib hom lus niaj hnub, thiab nws tau sib xws nrog ntau lub tsev qiv ntawv Java.
Yog tias koj muaj Android app, Koj tuaj yeem siv OnItemLongClickListeners-Interface txhawm rau txheeb xyuas thaum lub caij nyem. Lub moj khaum yuav hu rau onItemLongClick() txoj kev yog tias ib yam khoom tau nyem rau lub sijhawm ncua sijhawm. Txoj kev no ces xa lus mus rau AlertDialog.
Txhawm rau siv OnItemLongClickListeners, tsim ib qho kev ua haujlwm hauv koj lub app uas tsim cov haujlwm hu rov qab thaum twg ib yam khoom raug xaiv lossis nyem. Thaum ib yam khoom raug nias rau lub sijhawm ntev, lub Android Framework yuav lees paub nws ntev nias thiab yuav tso tawm cov ntawv ceeb toom luv luv los qhia tias qhov nias ntev tau sau npe. Ntxiv rau, Lub OnItemLongClickListening-Interface xyuas kom meej tias cov txheej txheem onItemClick raug siv. Yog tias koj tab tom sim ua qhov haujlwm no hauv Android app, nco ntsoov ua raws li cov piv txwv.
Android's onSaveInstanceState() txoj kev txuag tus neeg siv lub xeev nrog rau txhua yam kev ua tswv cuab hloov pauv. Txoj kev no yog ua raws li onRestoreInstanceState() txoj kev uas restores lub xeev app thaum nws rov pib dua. OnStart() rov qab cov ntaub ntawv los ntawm viewstatus, uas tuaj yeem suav nrog cov ntaub ntawv los ntawm ntau qhov kev pom.
Yog tias koj qhov haujlwm muaj ntau cov ntaub ntawv, Tej zaum koj yuav tau txuag nws tsawg kawg ib zaug. Tias yog vim li cas nws tseem ceeb heev kom hu rau ntawmSaveInstanceState() hauv koj lub Android app. Txoj kev no txuag cov haujlwm hauv lub xeev los ntawm kev xa rov qab Bundle-Object nrog nws lub xeev. Ces, koj tuaj yeem siv cov khoom no los tsim qhov Kev Ua Haujlwm. Koj tuaj yeem siv Lifecycle Callback Methods los kho lub xeev ntawm ib qho haujlwm.
OnSaveInstanceState() tsis yog ib txwm hu, yog li koj yuav tsum ua tib zoo siv nws. Tsuas yog hu rau nws thaum koj qhov haujlwm tseem ceeb, thiab tsis txhob ua cov ntaub ntawv khaws cia thaum lub sijhawm ua haujlwm tsis ua haujlwm. Qhov no yog vim tias Android system tuaj yeem tshem tawm cov haujlwm vim yog daim ntawv thov tus cwj pwm zoo lossis los ntawm nias lub pob rov qab. Qhov ntawd txhais tau hais tias qhov kev ua haujlwm piv txwv tsis ua haujlwm lawm.
Lwm qhov tseem ceeb ntawm onSaveInstanceState() yog tias nws tso cai rau koj txuag UI-State ntawm Aktivitat, uas txhais tau tias nws khaws lub xeev ntawm lub app. Ntxiv rau, txoj kev no tuaj yeem siv rau kev khaws cia tsis tu ncua. Nws tuaj yeem siv los khaws cov ntaub ntawv teeb tsa. Thaum lub configuration hloov, Android code yuav daws nws. Ntxiv rau, Koj tuaj yeem siv Android.screenOrientation thiab android.configChanges los tso saib Toast-Meldings raws li kev taw qhia ntawm lub vijtsam.
Yog tias koj tab tom tsim Android app, koj yuav tsum paub txog Activity Lifecycle Callbacks (ALC). Cov no yog cov txheej txheem uas tau hais thaum muaj kev ua si pib lossis nres. Lawv pab koj tswj cov peev txheej ntawm koj txoj haujlwm, sau npe mloog, thiab khi rau cov kev pabcuam. Koj tuaj yeem siv lawv los khaws cov ntaub ntawv thov. Koj tuaj yeem kawm paub ntxiv txog lawv nyob rau ntu tom ntej. Cov kev hu rov qab no muaj txiaj ntsig zoo thaum tsim ib qho app hauv Android thiab tuaj yeem pab koj tsim kom muaj txiaj ntsig zoo dua.
OnCreate() raug hu thaum tsim kev ua si, thiab nws tsim UI Cheebtsam, kev khi, thiab views. Hauv Pause() yog hu thaum qhov kev ua si mus rau hauv keeb kwm yav dhau los yog raug kaw. Cov haujlwm saum toj kawg nkaus thov rau ntawmPause(). Yog tsis hu txoj kev hu rov qab no, cov haujlwm yuav tsis rov ua dua kom txog thaum onResume() rov qab los.
Lub onCreate() txoj kev ntawm ib qho kev ua ub no yog ib txoj hauv kev teeb tsa kev ua ub ua no uas ua rau kev pib ua haujlwm. Nws tshaj tawm UI, txhais cov tswv cuab variables, thiab configures lub app. Nws kuj hu SDK_INT, uas tiv thaiv cov txheej txheem qub los ntawm kev ua tiav APIs tshiab. Android 2.0 (API qib 5) thiab ntau dua versions txhawb tus chij no. Yog siv cov txheej txheem qub, lub app yuav ntsib kev zam runtime.
Activity Lifecycle Callbacks tseem hu ua thaum muaj kev hloov pauv hauv xeev. Lub OS hu rau onCreate() hu rov qab yog tias qhov kev ua si raug tsim, onResume() yog tias nws rov pib dua, ntawm Pause() thaum qhov kev ua si nyob rau hauv pem hauv ntej, thiab ntawm Destroy() thaum lub luag haujlwm tau raug rhuav tshem. Yog tias koj override ib qho ntawm cov callbacks no, koj yuav tsum hu rau txoj kev ntawm cov chav kawm super. Lwm yam, qhov kev ua yuav poob los yog xaus rau hauv lub xeev coj txawv txawv.