Yuav kawm android App Programmieren

Yog tias koj xav kawm Android app programming, koj tsis yog ib leeg. Qhov tseeb, nws yooj yim pib! Pib nrog Android Studio, Google txoj kev loj hlob dawb ib puag ncig. Koj tseem yuav xav tau Java Development Kit. i, koj tuaj yeem pib sau koj thawj cov apps. b, koj yuav txav mus rau Intents, Java, Activity Lifecycle Callbacks, thiab ntau dua!

Luag-thiab-poob

Luag-thiab-poob Android app programming yog ib qho yooj yim thiab muaj zog uas tuaj yeem pab koj tsim cov ntawv thov sib tham sib heev. Lub luag thiab poob mechanism tso cai rau koj mus txav cov khoom nyob ib ncig ntawm lub app tsis muaj kev cuam tshuam rau tus so ntawm daim ntawv thov. Luag txheej xwm yog xa mus rau listeners los ntawm ib tug Android kev tshwm sim. Lub luag kev tshwm sim muaj cov ntaub ntawv hais txog lub xeev ntawm qhov khoom thiab yuav muaj xws li cov ntaub ntawv xws li ib tug X-y coordinate. Lub luag kev tshwm sim listener tau txais cov ntaub ntawv thiab hu rau txoj kev getX() los yog getY() kom tau txais txoj hauj lwm tam sim no ntawm lub luag point. Yog hais tias lub luag ua hauj lwm tau ua tiav, tus listener rov qab ib tug boolean muaj tseeb los yog cuav.

Luag-thiab-nco Android app programming yog ua tau nrog dab noj hnub 4.4 (Luna) thiab Java 1.7. Yuav kom siv luag-thiab-poob, koj yuav tsum tau ntxiv ib tug OnTouchListener rau koj Activity. i, tsim ib tug DragShadowBuilder uas qhia txog daim duab yuav tsum tau tso tawm kom pom thaum lub sij hawm luag ua hauj lwm.

Luag-thiab-nco Android app programming koom nrog kev siv luag txheej xwm chav kawm thiab luag listeners. Luag txheej xwm pib nrog ib tug neeg siv txhais. i, lub app muab ib tug startDragAndDrop() callback. Yog hais tias lub luag txheej xwm listener rov qab cuav, lub kaw lus yuav tsis hu rau txoj kev hu rov qab. Lub DragEvent chav kawm yog zoo ib yam li onTouchEvent.

Koj tuaj yeem hloov tus cwj pwm ntawm luag-thiab-poob kev tshwm sim los ntawm kev hla txoj kev onProvideShadowMetrics. Txoj kev no rov qab cov ntaub ntawv hais txog qhov loj me thiab kov qhov chaw ntawm qhov kev tshwm sim luag. Koj tseem tuaj yeem hloov kho qhov luag-thiab-poob piav tes piav taw los ntawm kev hla txoj kev onDrawShadow.

Luag-thiab-poob Android app programming yog ib qho yooj yim thiab hloov tau yooj yim uas tso cai rau koj tsim cov ntawv thov mobile zoo. Nrog luag-thiab-poob, koj tseem tuaj yeem ua rau cov txheej txheem system thaum cov neeg siv ua haujlwm luag thiab xa kev ua.

Intents

Intents yog siv los sib txuas lus ntawm cov khoom sib txawv hauv Android app. Ib daim ntawv thov Android tuaj yeem txhawb nqa ob qho tib si meej thiab implicit intents, Uas yog siv los tswj cov ntaub ntawv ntws los ntawm ib daim ntawv thov mus rau lwm qhov. Ib qho piv txwv ntawm qhov no yuav yog lub qhov rai browser uas xa tus neeg siv mus rau lwm daim ntawv thov thaum lawv qhib nws.

Lub hom phiaj tuaj yeem yog ib tus lej lossis txoj hlua, thiab siv los ua rau lwm yam haujlwm hauv ib qho app. Ntxiv rau kev ua rau lwm yam ntawm ib qho app, cov hom phiaj kuj tseem tuaj yeem siv los txav cov haujlwm hauv ib qho app. Tus yuam sij yog siv lawv kom zoo. Koj yuav tsum zam cov ntaub ntawv serializable lossis parcelable thaum ua haujlwm nrog lub hom phiaj.

Piv txwv, koj tuaj yeem siv ib txoj hlua los qhia cov ntaub ntawv Tshuag rau tus neeg siv. i, lawv tuaj yeem nyem rau ntawm lub ntsiab lus mloog kom pom cov ntsiab lus nyiaj txiag ntawm cov Tshuag. Lub app yuav tom qab ntawd tso saib cov ntsiab lus no hauv daim ntawv teev npe saib. Lub app tej zaum yuav txawm yuav customized los ntawm kev tso cai rau cov neeg siv xaiv cov Tshuag xav tau. Nws mam li tso saib ib daim ntawv teev cov stocks raws li lawv xaiv cov cai, including any pending purchases and selling orders.

Android apps often consist of several screens. Sometimes, users need to switch between apps for various reasons. To accomplish this, they use the Intent mechanismu. Intents are used to connect activities within the same app, as well as between apps. To switch between apps, you should create a new intent object and use a suitable Android method.

Intents allow Android apps to provide functionality similar to the web. To do this, Android apps can implement an intent filter for web links. This means that links that point to web sites will open the Android app instead of a web page. Tsis tas li ntawd, android 12 introduced generic web intents, which are used to open the user’s default browser app.

Activity Lifecycle Callbacks

When you write code in Android apps, Tej zaum koj yuav feem ntau tuaj hla Kev Ua Haujlwm Lub Neej Hu Rov Qab. Cov kev hu rov qab no qhia rau koj paub thaum twg koj daim ntawv thov yuav tsum raug kaw, rov pib dua, lossis rov qab mus rau lub xeev dhau los. Hmoov zoo, Cov kev hu rov qab no tuaj yeem siv rau hauv ob qho tib si Kev Ua Haujlwm thiab Fragment cov ntsiab lus.

Muaj peb hom Kev Ua Haujlwm Lub Neej Callbacks. The first one, onStart(), yog invoked thaum twg ib qho haujlwm tshwm sim thawj zaug ntawm lub vijtsam. Qhov thib ob, onResume(), yog hu thaum ib qho haujlwm rov qab los ntawm kev ncua. Qhov no yog qhov tseem ceeb hu rov qab rau txhua Android app vim nws tuaj yeem tiv thaiv koj lub app los ntawm kev khiav ntev.

Koj yuav tsum nkag siab txog Android API los ua cov kev hu rov qab no. Cov onStart thiab onStop txoj kev raug hu ua ob peb zaug los ntawm qhov system. Qhov no txhais tau tias koj lub app yuav hu rau onStart txoj kev ob peb zaug. Qhov no yuav ua rau koj txoj haujlwm pom thiab zais. Koj kuj yuav tsum muaj peev xwm qhia thaum qhov kev ua ub no raug rhuav tshem los ntawm kev saib cov lus logcat.

Lub onCreate thiab onDestroy callbacks yog triggered los ntawm OS raws li qhov tshwm sim ntawm cov neeg siv kev sib cuam tshuam. Cov neeg tsim khoom tseem tuaj yeem hla cov callbacks. tiam sis, Thaum overriding cov callbacks, cov neeg tsim khoom yuav tsum nco ntsoov hu rau txoj kev kawm super. Tsis ua li ntawd tuaj yeem ua rau lub app khiav hauv lub xeev weird lossis txawm tias sib tsoo.

Kev ua haujlwm lub neej hu rov qab pab koj nkag siab thaum koj daim ntawv thov yuav tsum nkag mus rau lub xeev nres lossis nres. Koj yuav tsum tsis txhob ua tiav kev xam siab thaum lub sijhawm no, Raws li nws tuaj yeem ncua kev hloov mus rau lub xeev tom ntej thiab xaus rau tus neeg siv kev paub.

Logging

Logging Android daim ntawv thov tuaj yeem yog cov cuab yeej muaj txiaj ntsig zoo rau cov neeg tsim khoom. Android siv lub kaw lus nruab nrab rau kev khaws cov lus cav, uas tuaj yeem lim los ntawm qeb lossis qhov tseem ceeb. Koj tuaj yeem kho cov lus los ntawm kev sau cov lus teev npe kev cai uas muaj feem xyuam rau koj lub app kev ua haujlwm. Muaj ntau txoj hauv kev los teev thiab txheeb xyuas cov lus cav.

Ib txoj hauv kev yooj yim tshaj plaws los sau yog los ntawm kev siv chav kawm Log built. Txoj kev teev npe lees txais ob lossis peb qhov kev sib cav. Feem ntau cov lus cav muaj ob qho kev sib cav. Cov lus sib cav yuav tsum yog hom Hlua. Hom kev teev npe no yog txwv, tab sis nws yog ib qho cuab yeej muaj txiaj ntsig zoo rau ntau lub hom phiaj.

Logging Android apps tau dhau los ua qhov nrov programming xyaum rau cov neeg tsim khoom. Nyob rau hauv dav dav, Android app yuav tsum tau teev cov xwm txheej lub neej thaum twg lawv tshwm sim. Yog tias daim ntawv thov yuav tsum tau debug ib qho teeb meem, Nws yuav tsum sau cov ntaub ntawv uas pab cov neeg tsim khoom debug daim ntawv thov. You can also log debug information using the Log.d() txoj kev. The latter method can also log variable values and print messages.

While debugging is helpful in case of errors, over-logging can reduce performance. The best practice is to use debug logging only for development, and remove the verbose logging before publishing your application. As a developer, you should always review the logging output prior to publishing it. Android SDK comes with an integrated logging class. It writes the application’s data to a log called LogCat. tiam sis, this method has some performance issues, so it should be used only when necessary.

You can also view the system logs in Android. These logs contain information on everything from analytics events to location and booking logs. You can filter the log output by application package with the help of a tool such as Android Studio.