MobileDevelopmentWorkshopDAY3:BASICANDROIDAPPLICATIONS

OverviewMorningsession◦ Views,layouts,andactivities◦ Binding toviews◦ Android intentsandinformation passing

ViewsThebasicbuildingblocksofaUserInterface

Responsiblefordrawing theinterfaceandresponding toevents

Somecommonviews

LayoutsSpecialtypesofviewsthatholdotherviews

Invisible

Eachlayouttypehavedifferentrulesandpropertiesforpositioningtheirchildviews

Layoutsformthevisibleaspectofactivities(moreonthatlater)

CreatingalayoutfileDescribethelayoutinXML

Describeitschildren

LoadingalayoutfileInyouractivity,setthelayoutfiletobetheview◦ setContentView(R.layout.layout_file_name)

Somecommonlayouts

Organizesitschildrenintoasinglehorizontalorverticalrow

Allowsyoutospecifythelocationofachildobjectrelativetoothersortotheparent

Displayswebpages

LinearLayout RelativeLayout WebView

ViewparametersViewsinsidealayoutwillhaveparametersthattellthemhowtheylook,behave,etc.◦ Examples◦ ID◦ Visibility◦ Size,paddingmargins◦ Position

Exercisepart1/2DesignthelayoutforanAndroidversionoftheSlotMachineJavaprogram

UseamixtureofLayouts

ActivitiesAnAndroidapplicationisacollectionofcomponents

AnActivityisoneofthemaincomponentsofAndroid◦ containsapplication logic(code)

Applicationsgenerallyconsistofoneormoreactivities◦ OneactivityisdelegatedastheMain activity◦ Themainactivityisstartedautomaticallywhentheapplicationisstarted

DeclaringactivitiesActivities,likeallothercomponents,aredeclaredintheAndroidManifest

Themanifestdescribesyourapplicationtotheoperatingsystem◦ Examples◦ Application name◦ Version◦ Permissions

Androidstudiowilldeclarecomponentsautomaticallywhentheyarecreated,butyoucanchangepropertiesmanually

ActivitylifecycleAnactivity’slifecycleistheseriesofstatesthatitpassesthroughfromcreationtodestruction

Understandingthelifecycleallowustobuildflexible,responsiveapps

Activitylifecycle

EventsEventsaretriggeredwhenauserinteractswithaview

Eventlistenersareusedtospecifywhatshouldhappenwhenaparticulareventtakesplace

Manystandardeventlistenersarefoundinside theView class

EventlistenercallbacksAndroidprovidesmanyView.On*Listenerclasseswithappropriatecallbackmethods

onClick◦ Calledwhentheusertouchestheview

onLongClick◦ Calledwhentheusertouchesandholds theview

onFocusChange◦ Calledwhenausernavigateto,orawayfromaview

Exercisepart2/2Inanactivity’sonCreate()method◦ Wireupthethelayoutfrom part1 toanActivity◦ Linkstheviewsinthelayouttoobjectvariablesinouractivity

◦ ExecutethegamelogicwhentheuserclicksaPlay button

WorkingwithmultipleactivitiesInAndroid,asingleactivityshouldbeusedforasinglejob

Assuch,anappwithmultiplejobsshouldutilizemultipleactivities

Fromoneactivity(suchasMain)youcanlaunchotheractivities

StartinganactivitystartActivity(intent);

Theintent isanobjectthatspecifiestheactivitytostart

IntotointentsAmessagingobjectusedtorequestthatactionbetaken

GenerallyusedtoStartcomponents such asactivitiesSendinformation fromonecomponent toanother

Intentsinaction

TocreateanIntentTwotypes◦ Explicit◦ Providecontext◦ Specify arecipient

◦ Implicit◦ Specify anaction

ContextContextprovidesinformationaboutacomponentaswellastheapplication’senvironment

Contextcanberetrievedfrommanyplaces,buttheinformationandcapabilitieswillvarybasedonsource

AcommonsourceofcontextisActivityName.this

ExerciseCreateatextmagnifier◦ Collecttextinformation inoneactivity◦ Passthatinformation toanotheractivitytobedisplayedinalargerfont