Android chapter03 life cycle

9/12/2011 1 Part3 Android Application’sLifeCycle VictorMatos ClevelandStateUniversity Notesarebasedon: Ul ki Ad id U n l oc ki ng A n d ro id  byFrankAbleson,CharlieCollins,andRobi Sen. ISBN978‐1‐933988‐67‐2 ManningPublications,2009. AndroidDevelopers http://developer.android.com/index.html 3.Android– Application'sLifeCycle AndroidApplications Anapplicationconsistsofoneormorecomponents thatare defined in the application ' s manifest file. A component can be one defined  in  the  application s  manifest  file.  A  component  can  be  one  ofthefollowing: 1. AnActivity 2. AService 3. Abroadcastreceiver 4. A contentprovide r 22 9/12/2011 2 3.Android– Application'sLifeCycle AndroidApplications 1.Activity Anactivity usuallypresentsasinglevisualuserinterfacefromwhichanumberof actionscouldbeperformed. Altoughactivitiesworktogethertoformacohesiveuserinterface,eachactivity isindependentoftheothers. Typically,oneoftheactivitiesismarkedasthefirst onethatshouldbepresented 3 totheuserwhentheapplicationislaunched. Movingfromoneactivitytoanotherisaccomplishedbyhavingthecurrent activitystartthenextonethroughsocalledintents. 3 Reference:FriedgerMüffke(friedger@openintents.org) 3.Android– Application'sLifeCycle AndroidApplications 2.Service Aservicedoesn'thaveavisualuserinterface,butratherrunsinthebackground foranindefiniteperiodoftime. It'spossibletoconnectto(bindto)anongoingservice(andstarttheserviceifit's notalreadyrunning). 4 Whileconnected,youcancommunicatewiththeservicethroughaninterface thattheserviceexposes. 4 Reference:FriedgerMüffke(friedger@openintents.org) 9/12/2011 3 3.Android– Application'sLifeCycle AndroidApplications 3.Broadcastreceiver Abroadcastreceiver isacomponentthatdoesnothingbutreceiveandreactto broadcastannouncements. Manybroadcastsoriginateinsystemcode(eg.“yougotmail“)butanyother applicationscanalsoinitiatebroadcasts. Broadcastreceiversdonotdis p la y auserinter f ace.However , the y ma y startan 5 py f , y y activityinresponsetotheinformationtheyreceive,or‐ asservicesdo‐ they mayusethenotificationmanagertoalerttheuser. 5 Reference:FriedgerMüffke(friedger@openintents.org) 3.Android– Application'sLifeCycle AndroidApplications 4.Contentprovider Acontentprovider makesaspecificsetoftheapplication'sdataavailableto otherapplications. Thedatausuallyisstoredinthefilesystem,orinanSQLitedatabase. Thecontentproviderimplementsastandardsetofmethodsthatenableother applicationstoretrieveandstoredataofthetypeit controls. 6 However,applicationsdonotcallthesemethodsdirectly.Rathertheyusea contentresolverobjectandcallitsmethodsinstead.Acontentresolvercantalk toanycontentprovider;itcooperateswiththeprovidertomanageany interprocesscommunicationthat'sinvolved. 6 Reference:FriedgerMüffke(friedger@openintents.org) 9/12/2011 4 3.Android– Application'sLifeCycle AndroidApplications EveryAndroidapplicationrunsinitsownprocess ( with its own instance of the Dalvik virtual machine ). ( with  its  own  instance  of  the  Dalvik  virtual  machine ).  Wheneverthere'sarequestthatshouldbehandledbyaparticularcomponent, • Androidmakessurethattheapplicationprocessofthecomponentis running, • startingitifnecessary,and • thatanappropriateinstanceofthecomponentisavailable,creatingthe instanceifnecessary. 77 3.Android– Application'sLifeCycle Application’sLifeCycle ALinux p rocessenca p sulatin g anAndroida pp licationiscreatedforthe p pg pp applicationwhensomeofitscodeneedstoberun,andwillremain runninguntil 1. itisnolongerneeded,OR 2. thesystemneedstoreclaimitsmemoryforusebyother applications. 88 9/12/2011 5 3.Android– Application'sLifeCycle Application’sLifeCycle AnunusualandfundamentalfeatureofAndroidisthat ana pp lication pp process'slifetimeis not directlycontrolledbytheapplicationitself. Instead,itisdeterminedbythesystemthroughacombinationof 1. thepartsoftheapplicationthatthesystemknowsarerunning, 2. howimportantthesethingsaretotheuser,and 3. how much overall memory is available in the sys tem. 9 3. how  much  overall  memory  is  available  in  the  system. 9 3.Android– Application'sLifeCycle ComponentLifecycles Applicationcomponentshavea lifecycle 1. Abeginning whenAndroidinstantiatesthemtorespondto intents 2. Anend whentheinstancesaredestroyed. 3. Inbetween,theymaysometimesbeactive orinactive,or‐inthe caseofactivities‐ visible totheuserorinvisible. 1010 LifeasanAndroidApplication: Active/Inactive Visible/Invisible Start End 9/12/2011 6 3.Android– Application'sLifeCycle Activty Stack • Activitiesinthes y stemaremana g edasanactivit y stack. y g y • Whenanewactivityisst arted,itisplacedonthetop ofthe stackandbecomestherunningactivity‐‐ the previous activityalwaysremainsbelowitinthestack,andwillnot cometotheforegroundagainuntilthenewactivityexits. 1111 • IftheuserpressestheBackButtonthenextactivityonthe stackmovesupandbecomesactive. 3.Android– Application'sLifeCycle ActivityStack NewActivity RunningActivity LastRunning Activity Activityn‐1 . . . NewActivity started Backbuttonpushedor runningactivityclosed Activity Stack 1212 Activity1 Activity2 Activity3 .  .  . Activity  Stack Previous Activities Removedto freeresources Figure1. 9/12/2011 7 3.Android– Application'sLifeCycle LifeCycleStates Anactivityhasessentially threestates: 1. Itisactive orrunning 2. Itispaused or 3. Itisstopped . 1313 Figure2. 3.Android– Application'sLifeCycle LifeCycleStates Anactivityhasessentiallythreestates: 1. Itisactive orrunning whenitisintheforeground ofthescreen (atthetopoftheactivitystackforthecurrenttask). Thisistheactivitythatisthefocusfortheuser'sactions. 141414 9/12/2011 8 3.Android– Application'sLifeCycle LifeCycleStates An activityhasessentiallythreestates(cont.): 2. Itispaused ifithaslostfocusbutisstillvisibletotheuser. Thatis,anotheractivityliesontopofitandthatnewactivityeitheris transparent ordoesn'tcoverthefullscreen. Apausedactivityiscompletelyalive (itmaintainsallstateandmember informationandremains attachedtothewindowmana g er ), butcanbe 151515 g), killedbythesysteminextremelowmemorysituations. 3.Android– Application'sLifeCycle LifeCycleStates Anactivityhasessentiallythreestates(cont.): 3. Itisstopped ifitiscompletelyobscured byanotheractivity. Itstillretainsallstateandmemberinformation.However,itisnolonger visibletotheusersoitswindowishiddenanditwilloftenbekilledby thesystemwhenmemoryisneededelsewhere. 161616 9/12/2011 9 3.Android– Application'sLifeCycle Application’s LifeCycle 1717 Figure3. 3.Android– Application'sLifeCycle Application’sLifeCycle Yourturn! EXPERIMENT1. Teachingnotes 1. W r iteanAndroidapp.(“PuraVida”)toshowthedifferentcyclesfollowedbyan application. 2. Themain.xmllayoutshouldincludeaButton(text:“Finish”,id:btnFinish)and anEditTe xt container(txt:“”andidtxtMsg). 3. UsetheonCreate methodtoconnectthebuttonandtextboxtotheprogram. Addthefollowinglineofcode: Toast.makeText(this, "onCreate", 1).show(); 4. Theclickmethodhasonlyonecommand:finish(); calledtoterminatethe 1818 application.AddaToast‐command(astheoneabove)toeachofthe remaining sixmainevents.Tosimplifyyourjob usetheEclipse’stopmenu:Source> Override/ImplementMethods… 5. Ontheoptionwindowcheckmarkeachofthefollowingevents:onStart, onResume,onPause,onStop,onDestry,onRestart (noticehowmanyonEvent… methods arethere!!!) 6. Saveyourcode. 9/12/2011 10 3.Android– Application'sLifeCycle Application’sLifeCycle Yourturn! EXPERIMENT1(cont.) Teachingnotes 7. Compileandexecuteapplication. 8. W r itedownthesequenceofmessagesdisplayedbytheToast‐commands. 9. PresstheFINISHbutton.Observethesequenceofstates. 10. Re‐executetheapplication 11. Pressemulator’sHOMEbutton.Whathappens? 12. Clickonlaunchpad,lookforiconandreturntothe“PuraVida”app.What sequenceofmessagesisdisplayed? 13. Click ontheemulator’sCALL ( Green p hone ) .Isthea pp  p ausedorsto pp ed? 1919 ( p) pp p pp 14. ClickontheBACKbuttontoreturntotheapplication. 15. Long‐tapontheemulator’sHANG‐UPbutton.Whathappens? 3.Android– Application'sLifeCycle Application’sLifeCycle Yourturn! EXPERIMENT2 Teachingnotes 7. Runasecondemulator. 1. Makeavoice‐calltothefirstemulatorthatisstillshowingourapp.What happensonthiscase?(real‐timesynchronousrequest) 2. Sendatext‐messagetofirstemulator(asynchronousattentionrequest) 8. W r iteaphraseintheEditText box(“thesearethebestmomentsofmylife….”). 9. Re‐ex ecutethea pp .Whatha pp enedtothetext? 2020 pp pp [...]... LAYOUT 3. Android – Application's Life Cycle Example Life Cycle Example The following application  demonstrates some of  the state transitioning  situations experienced in  the life cycle of a typical  Android activity   /T Vi 35 3. Android – Application's Life Cycle Example: Life Cycle Code: Life Cycle Demo. Part 1... 45 3. Android – Application's Life Cycle Example: Life Cycle Code: Life Cycle Demo. Part  10 @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); Toast.makeText(getBaseContext(), "onSaveInstanceState BUNDLING", Toast.LENGTH_LONG).show(); } // onSaveInstanceState }//LyfeCicleDemo 46 23 9/12/2011 3. Android – Application's Life Cycle Example: Life Cycle. .. 3. Android – Application's Life Cycle Example: Life Cycle onCreate… onStart… onResume… 47 3. Android – Application's Life Cycle onPause… Example: Life Cycle onStop… After pressing “Back Arrow” onDestroy… 48 24 9/12/2011 3. Android – Application's Life Cycle Example: Life Cycle After  pressing “Home” After  re‐executing AndLife2 After   “Back Arrow” or  Finish onSavedInstanceState >  onPause >  onStop > onRestart... android: layout_width="fill_parent" android: layout_height="fill_parent" android: background="#ff000000"  >