Android Message Handling

7/28/2019 Android Message Handling

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Development


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MessageHandling

Intents


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Manifestfile

AndroidManifest.xml Presentsessen7alinforma7onaboutthe

applica7ontotheandroidsystem

Systemmusthaveitbeforeitcanruntheapplica7on


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ManifestfileApplica7onManager

AppB

AppB

Manifest

AppA

AppA

ManifestRead

Run


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Manifestfile

ItnamestheJavapackagefortheapplica7on. Thepackagenameservesasauniqueiden7fierforthe

applica7on.

Itdescribesthecomponentsoftheapplica7ontheac7vi7es,services,broadcastreceivers,andcontentprovidersthattheapplica7oniscomposedof.

Itnamestheclassesthatimplementeachofthecomponentsandpublishestheircapabili7es.

Thesedeclara7onslettheAndroidsystemknowwhatthecomponentsareandunderwhatcondi7onstheycanbelaunched.


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Manifestfile

Itdetermineswhichprocesseswillhostapplica7oncomponents. Itdeclareswhichpermissionstheapplica7onmusthaveinorderto

accessprotectedpartsoftheAPIandinteractwithotherapplica7ons.

Italsodeclaresthepermissionsthatothersarerequiredtohaveinordertointeractwiththeapplica7on'scomponents.

ItliststheInstrumenta7onclassesthatprovideprofilingandotherinforma7onastheapplica7onisrunning.Thesedeclara7onsarepresentinthemanifestonlywhiletheapplica7onisbeingdevelopedandtested;they'reremovedbeforetheapplica7onispublished.

ItdeclarestheminimumleveloftheAndroidAPIthattheapplica7onrequires.

Itliststhelibrariesthattheapplica7onmustbelinkedagainst.


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Example:Manifestfile


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Manifestfile

Basically,itisasetupfilethatandroidusespriorofrunningtheapplica7on

Applica7oninforma7on Ac7vity,services,receiver,provider

Itwillstatethecomponentsandthepermissionthatyourapplica7onrequirestorun Permissionfromtheuser Permissionfromyourapplica7on

Lis7ngoflibrariesandinstrumenta7onclasses


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Securityconcept

Androidapplica7onrunsontheconceptofsandbox Thesandboxisdesignedtopreventapplica7onsfrom

disrup7ngeachother,exceptbyexplicitlydeclaringthepermissionstheyneedforaddiGonalcapabiliGesnotprovidedbythebasicsandbox

Thepermissionsrequiredbyanapplica7onaredeclaredsta7callyinthatapplica7on,sotheycanbeknownup-frontatinstall7meandwillnotchangeaWerthat


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Communica7on?

CorecomponentsofanAndroidapplica7onAc7vi7esServicesBroadcastreceivers

ithsomuchrestric7on,howiscommunica7ondone?


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Intent

ThroughmessagescalledIntents Facilityforlaterun-7mebindingbetween

componentsinthesameordifferentapplica7ons

SimplelowoverheadIPC(Inter-processcommunica7on)

passivedatastructureholdinganabstractdescrip7onofanac7ontobeperformed


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Manifestfile

Ac7vityB

Intent

Ac7vityA

OS

Ac7onData

Intent


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Intentcontent

Primarypiecesofinforma7onareAc7on

ACTION_VIE ACTION_EDIT ACTION_MAIN

Data Thedatatobeworkedon

Ac7vity1 Ac7vity2

Intent:ac7on+data

Op7onalResults


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Intentusage Ac7vity

Usedtostartac7vity Explicitly

Specifyingwhichclasstoload Implicitly

Reques7nganac7ontobeperformedonapieceofdata Services

ini7ateaserviceordelivernewinstruc7onstoanongoingservice. Broadcastreceivers

AndroidusesbroadcastIntentstoannouncesystemevents Applica7onwillreactaccordingtoanyreceivedevents

Androidsystemfindstheappropriateac7vity,service,orsetofbroadcastreceiverstorespondtotheintent,instan7a7ngthemifnecessary


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Intentuses

Ac7vityMakesuseof

startAc7vity(Intentobject) startAc7vityForResult(Intentobject)

Asmen7oned,twowaystostartanac7vity Implicit Explicit


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Intentuses

Implicitmethodofstar7ngac7vity Constructor

Intent(Stringac7on,Uri); Intent(Stringac7on);

E.g. Intentintent=

newIntent(Intent.ACTION_DIAL,Uri.parse(tel:555-2368));

startAc7vity(intent);

NewAc7vitywillbecreatedandbecomevisibleandac7ve,movingtothetopoftheac7vitystack


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Example:Dialer


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Intentuses

Explicitmethodofstar7ngac7vity Constructor

Intent(ContextpackageContext,Classcls) E.g.

Intentintent=newIntent(MyAc7vity.this,MyOtherAc7vity.class);startAc7vity(intent);

NewAc7vitywillbecreatedandbecomevisibleandac7ve,movingtothetopoftheac7vitystack


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Intentuses

startAc7vity()Independentcallfromitsparent(caller)illnotprovideanyfeedbackwhenitcloses

Howistheparenttodetecttheac7vityhasended?

Ac7vity1 Ac7vity2Start


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Intentuses

startAc7vityForResult() PossibletostartansubAc7vitywhichisconnectedtoits

parents

subAc7vitytriggeraneventhandlerwithintheirparentac7vitywhentheyclose

Anyac7vityregisteredinthemanifestcanbestartedasansub-ac7vity

Ac7vity1 Ac7vity2Start

Ended,Myresultsare


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LaunchingSubac7vity

publicclassMyAc7vityextendsAc7vity{...

sta7cfinalintSHO_SUB_ACTIVITY=99999991;

protectedbooleanonKeyDown(intkeyCode,KeyEventevent)

{Intentintent=newintent(this,MyOtherAc7vity.class);

startAc7vityForResult(intent,SHO_SUB_ACTIVITY);

}

returnfalse;

}

.}


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Returningresults

publicclassMyOtherAc7vityextendsAc7vity{

...

protectedvoidonMyOwnMethod()

{

intresult=0;

//settheresultstobereturnedtoparent setResult(RESULT_OK,result);

//Endsthesub-ac7vity

finish();

}

.}


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ReceivingResult

publicclassMyAc7vityextendsAc7vity{

...

protectedvoidonAc7vityResult(intrequestCode,intresultCode,Intent

data)

{

if(requestCode==SHO_SUB_ACTIVITY){ if(resultCode==RESULT_OK){

startAc7vity(newIntent(Intent.ACTION_VIE,data));

}

}

}}


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IntentFilter

Serviceimplicitintents UsedtoregisterAc7vi7es,Servicesand

BroadcastReceiversasbeingcapableof

performinganac7ononapar7culardata Tellandroidthattheycanserviceac7on

requestsfromothers


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Manifest

IntentFilter

Ac7onFilter

Ac7onFilter

CategoryFilter

DataFilter

DataFilter

Intent


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ManifestA

IntentFilter

Ac7onFilter

Ac7onFilter

CategoryFilter

DataFilter

DataFilter

ManifestA

Ac7onFilter

Ac7onFilter

CategoryFilter

DataFilter

DataFilter

IntentPASS

FAIL


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IntentFilter

AsAndroidmustknowthecapabilityofacomponentbeforeitcanlaunch,intentfilters

aregenerallynotsetupinjavacode.But

ratherinthemanifestxmlfile Useintent-filtertagtoregisteran

applica7oncomponentasanintenthandler


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IntentFilter

Intentsofacomponentsarerequiredtoprovidethe

Ac7onDataCategory

FailinganyoneofthemwillresultinAndroidnotdeliveringtheintenttothecomponent


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Intentfilter

Ac7on Specifythenameoftheac7onbeingserviced Shouldbeinuniquestrings

E.g.

...


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Intentfilter

Possibletolistmorethanone Afiltermustcontainatleastone

elementoritwillblockallintents

ToPass,onlyonemustmatch Iffail

Nointentgoespass Ifintentobjectdoesntspecifyanac7on,automa7callypasses

thetest


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Intentfilter

Category Specifyunderwhichcircumstancestheac7onshouldbe

serviced

Canincludemul7pleintentfiltertag Specifyyourownorusethestandardvalues

E.g.

...


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Intentfilter

Everycategoryintheintentobjectmustmatchacategoryinthefilter

Filtercanlistaddi7onal,butcannotomitanyintheintentobject

Intentobjectnocategoriesshouldalwayspassthistest


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Intentfilter

Data Specifymatchesfordatayourcomponentcanacton Canincludemul7pleschemataifyouarecapableofhandlingmorethanone

E.g.

...

Mainlyspecifies datatype(MimeMediaType) URI(UniformResourceIden7fier)


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Intentfilter

URI Scheme://host:port/path E.g.

content://com.example.project:200/folder/subfolder/etc Schemeiscontent Hostiscom.example.project Portis200 Pathis/folder/subfolder/etc

Host+port=Authority Aributesareop7onalbutnotindependentfromeachother

Authorityneedsschemetobemeaningful Pathneedsbothauthorityandscheme

Moreathp://en.wikipedia.org/wiki/URI_scheme


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Intentfilter

Topass.. AnintentobjectwithoutURIordatatypeiffilterdoesnot

specifyanytoo ObjectwithURIandnodatatyperequiresthesameforthefilter ObjectwithdatatypeandnoURIrequiresthesameforthefilter

ithbothURIanddatatype Objectwithdatatypematchesoneofthedatatypelistedinthe

filter

URImustmatchfiltersURI ObjectURIhasacontent:orfile:URIandfilterdoesnotspecifyan

URI


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SendBroadcast

hoistransming?SystemmessageswillbetransmiedbytheOSApplica7onspecificwillbesentvia

Context.sendBroadcast();


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SendBroadcast

Intentac7onstringisusedtoiden7fytheeventbeingbroadcast

Ac7onstringusedistobeunique. E.g.

Publicsta7cfinalStringNE_LIFEFORM_DETECTED=com.paad.ac7on.NE_LIFEFORM

Intentintent=newIntent(NE_LIFEFORM_DETECTED);

Intent.putExtra(lifeformName,lifeformType);

sendBroadcast(intent);


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ReceivingBroadcast

Updatecontent Launchservices/ac7vi7es 5secondruletoensurethatnomajor

processingisdone


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ReceivingBroadcast

PublicclassmyBroadCastReceiverextendsBroadcastReceiver{

publicvoidonReceive(Contextcontext,intentintent)

{

Stringtype=

intent.getStringExtra(lifeformName);

if(type.equals(alien)

{

context.startAc7vity(startIntent);

}

}

}


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RegisterBroadcastreceiver


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IntentExtras Usedtostorevaluesforthereceivingcomponent Primi7vetypesonly Assignnametoextras Retrievingvalueswithassignedname


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IntentExtras MakeuseofputExtramethodtoplaceExtravaluesintotheintent putExtraisoverloadedtotakeinalldifferent

primi7vetypes

Int,boolean,long,char,etc.. Beware:retrievalmethodisnotoverloaded

getXXXExtra();


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Example:IntentExtras SendingpartypublicvoidonClick(Viewv){

//TODOAuto-generatedmethodstub

myIntent=newIntent(myContext,

myReceivingIntent.class);

myIntent.putExtra("MyExtra",65501683);

startAc7vity(myIntent);

}


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Example:IntentExtras Receivingparty

publicvoidonCreate(BundlesavedInstanceState){

IntentreceivingIntent;

intmyInt;

TextViewtv=(TextView)findViewById(R.id.myRecvTV);

receivingIntent=getIntent();

myInt=receivingIntent.getIntExtra("MyExtra",0);

tv.setText(""+myInt);

}

Android Message Handling

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