- PDF Free Download

Size: px

Start display at page:

Download ""

Jacob Grant
5 years ago
Views:

Andrid prgramming curse Asynchrnus Techniques Intrductin Sessin

AsyncTask Service & IntentService AsyncQueryHandler Lader By Võ

cm/ 2 Lifecycles Bradcast Receiver Linux Prcess Java Objects

1 Andrid prgramming curse Asynchrnus Techniques Intrductin Sessin bjectives Intrductin Asynchrnus Techniques Executr Handler AsyncTask Service & IntentService AsyncQueryHandler Lader By Võ Văn Hải Faculty f Infrmatin Technlgies 2 Lifecycles Bradcast Receiver Linux Prcess Java Objects Service Cntent Prvider UI Andrid Cmpnents Bradcast Receiver s Service Cntent Prvider 3 4 1

2 Native Lifecycle Example: Lifecycle Cmpnent ncreate() ndestry() ncreate() ndestry() UI Applicatin Start Linux Prcess Prcess Example: Lifecycle Cmpnent Object Object ncreate() ndestry() ncreate() ndestry() new() new() GC Applicatin End GC Time 5 Time 6 Reference Object Object new() Start Example: Lifecycle Cmpnent Reference Object Object new() ncreate() ndestry() ncreate() ndestry() new() Start new() Time 7 Time 8 2

3 Backgrund s Asynchrnus Techniques A thread is a GC rt Implement cancellatin plicy fr yur backgrund threads! Use Cases UI Get ff the UI thread early! D lng running task UI Get ff the UI thread early! Reprt result r update UI D lng running task Executr Handler AsyncTask Service IntentService AsyncQueryHandler Lader Plain ld Java

4 Creating Tasks and s (1) - Example Tasks are bjects. T create tasks, yu have t first define a class fr tasks. A task class must implement the Runnable interface Yu need t implement run methd t tell the system hw yur thread is ging t run Creating Tasks and s (2) Or yu can use Callable<V> t imprve sme prblems Dis-advantages and using Pitfalls Nn-retained threads Missing cancellatin plicy (runnable) Starting ver and ver again Gd Use Cases One-sht tasks Pst messages t the UI thread at end

5 Task / Executin Envirnment Executr Executr and ExecutrService Executr Executr Service Pl Executr Task submissin: Pwerful task executin framewrk. executrservice.submit(mytask); executrservice.invkeall(cllectin<tasks>); executrservice.invkeany(cllectin<tasks>); Lifecycle management: executrservice.shutdwn(); executrservice.shutdwnnw(); Lifecycle bservatin: executrservice.isshutdwn(); executrservice.isterminated(); executrservice.awaitterminatin(); Task: Independent unit f wrk executed anywhere Runnable run() Callable call() Executin Envirnment: Technique used t execute the task Executr execute(runnable) Pls Fixed Pl Cached Pl Single Pl Custm Pl Executrs.newFixedPl(3) Executrs.newCachedPl() Executrs.newSingleExecutr() Task manager/bserver: Future isdne() iscancelled() cancel() Future future = executrservice.submit(callable); new PlExecutr(crePlSize, maximumplsize, alivetime, unit, wrkqueue)

Dis-advantages and using Pitfalls Lst thread safety when switching frm sequential t cncurrent

prcessing Use cases gaining perfrmance frm cncurrent executin.

Maximum platfrm utilizatin Handler Class http://vvanhai.wrdpress.

with a message queue and prcessing lp. Handles bth Message and Runnable.

6 Dis-advantages and using Pitfalls Lst thread safety when switching frm sequential t cncurrent executin Gd Use Cases Execute tasks cncurrently Multiple Http requests Cncurrent image prcessing Use cases gaining perfrmance frm cncurrent executin. Lifecycle management and bservatin f task executin. Maximum platfrm utilizatin Handler Class Handler Class Inherits frm and encapsulates a Lper-bject. with a message queue and prcessing lp. Handles bth Message and Runnable. t = new Handler("Bg"); t.start(); 3 h.sendemptymessage(42); Add Lper and Handler Create and Start 1 Message Queue 2 Prcess Handler 2 Handler h = new Handler(t.getLper()) public vid handlemessage(message msg) { //Prcess message } 23 }; 24 6

7 Handler Example using messgae Runnable/Message submissin: pst(runnable); pstdelayed(runnable); pstattime(runnable) pstatfrntofqueue(runnable); sendmessage(message); sendmessagedelayed(message); sendmessageattime(message); sendmessageatfrntofqueue(message); Runnable/Message remval: remvecallbacks(runnable); remvemessages(message) Using sendmessage Backgrund Main Using pst

8 Gd Use Cases AsyncTask Class Keep a thread alive Sequential executin f messages Avid cncurrent executin n multiple buttn clicks State machine Detailed cntrl f message prcessing. AsyncTask Class AsyncTask enables prper and easy use f the UI thread. This class allws t perfrm backgrund peratins and publish results n the UI thread withut having t manipulate threads and/r handlers. AsyncTask is designed t be a helper class arund and Handler and des nt cnstitute a generic threading framewrk. An asynchrnus task is defined by a cmputatin that runs n a backgrund thread and whse result is published n the UI thread. Hw it wrks new AsyncTask.execute() 1 npreexecute() 2 4a 4b npstexecute() ncancelled() UI 3 dinbackgrund() AsyncTask.cancel() publishprgress() nprgressupdate()

9 AsyncTask class Service AsyncTask's generic types 1. Params, The type f the parameters sent t the task upn executin. 2.Prgress 3.Result Example The type f the prgress units published during the backgrund cmputatin. The type f the result f the backgrund cmputatin Services A Service is an applicatin cmpnent that can perfrm lngrunning peratins in the backgrund and des nt prvide a user interface. Anther applicatin cmpnent can start a service and it will cntinue t run in the backgrund even if the user switches t anther applicatin. Additinally, a cmpnent can bind t a service t interact with it and even perfrm interprcess cmmunicatin (IPC)

Services s states Service s call-back methds State Started Bund Service lifecycle Descriptin A service is started when an applicatin cmpnent, such as an activity, starts it by calling startservice().

A bund service ffers a clientserver interface that allws cmpnents t interact with the service, send requests, get results, and even d s acrss prcesses with interprcess cmmunicatin (IPC).

cm/ Descriptin The system calls this methd when anther cmpnent, such as an activity, requests that the service be started, by calling startservice().

10 Services s states Service s call-back methds State Started Bund Service lifecycle Descriptin A service is started when an applicatin cmpnent, such as an activity, starts it by calling startservice(). Once started, a service can run in the backgrund indefinitely, even if the cmpnent that started it is destryed. A service is bund when an applicatin cmpnent binds t it by calling bindservice(). A bund service ffers a clientserver interface that allws cmpnents t interact with the service, send requests, get results, and even d s acrss prcesses with interprcess cmmunicatin (IPC) Callback nstartcmm and() nbind() nunbind() nrebind() ncreate() ndestry() Descriptin The system calls this methd when anther cmpnent, such as an activity, requests that the service be started, by calling startservice(). The system calls this methd when anther cmpnent wants t bind with the service by calling bindservice(). The system calls this methd when all clients have discnnected frm a particular interface published by the service. The system calls this methd when new clients have cnnected t the service, after it had previusly been ntified that all had discnnected in its nunbind(intent). The system calls this methd when the service is first created using nstartcmmand() r nbind(). The system calls this methd when the service is n lnger used and is being destryed. Creating Service There are tw classes yu can extend t create a started service Service This is the base class fr all services. When yu extend this class, it's imprtant that yu create a new thread in which t d all the service's wrk, because the service uses yur applicatin's main thread, by default, which culd slw the perfrmance f any activity yur applicatin is running. IntentService This is a subclass f Service that uses a wrker thread t handle all start requests, ne at a time. This is the best ptin if yu dn't require that yur service handle multiple requests simultaneusly. All yu need t d is implement nhandleintent(), which receives the intent fr each start request s yu can d the backgrund wrk

11 Creating Service Extends the IntentService class Creates a default wrker thread that executes all intents delivered t nstartcmmand() separate frm yur applicatin's main thread. Creates a wrk queue that passes ne intent at a time t yur nhandleintent() implementatin, s yu never have t wrry abut multi-threading. Stps the service after all start requests have been handled, s yu never have t call stpself(). Prvides default implementatin f nbind() that returns null. Prvides a default implementatin f nstartcmmand() that sends the intent t the wrk queue and then t yur nhandleintent() implementatin Creating Service Extends the Service class If yu require yur service t perfrm multi-threading (instead f prcessing start requests thrugh a wrk queue), then yu can extend the Service class t handle each intent

Running a service in its wn prcess Yu can als specify that yur Service runs in a separate prcess via the andrid:prcess=":prcess_descriptin" attribute. Define yur service in AndridManifest.

12 Running a service in its wn prcess Yu can als specify that yur Service runs in a separate prcess via the andrid:prcess=":prcess_descriptin" attribute. Define yur service in AndridManifest.xml file Service restart behavir In its nstartcmmand() methd call, the service returns an int which defines its restart behavir in case the service gets terminated by the Andrid platfrm. Yu can use the cnstants, the mst cmmn ptins are described by the fllwing table. Optin Service.START_STICKY Service.START_NOT_STICKY Service.START_REDELIVER_INTENT Descriptin Service is restarted if it gets terminated. Intent data passed t the nstartcmmand methd is null. Used fr services which manages their wn state and d nt depend n the Intent data. Service is nt restarted. Used fr services which are peridically triggered anyway. The service is nly restarted if the runtime has pending startservice() calls since the service terminatin. Similar t Service.START_STICKY but the riginal Intent is re-delivered t the nstartcmmand methd. Yu can check if the service was restarted via the Intent.getFlags() methd Running a service in its wn prcess will nt blck the applicatin in case the service perfrms lng running peratins in its main thread. But as the services runs in its wn prcess, yu need t use sme interprcess cmmunicatin (IPC) t cmmunicate t yur service frm ther parts. Even if the service runs in its wn prcess, yu need t use asynchrnus prcessing t perfrm netwrk access, because Andrid des nt allw netwrk access in the main thread f a prcess. Cmmunicating with services Using Intent data: The service receives the intent data frm the starting Andrid cmpnent and perfrms its wrk Using receiver: Yu can als use bradcast events and registered receivers fr the cmmunicatin. binding t lcal service: If the service is started in the same prcess as the activity, the activity can directly bind t the service. Handler and ResultReceiver r Messenger : If the service shuld be cmmunicating back t the activity, it can receive an bject f type Messenger via the Intent data it receives frm the activity. If the Messenger is bund t a Handler in the activity, the service can send bjects f type Message t the activity. AIDL fr services in a different prcess :T bind t a service which runs in a different prcess, yu need t use Inter Prcess Cmmunicatin (IPC) as the data needs t be sent between different prcesses

13 Service cmmunicatin Using BradcastReceiver AsyncQueryHandler Service cmmunicatin Using BradcastReceiver AsyncQueryHandler Asynchrnus peratins n a CntentReslver Query Insert Delete Update Wraps a Handler Cns N cursr management N cntent bservatin N data retentin n cnfiguratin changes Backgrund thread can t be frced t quit

14 Hw it wrks AsyncQueryHandler dem UI 1 2 new AsyncQueryHandler(); startquery(); startinsert(); startupdate(); startdelete(); AsyncQueryHandler sample class nquerycmplete(); ninsertcmplete(); nupdatecmplete(); ndeletecmplete(); DB peratins AsyncQueryHandler dem

15 Basics Lader 3 Lifecycle management 4 Retained n cnfiguratin change Lader Lader API added in Hneycmb Available in cmpatibility package Lad data in a backgrund thread Observes data changes Retained n cnfiguratin changes Cnnected t the and Fragment lifecycles Pitfalls Data lading will stp when /Fragment is destryed Http requests nt finished Gd Use Cases Lading data frm Cntent Prviders Lad data in 2 Observe data Hw it wrks Data Surce Custm Lader Any Data Surce Cursr Lader Cntent Prvide r

AsyncTask Cncurrent executin Subsequent executin One task with UI callback newsingleexecutr Execute Message and Runnable Better clean up

16 Summary One sht tasks AsyncTask<Vid, Vid, Vid> AsyncTask.execute(Runnable) Executin abstractin Repetitive tasks Cncurrent executin Sequential executin Executin management Task management Handler AsyncTask Cncurrent executin Subsequent executin One task with UI callback newsingleexecutr Execute Message and Runnable Better clean up Executr Task cntrl Custm Lader Service Cntinuus lifecycle independent tasks On demand 61 Asynchrnus CRUD Async Query Handler Full CRUD Lad data frm CP Data bserving Lader Intent Service

Design Patterns. Collectional Patterns. Session objectives 11/06/2012. Introduction. Composite pattern. Iterator pattern

Design Patterns. Collectional Patterns. Session objectives 11/06/2012. Introduction. Composite pattern. Iterator pattern Design Patterns By Võ Văn Hải Faculty f Infrmatin Technlgies HUI Cllectinal Patterns Sessin bjectives Intrductin Cmpsite pattern Iteratr pattern 2 1 Intrductin Cllectinal patterns primarily: Deal with