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Reactive Android
just a little introduction!
Presented by Akhyar Amarullah
at Engineering Brownbag Session in Ansvia
on Friday, July 10th 2015"
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“In computing, reactive programming is
a programming paradigm oriented around
data flows and the propagation of change.” !
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RxJava!
• RxJava is reactive extension implemented on
Java Virtual Machin. !
• Other language implementations also available:
RxScala, RxGroovy, RxKotlin, RxJS, etc.
All of them are implemented with respect to
respective languages’ style & idioms.!
• RxAndroid is RxJava + Android helper classes!
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Ease Android Development"
• Doing long running tasks in background thread and fire the
callbacks on UI thread (actually, any threads)!
• Chaining sequential tasks without callback hell !
• Using multiple data sources (e.g. remote API, disk cache, memory
cache, etc)!
• Batch processing big amount of data into small chunks!
• Threat anything as data streams:!
– Social stream from API!
• Streams are flexible, you can:!
– Transform!
– Filter!
– Throttle!
– Combine it with other streams!
• Observables can act as event bus!
• Supported by Retrofit library out of the box!
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RxJava Building Blocks!
• Observable!
– Source of data!
– Emits items (Objects, Strings, etc)!
– There are two types:!
• Cold observable!
• Hot observable!
• Observer/Subscriber!
– Consumes data!
• Operators!
– Combining: concat, merge, zip, join, etc!
– Filtering: filter, first, last, etc!
– Transforming: map, flatMap, groupBy, buffer, scan, etc!
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Observable!
• Source of data!
• Basic building block of reactive
programming!
• Composable!
• It doesn’t care of its implementation:!
– Synchronous or asynchronous!
– Which threads are you using!
– Use actors or thread pools!
– etc!
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Observable!
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Observable vs Iterable!
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Observable Callbacks!
• Observable
– onNext(T
t): emits data!
– onError(Throwable
e): when error occurs
and the observable should terminate!
– onComplete(): when no more data available
and observable terminates without error!
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Observable Callbacks!
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Observable Marble Diagram!
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RxJava on Actions"
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Setting Up RxJava for Android!
• compile
'io.reactivex:rxandroid:+'
• Optional but highly recommended: !
apply
plugin:
'com.android.application'
apply
plugin:
'me.tatarka.retrolambda'
buildscript
{
repositories
{
mavenCentral()
}
dependencies
{
classpath
'me.tatarka:gradle-‐retrolambda:+'
}
}
!
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Creating Observable
for Long-Running Tasks"
• Use simpler defer() or more
verbose create()!
• Do not forget to check for
subscriber. It might be already
unsubscribed.!
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Creating Observable
using Retrofit"
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Subscribing to Observable"
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Batch Processing in 10-sized chunks"
Divide and conquer!!
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Multiple Data Source with Fallback"
Credit: http://blog.danlew.net/2015/06/22/loading-data-from-
multiple-sources-with-rxjava/!
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Chaining sequential tasks!
Callback HELL @!#$!$@#" Much better and readable"
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Handling view clicks"
With throttling!!
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おわり!