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RxJava is a library of code used to handle data using a push and pull mechanism. Just like a notification on your phone, some data will be pushed to a receiver of that data. It’s a different way to think about existing coding patterns you know.
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Hi, my name's Jamie Huson, and
I'm an Android developer at Etsy.
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In this workshop, we're going to
get you started using RX Java.
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We'll cover the concepts and
0:13
API's by integrating RX Java into
a familiar project, a toDoList app.
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Let's dive right in.
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RX Java is a library of code to handle
data using a push and pull mechanism.
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Just like a notification on your phone,
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some data will be pushed
to receiver of that data.
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It's a different way of thinking about
existing coding patterns you know.
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For instance, let's take a look
at this array of to-do's.
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In your app, you might have a list or
array of to-do items.
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Usually, you'll [SOUND] iterate over those
items using an index starting at zero and
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moving to the last item.
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Each time you iterate,
you'll perform some action with that item.
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In our next Java, we think of these items
as being pushed to us one at a time.
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Over time, each item is emitted and
we can handle that item as we did before.
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This is very similar to a callback
like on a click in Android,
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where we receive a notification when
an item is tapped on the screen.
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In this model our data is being
provided as it becomes available.
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In our next job the object that emits
items is [SOUND] called an Observable.
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The callback that receives items
[SOUND] is called the Observer.
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And Observer subscribes to the observables
and starts receiving data and
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un-subscribes and
the data is no longer received.
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Here we can see the Observable
emit items [SOUND] and
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as they're emitted they're
passed along to the Observer.
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Here's what that would
look like in RX Java code.
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Observable.just creates an Observable that
will emit each item from our data set.
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In this case a todoList [SOUND].
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Now, we've subscribed to the Observable.
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An observer's past of
the subscribe method.
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It's type to the kind
of data being emitted.
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In this case a Todo object.
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Observer contains the callbacks
required for subscription.
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On next is called for each item emitted.
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Uncompleted is called when the Observable
has no more items to admit.
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Finally, on errors call
if an error occurs.
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It's important to note that on completed
and on error are only ever called once.
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And after they are called,
on next will not be called again.
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[SOUND] Calling subscriber turns
back a subscription object.
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[SOUND] With our subscription
we can later call unsubscribe.
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For instance,
in on passive our activity in Android.
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These are the basics of the RX Java model.
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Data is submitted from Observables
which are subscribed to by Observers.
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Data is pushed to the observables
as it becomes available.
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If you've worked with
loaders on Android before,
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it's similar except this
API is much cleaner.
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RXJava does include
a couple of helpful classes
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that it makes working with observables
much easier in certain situations.
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For instance, sometimes you may not
care about all three callbacks.
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You may not care about on completed or
on error.
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And just want to know
when items are emitted.
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If that's the case, you can simply pass
an action to the subscribe method.
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The actions call method will be called for
each on next called by the Observable.
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By default, Observables emit up
to an infinite number of items.
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However, sometimes you may only
want to emit a single item.
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For that there's a special
observable called single.
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Single is an observable that
emits only a single item.
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Because of this, unlike the regular
onCompleted, onError, and
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onNext calls, there is a simpler
onSuccess or onError callback.
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Next, Rx Java adds
additional power by letting
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us manipulate the data through a pipeline
before it reaches our observer.
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Here's what I mean by that.
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