hmmm... let's try this again...

hello, EGHDK!

how can I help you today?

Hey Mark. Couple of rapid fire questions for ya

go right ahead

1st. Trying to make sure I don't cause any memory leaks. Is this statement correct? "An annonymouse inner class always holds a ref to the outer class."

yes

If activity has button.setOnClickListener(new OnClickListener) isn't that anonymous inner class holding onto the outer class?

yes

Hello, everyone.

So why don't I do anything onDestroy()?

(hello, Ken -- I will be with you shortly!)

EGHDK: because you don't need to

the outer class is the activity

the activity holds the button, which holds the listener, which holds the activity

it's a loop

so the whole loop can get garbage-collected

Yeah, so if the Activity gets destroyed... the button listener does NOT... right?

listeners don't get "destroyed"

Well, marked for gc?

then yes, the listener should be eligible for GC

again, the activity holds the button, which holds the listener, which holds the activity (the outer class instance)

as soon as the activity can be GC'd, so can the button and listener

So how would you cause a mem leak. Isn't every anonymouse inner class a loop? So I never have to worry about doing anything with them?

"Isn't every anonymouse inner class a loop?" -- not necessarily

Sorry, you just threw me off with the "loop" thing. I could have sworn that onDestroy()s super was doing something in the background to get rid of all my listeners and such.

it's not necessary, so long as the activity can be garbage-collected

let me take a question from Ken, and I'll be back with you shortly

Ken: your turn! do you have a question?

So a running thread... or asynctask would keep it from being gc'd right?

No prob

hi

Mostly I just wanted to see if you are actually here. Seems you are. But I do have a question.

I'm here, for some definition of "here". And some definition of "I'm". :-)

I am fooling around with setting up a backend server from AS

Mostly just copying code blindly at this point.

But I have it working with the local version of the server, as long as I use the emulator

I can't figure out how to do the same thing with the client running on an attached actual phone.

"local version of the server" meaning running on your development machine?

Do have any experience with this? Is targeted to the Google App Engine

yes, exact.

I have never used Google App Engine

that being said, you need to make sure that your app uses an IP address that identifies your development machine, and that the app server is listening on that IP address

for example, if the app server is listening only on localhost (127.0.0.1), an emulator running on your development machine could talk to that server, but a device could not

The app server is listening on a a dummy address: 10.0.2.2:8080

it needs to be reachable by the device

I think, anyway.

RIght.

I can't think how to make it happen

typically, that means that the device has to be on WiFi, and the server has to listen on an IP address that's for the same network

Right. But

The device is actually connected by USB.

that does not help you

no, but does it hurt?\

it shouldn't

Okay, well, let me look up some more stuff and get back to you.

OK

EGHDK: back to you! do you have another question?

So a running thread... or asynctask would keep it from being gc'd right?

I think I don't understand the Registration.Builder well enough.

EGHDK: correct

Anything else that would be an annonymous inner class that would hold a ref and make a mem leak?

or are threads/runnables basically it?

the same things that cause anything to be a memory leak: static data members and threads

anonymous inner classes don't really change that

[I'll be back-- some day. See you later]

(Ken: OK!)

Okay. so I guess I was looking at this wrong. Yes, anonymous inner classes have a reference to the outer class, but to cause a memory leak, a static member or thread would have to be misused.

Is that a correct statement?

correct

yes

now, occasionally, you will run into a case where the static reference is made by somebody else, not you

this is the "don't make an anonymous inner subclass of Handler" problem

Got it.

Handler itself sets up a static reference

Oh

Alright

listeners, though, are usually interfaces, and therefore there's no hidden code from a superclass that can bite you

So whats the deal with AsyncTask. Does it create a static ref, or is it the threading part of asynctask that can cause a memory leak?

AsyncTask uses a thread pool

while that thread is running the task, nothing the task can reference can be garbage-collected

gotcha. So since I can get the activity from an asynctask that means it can't be gcd

I'd phrase it as "if I can get to the activity from the AsyncTask, then it can't be GC'd"

there's nothing intrinsic to an AsyncTask that makes it tied to activities

Whats the error you get if you try to update an activity that was destroyed from an asynctask?

Is the error that the activity doesn't exist... or that the activity was destroyed already?

there's probably a few possible exceptions

I seem to recall getting a NullPointerException once

True. I can look into that. No biggie.

there's no specific ActivityGotNukedException, if that's what you mean

So asynctask is pretty touchy in an activity. you want to make sure you keep that short, or at least end it onDestroy.

AsyncTask is a little nicer in a Service then... huh?

hang on

because no lifecycle changes from config changes

okay. *hanging*

if by "end it onDestroy", you mean "cancel() it in onDestroy()", then yes, that's a good pattern

Yep. That's what I meant.

onPostExecute() will not be called on the task, if the task is still running, and you can call isCancelled() to see if you were canceled from within onProgressUpdate() if needed

with respect to a service, there is usually no point to an AsyncTask, over a thread, in a service

the point to AsyncTask is specifically to do certain work on the main application thread

and you rarely want to do work in a service on the main application thread

Let's say I wanted to make a broadcast, for an internal eventbus to my app. Doesn't a broadcast have to be made from the ui thread?

no

oh. that's not bad then.

I guess I had that mixed up... maybe it's the broadcast receiver in my activity that has to be on the ui thread.

sendBroadcast() on Context (for system broadcasts) and sendBroadcast() on LocalBroadcastManager (for local broadcasts) can be called from any thread

the broadcasts are *received* on the main application thrad

Thats pretty nice. Okay. Wasn't sure about that.

er, thread

Makes sense. Perfect.

So asynctask... kinda pointless in a service then.

right

Would asynctask make sense to use in another class? Like I had a GCMTask that I used an asynctask in it. To start the GCMTask I took a context... but then internally, I always just did context.getApplicationContext()

usually, you only use AsyncTask in conjunction with activities and fragments, because usually that's the only time when you have magic work (updating the UI) that has to be done on the main application thread

there may be other use cases, but I can't think of any off the top of my head

I implemented GCMTask as a singleton... and put an asynctask in it. Seems to work well (because I make a network call in the background) and on success of the network call I save some data. It just led me to believe that AsyncTask can be used in a class, but not in an Activity directly.

why is that not just an ordinary thread?

I'm not sure. I'd probably have to go back and look (I think) it's because google docs show gcm with asynctask... so i copied it

That might be another question for another day though

Got a couple of other questions to run through.

Next is. I have a friend that I created a spiffy service for. I want him to integrate it into his App. I don't want to host it in a repo on jcenter. How would I send him something in an email, and have him use it in his project?

I know theres jar, aar, or add a module

are you using any resources or assets?

No. No resources

You mean xml or images... right?

right

It's just java

stuff in res/ or assets/

then a JAR, plus some instructions for how to add it to the manifest, would work

[BTW] What's the deadline for soft typos for the next edition? I have a collection of suggestions, but I have been saving them up.

Nope. Just java.

Ken: my apologies! I am not paying attention and thought you left the chat!

I did.

He's back.

OK

Ken: to answer your question, there's no strict deadline, insofar as I make bug fixes continuously

plus, I don't know the precise ship date for the next update, other than "early June"

I'll have a better sense of it after Google I|O

Cool. So I'm working in Android Studio and have a sample app, and in the same package as my sample activity, I have my service and one extra java class. How would I take my extra java class and service and create a jar?

okay, that's good enough.

EGHDK: there may be easier ways than this, but I create a custom Gradle task for it

that's a Stack Overflow answer from Jake Wharton on creating custom Gradle tasks for generating a JAR from an Android library module

Interesting. That'll work for me. Got a resource handy to point me towards? I would just make the jar in IntelliJ IDEA, because I know how to do that. But IntelliJ doesn't know about the android sdk I think, so I don't know how that would work.

Okay. Thanks for the resource.

IntelliJ certainly can know about Android -- there's the Android plugin for it

I haven't used straight-up IDEA in a while

let me take other questions from Ken for a bit, and I'll be back to you

Ken: do you have other questions?

EGHDK: back to you, then

Yeah, but I just get confused, because I just feel like you can't create a jar that has Android APIs in it. Like some of my stuff is plain java, but the second I use Log.e() in my java class... I doubt that I'll be able to make it a jar.

sure you can

most of my CWAC libraries are available as JARs

Okay, so I'll stop worry about that then.

a regular Java program can't use those JARs

but an Android app certainly can

Got it.

if you prefer, package the service as an Android library module, ZIP up the directory, and send that

So if I just wanted to send it as a module,

read my mind.

so I have activity service and java class in one package. I want to send him service and java class as a module. Would I move the service and java class into a different directory and then zip that?

if by "different directory" you mean an Android library module, yes

your app would then depend upon that module, to pull in that code

and you can distribute that module, such as via a ZIP file, far and proverbially wide

Okay. I should be able to google that if anything. the jar info you gave me was gold though. thanks

Okay.... 15 minutes. Got the rest of my list ready here. For instance, if you select NEW > Fragment in Android Studio to add a new Fragment, with """Include interface callbacks" checked, you'll get an interface inside of the Fragment class. The fragments interface is used so that you can do a click in the activity. But onDetach of the fragment you see the interface being set to null. Why is that?

beats me

I have never created a fragment through the wizard

so I haven't looked at the code that it generates

Okay. It is very interesting.

The code that the service wizard generates is interesting as well.

It creates static methods to "start" tasks for an IntentService. Thought it was interesting to see it done that way.

yeah, I think I saw that code in a Stack Overflow question

it's not a bad idea

I have considered doing that for activities

it's kinda like the factory method pattern

Yeah. I liked it. Definitely take a look when you get more than 0.5 seconds of down time.

Talking about patterns.... all of my next questions are on patterns. I'm reading a design patterns book. head first series. pretty good. and its java based, so easy for me to follow.

I bought that book

made it through a couple of dozen pages

decided that the Head First style wasn't my cup o' tea... :-)

One of the first lessons is to program to an interface not an implementation. I know interface doesn't mean "java interface" but now I want to make everything a damn interface. Is that good or bad? I know its kinda a silly question... but I never used interfaces before and they seem to make sense now.

And yes, this is one of my least favorite in the head first series personally. I thought their java book was really good, their software development book was alright, but this one is hard to read.

generally speaking, I tend to use interfaces (or sometimes abstract classes) in cases where I might want to use N different implementations of the same thing

Okay. Yeah, I just feel like I'm getting interface happy over here.

it's more important with libraries, IMHO, as the user of the library might want to plug in her own implementation of various things

OnClickListeners... is that an observer pattern? Are all callbacks observer patterns in a nutshell?

um, I forget how the Gang of Four defines the observer pattern, to be honest -- I tend to think of listener as being its own pattern

OK

Cool. I have my gof book sitting here. Just figured I'd go through the head first one to give me a good prep into gof.

with observers, usually there's a collection of 'em

in the case of most Android listeners, there's one one listener for the event

IOW, it's setOnClickListener(), not addOnClickListener()

Gotcha.

so you can think of Android's use of listeners as being a limited implementation of the observer patern

er, pattern

Head First is releasing an android book in the next few months. I'm going to keep on top of those reviews. Interesting to see what people think of that book. Like I said before, I thought theyre Java book was gold. They explained something... and I would have a question and BAM they had my question written down with an answer. It's like they were reading my mind the entire time I read that book. super helpful.

well, Kathy Sierra co-wrote Head First Java

she's one of the best tech writers out there

OTOH, she also co-wrote Head First Design Patterns

which is why I assumed that it was the Head First style that bugged me

Gotcha.

Have you read HF java?

no, mostly because I learned Java a long time ago

I'll check out other kathy sierra books also. thanks for the tip

I'm still looking for a place that'll print out the whole pdf of your book for a fair price. I just like reading in print too much.

somewhere, a tree weeps

(possibly a willow... :-)

Being able to circle and underline things... and I love reading books fron to back, so even though I've jumped around your books and read a few hundred pages, I wish I could read it all.

Oh man ba dum tsss. that was a good one.

hahaha

anyway, that's a wrap for today's chat

next one is Thursday, also at 7:30pm US Eastern

Okay mark. Hit all my questions today. Appreciate it. as always.

have a pleasant day!