hello, Yaniv!

how can I help you today?

Hi Mark

my problem is this

I have a service that runs on BOOT COMPLETED

and basically never destroyed

it listens for messages

what I want is for other applications to be able to use this service like a server

and bind to it, so when a message is received it is sent to other apps that bind to it

I coudn't find how to do that

how to send message from a service to other apps

every guide shows how to send a message from the client to the service

not every guide

for example, you are a subscriber to my book

and my book certainly covers other options

particularly in the "Remote Services and the Binding Pattern" chapter

starting on page 2471 in the PDF edition of Version 6.4 of the book

is there an example on how to do that?

well, first we need to determine what the right answer is for "that"

you wrote: "so when a message is received it is sent to other apps that bind to it"

I was thinking , 5 min ago , that maybe creating custom broadcast receiver is also an option

that is definitely an option

and my service will broadcast the message when it gets it

and other apps will pick it up,

as would be publishing a ContentProvider and having the clients register a ContentObserver to find out about changes

so, let me ask a couple of questions:

yes but content provider means i need to obtain the messages in some sort of database

and i dont want that

1. if a message arrives, what client apps need to find out about it? all of them regardless of whether they are running? or only those currently running?

i dont want to save the messages if no other app listens for it

umm.. not sure I understand

OK

let's suppose that your app is installed on a phone

and a message comes in

ok

there are 2,137 other applications, also installed on this phone, all of which *could* be interested in your message

however, only 6 of them are running right now

when the message comes in, how many apps should receive it: 6? 2,137? or something else?

which ever app is listening for this particular message

for this particular service

If im creating my custom broadcast

only apps that listen for this specific broadcast will receive the msg , no

?

I am trying to understand how all of this is supposed to work at a logical level

are all of these apps (the one with the service and the ones listening for messages) yours?

yes

ah, OK, that helps

next: are you building your own hardware?

yes sorry for not being clear

or your own ROM mod?

no , I have an android based device that Im working on

and these apps will be pre-installed on that device?

or are these apps being publicly distributed, such as through the Play Store?

they will be pre installed , sort of

meaning that each client will have his own device with his own applications installed on the device

can the client uninstall these apps? in particular, can the user remove the app that contains this message-collecting service?

there wont be play store on the devices

well , right now it can be deleted but the goal is that the message collecting service will stay installed and running and could not be removed

OK

in that case, having the central message collecting service is fine

lets say that this is a service that it's in the client's interest to delete

you mean, not to delete, right?

no i mean to delete .

we don't want clients to be able to delete that service is my point

OK, that is what I thought that you meant

next: how big are these messages? is a message something small (such as a bit of JSON) or something large (such as a photo)?

so , which options is better, a bound service or a broadcast

we are getting to that -- I need some more design information before I can give you a recommendation

the message is small , its basically a bundle of 2 int's and a string

OK, so that is something that most IPC can handle

now, let's go back to a point I was trying to uncover earlier...

let's call your app with the message-collecting service S

so, S is installed on the device

and let's say that there are three other apps that are supposed to get messages from S, called A, B, and C

when S gets a message that A needs, if A is not running (has no process), what is supposed to happen?

does A need to be started up and handed the message?

does the message get queued somewhere for A to pick up later?

or is the message lost?

no, the message is lost and i dont care about it

only when A is running and requesting messages will the messages be received

in that case, a broadcast is probably not what you want

as the broadcast would cause A to start running if it was not already running

oh

and, since you do not need message persistence, the ContentProvider/ContentObserver approach (that you did not like) is not needed

and so, your original plan of the service binding is probably the right one

in the chapter on "Remote Services and the Binding Pattern", I have a sample showing how to pass data from the service back to the client

but is the client a different app?

in the sample, the client is asking the service to download a file, and the service sends back a success/failure indication

yes, they are separate apps

for binding between apps, you need to use AIDL to describe the interface

normally, we think of this as being the service having a Binder based on that AIDL that is the implementation of the interface

and the client has a proxy that allows it to invoke methods on that interface, as if the service were a local object, when in reality is it in another process

however, given that you already have an established client->service binding, you can also use AIDL to send data from service to client

in this case, the *client* has the Binder, and the *service* gets the proxy

and that's what I cover in the book

so it sounds like exactly what I need.

particularly, you will want to read the "Servicing the Service" section, starting on page 2486 of the Version 6.4 PDF

are you sure thats the page num?

it jumps to JVM scripting

it is the page number as seen at the bottom of the page

oh ok

if your PDF viewer ignores my page numbering, try page 2535

page 2486 is "Traceview"

are you looking at Version 6.4?

oh no! I have 6.2

oops

im not updated :(

the material is in there too, though I rewrote that chapter relatively recently

you're obviously a subscriber, so download Version 6.4 from the Warescription site when you get a chance

ok so just to be clear , I need to read Servicing the service and Remote Services and the Binding Pattern.

yes, where "Servicing the Service" is a section in the "Remote Services and the Binding Pattern" chapter

ok Mark, thank you for your help

you are very welcome

(Im staying here just because I want the transcript in front of me)

also note that that chat transcript will be uploaded to http://commonsware.com/office-hours/ shortly after the chat ends

thanks

and, if you have other questions, go right ahead -- it is a quiet chat room today

thats it for now , got some reading to do :)

OK

that's a wrap for today's chat -- the next chat is tomorrow at 4pm US Eastern

have a pleasant day!