Collect data on an offline device...for later merge to online datastore?

Joseph_Sliker

Hi; I've typically been able to build my data apps assuming that the user will be online and able to complete web-delivered forms in order to collect data. But now I am being asked to do something that I have never done:

Let's say the users have tablet devices in an environment where they do not have access to WiFi or smartphone type connections to any network.

Can anyone point me to the basic concepts I need in order to
1-create forms on an offline device, (can php help me create forms that will open on an android device or ipad?)
2-collect the "submitted" (or collected) data into a file on the device (say .csv format or something like that), and then...

3-when they get somewhere that will provide them with a network connection, allow them to post the data to the online datastore? (I think I get how to do this last part, uploading a file and then reading the file into my mysql database).

bradgrafelman

Well this is obviously not a PHP question, since PHP is a server-side language.

As for the actual concept, it might be possible to use some Javascript to periodically "auto-save" the contents entered in the form in a cookie (the new vBulletin software here at PHPBuilder does this). That way, you could re-populate the form using PHP/Javascript (either or both, really) by checking for that cookie.

Joseph_Sliker

...having learned this stuff from somewhere in the middle, my ignorance of basic concepts (as well as advanced ones) knows few bounds:o

I should have known that php would not ordinarily be much help on an isolated device. But somehow I find it helpful construct/post my problem here. I SHOULD however, be able to create an html form file that the user can save to their device....I am wondering if there is a way to submit such a form to save the data into a .csv file that somehow lives directly ON that same device...rather than to the web. If so, I can make an online form that provides a place to upload said file when connetivity is available.

bradgrafelman

Joseph Sliker;11013861 wrote:
I am wondering if there is a way to submit such a form to save the data into a .csv file that somehow lives directly ON that same device...rather than to the web

Not that I know of; there's certainly nothing in W3C-compliant HTML that would allow you do this. And of course you can't do anything like this in Javascript (who in their right mind would design a browser that allows such a scripted language access to read/write files directly to/from your hard drive these days?!). So it probably comes down to either writing your own application for the target mobile OS (e.g. Android and/or iOS), or finding a different way to do this...

... which leads me to ask why you didn't consider the approach I proposed above. After all, it would be a lot simpler than what you're describing (assuming for a moment that what you were describing was even possible, that is).

Joseph_Sliker

Here goes my ignorance again: I have actually not used cookies in anything that I have written, and have only used a couple tiny snippets of javascript (concretely copied from some web examples, that I somehow got to work in my scripts...I don't know javascript beyond that). Not sure of where to start with the vBulletin suggestion.

I DID take a course in MS Visual Basic about ten years ago and the more I think about it, I may have learned enough to build a very simple local app that gives me a form and saves data to a local file. I should try to refresh that dusty old corner of my brain and see if I can do this...then I can try to figure out if there is a method of porting it to Android or iOS.

Thanks very much for your replies.

johanafm

bradgrafelman;11013863 wrote:
And of course you can't do anything like this in Javascript (who in their right mind would design a browser that allows such a scripted language access to read/write files directly to/from your hard drive these days?!).

Pretty much everyone, and if they don't allready, it's coming. But it'll be sandboxed data adhering to the same origin policy

Check out the offline storage capabilities of your intended target browser(s): web storage, indexeddb, web sql db.

Web storage consists of localstorage and sessionstorage. See if you can get a javascript wrapper for it (such as jStorage - never used it myself though) since it will fall back on userData for older IEs. I believe all current IEs lack support, but since they have userData, there should be no need to fall back to cookies and window.name for local and session storages respectively. The difference between local and cookies is mainly that cookies are always sent with every request, which you want to avoid if you store a lot of data.

IndexedDB is simple, but lets you index fields to do range searches etc, and also implements a cursor so you can iterate over your result sets. Present in FF and Chrome. Announced for IE10.

WebSQL is pretty much supported by everyone but IE and FF. But mozilla doesn't seem to want to implement it.

Either way, if you target specific browser(s) only, choose what's available. If you can force users to go with a specific browser, choose whatever seems best to you. Else, I'd recommend webstorage through a js wrapper with userData fallback.

johanafm

Bloody double postings due to the server timeouts...

bradgrafelman

Interesting... looks like I'm quite behind the times. (Although for me that just further confirms my career choice being in embedded software development rather than web development :p.)

I wonder, though... how widely supported are the web storage types on mobile OS's?

johanafm;11013941 wrote:
Bloody double postings due to the server timeouts...

QFT!

johanafm

bradgrafelman;11013977 wrote:
I wonder, though... how widely supported are the web storage types on mobile OS's?

Some information in the comments in this thread on stackoverflow.
In short: Mozilla and IE manged to get WebSQL deprecated, which means you don't know for how long support fort will continue to exist. But at the time, it's supported by android and iOS browsers, according to the info on that page. I havn't used it myself.
They also mention jayData as a means of accessing data in a consistent manner across platforms.