iPhone, I need to DB refresh func for a few seconds, how can I show progress before a table screen from tab selection?

Question

I'm developing an app which has a tab bar and a UITableView, sometimes I'll need to run a function to update the database, which takes a few seconds. However, this is only needed if they want to look at a certain screen (and the data need updating) which has a UITableView on it.

I want some advice as to how, what, when and where I should show a progress indicator.

I'm thinking that I'll need something which pops up when the table view is about to be shown ?

As I say I don't know what to use to show the progress?

Also where would it be shown, would I need a new screen which is shown before the the table view or can I use and action sheet which will be dismissed automatically ?

Would like some sample code too.

Answer 1

There are many options for what. You can use a UIActivityIndicator (the spinning circle) or a Progress View (thermometer style) or a UILabel with the text xx% or nothing at all. If you're connecting to the Internet to get data, you should also call [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES] to show the spinning circle in the status bar.

Where is entirely up to you. Apple's own apps have put it into toolbars (c.f. EMail), in the middle of an otherwise blank view (c.f. App Store), or in a single UITableViewCell (c.f., Settings. It shows "Loading applications..." at the bottom when the app first starts while loading Settings.bundle from all installed apps.)

How largely depends on the where and what chosen, but in all cases your DB update needs to be in a background thread so you minimize the effect on the UI. If you're using a Progress View or some numerical feedback you'll want to periodically call something like:

[myViewController performSelectorOnMainThread:@selector(updateProgress:) withObject:[NSNumber numberWithFloat:(1.0 * currentRecord / totalRecords)] waitUntilDone:NO]