CODEWITHSUNDEEP
iphoneiosuiview
mmr
mmr

Reputation: 14919

iPhone programming-- UIView elements appear to be ignoring Hidden=NO calls

Using XCode 4.4 and Mountain Lion,

I have a UIImageView, and on that view, I have a UIProgressView and a UIButton. When the app starts, the progress view and button are both hidden, as set in the storyboard. I then try to unhide them, first the progress bar when I'm doing something, and then the button when I'm done. I have called, for both items,

[self.view bringSubviewToFront:saveToCameraRoll];

to try to put them in front of the UIView.

Problem is, when I programmatically try to unhide them, it doesn't work. I can call:

progressBar.hidden = NO;
[self.view bringSubviewToFront:progressBar];

And that does nothing.

So then I tried to set everything as visibile in the storyboard and then programmatically set everything to be invisible once the controller loads. No deal; now my calls to hidden = YES seem to be ignored.

I then removed all actual programming, so that hitting buttons should just cause the button and progress bar to appear, reasoning that maybe the main thread was getting starved and couldn't update.

How can I force elements to pay attention to being hidden?

EDIT: I've now also tried programmatically modifying the alpha from 1 to 0. No change. It's like everything I'm doing is getting ignored. I made these items via the ctrl-drag method into the @interface section of the .m file; maybe I don't have some more delegates or interfaces or whatever hooked up?

Upvotes: 1

Views: 2464

Answers (2)

JustSid
JustSid

Reputation: 25318

As you said that you connected the ivars with your XIB file, it seems like your problem is that you are doing stuff on the main thread which in return blocks the run loop and your UI doesn't get redrawn anymore. When you update UI elements by changing their properties, those changes aren't applied instantaneous but the next time the UI gets redrawn which only happens when you give the main threads runloop a chance to run. However, if you do something like the following code, the changes will never appear:

[button setHidden:YES];

[self doSomethingReallyExpensiveAndTimeConsuming];

[button setHidden:NO];

The result of this code is that the button is set to be hidden, but doesn't get redrawn because the system has no chance to do it and when the system actually has a chance to redraw the UI, the button is already set to be invisible. A fix for this is to either split the work up and schedule it via timers on the main thread, or to use something like GCD to offload the work on a secondary thread (but then you need to make sure that your code is threadsafe!)

Upvotes: 3

danh
danh

Reputation: 62686

Is it possible the outlets are nil because they aren't hooked up in IB? If so, no amount of manipulation will have an effect.

Try NSLog(@"%@", saveToCameraRoll);

Is it null? Fix by reconnecting outlets in IB. If that works, then .hidden = NO will work and you can get rid of any code you added to manipulate the view hierarchy.

Upvotes: 2

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