Blank Page when flipping

[ahmedbenahmed]

when flipping, a blank page appears randomly.

[FakerLuo]

Did you solve it? :)

[teffi]

Im experiencing this as well. Is there anybody here who can clear things out?

[FakerLuo]

when rapidly flipping, a blank page appears randomly.
I guess the blank pages occur because of the pdf view.
didn't you happen that when rapidly flipping? :)
btw, my test environment is ios7.1 of ipad3.

[teffi]

I think its not related to the pdf view. I am using flipper to one of my projects and it still occurs. I think its being caused by the flipper gesture recognizer setting the alpha value of the page. I'm still trying to figure out how to fix it.

[burrows111]

Guys, did anyone resolve this? currently experiencing this myself. Not related to PDF as I am now supplying UIImageView's that have images supplied from the bundle. Nothing is null that shouldnt be (As far as I can see)
I can see the subview count at 'CleanUpFlip' is less than 2 every time I get a blank 'page'
Thanks

[ahmedbenahmed]

the best way is to use an other project. Try with this https://github.com/mpospese/MPFlipViewController. it works very well

[teffi]

@burrows111 does it happen when you're rapidly flipping or not?

[burrows111]

Yeah when flipping rapidly. @teffi

[burrows111]

I hope someone can help @teffi . @ahmedbenahmed moving to a different solution is not an option as of yet but thank you for the heads up

[burrows111]

I fixed it, to my belief. If someone will be kind enough to validate what I have done that would be good. I will attached the files :)

[ahmedbenahmed]

could you attach the correct files?

[burrows111]

@ahmedbenahmed how do I attach files? sorry

[ahmedbenahmed]

Attach images by dragging & dropping, selecting them, or pasting from the clipboard.

[burrows111]

Cool ill sort that shortly, im currently testing on the iPad to make sure the issue is fixed.

[burrows111]

Be easier like this:
in instance method 'cleanupFlip' you previosuly had
'
if (setNextViewOnCompletion) {
[self.currentView removeFromSuperview];
self.currentView = self.nextView;
self.nextView = Nil;
} else {
[self.nextView removeFromSuperview];
self.nextView = Nil;
}

'
No I dont know why, but after an hour of debugging I noticed if the currentView was removed from superview when there was less than 2 subview on the PageFlipper you get the blank.

so, I placed an if statement in it

so

'
if (setNextViewOnCompletion) {
if(self.subviews.count ==2)
{
[self.currentView removeFromSuperview];
}

    self.currentView = self.nextView;
    self.nextView = Nil;
} else {
    [self.nextView removeFromSuperview];
    self.nextView = Nil;
}

'
Shoot the technique down all you wish, but its working for me. No issues picked up anywhere, what are your thoughts?

[teffi]

"Rapidly flipping" still left us clueless on where or what causes the blank. Luckily, sort of, I figured one scenario where it happens. So far, it does give you a blank page when the user touches/swiped the next view while the current view is on the process of flipping causing a mess in subviews (Well, in reality most people I think won't be doing such but for a developer a bug is a bug and we can't just sleep it off).

Disabled user interaction to prevent user to swipe/interact while the flip is still on

//Under  case UIGestureRecognizerStateRecognized:
if (fabs((translation + [recognizer velocityInView:self].x / 4) / self.bounds.size.width) > 0.5) {

                setNextViewOnCompletion = YES;
                [self setFlipProgress:1.0 setDelegate:YES animate:YES];
                self.userInteractionEnabled = NO;  // Add this
                 progress.
            }

Revert back to default.

if (setNextViewOnCompletion) {
        [self.currentView removeFromSuperview];
        self.currentView = self.nextView;
        self.nextView = nil;
    } else {
        [self.nextView removeFromSuperview];
        self.nextView = nil;
    }
    self.userInteractionEnabled = YES; //Add this

@burrows111 I don't think this is the most appropriate / permanent solution to fix the blank page issue but so far with what I know this could at least lessen the possibility of users getting a blank page. Hope it helps.

[burrows111]

@teffi hey thanks for your input, check out my fix above. seems ok, running no issues so far and no blank page. not seeing the userInteraction issue though.

[burrows111]

im sorry for the formatting guys, i couldn't see a way to indicate what i pasted was code.

[teffi]

@burrows111 on my project the subviews are not less than 2 but 1.

Edit: Been testing your solution on my end it messes up my pages.Anyway if its working good on your end then great! :)

[burrows111]

@teffi unsure, it may prove helpful. When I'm done with the project I'm doing ill fork my solution as I merged changes for a different fork that had shadows on the page turns aswell.