Question

I have a small application with some detail controller. Detail controller is a web view put inside scroll view:
Here is a code of detail view controller:

- (void)loadScrollViewWithPage:(int)page

{

if (page < 0)
    return;
if (page >= detailTotalJobs)
    return;

// replace the placeholder if necessary
SearchJobDetailWebViewController *controller = [viewControllers objectAtIndex:page];
if ((NSNull *)controller == [NSNull null])
{



    NSLog(@"Vytvaram web controller: %d", page + 1);

    if (detailJobIndex == page) {

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:detailExportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    } else if (detailJobIndex + 1 == page) {

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:detailNextExportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    } else {

        [self performSelector:@selector(downloadData:) withObject:[NSNumber numberWithInt:page] afterDelay:0.1];
        //[self downloadData:[NSNumber numberWithInt:page]];

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:nextArray.exportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    }

}

// add the controller's view to the scroll view
if (controller.view.superview == nil)
{

    CGRect frame = scrollView.frame;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0;
    controller.view.frame = frame;
    [scrollView addSubview:controller.view];

    //NSDictionary *numberItem = [self.contentList objectAtIndex:page];
    //controller.numberImage.image = [UIImage imageNamed:[numberItem valueForKey:ImageKey]];
    //controller.myLabel.text = @"Test";
}

}

- (void)scrollViewDidScroll:(UIScrollView *)sender

{
// We don’t want a “feedback loop” between the UIPageControl and the scroll delegate in
// which a scroll event generated from the user hitting the page control triggers updates from
// the delegate method. We use a boolean to disable the delegate logic when the page control is used.
if (pageControlUsed)
{
// do nothing – the scroll was initiated from the page control, not the user dragging
return;
}

// Switch the indicator when more than 50% of the previous/next page is visible
CGFloat pageWidth = scrollView.frame.size.width;
int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
pageControl.currentPage = page;

NSString *detailTitleText = [NSString stringWithFormat:@"%d / %d", page + 1, detailTotalJobs];
[self setTitle:detailTitleText];
//[detailTitleText release];

// load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
[self loadScrollViewWithPage:page - 1];
[self loadScrollViewWithPage:page];
[self loadScrollViewWithPage:page + 1];

// A possible optimization would be to unload the views+controllers which are no longer visible

}

Code inspired by Apple page control.

Problem is here:

if (detailJobIndex == page) {

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:detailExportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    } else if (detailJobIndex + 1 == page) {

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:detailNextExportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    } else {

        [self performSelector:@selector(downloadData:) withObject:[NSNumber numberWithInt:page] afterDelay:0.1];
        //[self downloadData:[NSNumber numberWithInt:page]];

        controller = [[SearchJobDetailWebViewController alloc] initWithNibName:@"SearchJobDetailWebViewController" bundle:nil page:page url:nextArray.exportUrl];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];

    }

First part and second part of if work correctly, because I have data for first web view and for second web view.

But last part of if have a problem. when I scroll from second web view to third web view, scroll view show blank page. Next pages work correctly.
Where is problem, please ?

Answer 1

Just put a breakpoint in debug mode on the braces.
Is controller nil ?
Check your custom init method.

Does it return nil if there is a problem ?

[self = super initWithNibName..................];
if (!self) return nil;

// some inits

return self;

If this is done and controller is nil, check your URL, and try it into a web browser. Does it showsup ?

How do you fill your webView ? Is there an error returned when filling it ? No encoding problem returned ?

Well, some code would help, but these indications are the most common problems you can have.