I'm working on an ios app written in swift, xcode7
A view has a UIWebView on it.
using loadRequest(NSURLRequest) we load a pdf file from disk.
This works fine, but sometimes the pdf file cannot be scrolled past the first page or what you see first on the screen. I can't pinpoint what causes the not-scrolling as sometimes I open the same file again and then it scrolls.
Trying to scroll when it doesn't want to bounces the bottom part of the screen and you can see there is another page, but you can't scroll it into view.
The UIScrollView contained inside the UIWebView (this is the default) knows there are more pages, because it shows "1 of 3" on screen.
The UIWebView
has 'scales page to fit' checked
has 'user interaction enabled' checked
has 'multiple touch' NOT checked
has 'autoresize subviews' checked
has mode 'Scale To Fill'
I have tried the following:
checking if the scrollview is not larger than the screen by placing a border around it: no, it fits on screen and is as large as you would expect
setting the internal UIScrollView.scollEnabled to true in code
In the application, when showing the UIWebview, it is resized on screen by collapsing an element above it, but I have tested this with fixed heights and it doesn't change anything.
When I call flashScrollIndicators() on the internal UIScrollView, this is consistent with the scrolling or non-scrolling. If you see the scrollbar flash, then scrolling is possible. If not, then you can't scroll past the first page.
Any other ideas I can try?
This sounds like a weird UIWebView problem.
Two additional things you can check :
Is the issue resolved after you rotate? (had this happen to me once)
If you call flashScrollIndicators on the internal UIScrollView and it's not responding. Is the internal UIScrollView a nil object?
Another solution is to try and use WKWebView. It might resolve the issue. Just be sure to only use it in the last versions of iOS.
You can also step down a layer and implement it with CoreGraphics since you have the PDF on the device itself and not on the web (official docs). There is probably a good CocoaPod or Carthage framework you can use for this.
The underlying problem was the fact that before loading a new pdf, the UIWebView was cleared each time by loading 'about:blank', which is the most suggested solution to clear the webview. However, when working with pdfs with different page sizes and different number of pages, this seems to mess with the built-in scrollview.
The solution in this case was to create a kind of 'blank' pdf with a single page (and maybe an application logo in it to distinguish it clearly for the user) and instead of loading about:blank, load this pdf instead before showing the webview to the user and while waiting for the real pdf to download to the device.
Related
My iOS app is working with web content, and at certain time I need to take a screenshot of the web content. I'm using WKWebView (UIWebView was deprecated) for that purposes. All works fine, but recently I start to notice, that not all content appears on the screenshot. After some research, I've learned that some HTML pages have CANVAS tag, which is used for some real-time rendering/video playback. And this canvas content didn't appear on my screenshots. This quite frequently happens with ads.
I'm always using the following method for screenshot:
webView.drawHierarchy(in: rect, afterScreenUpdates: true)
At the moment, I can't find a way to take the screenshot as it appears on the screen.
Any ideas here are welcome since can't find any solutions.
Update:
Also, when trying to capture the view using Xcode debugger, it renders all the layers, view hierarchy etc.. Except that "canvas" view. It remains black.
I have an app which drags messages dynamically from server, as scrolling to top, old messages will be retrieved and display on the screen like other messaging apps, but my app keeps generating UIlabel, even though no more old messages presents after all the old messages are retrieved, the UIlabel will still be generated if the list is being scrolled, and the source is from QuartzCore, responsible caller is CA::Render::Shemem::new_shmem(unsigned long).
Can anyone help me, I'm quite new at developing ios, and im using objective-C, the memory issue cause my app crashed on every version of iphones as the UILabel stacks and seems like it will never release unless I switched to other chatrooms. Thanks for any help!!
It sounds like you are adding labels to a scroll view. Change your app to use a table view or a collection view to display messages. These classes automatically remove and reuse cells that are scrolled off the screen.
I use a Launch Screen (xib) in my app to overcome the problem of the resizeable screen, since i don't always want add Launchscreens everytime, Apple create a new iPhone with a different screen resolution.
In my launchscreen, i placed a UIImageView directly in the center of the view using constraints. The image shows the logo of the company i work for.
The problem is, that sometimes the image is being hidden (mostly after install and first launch) and sometimes it shows (mostly after a view times using it). I'm not quite sure, what the problem is. Is it because at the first-launch-time(s) it has to load many ressources?
Figured out the problem: It seems, that if there isn't enough disc space left on the device, it doesn't show the xib's (Launch-Screen's) Image. iOS at some point clears out some disc-space (i guess from NSLibraryDirectory) and than the images show again.
If this is a major problem to any of your apps, use Launch-Images instead.
The setup
I have a UICollectionView that allows the user to page through pictures, 12 to a page. There are upwards of 200,000 pictures that should all be available in the app. I'm not expecting a user to scroll to page 20,000, so there's function to jump to a certain page.
The problem
In landscape orientation, paging breaks down on page 16,385. The collection no longer adjusts to the page boundary. If you go back before page 16,384, you can get it to start working again, but no page past 16,385 works.
My delegate also stops getting scrollViewDidEndDecelerating: the message when the bug shows up.
The hypothesis
Page 16,385 in landscape orientation happens to start at pixel 16,777,216 which happens to be 2^24. I think that there's something in UICollectionView or UIScrollView that breaks past 2^24.
Is this just an undocumented limit? Am I out of luck?
The example
I've uploaded a project that demonstrates the problem. Here's the relevant view controller. If you shake your iPad or the simulator, you'll be taken to page 16,384, one page before the bug shows up.
The snark
If you don't think a user should need to be able to go to page 20,000, that's cool. I don't think it's relevant to the question.
I'd say this is an undocumented limitation and would file a Radar bug report, attaching the sample project as evidence. If you are looking for an alternative method, you could try using a UIPageViewController with a collection view for each page. You can choose the swiping animation, rather than the default iBooks-esque animation, and replicate your sample project very closely.
You could just load say 10,000 pages and when the user jumps, load an appropriately different 10,000 pages.
I wonder whether you've tried using multiple sections? Is the limitation per section or for the entire CV?
I can not use UIWebView because I want the text to be accessible even if the user does not have Internet access on their phone. Also, I will need to have buttons to other screens on the app and I think that is not possible with UIWebView (right?)
Is there a way for me to edit the xml of the screen directly inside Xcode? My requirement is to have about 10 sections with header labels and buttons before each, so if I have to adjust it on the storyboard screen, it will be a bit nightmarish.
What is a reasonable approach for me here? I think only to edit the xml by hand and hardcode it with styles and text, right?
several things here:
webviews only need an internet connection if you are downloading the content for the view (which doesnt seem like what you want anyway, aren't you just building it locally?)
you can make the buttons in a webview do whatever you want. See this answer.
What is so complex about this UI that you can't just build it the regular way in code or IB?
Just because you consider using a UIWebView it doesn't mean you are restricting your application functionality to internet access.
You can just as well have HTML documents in the application bundle that you display in a webview. This is basically what PhoneGap is doing.
If you don't want to use webviews then nothing is stopping you from using UIViews, UILabels, UIImageViews etc and compose your app how you want.