I am bundling up 2000 - 5000 images in uiscrollview with names. The current scrollview has quite hiccups during scrolling.
So the question is about how to improve performance. What I have searched so far is that I would have to get on NSOperations, NSQueue like things. But I'm not able to get any code sample on that. I remembered watching some video on WWDC 2010 on boosting performance of UItableview loading images being exhibited. Unfortunately I'm not able to remember that title too (worst perhaps it was 2009 video session).
So please can anyone point to me in right direction about what tutorial or sample code should I see. Atleast apple ios library reference links?
UITableView uses lazy loading of reusable cells from a pool.
I'd advise you look at implementing something like this, so that only images objects that are actually viewed fetch an image.
NSOperations may be something you could look at to implement the actual fetch with but also consider using ASIHTTPRequest to asynchronously grab them as this handles all the queuing and threading for you.
Related
That may seem like a broad question, but I'm talking specifically here about apps that display a lot of content (image plus some text) pulled from the net in separate cells, rows, etc. And where each of those cells can get loaded asynchronously (independently from all the others).
So for example, for iOS, is it too inefficient to use uiwebview for each of these cells? It seems like this would be a simple approach, but I'm not sure about the performance. "Pulse" has a bunch of cells on the page at one time, and on iPad this could really get to a large number. Is it better to do this using lower level techniques, or is using UIWebView a decent choice?
Update:Clarification-->
Just to clarify, I understand that the typical approach is to use UITableView and then create table cells to hold and show the data (although the "Pulse" UI may be more involved). What I'm getting at here is if those UITableViewCells could hold UIWebViews? So instead of putting a UIImageView and a UITextView in each cell and so forth, if it makes sense to just put UIWebViews there instead, and give them URLs (could pass a param to indicated the row) to load as cellForRowAtIndexPath is called or something.
Well, if you talk about the YouTube app, its not UIWebview. The common and better approach is to use UITableViews along with the custom UITableCells. As far as asynchronous loading of images is the concern, we implement "Lazy Loading" mechanism. And in this way, we are able to keep the performance benefit of native UIView intact. Whereas, in UIWebView, you would need to design the iphone based webpages which will cost you learn about Dashcode tool, or may be someother opensource css library, etc.
In short, UITableView, with Custom UITableCells, along with Lazy Loading Mechanism (achieved by some Threading Techniques) will do all the Magic for you.
Hope this answer will give you some better idea....
Do not use UIWebViews with UITableViews like that. There are far too many moving parts for a UITableView!
I wrote the NYTimes iPhone app while I worked there. I only ever used a UIwebView to display article content. This is because NYT articles and log post layout is extremely complicated and impracticle to replicate programmatically. (I did override some of the CSS in app)
The UITableView is a super high performance implementation for butter smooth high speed scrolling. UIWebViews are the opposite of that: heavy, slow and memory intensive. In fact web views actually run internal virtual machines and threads (for JavaScript, rendering, etc).
Keep in mind that table view cells are recycled very aggressively. The instant a cell scrolls off screen bottom it will, in gneral, be immediately reconfigured for use as the new cell that scrolls in from the top.
With a UITableView, you need to create VERY highly optimized custom UITableViewCells. The data displayed in the cells should be cached aggressively by you so that you don't need to recompute it or perform intensive layout calculations. Uncacheable information such as remote images should be loaded asynchronously (which might mean they show up much later).
On caching:
The NYT apps have a high performance caching system for images. The trick is to request the imge data as soon as its "needed", but to also preempt downloading images which were needed a second ago, but no longer. You also don't want to cancel partially downloaded images because that wastes the already consumed bandwidth. Check out NSOperationQueue. It has most of the levers needed to build such a system.
Another note: consider building a web app if your project may also be accessed via web or an android app.
I have a scrolling grid of photos that looks and functions pretty much exactly like the photo picker on the iPhone. It is constructed from a UITableView that uses a custom UITableViewCell which displays a row of photos (very similar to how Three20 implements it).
It works great except that scrolling performance is poor. I'm already following most of the best practices for fast UITableView scrolling (à la Tweetie).
The images are all bundled with the app. I load them on the UI thread, on demand. I use UIImage's imageNamed: so that the images will be cached after they're first loaded. Once I've scrolled through the table view once, it scrolls very smoothly.
The problem is, the first time scrolling through the table view, scrolling is jittery. I've profiled the app and found that the majority of the time is spent loading the images from the file system. They are JPEG images, already sized correctly (small). I tried using PNG images instead, but performance doesn't improve very much.
The iPhone photo picker exhibits much better loading performance. I'm wondering if combining all the photos into a single image, which I load once and then split into smaller images would be faster. It certainly works in games, but I know that's really a totally different story. Has anyone had experience doing that?
Any other ideas for how I can improve performance?
Incidentally, I'm having a similar, albeit less, performance problem for another UITableView that just uses standard UITableViewCells with one image assigned to the imageView per row.
One thing to try could be pre-caching all the images when the view loads. Beyond that, perhaps loading the images in the background (even though it's loading from the filesystem and not the web). I haven't tried this myself, but perhaps you could use something like https://github.com/rs/SDWebImage and have the URLs point to the filesystem. Users might see some placeholder images at first, but then the UI wouldn't stutter while images are loading.
Setting the PagingEnabled property to off improves the scrolling performance.
I had a similar issue using a UITableView to display information parsed from an RSS Feed. I ran into scrolling performance issues when there was a significant amount of data. Though I'm still working on it I suspend the parsing when the table is being scrolled. It resumes when scrolling stops. I am not at my computer, but I believe I used tableViewDidScroll and tableViewDidEndDecelerating. You can check these tableview delegates. In any case it works very well, I just need a more elegant way to pause my parsing.
Fantastic. That does work like a charm! So efficiently I ended up using insertRowAtIndexPath rather that reloading the table. Now it behaves the way it
Thanks so much!
Joe
I am looking to replicate the image gallery view that shows thumbnails, like in the photos app on the iPhone.
Is there a view controller or any examples that anyone can provide to replicate this?
There isn't one provided by Apple. I would recommend looking at Three20. It has a few things with look a lot like the Photos app.
Another option is AQGridView.
Take a look at the video of Session 104 from the WWDC 2010. It's basically a 40 minute tutorial on how to do the photo app.
Bear in mind that allowing users to zoom will greatly increase the space required. If you use CATiledLayers, that is, which, depending on your desired zoom level, you should consider doing.
Oh, and there is source code ;)
What they don't tell you is how they did their tiling. I found that you can
a) download ready-made tiles from the server with the app or with a content update (you can use ImageMagick's crop tileWidthXtileHeight - e.g. crop 100x100 - to do the tiling). This has the disadvantage of large downloads.
b) download ready-made tiles from the server as needed (may lead to lags in your app, but then MKMapView does it quite nicely, doesn't it?)
c) tile on the phone as needed (here you can also consider caching the results, although that will likely mean you have to check space left on the device)
I've recently given enormego's PhotoViewer a try. It's easy to use, and it's much more focused than the Three20 project. (Which I also use and like a lot.)
This is a question for iPhone development and I'm hopin someone can point me to the right direction on how i should go about implementing this.
I am trying to write a chat application that supports emoticons/smileys. Where the smiley/emoticon images are stored can be figured out later. I think few iphone applications out there are already doing this (i.e. skype + ebuddy(?)) but not sure what method they went for.
After searching around, there seems to be a few ways of doing this (i think):
bubble chat style which has been discussed before. UITableViewController with custom UITableViewCell. For emoticons, might have to do a whole bunch of calculations to determine where to stick a UIImageView for each emoticon.
Use UIWebView as the whole "window". Style it to look like bubble chat. Takes away any manual calculations on image smiley placements.
I have no idea what the performance is like for each of these two methods, how complex it can get etc, so any comments and guidance will help for sure. Cheers
If you use custom UITableViewCell, then I'd probably implement drawRect: instead of adding labels and images. One will probably take as long to implement as the other, but it will perform much better.
The UIWebView might be worth a short, although you will have to make sure that everything looks right there, too. Instead of using one big web page, I suggest simply throwing in a web view into each table view cell.
Personally I prefer the first approach, measuring and layout of text is not too complicated, but then I've never been the ultimate HTML guru.
I agree with #Eiko on making custom UITableViewCells, especially using drawRect instead of adding labels, images, etc.
If you used a UIWebView how would you handle updating it? A complete reload each time new text is sent? That seems like it will be a cause of issues. Once you get a long conversation reloading the entire UIWebView's contents will cause some flickering which isn't acceptable in my opinion. Also using a UIWebView would require you to have 2 complete copies of each conversation in memory. 1 as your backend data and 1 as the HTML. Where using a UITableView you have your backend data, and only enough of that will be duplicated that can fill 1 screen at a time.
I have a set of tiled image collections created via Microsoft's Deep Zoom composer, and a Silverlight application that currently consumes them for display via MultiScaleImage - it's all working pretty well - I'd just like to get some experience with iPad programming and
have a couple of ideas for some iPad applications. All my ideas rely on me being able to display/manipulate these tiled image sets (on the iPad).
I just picked up a iMac to facilitate this. I'm not seeing any Objective-C / Cocoa-touch libraries for this though, so am assuming I will have to roll my own. (I saw the Seadragon Ajax component, which is pretty slick, but I'm dealing with collections here, which it doesn't support. I would also like to roll this as a native application just to get the experience.)
The only open source project I found for displaying/manipulating the tiled image sets was Openzoom - a Flash component. I'm not to familiar with ActionScript either (Python, Java, C#, and c are the only languages I have really used), but briefly inspecting the code I didn't really have any issues with it and can probably use it for hints on how to swap the tiles in and out, etc. But, as I'm pretty new to Objective-C/Cocoa-touch, some pointers in the right direction would be appreciated.
1) Are there any other projects out there I am missing, or is OpenZoom my best bet for some reference?
2) Should I be trying to do this display in the UIKit framework, or should I do it as an OpenGL display?
3) Any other suggestions/pointers that I didn't think to ask.
I have just been working on a few apps that rely on tiling large images to allow for deep zooming. I found a couple of examples but the best and most useful for me was Apple's "PhotoScroller" sample code.
It relies on CATiledLayer to handle the tiling. The result is an extremely smooth and responsive interface even with very large images and its not too complex. (A little complex but not too bad).
So to answer your question directly:
PhotoScroller Code
QuartzCore Framework (which is part of the SDK)
There is a great, free little mac app for slicing images into tiles that I use a lot: "Tilen"
In the WWDC 2010 source samples, under iOS, there is a project in the ScrollView Suite called Tiling. It corresponds to WWDC10 session 104. It is probably the best image tiling example out there.
You can take a look at they way RouteMe library does this, the dynamic loading of higher resolution tiles, panning, etc. https://github.com/route-me/route-me
I can't believe nobody has told you about UIScrollview; the UIScrollView component is designed for this very purpose! (think Google Maps, which uses it).
Check out the class reference...
UIScrollView
The delegate method you require is the following....
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
This allows you to check the zoom level, offset etc and then provide a view for zooming. This way you can maintain your 'position' within the tiled landscape independently of the graphics used to represent it.
Don't roll your own UIScrollView, no need to!
Take a look at CATiled Layer. See my answer to a similar question here: Drawing in CATiledLayer with CoreGraphics CGContextDrawImage