Hello guys how apple is loading table view cell image that
doesn't affect scrolling of
table view.How fast it is working. I want to make a table view like that which loads
image directly from URL and it doesn't effect scrolling of UITableview
Lazy Loading is the exact term, which you are referring to. (Apple Technologies uses LazyLoading wherever it can be applicable, whether it's iOS or Mac OS X -- and it gives best user experience, too, as user is not forced to wait)
Apple provides sample source code, which performs similar functionality -- Here is the sample code
Don't get confused with the ParseOperation Class. It is just the separate implementation of the XML Parsing functionality. Though, It is a better approach, You can write it in your own working class (from which you are invoking the connection request.)
Additionally -- Apple has updated this code to use Blocks (GCD).
Hope that will help you...
You dont need to look too far - Apple has this code in the Open - LazyTables.
If you want to know the magic sauce is the launching of bg thread to download images, after the downloads finish in background, then it updates the UI to show the image.
Related
I have seen some apps where when you launch them for the first time after downloading (e.g. Chrome app on iPhone), it shows you a list of animated gestures on the screen, kind of giving you a tour of the app.
How do I build one something like that? And how does the app know to launch only for the first time after download and not since then? For the second question, I am guessing a "shown=TRUE" value can be saved inside a PList file and checking the value each time when the app finished launching. But I am more curious about the mechanism involved in creating a guided app tour.
You can use transparent and semi-transparent images with a UIImageView, so you can make up an image with arrows and notes and put over the whole screen. You could fade it out when the user taps.
To know if it's the first time running the app, you should use NSUserDefaults instead of a plist; it's much easier, and you should be app to find a quick tutorial on that fairly easily.
Also, you could check around on this site for controls like this one. I haven't used any of them myself, so I'm not sure how much they differ from a regular UIImageView. They look nice though.
I am looking to integrate the ability to select images from the built in library into an iOS app.
UIImagePickerController seems like the obvious choice.
However, it only works as a modal view controller. For design reasons, the image selection in this app needs to be part of an UIViewController itself.
After some research on the web and searching the StackOverflow archives, it seems I will need to implement my own Image Picker from scratch using ALAssetsLibraryto access the images stored on the device. However this is quite a task (if done well).
Thus my questions are:
1) Is there already an existing library or class (or would someone be willing to share his/her existing code) for this purpose?
2) Alternatively, is there a way to extend the UIImagePickerController to add more interface elements to it?
For some of my own projects, I use the ELCImagePickerController, but this again is meant for modal presentation.
But since it's open source, you may be able to make modifications to allow it to be embedded in the way you want it to be presented.
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.)
Recently I've been looking to create some way of showing a user that something is being loaded. I'm sure anyone with an iPhone has seen this is apps before but what is the best way of doing it?
I started using UIProgressHUD, however it was pointed out to me that you shouldn't really use private (undocumented) API's.
I then I moved onto this which is a custom version called MBProgressHUD, however in my experience with this is wouldn't show the loading part when trying to call it not from a button and I found it very buggy (It wasn't very hard to crash the example code given by just clicking away).
I then went on to find this by James Brannan from his book, however I'm not quite sure why he claims this is the "proper way" of doing it when I've seen many apps in the past with what looks like the UIProgressHUD.
Does anyone have any ideas?
EDIT: This is pretty good...
Thanks
There is no one "best" way. Another way to do this is to simply put a UIView atop your main view's subviews, mark its userInteraction property and grey it out when needed. You could even add a UIActivityIndicator as a subview of this "foreground" UIView, starting its animation when needed. When your loading has finished, hide/stop the activity indicator and clear the foreground view's color.
If you are talking about loading over a network, one good thing to start with is to enable the status bar network activity indicator:
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
Note that you have to set it to NO when you are done! That should only be used to indicate network activity.
That's a bit subtle though, it's a great idea to have some kind of progress indicator IF you can tell exactly how long something is going to take - downloads where you know the size and count incoming bytes, or uploads where you also monitor bytes outgoing and know the total size.
If your call length is very small or the size is not really known (web service call is a great example) then some kind of overlay with a UIActivityIndicator can be very relaxing (you can also make a custom variant with a set of images added to a UIImage view to animate). The key is, that if possible it should not block the user from doing other things if possible.
Also if you have multiple things going on, you might want to add messages describing what state you are in (like, "adjusting image", "uploading image", etc).
It seems like the built in UIImagePickerController cannot accept sources other than its device camera Roll.
I would like to get the functionality of picking and enlarging pictures within my own app. Also I would like to allow the user to select the pictures and save it into their camera roll (so they can later use it as wall paper)
1) what is the recommended way of building a custom UIImagePickerController that supports what I need ? Is there another built in controller I am missing?
3) Is there a way to take a UIImage and save it to the desktop background of the device directly? Or is it a two step (first save to camera roll), then have the user load the picture from there to save as wallpaper
Thanks in advance!!
At this point, it seems that the only way to build a custom UIImagePickerController functionality is to subclass, and then muck with the view hierarchy directly. This allows you to move, hide, and replace UI elements and access the non-public classes that control the operation of the camera, but as you probably gather, this technique is both unsupported (in that it may, and probably will, break with future updates) and not recommended (in that it may, and probably will, get your app rejected from the App Store if detected).
As far as your second point (somehow numbered 3), John is right: there is no call in the public SDK to accomplish this. You could probably hack something together if you're clever, but remember the warnings in my first paragraph...
Regarding #3) there is no public call in the SDK to save an UIImage to the desktop.
I don't know about the rest of your questions though.
Just today I started a open source UIImagePickerController clone, it is not perfect but it works quite ok. Feel free to fork http://github.com/jeena/JPImagePickerController