In many cases using one of the 4 UITableViewCell 'of the shelf' styles is enough for what I need, except for one 'little' annoying thing: The cell.imageView.contentMode property is always set to Scale to Fill. If images have different ratios, it causes the cells labels to be pushed with different x per each Row. It looks ugly...
If I try to fix it in code, let's say in the cellForRowAtIndexPath method, by addressing the property and assigning it to Aspect Fit, I get no warning or error, but it simply does nothing - i.e. it remains with Scale to Fill.
That means, that if I have an app where I'm not responsible for all the images presented in the table view and therefore cannot cut them in the same size - for example, if I wish to allow the user to select images from library or download etc... - I have to use a Custom Cell, even if all it has to have is an Image and a Label.
Does anyone know how to solve this using the default styles, without subclassing UITableViewCell?
In this SO thread you have a couple of solutions for that.
However, you will find that those solutions are just another way to create a custom cell. Or you need to create an ImageView at runtime or you just create a custom cell. As far as I know it is the right way to do it. I know that is annoying but the time you take to do a custom cell is way shorter than find hacky ways to go around that issue. Don't fight the framework :).
Related
My CollectionView Cell has only Image in it. I want to resize that
image by user, and while resizing the image all the cell should
automatically rearrange (I have fixed image count i. e. 22):
I have used flow layout for
collection view but limitation is that needs fixed number of
height/width.
I have added resized library separately.
I Tried by searching many libraries and doing so many demos but not
able to get the required output. I want you to suggest me either the
way should i go with or If you have done such kind of stuff then your
thought are welcome.
Thank you in advance.
I have a screen in my app that pulls an unknown sized array from my user object, and must display an object for each item in the array that consists of a UIImageView for my background image, a UISwitch to activate/deactivate that particular item, a label with the name of the item, and a label that corresponds to the name of the item.
These are displayed in a UIScrollView, since there are nearly always going to be more items than will fit on the screen, especially on the iPhone 4.
I had initially quickly thrown together a static screen that consisted of 20 of these objects, but have found that I will often be exceeding that number of items in the array, and need to convert to a dynamic solution.
I have not used subclassing at all yet, and want to be sure that this is the proper solution before I dive into the implementation. Adding one subclass to my scrollView sounds a lot cleaner than adding each of those components individually and figuring out the spacing for various screens.
If this is the proper solution, are there any resources you could point me to to learn about how to properly do this subclassing? I.e., how to add a constructor for the objects where I can add the contents of the labels and state of the switch, and programmatically add constraints. I've only used constraints from the storyboard.
If you do not think that subclassing UIView would be the proper way to do this, what other solution would you suggest? I'm admittedly a novice when it comes to iOS development, so I apologize that this post seeks advice on where to start rather than help fixing a specific part of an implementation.
You should use UITableView or UICollectionView for that, and subclass UITableViewCell or UICollectionViewCell to create your custom view hierarchy.
UITableView and UICollectionView will handle reusing of cells which will help in memory management.
Update:
as you want to use UITableView so to add spacing between cells set number of sections to number of elements and then add header for section and set its height you can do that by implementing UITableViewDelegates visit below links for detail about UITableView and UITableViewDelegates
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableView_Class/
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewDelegate_Protocol/
I am trying to create a table to show posts by users with possibly variable lengths. I want each cell in my table to resize to fit the content of the UILabel containing the text of the post. Currently I am doing this with auto-layout, programmatically setting constraints and calculating the height of the table view cell based on the height of the UILabel. Everything looks as I want it to, except when rapidly scrolling through the table the performance is horrendous, with the CPU getting fully maxed out and unable to keep up with setting the constraints for each cell as they are reused and placed with new text.
I was wondering if anyone knows of a better way to do this. Is there a way I can continue to use auto layout to size my cells without sacrificing performance? Or would the best solution be to create different sized cells with different identifiers, and just choose the best fit based on the UILabel text size.
I also read somewhere that UICollectionView has much better performance in displaying variable-sized content, would it be worthwhile/possible to try configuring a UICollectionView to display the messages, and somehow make it look like a UITableView?
Essentially I just need a suggestion on how to display messages of variable sizes (up to about 7 or 8 lines of text max) in a TableView-like manner without causing massive slowdowns as the user rapidly scrolls through the table.
Thank you
The best trick in the book for things like this is cacheing. Add to your model anything that's expensive to compute (not the views themselves, but the computational results, like view bounds sizes). Make your datasource methods all about looking up and assigning, not at all about computing.
The way I had implemented adding the constraints, the constraints were updated whenever [self updateViewConstraints] was called, regardless of whether or not the cell had already had its constraints calculated and applied. I resolved this by adding a BOOL property to my custom TableViewCell called didUpdateConstraints, and setting it to YES as soon as constraints are updated the first time. Then in my [self updateViewConstraints] method I only update the constraints if !self.didUpdateConstraints
Now that constraints are not being needlessly updated when all views have already been correctly constrained, the performance is significantly better, and I don't observe any slowdown upon scrolling through the table.
I am working on a specific type of list for an iOS app, where cells would simply have a specific width and height and then float left (think of something like CSS float:left), creating then a list that would scroll if more than 12 items (like the picture bellow).
I was thinking that perhaps this could be done by customizing UITableViewCell and setting the frame's width and height, so I could re-use the various benefits UITableViewController, delegate and dataSource offer. but unfortunately it seems that's not possible.
So, I'm now simply creating many UIViews and positioning them across its parent programatically.
I just would like to make sure this would be the right approach to achieve such kind of lists and if someone could let me know if it's indeed not possible to have this kind of functionality on UITableView and inherit all the goodness it offers.
Thanks guys
I know this question is already answered, but still...
I believe you can simply use UICollectionView since iOS 6.0.
Documentation
And this is how it looks like (image)
Maybe this will help somebody.
UITableView can only have cells that go in one direction. It's perfectly okay to create many UIViews (table view cells are also UIViews), if the number of them is reasonable. You can usually have a few hundred UIViews in a scrollview without seeing any performance issues, but that also depends on the complexity of what's inside the uiviews. Try it for yourself and if you find out, that you need too many uiviews, or that their complexity it too high, you can optimize further. You can set the .layer.shouldRasterize property to "cache" the content of the views. Or you can use CATiledLayer, which is something like a UITableView, but it supports tiles in all direction (and scrolling, zooming, ...).
Take a look at this project, I think may be helpful to for your problem
link
I've finally finished my first large application, the only problem is that I've focued a lot on design, and I'm using custom nibs as cells with transparent backgrounds. When I tried testing the application on my iPhone, the performance was terrible.
Is there any way to get better scrolling performance while using transparent cells with a ImageView behind the UITableView?
I've read two articles mostly:
blog.atebits.com/2008/12/fast-scrolling-in-tweetie-with-uitableview/
cocoawithlove.com/2009/04/easy-custom-uitableview-drawing.html
Looks good, but what if I want to use transparent cells?
a) Uses solid color.
b) Uses imageview as background.
Any help will be greatly appreciated. I want to get this baby released as soon as possible, but the performance as it is now is terrible!
First off, stop using nibs. Every time a cell is created, you're now hitting the disk in order to unarchive the nib. 3.1 will actually make this better, but until then, please create your cell in code.
Secondly, remove transparency wherever you can. Anything that doesn't need to be transparent, shouldn't be. And anything that isn't transparent should have the opaque property set to YES.
A third suggestion is if you're using a lot of subviews, you will see a performance benefit by using a custom view to draw everything instead of a bunch of subviews. If you choose to go this route, you should consider how it behaves when rotating to landscape mode (e.g. how the stretch action occurs), or if you have any controls that need to handle touches separately from the cell itself.