I have a UICollectionView with a few different types of cells and am using Auto Layout to use self-sizing cells. To accomplish this, I am setting estimatedItemSize on my UICollectionViewFlowLayout and ensuring the constraints in each of the cells is correct (so I am not using the preferredLayoutAttributesFitting method). The first time the collection view loads, everything looks correct and I get no errors in the logs. Debug View Hierarchy doesn't show any issues either.
In one of the sections, there is a cell that has radio buttons and can cause the height of the content to change based on which radio button is selected. In order to resize the cell after tapping a button, I call collectionView.collectionViewLayout.invalidateLayout().
When this occurs, I get about 3000 lines of logs in the console complaining about broken constraints. It is seemingly complaining about every single constraint present in the cell that was adjusted. However, everything on the screen seems to look exactly how I would want it afterwards, and opening the Debug View Hierarchy doesn't show any issues.
Is this just a product of calling invalidateLayout when Auto Layout is involved? One of the constraints it is complaining about is the the height from the estimatedItemSize, so maybe that is what's causing all of this? Maybe it tries to lay out the view using the estimatedItemSize first and then realizes it should be treated as self-sizing?
Calling reloadData instead seems to work just fine, except it leads to other undesirable behavior and shouldn't need to be used as the underlying data hasn't changed.
Related
I seem to be having a very strange problem with my UITableview cells and autolayout. So my tableview is set up as follows:
I have a UITableView within a UIViewController that I created via Interface builder using Autolayout
My tableview is using UITableViewAutomaticDimension so that the cells can resize based on the text within them.
Each cell has 2 subviews within it. A front view and a back view. The back view contains the buttons for my slide-able cells
I am using NSFetchedResults controller to update the tableview
The problem occurs when I tap on a cell and am taken to the next view. Then I create a core data item within that view and save so that it is inserted into my tableview (now behind the current view controller).
What happens is that the newly inserted cell seems to lose all autolayout constraints and all view elements are on top of each other in the top left of the cell. It also looks like they are not even contained within the front view for the cell (or the front view has a width and height of 0).
Example:
It gets even stranger. If I refresh the tableview by pulling down and the cells are reloaded it corrects itself. However, if I refresh the tableview again then the problem appears again but on a different cell. This bug does not happen consistantly which is rather frustrating.
Any help would be appreciated as I only have a few remaining hairs on my head to pull out at this stage.
Thanks in advance!
So I found out what the issue was. The issue was that I was using size classes in Interface builder but I was only using the iPhone Portrait size class and did all my work in there instead of the "any" size class. Disabling size classes and setting the project to iPhone only fixed all these problems.
Weird I know
I am trying to do something like loading up different type of cells with custom height in a uitableview. The tableview cells are subclassed and consists of labels with the respective constraints. Each cell is having a dynamic height.
Now even before my table reloads the data, I am calculating the height that is required for the resizing of the cells and caching it in my model class so that I dont have to calculate the height when the data is rendered on the device.
To calculate height i did use the tutorial from Ray Wenderlich and I am having the right set of heights applies to the objects.
Now the problem comes. Whenever I am dequeueing the cells there is a
kind of a small jerk that gives me an indication that my cell is
dequeued while scrolling.
How can i make these movement smooth so that there is no jerk while scrolling the view ?
The height is getting assigned in and does get the value as per the current type of data getting loaded.
estimatedRowForIndexPath
Also I am calling layoutIfNeeded from my cellForAtindexPath
Suggestions are most welcome.
It's very hard to say without seeing your code in cellForRowAtIndexPath, and without seeing your cells and their respective code. Here are some general questions I would investigate:
What is the content of the cells and how complex is the view hierarchy in the cell?
Even though you are supplying the correct estimated height, an autolayout pass still needs to happen, and a complex view hierarchy will take time to resolve
Does the cell contain images?
Images that need to be decompressed from a file (UIImage imageNamed:) can be intensive and cause scrolling issues, check images are not bigger than they need to be. If needed, bump this work onto a background thread.
Are you calling a complex method to configure the cell for display in cellForRowAtIndexPath?
Look at the work actually being done in cellForRowAtIndexPath, is there a complex method being triggered in you cell subclass or view model?
Are you adding and removing views to the cell view hierarchy in cellForRowAtIndexPath?
If views are being added, removed, created, inflated from a xib, constrained etc during the cell config, this could slow things down. Try to do only what is strictly needed. Check if there is any code being run internally in the cell subclass during cellForRowAtIndexPath that could be moved to cells initWith... or awakeFromNib methods (ie code that could just run once when the cell is created, rather than every time the cell is displayed)
Also run the Instruments time profiler, see if that offers any more clues
I've used Visual Format Language (VFL) to set constraint of the UITableViewCustomCell's subviews.
its working fine when I scrolling my TableView slowly or normal speed.
But its now working when I scrolling TableView fast.
there are 3 different scenario comes.
TitleLabel --> one line text only
DetailTextLabel --> 0, 1 or 2 line only
see this screen shot which is looking correct when I scrolled it slowly
And when I scroll it fast then its not taking correct constraints
And one thing. Log does not displaying any warning. means that all constraints are complete and correct.
I've tried [self updateConstraintsIfNeeded]...etc so many things.
and its working correct when I used Different cell identifier for particular condition. but I don't want to use different-different cell Identifier.
For Autolayout to work correctly it only requires that all constraints are set and that there are no conflicts amongst the constraints. If you fulfill these promises and ensure that your table view rowHeight property is set to UITableViewAutomaticDimension (i.e. self-sizing cells), then everything should work properly. Also, a common mistake is to update the cell data inside of tableView:cellForRowAtIndexPath: instead of tableView:willDisplayCell:forRowAtIndexPath:. As stated in the documentation, the latter method gives the delegate to override state-based properties. Ensure that your table view is using self sizing cells.
I have a UITableView and one of my table cells is a UICollectionViewController subclass that contains a UICollectionView of displayed email addresses. When a user adds an email the UICollectionView and it’s cell in the table view should get taller.
I’m currently attempting to do this setting my collectionView height constraint to collectionView.contentSize.height in the LayoutSubviews method of my collection controller/cell class. My issue is that the cell in the UITableView is not changing size when this happens.
I am assuming that this is because there is nothing telling the table view that the height of the email entry cell has changed. I am currently using dynamic cell sizing - or trying to anyway. Even, if I call tableView.reloadData() this still does not work. I’m wondering if someone could give me a high-level idea of how they would set this up.
UPDATE:
I had a broken constraint issue that was part of my problem, but this is still not solved. While have proven that I can update the height constraint and that will update the size of the collection view, it's out of sync. It's always one update behind. Here's an image showing the 'UICollectionView' in green and you can see in the logs that I'm updating the constraint (yes, multiple times) each time after adding a new item to the collection, but it is not updating the bounds of the view instance. In this example, if I were to add a new item to the collection, the next time I inspect bounds.height it would be at 149.5. What am I missing!?
i had answered this question in another tableview inside tableview cell that will work for collection view too ,i explained it in this thread
ask me if you faced any problem
It seems you want to set the height of your table view cell dynamically. This detailed tutorial walks you through making a custom cell class that will have dynamic height. Unfortunately, this tutorial only walks you through how to do this with auto layout constraints and a storyboard. In the tutorial you'll notice that the height of the cell depends on the constraints put on a title label within the cell. Try doing the same thing, but applying the constraints on the content in your cell (the collection view cell).
http://www.raywenderlich.com/73602/dynamic-table-view-cell-height-auto-layout
Context:
Building an app that populates a table that takes in data from a asyc json dump.
The cells are of a custom class (I defined). The main label in the cell can be very long.
It is "placed" in storyboard within a prototype cell but customized via code (pretty standard stuff).
Labels are resized in cellForRowAtIndexPath and rows are resized via heightForRowAtIndexPath -- rows are resized by forcing a call to cellForRowAtIndex like Massimo's answer here
So per the question at hand - I've noticed some interesting (bad) things that happen.
First issue: When the table loads, the rows and labels are dynamically resized correctly! Great! However, when I scroll down and then scroll back up, the label heights will be incorrect -- (for example) the first row was correct at loading. Then when I scroll down and then scroll back up to see it again, it will be truncated. Specifically, the row size will be fine but the label height will change and become truncated to 2 lines only. Wondering if this is because I did both storyboard and coding to customize the cell. Anybody see this before?
Second issue: When I scroll down, while the rows are sized correctly (large), the labels are short (truncated.) Wondering if it's some reverse of the above "potential answer".
"potential answer" is that the rows are all calculated and stored "up front" so that scrolling down/then back up doesn't affect it. However, when cells go "out of view" and are dequeued then when they re-viewed (scroll down/then back up) it will rely on the storyboard.(inappropriately?)
All three of your issues are symptomatic of returning the wrong height in heightForRowAtIndexPath. In my data model classes I have a calculateHeight method that I call in heightForRowAtIndexPath. The model also caches the answer so it doesn't have to recalculate it after the first call. The cell class uses the model's calculated height to layout its subviews.
"ANSWERED" by deleting the prototype cell from the storyboard and making them fully in code, the issue went away. The fundamental workings are still not understood (ie. the interactions between storyboard vs. code when cells are put queued and then viewed again)