I am having a tableview in which I am displaying my data. As you can assume from the title, these cells are dynamic in their content, and so should their height be. Actually I got it working, but I have a strange issue with the row 0 and 7. These 2 rows take my entire screen, but when I scroll past them and go back again everything is fine. I am not sure but the 7. cell must be among the first cells that are being "dequed" when I scroll down. But as I said, this is just the first time they are being displayed, when I scroll again to one of them, everything is looking good (when filling the tableview with new data it is also fine).
I tried to reload the tableview twice when it is being populated for the first time, but without success. The presentation of the first cell I have fixed calling : self.tableView reloadAtIndexPaths ... when the table is being populated for the first time,
and it worked, it has the height it should have regarding its size. But I still have the issue with cell number 7 (the above fix does not work for this cell, I assume because it is not being displayed at that moment)
I am not using any fancy height calulation, just the iOS 8 feature:
self.tableView.rowHeight = UITableViewAutomaticDimension
self.tableView.estimatedRowHeight = 80
Is there a method, fix with which i can force the tableview to draw the cells again ?
Thanks
Cell size is calculated from constrains. So I assume there is something wrong with those or with data during computation.
try this:
in tableview cell subclass use -prepareForReuse method to clean cell data as before reuse.
Related
I'm struggling with wired kind of problem. I have UITableView with one cell. This cell is only holding containerView with childViewController (second tableView). My problem is that, first tableView(parent) must have UITableViewAutomaticDimension row height but it doesn't work (It dosen't know correct size of that cell with second tableView).
How to get correct size of second tableView) ?
Second tableView (inside Cell) have scrollingEnabled turned off (tableView.scrollEnabled = false), first tableView must have correct size of second tableView in order to provide correct scrolling experience.
Since a UITableView inherits from UIScrollView you can use the contentSize property to get this information. This is how the scrollbar works on the side.
I have done a similar thing before (long ago), so the following is somewhat hazy/ irrelevant/ unessecary. There might be some gotchas with unknown/unrendered cell heights in the embedded tableview. I rememeber having to set the tableview height to a large number (forcing all cells to render) fetching the contentSize then resetting the tableview height to the contentSize.height.
Are you shure you really need second table view? If you have just one cell probably you don't need it. I recommend you to calculate table view height as the summ of it's cells heights. If cells of embedded table view have constant height it could be simple. In other case you also could calculate cells height.
So, my problem is pretty simple. I have a UITableView in a UIViewController. The tableview has dynamic cells (custom cells with images , text, etc.. from a subclass I created) and these cells belong to a subclass I created. Everything is going fine since the content is different on each cell. The problem is that when I scroll the scrollview of the cell which is horizontal ( I have a UIScrollView in the subview of the cell. I created this scrollview on the cell subclass), on let's say, indexPath.row == 0, and scroll the tableview vertically, after about 8 cells, the ninth cell has the scrollview scrolled as well. This is because of dequeuereusablecells, so the ninth cell is actually the first one, only displaying different content but since it is the first cell, it has the same background operation (the scrollview scrolled).
I tried to unscroll in the cellForRowAtIndexPath: but although this solves the problem it creates another : The first cell that was scrolled is not anymore. So, to solve this new problem I am planning on adding a workaround here that is a dictionary of [Int:Bool], that is, the indexPath corresponding to a Boolean value. If I scrolled the first cell, then 0:true. If I reach the ninth cell (which is equal to the first cell, but with IndexPath = 8 ), I unscroll the cell's horizontal scrollview. If I come back to the beginning of the tableview and reach the first cell, I scroll the cell's horizontal scrollview back. What do you guys think?
The other workaround I can think of is just not use dequeue reusable cells since I don't think I will have more than 30-50 rows on my tableview.
In terms of performance, which operation is better?
Firstly, I would suggest you to carefully analyse whether removing scrolling offset from the first cell is such a bad idea. If I am a user and I scroll down to the very bottom, making the first cell invisible, are you sure that I want it to return to the scrolled position after I scroll back to top? The answer might be Yes, but you should think about this carefully because it might lead you to the simplest solution.
However, in case you really need to do it, I would have a variable which stores the state of the scrolling for each row. If you have an array of objects from which you pull necessary properties (title, image etc) you can add this as an extra property to these objects. Otherwise, you can create an array which will be storing this info (I would prefer an array over dictionary for this task).
Fundamentally it's an issue caused by table view cell reusability. You can have workarounds, but I'd say that, things that aren't supposed to be reused should not be reused.
If your cells are all similar (with minor differences), you could use just one cell identifier; If you have very different types of cells, say, one type has a horizontal scroll view inside, one type just has some labels and images, you might want to consider to have two identifiers, so cells that have UIScrollView won't be reused for normal cells.
And at the same time, you can still do necessary cleanup works in prepareForReuse: to make sure cells that just get dequeued have a fresh start.
I am trying to make my first iOS App with swift (iOS 8).
I have a UITableView and a CustomCell.
The app is kind of a news ticker. After launching the app it loads all news from a web server and saves the news to an array.
The custom cell has a dynamic height. I am calling cell.layoutIfNeeded() in the tableView:cellForRowIndexPath to get the dynamic cell height correctly working. Otherwise the cell height is not displayed correctly. I found that hint here at stack overflow.
Image: After getting all news, the cells are displayed correctly
With SIOSocket I get an event with a new news and I want to insert it into the UITable.
So I created a method that inserts the news into my array and calls the tableView.insertRowsAtIndexPath in between beginUpdates(), endUpdates().
And here is where the problem starts. The new cell is displayed correctly, but all the other visible cells are downsized to the default cell height (44pt).
Image: After I added a new entry, the old cells are too small
After some scrolling the cells are updated and are now displayed correctly again.
When I do not use the insertRowsAtIndexPath, but tableView.reloadData(), then it's working. But I think it's not good style to call reloadData for every new news. And of course there is no animation after reloading...
Can anybody please explain why this happens and is there any solution to fix that issue?
Thanks
When I set the estimatedRowHeight to any value, then the problem disappears.
tableView.estimatedRowHeight = 44
in the viewDidLoad method completely solves my problem.
Section header view with automatic dimension may create this type of issues
So removing below lines will solve the problem.
tableView.sectionHeaderHeight = 10;
tableView.estimatedSectionHeaderHeight = UITableViewAutomaticDimension;
Row with Automatic Dimension will not create any issues.
tableView.estimatedRowHeight = 15;
tableView.rowHeight = UITableViewAutomaticDimension;
I got a problem with the Tableview-Cells in iOS.
I got a tableview with custon cells in it. I wanted to lower the height of the cells.
The row height in the tableview was set to 105, I changed it to 55 (the actual height of the custom cells wich are provided as xib-files).
So far, so easy, but now to my problem:
After the tableview loaded, it showed only one entry, but all the other entries aren't shown. If I scroll down and up again on the other hand, the previously hidden entries are shown.
I tried to work a little with the heigh-values in the tableview-options, and as I increase the heigh the more of a cell is shown on the first loading, but its never a complete cell until I set it to 105 again. Scrolling fixes the broken entries.
There is by far enough size on the screen and the cells height is exactly 55.
Has anyone here has an idea what could cause that problem?
As allways, thanks for any help.
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)