By receiving data from an API, i need to compose a dynamic form. This in my head translated to a tableView with cells that have labels and input fields.
The task was completed, the cells were dynamically sized depending on the constraints, all was fine. When some input in some cell changed the following code run:
func valueOfFieldWithIDChanged(id: Int, value: String){
formFieldsTable.reloadRows(at: [indexPath,indexPath2], with: .none)
}
This updated my row and the new value was displayed properly after formatting etc.
The issue:
When the forms got bigger and spanned more space than a screenful, essentially making the table scrollable a huge issue occurred. When the table was scrolled even a tiny bit, using reloadRows made a glitchy table scroll animation.
The answer to that was essentially: DONT use UITableViewAutomaticDimension in heightForRow if you're gonna use reloadRows.
The thing is, some rows have multiline labels or need to be dynamically sized in some way or another. It seems like i have to calculate this by hand but i dont know how. Unless.. i'm missing something? Truly hope i am
EDIT: Someone mentioned in the comments that there are other ways to updating fields without reloading the rows. This might be a way to go about it but i dont know what those other ways are
Related
I already found entries with that topic on this page and also a website that provides a tutorial for that problem. But nothing worked very well.
The tutorial sad I should double the height of my tableView so cells loaded earlier, but with a higher tableView I never reached the last cells.
My problem is, I use a tableView to display my apps mainpage. This mainPage shows every time a topic and if its necessary for that topic it shows for example a cell with a map, one with pictures and sometimes not. Problem now, if I trying to scroll to my view its always lagging because it loads a map or this pictures. And scrolling back again because the loaded cells already deleted. I used a tableView because of the possibility to switch celltypes(mapCell, pictureCell, textCell) on and off.
I understand this feature, because of memory issues but in my case its not that much and it would be better if all my cells be preloaded and stay in memory until I change the topic.
Is there a swifty way to told my tableView to have this behavior?
Thanks a lot and nice greetings
I would suggest a different approach. Set up your table view controller to install placeholder images in your cells, trigger an async download that you cache to disk, and then update the cell with it's downloaded content if it's still visible when the download is finished.
There are various third party frameworks that do all this housekeeping for you.
Declare a cell array.
Follow these steps whenever change in your topic.
Clear you array
Create and configure all cells add to your array.
Return these cells to datasource methods using row index. Don't use tableview dequeue method here.
I'm new to IOS development, I have a few questions.
1) What's the purpose of property rowheight on table view cell, I mean it does nothing even if I change its value, it always takes the value from its parent view i.e a tableview property rowheight? It visually changes in the IB but nothing happens when I run the app.
2) What's the purpose of Content View why is it even there? Let's say If I have to make some image equal to the height of the cell it restricts me. Or is there any way a content view can be changed to be equal to the cell height & width? I have to put constraints on the image in relation with the cell which is not the immediate parent of the image and I don't know if this is the correct way to do it.
3)How does Xcode Autocomplete works? like if I want to write a function tableview(_:tableview didselectrowwithindex:IndexPath) and I type tableview it shows a list, what to do next? I mean I can't type the whole fucntion with params or find the func in the huge list.
The height of the cell set at the IB is primarily used for simulation, the views described at IB are normally resized when actually used. E.g. you can set rows height to be 100 for the table view, 30 for some of the cells and keep the whole controller simulating a nice screen of iPhone 6. The same view will be used for all devices and will be scaled accordingly as well as the cells with the help of your delegate.
The content view is there for the reasons directly related to your additional requests. It holds all the content while there other views that accompany your content and are part of the cell like separators, accessory views, slide action views. Without a content view the responsibility of managing all the additional parts would most likely fall on you as a developer and while you might think that that is fine at the simple layouts, a simple enhancement to it would make a huge impact.
Fuzzy autocompletion at Xcode seems to be something Apple is working on now. If you can't wait and find it too difficult to navigate through the list, there are Xcode plugins available that provide fuzzy autocompletion.
Answering the question in the topic:
example: tableview(_:tableview didselectrowwithindex:IndexPath)
if you write tableview it will show all the symbols that start with tableview. For functions, it will show all the functions sorted by the second parameter name (didSelectRowWithIndex).
[EDIT]
it will autocomplete as far as the answer is unique and then show you a list full of options. I don't know any tricks to skip looking through the massive list. But after a while you'll know what you're looking for and it gets faster.
[\EDIT]
when you press tab, it
by the way: the delegate functions names start with the name of the object they're related to.
So UITableViewDelegate functions start with tableview.
as for your first two questions there are tons of answers for those questions on SO. This one seems closely related to yours.
All,
I hope most of you know that with ios7 there is not need to do a null check for tableview reuse
if (cell == nil) {
But unfortunately, because of that the cells are always reinitialized, as we put the code in the same method for initializing values. The problem is only with text fields inside the tableview though.
Let me explain the scenario. I have a table view with multiple rows, and some rows contain multiple text boxes. I populate the textboxes with data from server when the page is loaded. Since the cells are always re-initialized as i explained above, whatever I enter in the field goes away and the server data is re populated once i scroll down and come back to the initial stage. This is because the populating the data code is also in the same place. After fetching a reusable cell it populates the data.
Previously till ios6, we used if(cell==nil) and hence we loaded server data inside the cell and when reusing the cell, this piece of code will never be called.
I have other dirty solutions, but would like to know if someone else has a graceful way of dealing this. Please help.
You just don't store any data in the table view cell but in the model that fills the table cell. This is always the way it should be done.
Looking from the MVC standpoint than the UITableViewCell is a view. Since it is reused by iOS you should use a model to the view.
Yes, this is the expected behavior of UITableView. For performance reasons, cells are reused. Thus, it is your responsibility to populate the views in a Table View Cell every time tableView:cellForRowAtIndexPath: is called.
The thing I don't understand from your question - are you making a network call every single time a cell comes into view? If so, cache the results somewhere. Or, if it's a small amount of data, consider just doing it all in one shot at the beginning (still need to be asynchronous though).
One thing I see a lot of developers do is move a lot of code into UITableViewCell subclasses, which sounds like a good idea because it's modular, but makes solutions for problems like this more difficult. Have the Table View Data Source manage the network calls.
If you need some inspiration, look at Apple's LazyTableImages sample.
I'm new to iOS and MonoTouch, and I have a pretty basic need - I have two vastly different views to display in the same table cell depending on whether it is selected or not. When you load the app I'll present a list of products in a custom UITableView, with all the rows deselected and each row basically just showing the product names in a label. As soon as a user taps one of the rows and selects it, I show a very different view with more of a shopping cart layout. Since the two views are so different they have vastly different sizes. What i need is for the cell itself (or row?) to grow and shrink according to the natural height of whichever view is currently being displayed.
I'm using descendants of UITableViewController, UITableViewSource, and UITableViewCell for the solution. What I do is add both versions to the cell's ContentView, then set the Hidden property as needed when the cell/row is selected/deselected to show the right layout. That works well. I'm in demo mode right now, so I'm not overly worried about efficiency or responsiveness, that will have to come later.
I know that GetHeightForRow is responsible for sizing the rows but it only gets called once, when the cell is first shown. It seems to me that I need to alert the TableView to re-poll the source for a new size as the views are changing, but I can't figure out how to do it.
I tried (rather hopefully) to cause GetHeightForRow to be invoked again manually using Cell.SetNeedsLayout and Cell.SetNeedsDisplay, hoping that would cause the table to re-query the source for new dimensions, but no joy.
I tinkered with the direct approach, trying to size the contentview itself but it didn't seem as if it was leading anywhere. I feel as if the table needs to be told to query for a new row size, but I'm open to any suggestions.
Surely I'm not the first to attempt this? What am I missing?
Try forcing GetHeightForRow to be called again by calling ReloadRows instead.
You may or may not have to specify begin/end updates (this might just be for animation, though?)
tableView.BeginUpdates();
tableView.EndUpdates();
I have a UITableView that collects data from a database. What I would like to know is if there is some way I can iterate in the UITableView collection and check the values of the cell? The reason I ask is because I would like to update each cell based on the current value that it has (change font, size, color, etc.). I've seen in another SO post regarding this topic, but since the cells are already created and their values are changed it is a bit harder for me. I was thinking of iterating through the UITableView before I call reloadData, but any other suggestions are welcome.
You should not iterate over the cells of UITableView, because some of them (in fact, most of them) may not be present until you request them. UITableView aggressively recycles its cells, so if a cell is not visible, it is very likely that you would be creating it from scratch only to put it back into recycle queue moments later.
Changing your model and calling reloadData the way your post suggests would be the right solution. iOS will ensure that it runs the update in a smallest number of CPU cycles possible, so you do not need to worry about the cells that are already created. This is also the easiest approach in terms of your coding effort.
A table view is for displaying data. The properties of your table cells should only be written to, not read from. The appropriate way of handling this situation would be to update your underlying model objects -- the objects that you use to populate the table view -- as the data changes, and then reload the affected rows.
The issue you'll encounter is that UITableView reuses table cells. Once a table cell scrolls off the screen, it's quite likely that the table view will reuse the same cell to display a different row.
This means it's fundamentally not possible to iterate over the table cells. When you need to refresh a row because its data has changed, you should call reloadRowsAtIndexPaths:withRowAnimation: (or reloadData if all rows have changed) and if the row is visible on screen, UITableView will call your data source methods and give you an opportunity to configure the cell for display.