i have a table view with a UITextField in each cell.the table has 30 lines。
i want to get all values from 30 UITextfield，But it works fine for 10 visible cells. I cant't access any invisible cells. the text returns null. please help me.I am a chese developer
I cant't access any invisible cells. the text returns null.
That's how it is supposed to work since UITableView optimizes its use of cells and only displayed cells are actually existing at any time. (at least, if you are using dequeueReusableCellWithIdentifier: as you will find in most UITableView tutorials).
You should possibly store the text entered by the user in each table row somewhere (in your model?) and then access it from there.
Alternatively, you could avoid using dequeueReusableCellWithIdentifier: but in that case you should manage the set of cells in the table view on your own. (I am not encouraging your to do this, it's just a possibility).
Related
I'd like to get every data that is within all cells in one tableview which is quite a long list.
I'm looking for an approach on how to retrieve everything including those hidden in view, which I know the views are reused. I think some of you might have experienced this problem before, what are your approach on this?
I've tried
let cells = self.tableView.visibleCells
then looping into every cell and saving each data to an array but it is not effective in getting those that aren't part of the view or hidden. Is there a way to get over this?
In cellForRowAtIndexPath, YOU are telling the table what is in each cell. So why would you turn around and ask the table what's in each cell? If the user puts "Hello" in your first cell, then scrolls the table enough to push that first cell out of view, then when the user scrolls back to the top, YOU are the one telling it to put "Hello" back in that first cell. YOU own the data source, not the table.
You need a data source. That can be "empty" at first, maybe an array of empty strings if that's what you want (each index in the array could map to a table row for example). But then, as the user interacts with the text fields in the cells, you need to update that data source with the text they entered.
You should use that data source as your source for the cellForRowAtIndex method. That way you can handle populating the cells when they are requested by the table, and you also know all the data when the user is done.
Why not just update the model each time the user taps a key when editing a textfield? You could create a protocol for that cell subclass and make your view controller the delegate for each cell. As long as cells are guaranteed to stay on the screen while you're typing (you'll get some weird behaviors if not) the cell can send a message to the view controller or whatever you hook it up to telling it what new value to store. Then everything is already stored for you when you need the full list, and you don't have to interact with the tableview.
I am getting really frustrated trying to solve this problem i tried implementing it in many many ways but no solution. I have a UIStepper in a custom cell and i want to change a value on the cell. Everything works fine expect when i scroll around the tableView the values from the UIStepper changes from one cell to another. Please help here are my screen shoots.
Link to tableview implementation and link to cell implementation
You are trying to store the stepper value inside each individual cell. That's not going to work because cells are reused; the cell that you now see in row 2 may reappear in row 20 when the user scrolls.
That is why you must store the value for the stepper in the model (your data) on a row-by-row basis, so that you can set it freshly and correctly for that row every single time cellForRowAtIndexPath: is called.
This, in turn, means that as the user steps the stepper, its valueChanged is going to need to talk to the table view data source so that the model can be updated ("the stepper value for row 5 has just been changed to 3") and maintained in the model.
I have a UITableView in which I create my own Cells by adding UIViews to the cell based on the index which is needed as I have about 15 very different cells in one table.
This all works fine, except when I have a UITextField; when I click on the text field, the application crashes which, what looks like something has been garbage collected and now it's still being used.
To reproduce , you simple make a UITableView with a cellForRowAtIndexPath which returns a Cell view to which you add, in the cellForRowAtIndexPath method a UITextField. When the UITableView appears you will see the text fields (and anything else you might have added to it), but clicking on the text field will crash when it becomes first responder.
I'm probably missing something trivial where it is logical somehow but I cannot find references to it from others (or i'm not searching correctly of course).
I know this has been asked a lot of times but theres so much different information and different cases, I just don't understand where to begin and cannot get it working in my app.
In my app I have a table view and I'm using a NSFetchedResultsController. In normal mode, the table cells shouldn't be editable but instead each click should be a segue to a new viewcontroller (which works). In edit mode however I want that if you click on the cell, that you edit the text and this gets automatically stored to the database. And here I don't have a clue.
I want it as simple as possible. What I've read so far I guess I have to subclass UITableViewCell and a TextField. Here's already my first question: In each post about this, the TextField is init with a Rect, however how do I know the exact width and height of my cells?
And do I add this cell directly in the cellForRowAtIndexPath? Or only if the mode gets changed to edit? And some posts suggest you have to be the delegate for UITextField, but why?
And is there some sample code for about exact the problem I have? I wasn't able to find it...
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.