Well, one might ask why should you do that ?
I have a collection view inside some view where the user can select a cell.
Then this selection is saved and later, when the user wants to enter that view again, he should be able to see his previous saved selection.
If his selection was at the end of the collection view, I will not be able to load the collection view with his previous selection, because:
for cell in collectionView.visibleCells()
// find and select previous cell
Will not loop through all cells, specifically the one the user chose (that does not exist yet).
Is there a solution to this problem?
You can remember the exact index paths of selected rows (using indexPathsForSelectedRows), but this is still not safe if your dataSource set changes/updates and the remembered indexes may become invalid with new/different set of data. Thus you should remember selection of “real world” objects (where you're filling specific cell data, like title etc.) for example by remembering object identifiers of your choice so you'll be able to re-map and re-select rows in case of reload with different data. The management of objects selection is generally completely in your hands.
Well after a lot of searching, what works for me is to set a local variable say: selectedCell , then when I want to show a previous user selected cell, i will just set the variable , and on :
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
{
if(indexPath.row==selectedCell)
}
I am checking if its already selected and mark it .
I could not find any other clever way of doing so automatically .
Related
i have a tableview with form fields, and there is a row that use segue to call an UICollectionView, everything is works except that i can't keep the selected cells (the visual effect that i show when the cell is selected) after go back to the tableview.
I mean, i selected my UICollectionView cells, after that i go back to the form, but if i need to again to my UICollectionView Cells, to deselect o select more cells before submit the data, once the UICollectionView appear my previous selection are there (i print the array, and i see the values) but i cant see the effect that i did for selected cells.
How i can keep the effect for selected cells if I'm going back to select again o deselect cells?
One thing to realize is that this is not going to happen by itself. When you segue back to the table view and the form fields, the UICollectionView is completely destroyed. The next time you show the collection view, it is a new and different collection view.
So, if you want to maintain a knowledge of what the selection was in the collection view, you are going to have to maintain it yourself, deliberately, storing it somewhere when you know that the collection view is being destroyed.
That way, the next time you show your collection view, even though that will be a completely new and different collection view, you can pass the knowledge of what the selection was to that collection view as you create and show it. The user will have the illusion of "returning" to the collection view, in the same state, but in fact you will have saved and restored its state.
It is then just a matter of reflecting the selected state in the collection view's display of its items. To do that, you need to configure your model so that when cellForItemAtIndexPath: is called, each cell looks selected if that item is supposed to be selected.
Every time you use segue to call an UICollectionView a new instance of UICollectionView is created and hence states of selected cells doesn't get restored.
I believe u must have taken an array of index paths of selected indexes to show the visual changes in the cell.
Make your tableView class as delegate of UICollectionView. Using its delegate methods return the selected index array to tableView class .And before pushing to UICollectionView send the same array of index paths back to the UICollectionView. Hope it helps.. Happy Coding.. :)
In my iOS app the user is supposed to fill in all fields in a table where each row may contain a:
a text view, or
a date picker or
a picker view, or
a switch.
I have created 7 different types of cell each of which contains one of those UI components with its specific tag. In this way I can access them when the table is only in "read mode".
The last row of the cell contains a "Save" button. When pressed, all these values should be collected together into an object which will be stored in a database.
The problem is that I don't know how to read those things from each row.
Is there a specific method?
To get all data from your cells best way would be to have an NSArray that will have all the data you need, and update these values in NSArray for corresponding data in the cells. You have to use some kind of dataSource to show the data in the tableView and you can use that exact NSArray to update values and on save to simply go through it and save these values.
For the other questions:
#NickCatib 1) I don't understand what the method func tableView(tableView: UITableView!, didSelectRowAtIndexPath indexPath: NSIndexPath!) does. Is it used to get data from each cell? When is it called? (in other words how can I link it to the IBAction of the submit button)
That method is called when you select particular cell. You can link it with selectRowAtIndexPath:animated:scrollPosition: method.
#NickCatib: 2) is it better to assign to each cell an unique tag to read the data when the submit button is touched?
You can, but again, better way would be to iterate thourgh NSArray as mentioned above.
I am using a UICollectionView, in which one UICollectionViewCell covers the entire screen. Inside my UICollectionViewCell, I give people the opportunity to add text (UILabel), images (UIImageView) and color (UIColor). Now when the user navigates to the next cell i want the color, labels and image views to be displayed exactly as they were added on the previous cell. The users also have the option to pinch and pan the labels and images. In short, how can i pass on data from one cell to another?
I see several ways how to do this depending on your realization:
use global properties/ivars to store the selected data from user input.
In either case you probably handle UITextFiledDelegate methods in your controller or extract the cell by indexPath and copy values from the current cell to the next one.
And when the user presses the "Continue" button you:
1) If you create all you collectionViewCells at once in cellForItemAtIndexPath, then you should only reload the necessary cell via - (void)reloadItemsAtIndexPaths:(NSArray *)indexPaths and set the values you have saved previously.
2) If you create cells but the next one is not ready (for instance you save the memory) - all almost the same - you add a new cell to the collectionView and read the data from your properties.
3) If you have not a "Continue" button or/and user can swipe the cell in every moment - so you can reload the cell in scrollViewDidScroll(or scrollViewWillBeginDragging) or extract the existent by indexPath and modify it without reloading.
If I create a UICollectionViewCell subclass like:
class StudentCell: UICollectionViewCell {
var student: Student?
}
And in my controller I implement UICollectionView's didSelectItemAtIndexPath and set the variable:
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
if let studentCell = collectionView.cellForItemAtIndexPath(indexPath) as? StudentCell {
studentCell.student = self.someStudent
}
}
When I click on the cell it should set student, but if the cell is scrolled off screen it seems like the whole cell might get wiped and when it comes back on screen it would need to rebuild itself in cellForItemAtIndexPath.
The problem I have is that I have a UICollectionView with cells that do not scroll off the screen that I'm storing data in. Because they don't leave the screen I assume they should not get wiped, but one of the cells does not seem to keep it's variable, which makes me think maybe it's getting wiped and I may need to move the state outside of the cells to a dictionary or something and in didSelectItemAtIndexPath instead of setting the variable in the cell I'd set the dictionary. Whenever I need to access the data instead of asking the cell for it I'd look it up in the dictionary.
But either way, I was wondering if it's possible (or a bad idea) to set it in the cell or not.
Yes, cells in both UICollectionView and UITableView can (will) be reused at the systems discretion and should not be used to store state information, only display information. Specifically, both views will reuse cells when they are scrolled off-screen, but there's no guarantee this is the only time they'll be reused. The usual way to handle this is to define some kind of cell data object which stores the data for each cell (visible and not) and refresh the cell view from that as needed/requested.
Tables display their data in cells. A cell is related to a row but it’s not exactly the same. A cell is a view that shows a row of data that happens to be visible at that moment. If your table can show 10 rows at a time on the screen, then it only has10 cells, even though there may be hundreds of rows with actual data. Whenever a row scrolls off the screen and becomes invisible, its cell will be re-used for a new row that scrolls into the screen.
firstly thank you in advance for any help and secondly I am very new to do the iOS development and swift so please bear with me and forgive me if I ask any stupid question.
MY ISSUE:
I created a table view and created an array of numbers. I iterated through the array and displayed each number in the array in a different table view cell. Now what I want to do is either have a button my table view cell or a check mark. And when ever I tap the button or the check mark the number that is being displayed on the table cell from the array is selected and then I tap another button or a check mark on a different cell and that number also gets selected and when I click the "done" button the both numbers are added and displayed on my root view.
Its kind of like a order taking app you can think of each cell as displaying the price of a food item and you can selected multiple food items and once you click done it adds up the price and displays it.
Im not looking for any advanced techniques, anything that can help me do this will be much appreciated. Again sorry for any stupid questions and thank you.
This is how you should break it down:
1) Implement the didSelectRowAtIndexPath delegate method after the table has been populated:
func tableView(tableView: UITableView!, didSelectRowAtIndexPath indexPath: NSIndexPath!) {
2) Within that method set the checkmark for the row:
cell.accessoryType = UITableViewCellAccessoryType.Checkmark
3) Declare a class Array:
var numberArray: [Int]
4) Finally, implement an array extension for the addition. Call it when tapping the done button:
How can we create a generic Array Extension that sums Number types in Swift?
There's some fine tuning depending on your implementation but I hope this gives you a head start.
Key things to look at:
UITableView has a var called allowsMultipleSelection. You want to set that to true (it's false by default.)
If you want to change the way a cell looks when it is selected, then you can either look into the table view's delegate didSelectRowAtIndexPath and didDeselectRowAtIndexPath. Or if you have your own subclass of UITableViewCell, you can override the setSelected:animated: method.
The basic idea is to give the user a button to say when (s)he is done selecting cells, then look at the tableView's indexPathsForSelectedRows to find out which items were selected.