I have a UITableView with a custom UITalbeCellView. Every cell has a title a body and a date. When I fetch the data some of the titles must be red so there is a Bool that is set to true for those cells which title has to be red.
The first time the data is fetched it looks fine, but as you scroll up and down a few times all of the titles end up being red.
Im using an array of structures to store the data and on the cellForRowAtIndexPath there is an if and if the boolean in that position of the array is true I change the color to red:
let cell = tableView.dequeueReusableCellWithIdentifier("CommentsRowTVC", forIndexPath: indexPath) as! CommentsRowTVC
let single_comment = self.AOS[indexPath.row]
cell.titulo_comentario?.text = single_comment.titulo_comment
if single_comment.flag == true {
cell.titulo_comentario.textColor = UIColor.redColor()
}
Im gessing it reuses Views or something like that. Does this have any easy fix? Or do I have to implement my own TableView to prevent this from happening?
Im also thinking the method dequeueReusableCellWithIdentifier might be the one causing my problem... but Im new on swift and cant think of any replacement for that.
It is happening similar thing on buttons there are on the cells, when you click a button from a cell it changes its color and disables it, but just the one on that cell. However when clicking on a cell, buttons from other cells are also suffering those changes.
Since cells get reused you end up with cells that were previously red because they hadsingle_comment.flag == true and are now used for another row where there actually is single_comment.flag == false. You have to reset the color in the else branch again:
if single_comment.flag == true {
cell.titulo_comentario.textColor = UIColor.redColor()
} else {
cell.titulo_comentario.textColor = UIColor.whiteColor()
}
UITableViews reuse their cells, meaning that you will get cells inside your cellForRowAtIndexPath which have previously been used before, maybe have have set the textColor to red. Your job is it now to revert the color of the text to its original state.
In general whatever change you make inside the if-branch of cell-customization has to be undone in the else-branch. If you remove a label in the if, add it in the else.
Related
So I have a table view with about 150ish rows in the cellForRowAt method I have the following code
cell.monthLabel.text = String(indexPath.row)
if indexPath.row == 0{
cell.backgroundColor = .blue
}
The question is why at index path 9, 18, 27 and so on have the background color of blue.
Cell are reused, you have to set all UI elements to a defined state.
So if you set the backgroundColor to blue in row 0
if indexPath.row == 0 {
cell.backgroundColor = .blue
}
you have to (re)set it to a default color in all other cases
else {
cell.backgroundColor = .white
}
As you do not show all the code of the tableView(_:cellForRowAt:) method just assume you are dequeuing cells (with the method dequeueReusableCell(withIdentifier:) and have registered you class for reusing (if you use a custom class).
With this approach the view of the cells gets reused. Meaning that if you do not re-set a property (e.g. background color) it will just use the one form the old cell.
To fix this you can easily include a else in your code and in there set the background color to white.
If you subclass the UITableViewCell class you can the prepareForReuse() function to clean up and e.g. reset the background color.
UITableView doesn't set the data on each item once, it keeps setting the data again and again on all visible items according to the activity going on. i can't give you the clear reason for this behavior but I can give you the solution. Whenever you are setting some data on items with some conditions, always use "Else" statement as well. So for this particular issue you just have to do is to add "Else" block with your "If" condition and set the white background of item in "Else" block.
I am trying to implement a table view design where a user can click a button outside of a table view cell and the display mode of all the buttons should change. However this is not the 'selected' mode for a given cell (that will be yet a third state that becomes accessible via switching to this second state). What's the proper way to accomplish this?
I am using dequeueReusableCellWith so I don't want to simply cycle through every cell because some that are out of sight probably shouldn't be modified. I simply want any cell that is visible, or becomes visible, while the table view cell is in this second display mode to follow a second design rather than the first design.
The second design, for now, is being modified via a method I added to a subclass of UITableViewCell like so:
- (void) p_refreshDisplay {
if (self.editing) {
self.buttonToClearWidth.constant = 20;
self.buttonToClearLeadingWidth.constant = 20;
} else {
self.buttonToClearWidth.constant = 0;
self.buttonToClearLeadingWidth.constant = 0;
}
}
However, I'm not sure how to trigger this p_refreshDisplay for every visible (and to become visible) cell. It seems unwise to call this many times and refresh the table view. What would be the proper way to accomplish what I want to do?
You do what should be done for any table view change:
Update your data model or some flag as needed.
Either call reloadData on the table view or call reloadRowsAtIndexPaths:withRowAnimation: passing in indexPathsForVisibleRows as the list of rows to reload.
Implement cellForRowAtIndexPath to provide appropriate cells for the given data/flags.
It sounds like you should have a custom cell class that has one or more properties that can be set on the cell in cellForRowAtIndexPath so the cell can render itself properly based on the specified state.
You can achieve this by doing three things:
Establish some property that indicates the "mode" of the table, either a boolean or perhaps an enum if there are more than three states
Ensure that cellForRowAtIndexPath configures the cell appropriately based on the value of this property. This will ensure that newly displayed cells are configured correctly.
When the "mode" changes you can use the tableview's visibleCells property to update any currently visible cells:
for cell in tableview.visibleCells {
if let myCell = cell as? MyCustomCellClass {
myCell.setButtonStyle()
}
}
I'm trying to create like button in tableview cell for my project. If like button clicked it must change tint color to red. I'm using Alamofire and if user liked it returns wich feed is liked and in cell:
let likerHash = data[indexPath.row]["liker_hash"] as? String
if(likerHash == ""){
cell.likeButton.tintColor = UIColor.blackColor()
}else{
cell.likeButton.tintColor = UIColor.redColor()
}
will set color of buttons for feeds. But if i click one button to like if it's not liked it changes color and iwhen i scroll down and come back again button color will change again to previous. (if on loading data it is not liked it will keep color when i scroll down.) I have tride to change value of liker_hash but it gives me an error: mutating method sent to immutable object. I am tying to change value like:
self.data[sender.tag]["liker_hash"] = ""
My data is from type [NSMutableDictionary](). Any idea how can i do it in swift language?
The main feature with using dequeueReusableCellWithIdentifier is that the cell is recreated every time you come back to it.
Based on the code that you've added, I don't believe you're editing your data source when the user hits the like button to save which cell has been changed the next time the tableView reloads.
What I'd suggest is holding all the cells in an array. Supposed you have 5 cells, create an array holding their current state:
var cellArr = ["Black", "Black", "Black", "Black", "Black"]
Then, if the user selects the like button, make sure to update this array with the right color as well. So if I select the second row, I update it like:
var cellArr = ["Black", "Red", "Black", "Black", "Black"]
And then in your cellForRowAtIndexPath function:
if cellArr[indexPath.row] == "Black"{
cell.likeButton.tintColor = UIColor.blackColor() }
else {
cell.likeButton.tintColor = UIColor.redColor()
}
Bit of a weird one i can't seem to understand so i have a tableview control in a viewcontroller and within the tableviewcell i have a button which is using a delegate.
So when the button is clicked it will change the tag number of the cell and also change the image of the button based on the tag of the cell in the tableview.
But the problem i'm having is that when you select a button in a row i.e. the first one it seems to be running the function to change the image for each item in a section almost. I.e choosing the 5th item will update every 5th button in a cell to the selected image which is weird. Since it's almost like the tableview is being split up to sections of 5.
Can anyone help prevent this behaviour so it only changes the icon for the button in the cell which has been pressed.
Below are the functions that i've used and a link to a video on dropbox showing the behaviour https://www.dropbox.com/s/a4aasti78872w6j/Help.mov?dl=0
Delegate
protocol StoryTableViewCellDelegate: class {
func didBookmarkItem(cell: StoryTableViewCell, sender: AnyObject)
}
Function for Delegate
#IBAction func bookmarkButtonDidTouch(sender: AnyObject) {
bookmarkButton.animation = "pop"
bookmarkButton.curve = "easeOut"
bookmarkButton.duration = 0.5
bookmarkButton.damping = 0.4
bookmarkButton.velocity = 0.4
bookmarkButton.animate()
// The delegate which will handle bookmarking items
delegate?.didBookmarkItem(self, sender: sender)
}
Function being used in tableview class
// MARK: StoryTableViewDelegate
func didBookmarkItem(cell: StoryTableViewCell, sender: AnyObject) {
// TODO: Implement bookmark functionality
switch cell.bookmarkButton.tag {
case 0:
cell.bookmarkButton.setImage(UIImage(named: "Bookmark-Selected"), forState: UIControlState.Normal)
cell.bookmarkButton.tag = 1
case 1:
cell.bookmarkButton.setImage(UIImage(named: "Bookmark-Not-Selected"), forState: UIControlState.Normal)
cell.bookmarkButton.tag = 0
default:
break
}
}
The reason is, you are probable creating a cell using :
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cellID")
...
like you should do. However dequeueReusableCellWithIdentifier re-uses a cell, so if you have changed anything in a cell (like adding buttons), those buttons will still be in that recycled cell.
So you must set the book mark status in your cellForRowAtIndexPath for each cell.
I once had a similar problem when adding buttons to a cell, and when scrolling the cells automatically had extra buttons. So the first thing I did when re-using a cell was remove all buttons.
Edit sample code
in your
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
you have to add code for setting the button to the desired state, it will be something similar to the code you're using in didBookMarkItem :
switch myProperty {
case 0:
cell.bookmarkButton.setImage(UIImage(named: "Bookmark-Selected"), forState: UIControlState.Normal)
cell.bookmarkButton.tag = 1
case 1:
cell.bookmarkButton.setImage(UIImage(named: "Bookmark-Not-Selected"), forState: UIControlState.Normal)
cell.bookmarkButton.tag = 0
default:
break
}
You'll need a myProperty variable of course, which you should change in your didBookMarkItem as well
As others have said, it's due to table cell reuse. You want your tableView(_:cellForRowAtIndexPath:) method to always update the cell state from your model. Your bookmark state should be a property of your model. When the bookmark button state for a cell is changed by the user, the new state should be reflected in your model. If you do these things, your table cell state will always be correct. If you don't already, it's nice to always define a custom UITableViewCell class that contains outlets for all of the views and controls within your table view cell (your bookmark button would have an outlet.) Also, within your custom cell class, when you capture the button selection, you can call back to the controller either via a delegate (as you are doing), or a "bookmarkChanged" handler (closure) defined on the cell. I prefer the closure method. If you would like to see an working example of this, let me know.
Also, nix the tag. You don't need the tag to keep track of your bookmark button selection state, unless there's more to it than you have shown/described. If you follow the approach I described, it's taken care of.
Table view cells are reused. Once you select a cell and change its tag number and scroll the selected cell out of the table view, it will be used again to show a row at the index path of the new row that appears. And since its tag represents that of a selected cell it is displayed as highlighted.
Try to look up about cell reuse in table views.
You need to change your approach about determining which cell is to be displayed as selected. Add it as a property in your data source and based on that set the bookmark as selected or not selected.
Ive got one question about using a subView in my custom TableViewCells. On certain rows i want to one or more images, and i am doing this programmatically with:
func addImageToCell(image: UIImage, initialYCoordinate: CGFloat, initialHeight: CGFloat, initialXCoordinate: CGFloat,imageUUID: String) {
imageButton = UIButton.buttonWithType(UIButtonType.Custom) as? UIButton
.....
imageButton!.addTarget(formVC, action: "imageButtonPressed:", forControlEvents: .TouchUpInside)
self.contentView.addSubview(imageButton!)
}
That works fine. But, when i scroll my TableView and it comes to an row with an Image, there is a small "lag". Normally it is totally smooth, but when he is trying to load this cell, there is a (maybe 0,1 seconds) lag in the software.
Is there a better way to do this programmatically without any lags? Ill load my Images on initializing the UITableViewController from a CoreData Fetch.
This is my cellForRowAtIndexPath
if(cellObject.hasImages == true) {
cell.qIndex = indexPath.row
var initialXCoordinate:CGFloat = 344.0
let questionImages = formImages[cellObject.qIndex] as [String: Images]!
for (key,image) in questionImages {
let thumbnailImage = UIImage(data: image.image)
cell.addImageToCell(thumbnailImage, initialYCoordinate: 44.00 ,initialHeight: cellObject.rowheight + cellObject.noticeHeight!, initialXCoordinate: initialXCoordinate, imageUUID: image.imageUUID)
initialXCoordinate += 130
}
}
Any Ideas? Thanks in advance
Edit: Ill use this to prevent the Buttons to get reused:
override func prepareForReuse() {
super.prepareForReuse()
if(self.reuseIdentifier != "CraftInit") {
for item in self.contentView.subviews {
if(item.isKindOfClass(UIButton)) {
item.removeFromSuperview()
}
}
}
The lag is most probably caused by the allocation of new memory for UIButton, adding it to cell's contentView and loading an image into it at the time of the cell being reused. That's one problem.
The other problem is that you're creating a button per every reuse of the cell. Basically, every time you scroll the cell out of the visibility range and scroll it back - you add another button with another image, that also consumes memory and performance.
To make this work properly you need to create a custom table view cell with a maximum amount of images (buttons) pre-rendered and hide the ones you don't need to show.
Do not add / remove subviews while reusing the table view cell, hide and show them instead, it's much faster.
Where are you removing these subviews? Because if you're not removing them, as the user scroll, you'll keep on adding subviews to the same cell over and over again, degrading performance.
My approach usually is to to have such views constructed when the cell is created rather than in cellForRowAtIndexPath, but I'm guessing you can't do that as you don't know the number of images. That said, you could still formulate a strategy where these subviews are added at cell creation, and then reused as per your model.
Another suggestion is to have the UIImage objects created all at once, outside cellForRowAtIndexPath.