I have an averagely sized table which is working perfectly, except for the row insertion animation (withRowAnimation). I've overriden it (with the help of stack community) to have a longer duration than the original system animation and it works just fine, but ...
Because i'm using custom cells as reusable cells - each time i scroll this effect is getting wiped out.
So the only solution i see is to stop the reuse.
I know this will interfere with the memory, but in this case its the only scenario left (of which i know).
My general question is how do i load a custom cell nib without using dequeueReusableCellWithIdentifier so that the reuse wouldn't happen.
Thank you.
You should use dequeueReusableCellWithIdentifier, not using it is a recipe for disaster.
Take a look into your code and when you dequeue a cell (reused or not, most of the time it'll be reused), the first thing you should do is set all elements in that cell back to the original state, so that that reused cell behaves like a non reused cell.
I don't know what you animation/implementation is about but here an example from a project I wrote with custom cells :
In each cell I added buttons, this could be 1, 2, 3,... buttons. If I did nothing in a reused cell I would have more buttons than expected because the old buttons would still be there...
So in my code the first thing I did after dequeing the cell would be to remove all the buttons.
let cell = tableView.dequeueReusableCellWithIdentifier("RelatedCell") as! RelatedCell
cell.removeAllActionButtons()
where my removeAllActionButtons (a method in my custom cell) method would be something like:
for button in actionButtons {
button.removeFromSuperview()
}
actionButtons is an Array containing all that buttons added to that custom cell
Related
I have a UIViewController with a collectionView inside it. The layout may seem confusing but I am making use of horizontal scrolling UICollectionViewCells, presented in 3 sections.
The main collection view is made up of 3 sections. I access 3 different UICollectionViewCell classes for each section becuase it is fetching different data for each one. Once the data is fetched, it dequeues another Cell class, which is the same one accessed for all the sections.
There are 2 buttons in each cell. When I press the button, a value changes within the database. When I re-run the program, the cell in which the button was pressed has moved to its corresponding section that it should be in as per the change. However, I want to achieve this as soon as I press the button. How can I move the cell from one section to another, baring in mind that they the cells presented are inside a collectionview cell making up the sections, which is then inside a greater UICollectionView.?
I've tried researching how to do this but no luck, and everyone seems to be using a drag and drop method which seems too complicated for what I am trying to achieve. Would appreciate any help.
Thanks
The approach I followed to achieve the above situation is using a custom Delegation when cell is removing from collectionviews. A container CollectionView has two sections with 2 different cells containing two different Horizontal UICollectionViews. These two collectionview's cells have UIButtons. When tap on one collectionView's button, that particular cell is removed, custom Delegate method calls and another CollectionView's cell is populated. This is the link of the project I have created for this particular scenario. For better understanding, here is a GIF for demonstration.
I am just thinking. Suppose, i have a tableview which have custom cell. It's simple. But My idea is that, when i click a tableview cell then another tableview is appear under that tableview cell, and again i click that cell then that sub tableview disappear. Similarly when i click second cell than work same. Is it possible? Please Provide me any idea or reference.
This is entirely possible, you're talking about Expandable cells.
My example here
The general idea is that your custom cell has a tableview at the bottom of the cell, and what you do is just change the cell height to display said tableview, on tap.
It's not easy, I'm not gonna lie it took us a while to do it, but we managed, and I'm telling you, it's very possible.
You can find a lot of help using the Expandable Cell keywords.
Note that you're gonna find yourself handling a lot :
What to do when the expanding cells is shown off screen?
What to do when you're expanding the first/last cells ?
What to do when expanding another cell ?
What to do when scrolling inside that cell (a scrollview inside a scrollview !)
There are many cases where it'll work, but won't work fine, and there is gonna be a lot of fine tuning. Specially in our case where we have rounded corners, but only when the cell is expanded, and not in cases where it's the last or first cell (next to section header).
They look cool and make you feel proud, but don't say to your PM it'll be done in a week, because it's a pain to build.
If you want to show additional cell information, you can add more cells after the cell indexpath you have clicked.
Create a custom table view cell classCustomTableViewCell by subclassingUITableViewCell class. And system will generate CustomTableViewCell.h, CustomTableViewCell.m, CustomTableViewCell.xib files for you.
Add protocols UITableViewDataSource and UITableViewDelegate in your CustomTableViewCell.h and implement the required methods in CustomTableViewCell.m files
Add a method for setting datasource and use the datasource for updating the table.
NOTE:
Handle table-dequeue mechanism properly, otherwise you will end up
with weird issues that may take time to investigate and resolve.
If you use this custom cell for all the cells in your parent table then the gestures will only listened by the child table. So plan for that too.
Please visit my blog for the sample code. https://myioslearnings.blogspot.in/2017/03/nested-table-view-in-ios-objective-c.html
I'm relatively new to Swift and iOS and I have one issue - I have a custom SwipeCell class that extends UITableViewCell. It's a cell that can be swiped left and right, and has buttons on each side. For some reason if I made the buttons out of the frame of the cell when user swipes the cell they would appear but could not call an action, so my solution was to make cell wider than it is (so buttons can fit in it). Because it was done this way my cell has to have an offset by default for the total width of the buttons of the left (let's say 100), so it's position is X:-100.
And that's fine, and everything works fines with the cells, however there is one huge issue - if I call the deletion of any cell from the tableView like this
tableView.deleteRowsAtIndexPaths([tableView.indexPathForCell(activeCell)!], withRowAnimation: .None)
tableView then deletes the cell, and all of the other cells that are currently visible (doesn't happen with cells above or below the screen bounds) get moved to X:0 instead of staying at X:-100, so I assume that deleteRowsAtIndexPaths calls some function that resets the visible cells positions to 0,0. I'm currently setting swipe cells positions with layoutSubviews() since the number of buttons is dynamic and couldn't be determined upfront, but layoutSubviews is not the function where the bug happens.
So to sum up question - what function does deleteRowsAtIndexPaths call after deleting a cell that resets/redraws the visible cells?
deleteRowsAtIndexPaths deletes a row(s) from the tableView. This is handled internally by iOS. From Apple documentation:
Deletes the rows specified by an array of index paths, with an option
to animate the deletion.
Another interesting thing to note here is that this method does not modify your model (object that holds data used by your table view cells to render on themselves). You have to do that yourself. The cells are deleted, but if you call reloadData without deleting the row from your Model, cell will reappear.
Expect that cells get deleted and created all the time. Cells are very, very temporary objects. Write the code to create one when needed, and don't make any assumptions. Don't assume the cell is there later, don't assume it's in the same row, don't assume it displays the same data (because cells are recycled).
Since I could find out what happens inside of deleteRowAtIndexPaths, and why it changes frames of each Cell, I decided to just do my own function that deletes a row, by obtaining cells with tableView.visibleCells, and then just moving cells bellow the deleted cell up by a height of deleted cell. Thank you all for trying to help me, and especially thanks to Abhinav who told me that it was handled internally, which help me decide to write a custom code for the deletion.
I have a UITableView, and I want to change text color of the selected row. But I see every other 15 row got affected along with the one I clicked. This is tested under the master-detail sample project.
if let indexPath = self.tableView.indexPathForSelectedRow(){
self.tableView.cellForRowAtIndexPath(indexPath)?.textLabel?.textColor = UIColor.redColor()
}
I checked cellForRowAtIndexPath value in debug session, it seems returning only one object, how come other cells got affected too?
Cells are reused - almost certainly you are not resetting your cells to a base state in prepareForReuse and configuring them correctly on each call to cellForRowAtIndexPath.
When you look at a table view that can display some number of cells at once, typically there will only exist one more cell than can be shown. When a cell is moved off the screen it is placed in a pool of cells for reuse. Just before a cell moves onto the screen it is configured by you, in cellForRowAtIndexPath. If you have configured something in the cell and you do not configure that explicitly every time you return a cell from cellForRowAtIndexPath then that configuration persists in the cell that is in the reuse pool. The function prepareForReuse is also called before each cell is reused - if you have subclassed UITableViewCell then you can implement this function to return the cell to a base configuration, so that settings like text color do not unexpectedly affect multiple cells.
This approach makes it possible to scroll through an entire table view smoothly with a minimum amount of memory used. It is an expensive operation to create and destroy cells every time one disappears and a new one is required.
The simplest fix is to always set the text color in cellForRowAtIndexPath - either to the base color or to the special color you want in some cells.
I use UITableView with static cells.
If I use reloadData, than everything is OK.
If I try reloadRowsAtIndexPaths it hides row. Row appears if I drag tableView up-down(when cell is updated).
If your table cells are static (i.e., you are using the same cell object to replace the one that's currently displayed), what you're seeing is an artifact of the transition animation.
Think of it this way. Lets say you set UITableViewAnimationOptionFade. When the cell is to be replaced, the cell it's to be replaced with (which in this case is the exact same object) has a fade-in animation added to it. Then, the cell that is being replaced (again, it's all the same object) has a fade-out animation added to it. At the end, the cell is actually there, but it's invisible because the fade-out animation has made that cell object invisible.
In a non-static tableview, one in which the replacement cell is a different object than the cell to be replaced, this isn't a problem, as the animations are added to two different objects.
I had the same problem, it seems to be a bug. I experimented some and the problem doesn't occur when I set the animation option to UITableViewRowAnimationNone. Some other interesting stuff happens when you set that option to UITableViewRowAnimationTop, too.
I solved this by removing animation
tableView.reloadRows(at: [yourIndexPath], with: UITableView.RowAnimation.none)
Hope this helps to anyone searching for this.