I am making app where a list of countries to be shown. When the first time app runs the user selects the no. of countries. I stored that list in nsuser defaults. I want to checkmark those countries in the TableView when the app runs again for second time.
One more problem is when I scroll through the TableView and again come to the previous position, the checkmark does not show. Why this happens??
In -tableView:cellForRowAtIndexPath: you should set wether or not a checkmark should be shown based on your internal model (which in your case comes from NSUserDefaults). In the tableView:didSelectRowAtIndexPath:, do not simply make the checkmark visible in the cell, but store in in your internal model as well. This way when a cell is being shown again, it will show up correctly.
This happens because the table Cells are reused so when you Scroll up they are cleaned and reused by the below data and when you go up again all the thing is happened again.
Regarding Checking again on second time.
Just store the index of the row in NSUserDefault and put the condition in cellForRowAtIndexPath that when the index is matched keep it Checked.
Hope this helps..
hAPPY cODING...
Related
I have a button inside each cell. When it's pressed, the image is changed (basically a checkbox) to denote a selection. When you scroll to the bottom ... then scroll back up to the top. The image is reverted to the original image.
This question is pretty similar to this:
Preserve Cell Image After Scrolling UITableView
And others. But, I can't seem to find a good answer. I understand that's it's reverting back to how the uitableview is setup when the cell goes off the screen. But, how do I save the changed image to the uitableview so when it scrolls it doesn't revert to the original?
Thanks in advance! =)
It's changing back because cells are reused. When your cell is going off the screen it is taken out of the view and put back into the reuse pool. Then you're getting it out of the queue again in cellForRowAtIndexPath and setting it back up as the default.
The question you linked to is exactly what you should follow. You should store the state of your cell in your view controller and then when you set it up again in cellForRowAtIndexPath you should load that state and set up the cell appropriately.
One simple way for your method would be to have an NSArray which you set up to be the same size as the number of rows in your table and then in that just store an NSNumber for each row which contains a boolean value on or off for your selection state. When the user toggles, toggle the value in the array and then in cellForRowAtIndexPath read that value and set it up appropriately.
I'm assuming the checkbox in your table view cell is changing state to a selected state because a user selected it. You shouldn't use UI elements to maintain the state of your app. That is, when the user taps the checkbox, you should use that event to somehow reflect that state change in a data object in your app. Then, when that cell needs to be displayed again, you configure it with the state you previously saved. This allows for things like cell reuse, and view unloading and is all-around a good habit.
I have a custom cell that contains a button in a table view. The button is used as a toggle to essentially serve as a "checkbox" for a user to check off certain items in the list. I was having the issue in which the buttons in these table cells seemed to be sharing memory locations as a result of the dequeuereusablecellwithidentifier. When a button was pressed, it would also press every 4th or 5th button in the list.
I changed it to create my cells in a method into an array which then populates the tableview. This works fine for what I am trying to achieve, however it poses an issue when dealing with large row counts. The tableview itself runs quickly, but the initial load can be 3-4 seconds at times when there are over 100 rows. The iteration to create the cells and then populate it to the tableview is quite cumbersome.
What other methods can you populate a tableview with custom cells and buttons while still retaining unique memory for the buttons within?
Any help would be appreciated!
Thanks :)
You definitely don't want to change the way the creation of cells work- dequeuereusablecellwithidentifier is a very good thing for the reasons your seeing.
The solution is that you should store the result of the button/checkbox press in a separate data structure, like an NSArray full of NSNumber. As your table scrolls and cells are reused, you reset the state of the checkbox to whatever state it should be based on your NSArray.
Good luck!
I have UITableView, which I fill from a JSON Query.
I fill it with Private Messages and it works.
The JSON Query has the properties of "site" in which I get for every site 20 PMs. So at the beginning I got Site=0 and got 20PMS which are loaded.
Now I wanna have the features like in the Email-app (i believe I saw it there): When you scroll down and reach the end (in my app reached the 20. PM), the application should load the next 20 and so on and so on.
Any ideas how to realize?
Save the index path of your last row and implement
[UITableView reloadRowsAtIndexPaths:withRowAnimation:]
Or you can use scrollToRowAtIndexPath:atScrollPosition:animated:
scrollPosition
A constant that identifies a relative position in the receiving table view
(top, middle, bottom) for row when scrolling concludes.
See “Table View Scroll Position” a descriptions of valid constants in docs
And once you get you last scroll position just reload your table view [tableView reloadData]
But there is problem i guess once you reload the data i think after reloading(I am not sure) tableView it will take you to first row again then you can always save the lastIndexpath of that tableView and after reloadData just scrollToRowAtIndexPath:atScrollPosition:animated: or you can use scrollToNearestSelectedRowAtScrollPosition:animated:
I think you can implement feature like email app using your custom logic. What you do is keep the last row of tableview for loading more data. There should be message like "Load more..." in that last row. Whenever user touches that row, you should load more data and update tableview.
Stephen James and his colleagues at Key Options Development came across a similar problem: http://blog.keyoptions.co/tableview-with-automatic-load-more
They have built a sample app (ContinousTableview) that should be of some help to you. The source code is available at GitHub: https://github.com/stephenjames/ContinuousTableview
Guys, I didn't find a clean and a simple solution for the following issue. I've a UITableViewController view which uses a UITextFieldCustomCell that I implemented.
The table has several rows, that requires the user to scroll down an enter values on each cell, which contains a UILabel and a UITextField.
Every time the user change the value on the UITextField the UIViewController gets notified and stores the value in a NSDictionary using the cell indexPath.row property, in order to identify what's the key for the cell where the value needs to be stored.
The problem is if the user keep focus on a cell and then scrolls up or down (removing the cell from the view) makes me unable to get the indexPath for the cell, since it's not visible.
So, I cannot store the value since I don't know from which cell the value is coming.
Have anyone run through this issue before?. It seems to be a common design between iPhone applications, does anyone have an idea if is this a good implementation or not?
Thanks!
I assume you're observing textFieldDidEndEditing:. Are you saying it's not firing, or that it is firing, but it's no longer in any of the cells (possibly because it's in the process of being removed)?
Assuming the latter, my approach would be to use setTag: on the UITextField to make it easy to keep track of its index. This would save you from ever hunting around in your cells, even in the case that they are on the screen.
i have two arrays one for search bar and other for contact array. and first one display as tableview. the problem is that when i select two contacts from contact list and then i try to go on my search bar the selected contacts gone as shown in figure 2.
i try to reload table data but it didnot work. please help me... tha nks in advance.
You have a issue with the cells my best guess you have to do something like this before acctually drawing the cell in cellForRowAtIndexPath:
cell.clearsContextBeforeDrawing = YES;
If that doesn't work it's probably a problem with the indexPath, could you provide some more information related to the code?
If your cells are being released or redrawn at any point, they won't remember they were selected unless you are storing this data somewhere. The cells will be redrawn to their original state OR potentially reused if you are enabling this. I would track your selected cells alongside your contacts array (maybe an NSDictionary?).