Keeping selection upon updating UITableView via reloadData - ios

Question

I am trying to implement a view similar to that of Apple's calendar application's setting the start time and end time view. I have the view looking great, but I am running into two problems. First, I want to have the first row selected automatically. I sort of have this working using:
NSIndexPath *indexPath=[NSIndexPath indexPathForRow:0 inSection:0];
[dateTableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionBottom];
However, an animation shows, visually selecting the rown when the view is loaded, I want it to already be selected when the view loads.
The second, and much more important, problem is that when I reload the data after the picker has updated I lose the selection, and my task simply doesn't work.
Now I know this is the default action of reloadData, I am looking for an alternative method to accomplish my goal, or perhaps how I can augment reloadData to not deselect the current selection.
My task is included below:
-(IBAction)dateChanged
{
NSIndexPath *index = self.dateTableView.indexPathForSelectedRow;
if(index == 0)
{
if (self.date2 == plusOne ) {
self.date = [datePicker date];
plusOne = [self.date dateByAddingTimeInterval:60*60];
self.date2 = plusOne;
}
else
{
self.date = [datePicker date];
}
}
else{
self.date2 = [datePicker date];
}
[dateTableView reloadData];
}
Note: plusOne is a variable that initially indicates an hour from the current time.
Thanks in advance!

Answer 1

For the first problem, set animated:NO on the method call. You are currently setting it to YES.
[dateTableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionBottom];
For the second problem, it's not really clear what you are trying to select after reloading the data, but I see a problem with this line:
if(index == 0)
You are asking if the pointer to the object is 0. I think what you want is either to check that index == nil or that index.section == 0 && index.row == 0 or something like that.
Anyway, if you call reloadData on the UITableView, you're going to lose the selection. At that point, you need to select a new row. If there is an item in your data model that you want to select, you need to figure out where it is and select it based on where it will be in the table (You should know this because you are providing that information in the UITableViewDataSource delegate methods.). Alternatively, if you want to select the NSIndexPath you saved in the first line of dateChanged, just select it after reloading the data.

Answer 2

For the first problem, write your code in didSelectRowAtIndexPath: in a method. You can then call this method from didSelectRowAtIndexPath: You should pass indexPath as argument to your function like,
-(void)doActionsInDidSelectRow:(NSIndexPath*)indexPath{
// write code.
}
In viewDidLoad call this method as
-(void)viewDidLoad{
NSIndexPath *indexPath=[NSIndexPath indexPathForRow:0 inSection:0];
[dateTableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionBottom];
[self doActionsInDidSelectRow:indexPath];
}
For the second problem my suggestion is, each time when you selecting a cell store that cell's text in a NSString. When you reload data, inside cellForRowAtIndexPath: just compare cell's text with the string content you stored previously. If they equal just make selection using
[dateTableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionBottom];
method. Hope this will solve your issues.