Accordingly to this question and the kind answer of KyleC I've implemented a UITableViewController which has many rows relying on a fetch from Core Data. Every row display a simple NSString (name of the object fetched) and has an UIPickerView hidden.
The issue is that it's absolutely evident that when I tap the row in the previous UITableViewController that opens the UITableViewController with picker views there's some delay in the segue transition.
I know this because the previous controllers (they even perform Core Data requests) are not so slow in the transition.
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Can some UIPickerViews make the transition so slow and pretty ugly? In which mode should I use Instruments to understand which is the slowly-guilty?
More important: if the slowness is derived from the numbers of UIPickerViews how can I optimize this?
I want to clarify that the app is very light and the fetched objects from Core Data are only 4, with 4 UIPickerViews.
It seems that UIPickerViews and UIDatePickers load very slowly from storyboards (and possibly xib's, but I haven't tried). On an iPad Air it's taking around 3 seconds to load a static UITableViewController that contains 4 UIPickerViews and 8 UIDatePickers in "hidden" cells. (3 seconds is an eternity for a native UI running on the latest and greatest hardware!)
The workaround I found is to create the UIPickerViews and UIDatePickers programmatically before the hidden row is revealed. What I did was create empty cells in Interface Builder, link those cells to IBOutlet properties, and then create the DatePickers and Picker views with these methods:
- (UIDatePicker*)datePickerForCell:(UITableViewCell*)cell { UIDatePicker * datePicker = [[UIDatePicker alloc] initWithFrame:cell.bounds]; [datePicker setDatePickerMode:UIDatePickerModeDateAndTime]; [datePicker addTarget:self action:@selector(pickerDateChanged:) forControlEvents:UIControlEventValueChanged]; datePicker.hidden = YES; [cell addSubview:datePicker]; return datePicker; } - (UIPickerView*)pickerViewForCell:(UITableViewCell*)cell { UIPickerView * picker = [[UIPickerView alloc] initWithFrame:cell.bounds]; [picker setDelegate:self]; [picker setDataSource:self]; picker.hidden = YES; [cell addSubview:picker]; return picker; }
This reduced the load time for the UITableViewController to a few tenths of a second and it doesn't seem to affect the animation of showing a hidden tableview.
Note: I did try creating the pickers in the viewDidAppear: method, but it still seemed to delay the UI.
