I want to handle case when user deselect row (that already selected) by tap on this row. It is well known that tableView:willDeselectRowAtIndexPath: / tableView:didDeselectRowAtIndexPath: delegate methods not called in this case: they are called only if you tap on other, unselected yet row (my table view have single selection mode).
tableView:didSelectRowAtIndexPath: method also not called when I am deselecting row.
Is there is any easy solutions?
Update
The problem was in tableView:willSelectRowAtIndexPath: method, where I return nil in some cases, thats why tableView:didSelectRowAtIndexPath: didn't call. Thanks #Nekto for useful information and helping.
Apple docs say next about - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
This method isn’t called when the editing property of the table is set to YES (that is, the table view is in editing mode).
That means that this method should be called unless your code has a bug or you haven't updated delegate of your table view or table is in editing mode.
One of the possible problems could be that you have incorrectly implemented - (NSIndexPath *)tableView:(UITableView *)tableView willDeselectRowAtIndexPath:(NSIndexPath *)indexPath and are returning nil for the selected row. In that case didSelect... isn't called:
Return nil if you don’t want the row deselected.
Alternatively you can implement another table view delegate method: - (void)tableView:(UITableView *)tableView didUnhighlightRowAtIndexPath:(NSIndexPath *)indexPath:
Tells the delegate that the highlight was removed from the row at the specified index path.
See more about managing selections in table views here.
You can still use tableView:didSelectRowAtIndexPath, just use it like a check mark system would work.
The answer here explains how to use a checkmark. You can use this, or use the answer here.
I have such use case. Why you don't create a variable for lastSelectedRow(here I have problem if it was NSIndexPath and I used two integers) and on the method for selecting row just compare currentSelectedRow with lastSelectedRow.
Related
I have two custom models of TableViewCell, one for just basic informations and another for detailed informations.
How can I switch to the detailed one with the didSelectRowAtIndexPath method? (and afterwards if the detailed one is displayed, toggle to the basic one on select)
Thank you.
When the row is selected, toggle a flag indicating that the row needs to switch from one type of cell to another. Then reload the the cell at that index path.
Then your cellForRowAtIndexPath method looks at the flag for the given index path and returns one of the two types of cells.
In whatever kind of object you use to represent cell data, keep a flag for whether it's selected or not. Turn the flag on or off in didSelectRowAtIndexPath and then reload the table view data. When you return a cell for an index path, choose which kind of cell based on the flag value.
You can create an array or set consist of indexPaths of cells type 1. Add or remove from it cells if needed. Return the right cell in
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
And if you want to reload specific cell, modify your array of cells and just call from tableView:
- (void)reloadRowsAtIndexPaths:(NSArray *)indexPaths
withRowAnimation:(UITableViewRowAnimation)animation
I'm an iOS newbie and I would like to know how to detect when the user scrolls and reaches the bottom of an UITableView so I can load new data into the table.
I would also like to know where such a method should be implemented (the tableview's class or the view controller in which this tableview exists)
Cheers!
You can use -(void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath to and check if the last cell will be shown in the TableView's data source.
iOS' TableViewController takes care of that automatically. It asks its datasource only for the currently visible rows of the table (tableview.cellForRowAtIndexPath)
See the documentation for the UITableViewDatasource Protocol Reference
If you've got a "known dataset" (as in, you don't need to make a network call to fetch new data), then like #zizoft said, it'll be handled automatically in tableview.cellForRowAtIndexPath
If, however, you've got an "unknown dataset", (as in, you'll need to pull down data from the internet), you'll need to do something a bit more interesting - #ansible's suggestion would be appropriate in that case.
I understand the concepts of cell re-usability for Xcode 5.0 table views. However, I have one very weird observation which I don't understand and wish anyone of you could enlighten me here. Thanks.
I have implemented a table view with a search bar utility (just on top of the table view). Under each custom cell (prototype cell), whenever a user clicks on it, it will be marked with a checkmark (UITableViewCellAccessoryCheckmark). The number of cells are more than 10.
Observation:
- Without using any search, marking and unmarking a cell is working as intended. Cells are updated instantly along with their checkmarks.
- When doing a search, from the results given, marking and unmarking a cell is also working as intended.
[Problem] Here comes the weird issue: when cancelling a search, an already marked cell (marked during search) does not refresh itself in the tableview unless scrolling up or down is performed!
And hence, I wrote [tableview reload] at the end of tableview:didSelectRowAtIndexPath: method. Obviously, it doesn't refresh the tableview for me. Without further changing any other code, merely modifying [tableview reload] to [self.tableview reload] under the same method works!
Why is the only addition of "self." able to make the table cells refreshed instantly? I have always thought the first argument, tableView, from the method (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath is as equal to self.tableview. Obviously, my interpretation in this case is wrong.
Thank you. I'm sorry for my lengthy post.
My guess is that this UISearchBar comes from a UISearchDisplayController. Is that correct?
If true, that is a common misconception, but an easy one to understand.
When filtering your UITableView entries and showing results, UISearchDisplayController actually overlays the view with its own tableView, UISearchResultsTableView.
Thus, this overlaid tableView also gets to call data source and delegate methods on your implementation, and this is when the tableView argument from tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath stops being equivalent to self.tableView.
This means that calling [tableView reloadData] during filtering actually asks UISearchResultsTableView to reload its contents, not self.tableView, a property of your viewController.
When is cellForRowAtIndexPath called when the cells of a TableViewController are added dynamicall? Is it after ViewDidLoad? We never trigger anything programatically to tell the app that we have done all the initial work we need to do and now you can start adding the cells with the corresponding details, discousure etc...
I am terribly confused and therefore I have no clue about the flow of execution of controls in a TableViewController. Please help me !
The delegate calls for the tableView will only be called if the table exists, for the table to exist the view must exist as it is part of the view. The viewDidLoad is called right after creating the view. So in short: viewDidLoad is called BEFORE tableView:cellForRowAtIndexPath:.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath is a delegate method of a UITableView. It is called every time a cell is becoming visible(appearing on the screen due to scrolling for example).
And at the beginning it is called after viewDidLoad as many times as necessary(depending how many cells should be present).
Hope it helps
it is called after viewDidLoad, and yes it is called for every cell dynamically. you can put breakpoints and check the flow. hope it helps. happy coding :)
The tableview knows that when it's unarchived it needs to load its data.
As a general tip, if you want to know when a method is executed you can set a breakpoint. Xcode lets you choose whether to pause or continue when a breakpoint is met, so you can trigger a set of actions when different methods are encountered to find out what order thet occur in.
My iOS app is current transferring control to a detail view when an item in a UITableView is selected. This ia a quiz program, and I'd like to change the app so that it just redisplays the same table view with the correct answer highlighted when a row is selected. What's a good approach for doing this?
Is not clear to me if you know why the detail view is appearing. So I'll explain just in case. If you are giving control to a detail view is because somewhere in your code you are pushing that detail view. It depends on what kind of UITableViewCell you are using. If you are using one of the defaults styles, your detail view is probably been pushed in either:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
or
- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath
If you are using a custom cell, then you need to look for the method in charge of pushing
that detail view.
I think a good approach would be to:
Remove that pushing wherever it is.
Not to use an `UITableViewCellAccessoryType, if you are using one.
Do something similar to the following on your tableView:didSelectRowAtIndexPath:
Find the row for the right answer in your model array, according to tapped cell.
Use that row number to generate an NSIndexPath.
Use that NSIndexPath to find the correct cell with cellForRowAtIndexPath:
Call setSelected:animated: on that cell to highlight it.
NOTE: If your quiz has more answers than the amount of UITableViewCells that fit in the screen you should scroll your UITableView to the right answer for better UX.