I have an iPhone app with a form input screen. I did this by making a custom UITableViewCell that has a UILabel and a UITextfield. I set it up so that the "cellForRowAtIndexPath" fetches the appropriate value from Core Data, and the UITextField's "textFieldDidEndEditing" method saves the appropriate value to Core Data. It works great... except:
If I edit a text field, then scroll it off screen, then click on another cell's text field:
The cell has been autoreleased because it scrolled off screen
The "textFieldDidEndEditing" gets a BAD ACCESS error
I understand the problem completely, I'm just not sure the best way to fix it. My first thought was to add the logic from "textFieldDidEndEditing" to "dealloc", but that seems hacky. Any suggestions?
I ended up using a delegate method for scroll view (which is built in to the UITableView). When the user starts dragging, I resign first responder.
This works perfectly because it looks nice, and "textFieldDidEndEditing" gets called when the user starts to scroll, which is always before the text field goes off screen.
disable scrolling while editing
retain your textField
that are the things you could do. In my opinion its best to disable scrolling while editing because the user has no need to, so make sure he also can not do so. Limit the things your user can do, makes it more "secure" for you and easier to use for the user.
If you are not sure about such things just look at what apple does, they are always right in their applications. Like in the settings app on iOS 5, when you change your phone's name. You simply get 1 row in the next tableview so you can't really mess anything up as the user..
In your custom cell's dealloc, set the textfield's delegate to nil
I had a similar issue... The problem lies in the reusable cells as part of the Table View. Every time the table is scrolled, the cellforRowatIndexPath gets called, and dequeues a cell and returns it. Sadly, this functionality doesnt work well with cells having retainable data such as labels. Hence you must opt for your own method of dequeueing the cell.
I have an NSMutableArray called cells which holds all my cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
CustomTableViewCell *cell = [self dequeuwReusableCellwith:indexPath];
if (cell == nil)
{
cell = [[CustomTableViewCell alloc] init];
[cells addObject:cell];
}
// Configure the cell.
NSString *temp = [NSString stringWithFormat:#"Cell %d",indexPath.row];
cell.textField.placeholder=temp;
return cell;
}
and this is my custom method to deque Reusable cells.
-(CustomTableViewCell*)dequeuwReusableCellwith:(NSIndexPath*)indexpath
{
if([cells count]>indexpath.row)
{
return [cells objectAtIndex:indexpath.row];
}
return nil;
}
Hope this helps...
Related
I want to disable reloading table view when scrolling. Now, my app when user scroll the uitableview, cellForRowAtIndexPath has been recalled.
Things in viewDidLoad
[listingTableView registerNib:[UINib nibWithNibName:#"TripCardCell" bundle:nil] forCellReuseIdentifier:[TripCardCell cellID]];
Things in cellForRowAtIndexPath
if (cell == nil) {
cell = [[TripCardCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:[TripCardCell cellID]];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}
UITableViewCell Class Reference
The reuse identifier is associated with a UITableViewCell object that
the table-view’s delegate creates with the intent to reuse it as the
basis (for performance reasons) for multiple rows of a table view. It
is assigned to the cell object in initWithFrame:reuseIdentifier: and
cannot be changed thereafter. A UITableView object maintains a queue
(or list) of the currently reusable cells, each with its own reuse
identifier, and makes them available to the delegate in the
dequeueReusableCellWithIdentifier: method.
Advantage of reuseIdentifiers
Using dequeueReusableCellWithIdentifier for the tableView, you can
greatly speed things up. Instead of instantiating a lot of cells, you
just instantiate as many as needed, i.e. as many that are visible
(this is handled automatically). If scrolling to an area in the list
where there are "cells" that haven't got their visual representation
yet, instead of instantiating new ones, you reuse already existing
ones.
disable reloading tableview when scrolling
You cannot block the cellForRowAtIndexPath: from calling when
scrolling the tableview. If something need not happen every time, You
may keep it in if condition.
if (cell == nil)
{
//Functionality goes here when it not needed to happen every time.
}
So, I've been implementing Automated testing for my iOS app and I've come across a strange issue.
With the testing framework I'm using (Frank), it attempts to Touch views/buttons/everything based on Accessibility labels. This works great, except for with UITableViews because of how they cache and reuse UITableViewCells. If I "delete" a cell from the table, the table caching system will flip the cell to Hidden. But it will still be there waiting to be reused, and my framework can still see it, which is causing issues.
So, Question: How can I force a UITableView to release all deleted/cached cells so they will no longer be part of the View hierarchy?
This trick might help:
while([tableView dequeueReusableCellWithIdentifier:cellId]!=nil);
Of course, it needs manually repeat it for every possible cellId.
Note, cached cells is not a part of view hierarchy.
One more option. If UITableViewController is not currently visible, then invocation of didReceiveMemoryWarning method releases all its UITableViewCells.
In the method - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath, use this:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]`
then check if your cell is nil. If it is, allocate a new instance of the cell.
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
[cell setDelegate:self];
}
Hi
I've got simple question which I don't know how to answer.
In my app I've got UITableViewController with cells. When I select one item (cell) it's getting higlighted and in other thread I'm loading chunk of data to display to the user (after load is done new VC is pushed). When doing it with thread user still can interact with application like, going back to other NavController and I do want that to happen. What I don't want to happen is that when loading isn't complete user can select other cell in table and it get's highlted. How I can prevent that (only highlit, I'm checking if there was a previous request so I'm not putting another thread untli previous request is done).
So basicly my question is, how can you foribd user from interacting with table view controller?
Set the selectionStyle of the UITableViewCell's to UITableViewCellSelectionStyleNone.
You can use the following to check if row can be selected:
- (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if (rowSelected) {
return nil;
}
return indexPath;
}
So, you only select it if no row is selected. In your didSelectRowAtIndexPath method:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
rowSelected = YES;
// call method that is going to do something and mark rowSelected = NO;
}
You can deselect the row by using
[[tableView cellForRowAtIndexPath:indexPath] setSelected:NO animated:YES];
There is a risk that your users will be confused. A highlight is not enough. There should be very clear visual feedback that a network opperation is ongoing and that different rules apply.
either push the details view immediately after the user selected a row and show an activity indicator in there.
or give the whole table view a different look while loading data for the selected row: e.g. Show activity indicator in the selected row & hide the disclosure chevrons in all the other. While doing that, you can set the selection style to 'none'
I have a inherited UITableViewCell class from which I create a custom cell containing a UITextField.
The UITextField is 25 pixel height by default.
The behavior I want is that when the user clicks in the textField, the UITextField should change to 100 pixel height and the cell should grow accordingly.
I can detect when the UITextField receive focus thanks to notifications and observers but I wonder how to programmatically make that tableView:HeightForCellAtindexPath: be called.
Like Endemic says, tableView:heightForCellAtIndexPath: is the method you need to implement. According to Apple, the most efficient way to trigger a resize is an empty beginUpdates / endUpdates block, like this.
[tableView beginUpdates];
[tableView endUpdates];
It saves you the overhead of reloading the cell contents and, I believe, gives you a nice animation you wouldn't otherwise get from reloadData.
You must have a link between the cell and the table view controller. Since you are already creating your custom cell in your controller the easiest way would be to use the delegate pattern.
#class CustomTableViewCell;
#protocol CustomTableViewCellDelegate
- (void)customTableViewCellDidEnterTextMode:(CustomTableViewCell *)cell;
#end
#protocol (nonatomic, assign) id<CustomTableViewCellDelegate> delegate;
and just call the delegate method where you are detecting when the text field gets focus
[self.delegate customTableViewCellDidEnterTextMode:self];
and in the controller
- (void)customTableViewCellDidEnterTextMode:(CustomTableViewCell *)cell {
self.editingIndexPath = [self.tableView indexPathForCell:cell];
// from Jablair's answer
[tableView beginUpdates];
[tableView endUpdates];
}
And then in tableView:heightForCellAtIndexPath: just return your special height for self.editingIndexPath.
You would probably have to include another delegate method to know when focus is leaving the text field as well.
Another approach would be to use notifications but that will just complicate your code and if there is only one receiver of the message a delegate is the preferred way. A third approach would be to set the delegate of the text field to your controller instead of to your cell.
The bottom line, you need to provide the link between the cell and table view your self and I believe using a delegate pattern is the best approach.
The tableView:heightForCellAtIndexPath: method is called whenever the table view loads data, so simply calling reloadData (or one of the other, more selective reload methods) on the table view should work fine.
I'm using custom headers for my tableview...
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
CustomHeaderController *header = [[CustomHeaderController alloc]
initWithNibName:#"TableHeader" bundle:nil];
header.title.text = #"Test";
return header.view;
}
The title label is never set though. I even tried creating a viewWillAppear method and setting it there, but that didn't work. My outlets are set up too!
Thanks!
SOLUTION: View wasn't load on the return header.view call. Call header.view or add a viewDidLoad method to the class of header to get it to work! Thanks all!
So I'm not sure "title" here means what you think it means. Setting the title on a view controller isn't going to affect what's in the view. If you're trying to set a title on a section, you may just want to use tableView:titleForHeaderInSection. tableView:viewForHeaderInSection is for more complex section headers (like if you wanted to put buttons, or multiple rows of text or something like that). If it matters, you can use both of these methods. I'm not 100% certain on the order they're called, but I'm pretty sure it looks for a viewForHeaderInSection and then if that's nil it goes to titleForHeaderInSection.
The function expects a UIView to be returned, but you appear to be returning a UIViewController. Did you mean to do return header.view?