Something weird is going on with my tableview when changing data. I have something like this:
// fadeout existing data
... // change data (new values for the cells are blank)
for{ // loop all rows
[TableView reloadRowsAtIndexPaths: withRowAnimation:]; // smooth fade out
}
// add one new row to the table
... // change data (just add one new row but leave the cells empty)
[TableView reloadData] // reload all of the data (new row should be added)
... // change data (just add values to the existing cells)
for{ // loop all rows
[TableView reloadRowsAtIndexPaths: withRowAnimation:]; // smooth fade in
}
In theory, at least what I think, this should work. But I had some glitches so I added NSLogs in the for loops and in the: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath so I noticed that my [tableView reloadData] executes after the first row of fade in loop!##
I was thinking about making some kind of a delay between reloadData and fade in loop, but I don't want to force it to work, I want it to work properly.
Is there a better way to accomplish what I'm trying to do?
Can I dynamically add one row at the bottom of the table without calling the 'reloadData' method?
Thanks.
Yes, just use the tableView insertRowsAtIndexPaths method, which will then call your dataSource to load those new rows.
To load a single row at the end of your table, you'd first update your data source to include the new row, then generate the indexpath using:
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[yourdata count]-1 inSection:0];
NSArray *indexPaths = [NSArray arrayWithObject:indexPath];
[tableView insertRowsAtIndexpaths:indexPaths withRowAnimation:whateveryouwant];
Remember, that will immediately call your tableView:cellForRowAtIndexPath method, so update your dataSource to include the extra row before inserting the new row into your table, and be careful that the row index in the indexPath you specify matches the newly added item in your data source.
Related
I have been searching and reading all over but couldn't find any conclusive method to achieve what I want to and hope to find help here...
I have a UITableView which allows the user to add multiple Flavours and Percentages to a Recipe. I have implemented the method to add or delete rows of Flavours with a custom Cell / Nib and it works perfectly well.
The issue I'm facing now, is how to retrieve the values the user has provided per added row.
(Edit for Clarity: My problem is not the populating of data, but only the dynamic reading of all data so I can save it)
I do manage to get the values for the visible rows (I do understand how the Reuseidentifier and the Tableview works, per se that for memory management's sake, iOS only keeps track of the visible rows), but not the hidden ones.
I assume in theory that I have to create an Array of Cells outside of 'cellForRowAtIndexPath' which maintains all cells. But then I'm facing another conceptual problem that my custom Nib / cell doesn't show.... basically:
How can I then use / register a nib without using the dequeingidentifier
Or in General, how can I solve the overall problem to be able an read all user entered values per row
Here the code I'm using within my cellForRowAtIndexPath. As mentioned adding and remove cell works like a charm, that isn't the issue...
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
RecipeFlavourTableViewCell *cell;
int section = (int)indexPath.section;
if(section==0)
return [super tableView:tableView cellForRowAtIndexPath:indexPath];
if(!cell){
[tableView registerNib:[UINib nibWithNibName:#"RecipeFlavourCell" bundle:nil] forCellReuseIdentifier:#"Cell"];
cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
}
cell.selectionStyle = UITableViewCellSelectionStyleNone;
return cell;
}
I have seen some Libraries doing it (e.g. XLForm) but do not understand (also when checking their sources) how they iterate through the values and overcome this dequeuing problem...
Any help is highly appreciated
EDIT 2: here the code I'm using to iterate through the cells in order to save the data, but as said I can only iterate through the visible cells:
- (IBAction)saveRecipe:(id)sender {
NSInteger dynamicRows = [self.tableView numberOfRowsInSection:1];
for (int i=0; i<dynamicRows; i++) {
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:i inSection:1];
RecipeFlavourTableViewCell *cell = (RecipeFlavourTableViewCell *)[self.tableView cellForRowAtIndexPath:indexPath];
NSLog(cell.flavour.text);
}
}
After 2 days of searching I finally came up with a solid solution. In case someone bumps into the same problem of dynamic forms with a tableview, here the solution:
As we understand, what ever cell is created in cellForRowAtIndexPath, it only persists as long as it is displayed. As soon as you scroll and the cell disappears, it gets automatically thrown out of memory. This behaviour makes it impossible to iterate through all cells at a later stages.
The steps to follow in order to make it work are as follows:
Preparation
Create an NSObject with all properties you want to persist in one form cell (-> cellObject)
In the ViewDidLoad of your controller create a NSMutableArray which will contain the cellObjects (-cellsArray)
Add as many cellObjects to the cellsArray as you initially want to appear in the Tableview
In numberOfRowsInSection return the count of you cellsArray
In the cellForRowAtIndexPath build your cells as usual BUT add a Textfield Delegate (self) to every Textfield in a cell
TextField Delegate
Implement:
- (void)textFieldDidEndEditing:(UITextField *)textField
and update your cellsArray Objects every time a Textfield ends editing. Per se, get the cellObject for the row and edit the properties with the value of the TextField
Add Row
When ever you add a row, just add an empty cellObject to your cellsArray and use the beginUpdates / insertRowsAtIndexPaths / endUpdates on your tableView (NOT reloadData as the already typed in data would get lost). Also add the following at the very beginning of your addRow method, as you want to make sure that if the user adds a row while editing a textfield, the latter gets persisted as well:
[self.view.window endEditing: YES];
Remove Row
Same as Add Row just reverse, remove the cellObject from your cellsArray and use deleteRowsAtIndexPaths on your tableView
Save Data
Now comes the trick: since you ought to always persist your data when a field ends editing mode, there is one case you need to cover: What if the user pushes "Save" when the focus is set on one TextField? Well at the very beginning of your Save Action insert the following:
[self.view.window endEditing: YES];
This make sure the the textFieldEndEditing will be triggered one last time for the current textField and that its data will also be persisted.
Finally iterate through your cellsArray and do whatever you want with it (validate, save etc)...
That's it, hope this can help anyone else as I couldn't find any valuable explanation anywhere else...
Lets assume that you have an NSArray and that it contains data you want to show. Your code should look something like this:
// Add this property to the class and fill it in with data you want to show
#property NSArray flavourElements;
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
RecipeFlavourTableViewCell *cell;
int section = (int)indexPath.section;
if(section==0)
return [super tableView:tableView cellForRowAtIndexPath:indexPath];
if(!cell){
[tableView registerNib:[UINib nibWithNibName:#"RecipeFlavourCell" bundle:nil] forCellReuseIdentifier:#"Cell"];
cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
// At this point your cell is ready for showing
// And you can change values in it by getting element from array that contains data
cell.flavorTextField = flavourElements[indexPath.row].flavour
cell.precentageTextField = flavourElements[indexPath.row].precentage
}
cell.selectionStyle = UITableViewCellSelectionStyleNone;
return cell;
}
I wrote a code for accessing elements without knowing what you actually have, so you will need to adjust it a little bit to fit your app.
Here is my program. I want to create a simple list of items that display a number. When the rows are tapped the number will increment by one.
EDIT: Is it proper to change the UI of a row in the didSelectRowAtIndexPath function?
I created a UIViewController in Xcode 5 through a storyboard and it does everything right except I can't seem to stop the [tableView reloadData] from deselecting my row after being tapped. Specifically, I want the row to turn gray and then fade out normally.
I have tried selecting the row and then deselecting the row programatically after calling [tableView reloadData], but it doesn't work.
I know that if I was using UITableViewController that I could just call [self setClearsSelectionOnViewWillAppear:NO], but I'm not.
Is there a similar property I can set for UIViewController?
Here is the code:
[tableView beginUpdates];
[counts replaceObjectAtIndex: row withObject: [NSNumber numberWithInt:newCount]];
[tableView reloadData];
[tableView endUpdates];
I feel I may not be describing what is going on. I have a row that uses UITableViewCellStyle2, which displays a label to the left and right. On the right aligned text is a number that increments each time the row is tapped. Simply updating the data structure does not solve the problem. I need to update it visually. I don't need or want to replace the row, unless I have too. I just want to update the right-aligned text field AND keep the row from being deselected immediately without animation. I can do one or the other, but not both.
Is there a way to just update the right-aligned text field while still staying true to the MVC model?
Remove the [tableView reloadData]; from the code. It should not be called in the methods that insert or delete rows, especially within an animation block implemented with calls to beginUpdates and endUpdates .
Call reloadData method to reload all the data that is used to construct the table, including cells, section headers and footers, index arrays, and so on. For efficiency, the table view redisplays only those rows that are visible. It adjusts offsets if the table shrinks as a result of the reload. The table view's delegate or data source calls this method when it wants the table view to completely reload its data.
[tableView beginUpdates];
[counts replaceObjectAtIndex: row withObject: [NSNumber numberWithInt:newCount]];
[tableView endUpdates];
See the developer.apple section - reloadData
If you want to keep the selection after reload, the easy way is
NSIndexPath *selectedRowIndexPath = [tableView indexPathForSelectedRow];
[tableView reloadData];
[tableView selectRowAtIndexPath:selectedRowIndexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
I have a UITableView of custom cells. Each cell has an NSTimer that can be set by the user and started by tapping a button. The timers work except when a new cell is added to the TableView. In the unwind method (coming from creating a new object for a new cell) I have to reload the data in the TableView so that the new cell appears. This however reloads all the cells causing any running timer to restart. Is there a way I can add the cell without restarting the running timers?
EDIT:
I have a ViewController that creates a new object and then back in the FirstViewController.m I have an unwind method that should update the tableView with a row for the new object. Using the reloadData method won't work because it reloads all of the cells. I would like to just add a new cell without reloading the entire tableView.
-(IBAction)unwind:(UIStoryboardSegue *)segue {
ABCAddItemViewController *source = [segue sourceViewController];
ABCItem *item = source.object;
if (item != nil) {
[self.objectArray addObject:item];
[self.tableView reloadData];
}
}
To do this I've tried adding these lines instead of [self.tableView reloadData]:
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[self.objectArray indexOfObject:item] inSection:0];
[self.tableView insertRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationLeft];
However, the app crashes and I get this message:
'Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (1) must be equal to the number of rows contained in that section before the update (1), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'
The number of rows in the tableView is determined by [self.objectArray count] in the numberOfRowsInSection: method.
It is not a good idea to add timers to cells because they are reused. They are views. My recommendation is to create some objects which have the text / info you want to display in these UITableViewCells and add the timers to those objects. This way the timer info is not stored in the cells and they will store state
There is no need to reload entire table for just inserting one cell. You can add the cell like
self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:#[[NSIndexPath indexPathForRow:row inSection:section]] withRowAnimation:UITableViewRowAnimationLeft];
[self.tableView endUpdates];
I have a UITableView with Dynamic Prototypes.
I implemented the code below so that when I select a row, it will be marked and the previously selected row will be unmarked.
However, for example, the row I selected is displayed in the middle of the screen, then when I scroll up or down, another cell (which is in the same middle position of the screen) is marked. In short, every view, there is a selected cell at the middle.
Please advise.
- (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSIndexPath *oldIndexPath = [self.tableView indexPathForSelectedRow];
[self.tableView cellForRowAtIndexPath:oldIndexPath].accessoryType = UITableViewCellAccessoryNone;
[self.tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark;
return indexPath;
}
Probably you are overwriting accessoryType in your cellForRowAtIndexPath method - this is called each time table is about to draw new rows which were invisible before (as you described when you scroll up / down).
You need to handle it also in that function and update accessoryType there - otherwise it will randomly reuse a cells with different accessoryTypes.
You are modifying just the visuals of cell, you're not updating the data model. Store the selected index path in a #property somewhere, and adjust accessoryType inside cellForRowAtIndexPath.
Ok, I'm stuck. This is an extension of a previous post of mine. Here is what I am trying to do.
I have an Edit button on a navigation bar that when pressed adds a cell at the beginning of my one section table view. The purpose of this cell if to allow the use to add new data to the table; thus it's editing style is Insert. The remaining cells in the table are configured with an editing style of Delete.
Here is my setediting method:
- (IBAction) setEditing:(BOOL)isEditing animated:(BOOL)isAnimated
{
[super setEditing:isEditing animated:isAnimated];
// We have to pass this to tableView to put it into editing mode.
[self.tableView setEditing:isEditing animated:isAnimated];
// When editing is begun, we are adding and "add..." cell at row 0.
// When editing is complete, we need to remove the "add..." cell at row 0.
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
NSArray* path = [NSArray arrayWithObject:indexPath];
// fill paths of insertion rows here
[self.tableView beginUpdates];
if( isEditing )
[self.tableView insertRowsAtIndexPaths:path withRowAnimation:UITableViewRowAnimationBottom];
else
[self.tableView deleteRowsAtIndexPaths:path withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
// We nee to reload the table so that the existing table items will be properly
// indexed with the addition/removal of the the "add..." cell
[self.tableView reloadData];
}
I am accounting for this extra cell in my code, except I now have two index paths = [0,0] - the new cell and the old original first cell in the table. If I add a call to reload the table view cell in setEditing, the cells are re-indexed, but now my table view is no longer animated.
I want my cake and eat it too. Is there another way to accomplish what I am trying to do and maintain animation?
--John
You can do what you want but you need to keep your data source consistent with the table. In other words, When the table is reloaded, tableView:cellForRowAtIndexPath and the other UITableViewDataSource and UITableViewDelegate methods responsible for building the table should return the same cells depending on editing state that you are adding/removing in setEditing:antimated:.
So, when you insert/delete a cell in setEditing:animated: you need to also make sure your data source reflects the same change. This can be tricky if you are adding a special cell to the beginning of a section but the rest of the data is from an array. One way to do this is while reloading the table, if editing, make row 0 the add cell and use row-1 for your array index for subsequent cells. If you do that you'd also need to add one to tableView:numberOfRowsInSection: to account for the extra cell.
Another way would be to have a section for the add cell and it would have 0 rows when not editing, 1 row otherwise and you return the appropriate cell. This will also require you to configure your table and cell(s) appropriate depending on how you want things to look.