I have a table view with custom cells. Cells have an image view, a label and a progress view. What I want to achieve is to update progress view in a specific cell according to the event that fires. My idea is to find the cell by name label that is in the event and then update progress view. This may not be an efficient way but I couldn't think of some other way. Other ideas are also appreciated. Thanks in advance.
You could use a NSDictionary with the name as the key and the NSIndexPath as the object. Then to can look up the index path for a given cell using the name in the dictionary.
UITableView has a 'cellForRowAtIndexPath:` method that should give you the cell for a specific row.
i.e. something like
// Get visible cell for data item
NSInteger row = [myArrayOfThings indexOfObject:thing];
NSIndexPath *inedexPath = [NSIndexPath alloc] initWithRow:row section:0];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indeexPath];
// Update cell here ...
...
Disclaimer : Code typed from memory - you may have to look at the documentation for some of the method names :)
the more better way is with tag,
you can give each cell a unique tag and access that cell by this method
//method of UIView(UIViewHierarchy)
- (UIView *)viewWithTag:(NSInteger)tag;
// can be used like this
UITableViewCell *cell = (UITableViewCell*)[tableView viewwithtag:tag];
Related
I have custom cell having switch in few cells at right side. what I want is to store value of specific cell on switch change event. Table view has number sections so I can't set tag for switch because I need section as well as row to obtain index path.
Any suggestion any alternative but I have to use UISwitch in section based table view.
Thanks
In your custom cell add properties which help you identify the information the cell represents. Index path, indexes for your data model etc...
Then add a block property to the cell which you can call to tell a UITableView or any other piece of code when a cell switch changes. e.g.
#property (nonatomic,copy) void (^onSwitchChange)(UITableViewCell *cell);
Inside your custom cell code, add an action handler for the UISwitch. When it fires, call self.onSwitchChange(self) which will notify the code which registered an onSwitchChange block that a switch has changed and on which cell.
In your table view when you create the cell, set the onSwitchChange block as follows:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath (NSIndexPath *)indexPath
{
<snip>
YourUITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:yourCellIdentifier forIndexPath:indexPath];
cell.onSwitchChange=^(UITableViewCell *cellAffected){
// Add code to deal with the swicth switch using properties of cellAffected
... Your handler code here ...
}];
<snip>
}
This lets you handle all the changes in the table view controller. Hope this helps.
The answer from #Jageen works. I had to find out which superview the cell is, mine was one more level higher.
UITableViewCell *cell = (UITableViewCell*)[sender superview].superview.superview;
NSIndexPath *indexPath = [self.myTableView indexPathForCell:cell];
NSLog(#"Section %ld Row : %ld",(long)indexPath.section,(long)indexPath.row); // print row section and index
You can still create tags even if you have sections if you have some idea of about max rows in a largest section. For example if you think there will be 1000 rows in a section then you can create tag using following formula.
tag = section * 1000 + row;
later in your IBAction of switch you can find out the indexpath (section and row) using following:
section = tag/1000;
row = tag%1000;
If you have no idea of how many rows your section will have you can find out the cell using sender.superview.superview (be careful if have added any other views in hierarchy).
Rory McKinnel's answer is still the cleanest solution for your problem.
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.
I have the tag for a custom UITableViewCell but I am not sure how I should reference it?
What is the standard approach here.
I thought something close to this but of course this will not work right?:
CustomCell *cell = (CustomCell*)[self.mainTableView cellForRowAtIndexPath:[NSIndexPath indexPathForItem:tag inSection:0]];
I make this reference when a button is pressed in the custom implementation of that cell using a delegate method to pass it to my view controller.
You should not refer to cell itself, because is just interface to show your data. Cells can be (and should be) reused and filled with different data.
Better is store data id, or at lest index of element that cell.
Read more in docs A Closer Look at Table View Cells
To get from a button in a cell to the cell itself, walk up the view hierarchy:
UIView* v = sender; // sender is the button that was tapped
do {
v = v.superview;
} while (![v isKindOfClass: [UITableViewCell class]]);
DiscoverCell* cell = (DiscoverCell*)v;
I'm creating an app which contains a screen that shows a table view with custom cells. Each cell contains two labels and a subview, which further contains other subviews. I'm handling the click event on the cell to hide/show the subviews within the subview in the cell. How can I make it so that when I click on a single cell, the subview of all the cells will change?
It is like the Stock application in iPhone (using iOS 7), here is a screenshot:
As in the image above, when you click on any of the green box, all the boxes change to reflect the same type of value.
Please let me know if this approach is fine, or how this can be implemented.
There are a couple ways of doing this. The first that comes to mind would be to handle the different states within the UITableViewCell subclass, and just reload the visible cells:
[self.tableView reloadRowsAtIndexPaths:[self.tableView indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationAutomatic];
If you're looking for more control over the process though, this process could also be achieved by changing the state future cells should load into, and then calling a method on every visible cell. This would provide you with an easy way to have complete control over how the contents of the cell update.
// Change flag for cell state then...
for (NSIndexPath *indexPath in [self.tableView indexPathsForVisibleRows]) {
if (condition) {
MyCellSubclass *cell = (MyCellSubclass *)[self.tableView cellForRowAtIndexPath:indexPath];
[cell someMethodWithArg:(id)state];
}
}
To do something as in Stock app you should handle two method cellForRowAtIndexPath: and click action method.
In cellForRowAtIndexPath: you should do the check which cell/button was pressed and display value base on it:
//Pseudo code
//cellForRowAtIndexPath
if (cellNo3Pressed)
{
//set up text with the right value.
}
else if (otherCell)
{
//set up text with the right value.
}
This will handle the cell which are not visible on the screen.
The next action method should handle nice animation on all of the visible cell:
NSArray *paths = [tableView indexPathsForVisibleRows];
for (NSIndexPath *path in paths)
{
UITableViewCell *cell = (UITableViewCell *)[self.tableView cellForRowAtIndexPath:path];
//Animate changes for cell
}
I have a custom UICollectionViewCell that has a custom background view which is drawn using one of several colour schemes. The colour scheme for the background view is set in my custom initializer -(id)initWithFrame:andColourPalette: for the View.
I have a similar custom initialiser in my UICustomViewCell subclass but I can't figure out how to call this initialiser when I am setting up the cell in cellForItemAtIndexPath:
Can anyone help me do this? Or offer alternative solution for passing this Dictionary of colours into the Cell to pass on to the subView?
EDIT to show more detail:
This is what I have in my UICollectionView VC:
In ViewWillAppear:
[self.collectionView registerClass:[OPOLawCollectionViewCell class] forCellWithReuseIdentifier:CELL_ID];
self.colourPalette = [OPOColourPalette greenyColourPalette];
In cellForItemAtIndexPath:
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CELL_ID forIndexPath:indexPath];
OPOLawCollectionViewCell *lawCell = (OPOLawCollectionViewCell *)cell;
MainLevel *level = self.collectionData[indexPath.row];
lawCell.delegate = self;
lawCell.colourPalette = self.colourPalette;
In my Custom UICollectionViewCell
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
// get background view
OPOLawBook *lawBookView = [[OPOLawBook alloc]initWithFrame:CGRectMake(0, 0, 200, 265) andColourPalette:self.colourPalette];
But that doesn't work - I guess because the propertys are not set up.
If I change the last line to this, then it works fine:
OPOLawBook *lawBookView = [[OPOLawBook alloc]initWithFrame:CGRectMake(0, 0, 200, 265) andColourPalette:[OPOColorPalette greenyColorPalette]];
So i guess I need to use a custom intialiser here but I cant figure out how to call it , or from where...
Thanks
Yuo have to register your customCells in collectionView:
[self.collectionView_ registerClass:[YourCustomClass class]
forCellWithReuseIdentifier:#"CustomCell"];
And then in your method cellForItemAtIndexPath:
YourCustomClass *cell = (YourCustomClass *)[collectionView
dequeueReusableCellWithReuseIdentifier:#"CustomCell" forIndexPath:indexPath];
It is done because collectionView might have 1000 cells and 10 visible. You don't keep all of them initialized and reuse when possible.
EDIT
You should set colorPaletter after you deque the reusable cell. Think of it as a container which can hold any color. You need to determine (by indexpath) what color to paint.
You shouldn't do below if your custom cell is in the Storyboard,
[self.collectionView registerClass:[OPOLawCollectionViewCell class] forCellWithReuseIdentifier:CELL_ID];
Because Storyboard take responsibility to register Cell_ID own.
Now, It will conflict to be generated invalid Cell if you use both.
Way off, every answer. The questioner is looking for a way to uniquely identify each cell upon initialization, which happens prior to dequeuing a cell, and prior to a cell's access to its index path property.
The only way to do this is to assign a unique reuse identifier to every cell based on what the index path value will be (assuming you will know what that will be—and, in your case, you will); then, when dequeuing the cell, use the index path to find the cell with the corresponding reuse identifier.
Does this negates the purpose of reuse identifiers? Absolutely not. You'll be reusing that cell every time you need to use it again. Reuse identifiers were not meant to limit you to a cookie-cutter cell for every cell in your collection view; they are also intended to be "unique use" identifiers.