I have a bunch of cells, all of which have a label that displays its row. When I move cells in the table, I would like the cells to renumber according to their new rows. After trying the code below, the numbers are all off. How would I fix this?
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{
for (int section = 0; section < [tableView numberOfSections]; section++) {
for (int row = 0; row < [tableView numberOfRowsInSection:section]; row++) {
NSIndexPath* cellPath = [NSIndexPath indexPathForRow:row inSection:section];
CustomCell* cell = (CustomCell *)[tableView cellForRowAtIndexPath:cellPath];
NSString *rowString1 = [NSString stringWithFormat:#"%d.", row + 1];
cell.periodLabel.text = rowString1;
}
}
}
Let Model-View-Controller be your friend.
Instead of thinking "renumber the cells", think "renumber the objects". Use a Model object (say MyNumberedRow) to represent the data in the cell. When the cell moves, retrieve that cell's MyNumberedRow instance, update that.
Even if you have hundreds of items in your logical table, you'll only see a few of those realized as CustomCell instances. If it's not on screen, the cell won't exist.
Side note: use NSInteger, not int. It avoids type problems in 32/64 bit conversions. It's also the return type of -numberOfSections.
Related
I have a custom UITableViewCell called CustomCell which has a UILabel in it which it is supposed to show the current index number + 1 (It is a queue of things to do).
I am using the setEditing method to allow the users to move cells around however I just cannot get the cells to be numbered correctly (in order) with the following code. Basically I am just trying to access the cells in the region the method parameters are passed but the numbers are simply returning out of order. What am I doing wrong here?
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
[queuedToDoArray moveObjectAtIndex:fromIndexPath.row toIndex:toIndexPath.row];
NSIndexPath *lowerIndexPath = (fromIndexPath.row < toIndexPath.row ? fromIndexPath : toIndexPath);
NSIndexPath *higherIndexPath = (fromIndexPath.row > toIndexPath.row ? fromIndexPath : toIndexPath);
//Update all the queue numbers in between moved indexes
for (int i = lowerIndexPath.row; i <= higherIndexPath.row; i++) {
NSIndexPath *currentIndexPath = [NSIndexPath indexPathForRow:i inSection:0];
CustomCell *currentCell = [todoTable cellForRowAtIndexPath:currentIndexPath];
[currentCell.queueNumber setText:[NSString stringWithFormat:#"%i", currentIndexPath.row + 1]];
}
}
You should not configure your tableview cell a.k.a customCell in moveRowAtIndexPath method, instead, just updating the data-model array for the relocated row.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath {
NSString *stringToMove = [self.queuedToDoArray objectAtIndex:sourceIndexPath.row];
[self.queuedToDoArray removeObjectAtIndex:sourceIndexPath.row];
[self.queuedToDoArray insertObject:stringToMove atIndex:destinationIndexPath.row];
}
After that, just call [self.tableView reloadData] and it will automatically do that for you.
Please check out the Apple Developer Document for more details.
Edit:
A better solution is just reloading the relative sections or rows as #Paulw11 commented.
I intended to add items to a UITableView when this method was called. New items are successfully added (but there's a problem, mentioned below), but I think its odd because I thought "begin updates" to "end updates" was supposed to handle this (Inserting a new row). The initial if condition I had put in never ran so the whole area never got executed. I only realized this recently and updated the condition to what it is now. Now the if block get executed and it crashes the app.
When it is commented out like it is now... New items are added but the newNameOfItem replaces any existing cell labels.
I would like this to add x(newNumberOfItems) new items preferably into a new section each time its called. How can I achieve this?
- (void)addNew:(NSString *)newNumberOfItems :(NSString *)newNameOfItem
{
if(!self.numberOfRows){
NSLog(#"Initially no of rows = %d", self.numberOfRows);
self.numberOfRows = [self.numberOfItems intValue];
NSLog(#"Then no of rows = %d", self.numberOfRows);
}
else
{
self.numberOfRows = self.numberOfRows + [newNumberOfItems intValue];
NSLog(#"New no rows = %d", self.numberOfRows);
}
NSLog(#"run = %d", self.run);
Begin updates if statement ...
/*if(self.secondRun){
NSLog(#"run = %d it it", self.run);
[self.tableView beginUpdates];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:self.numberOfRows-[newnumberOfItems intValue] inSection:0];
[self.tableView insertRowsAtIndexPaths:#[indexPath]withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
}
*/
[self.tableView reloadData];
}
...
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"UITableViewCell" forIndexPath:indexPath];
cell.textLabel.text = self.nameOfItem;
return cell;
}
...
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.numberOfRows;
}
If you want to add new items to a new section every time you call -addNew…, you should create an NSMutableArray of sections where each member is an array of objects representing row data (in this case seems like you'd want NSStrings that represent the item's name. The structure would look something like:
mySections = #[ #[#"section 0 row 0 name", #"section 0 row 1 name", …], #[#"section 1 row 0 name", #"section 1 row 1 name", …], …]
Then in numberOfRowsInSection: return mySection[indexPath.section].count.
Each label has the same value because you're setting every single label for every cell that you dequeue to self.nameOfItem. It's doing exactly what you told it to do. If your intent is to set a different text for every section/row, you have to fetch that text from somewhere. If you created a mySections array as above, you could:
cell.textLabel.text = mySections[indexPath.section][indexPath.row] ;
A note about -addNew:…: simply adding new items to your mySections array will not cause the tableview to update. As you know above, [self.tableView reloadData] will do this for you. However, it will reload the entire table instead of just updating the rows that you added. To do this more efficiently (and with a nice animation), you instead use [self.tableView beginUpdates/endUpdates]. In the case above, where you're adding entire sections and not just rows, you should use insertSections:withRowAnimation:.
Using this code
- (IBAction)testAdd:(id)sender
{
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:self.numberOfRows inSection:0];
[self.tableView beginUpdates];
self.numberOfRows++;
[self.tableView insertRowsAtIndexPaths:#[indexPath]withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
}
I'm able to add a new item to a tableView via an 'add' button on the app. This basically adds an item identical to the item already on the table that preceded it.
For example, I have a tableview with the first row displaying a string "TEST", hitting add adds another row that displays "TEST".
I would like to be able to pass in a custom value for the new row, so hitting add outputs a row with say "NEWTHING".
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"UITableViewCell" forIndexPath:indexPath];
// Configure the cell...
cell.textLabel.text = self.val2;
return cell;
}
My data source is actually another view controller that takes user inputs and sends it to my tabelViewController, with the text for the item as "val2".
What I actually want to achieve is the ability to hit add, go back to the user input view controller, get the new data and send it back to my tableViewController to be displayed
What you're asking, is the kinda stuff that is to be done in -cellForRowAtIndexPath: (most of the times, it depends on the way you have designed your datasource) but if it doesn't matter to you, then you can do:
- (IBAction)testAdd:(id)sender
{
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:self.numberOfRows
inSection:0];
self.numberOfRows++;
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
[cell.textLabel setText:#"NEWTHING"];
}
But note that when you scroll far up/down and return to this cell, it will most probably show "TEST" (that's where -cellForRowAtIndexPath: will show it's true purpose)
PS: Include your -cellForRowAtIndexPath: method implementation in the question if you want to proceed further
EDIT:
Your -cellForRowAtIndexPath is too static... in the sense that it simply sets self.val2 to cell.textLabel.
Lets say you start with 10 rows, -cellForRowAtIndexPath will be called 10 times and every time, it will set self.val2 onto the current cell's textLabel.
Now... when you add one row (on a button tap), the -cellForRowAtIndexPath will be called for the 11th cell and the same* text will be set to it.
*this technically happened but we quickly changed the cell's text
Basically, the tableView doesn't know how to differentiate between an existing cell and a new added cell because the datasource itself is not dynamic.
To direct the tableView on how to handle different cells, we need to create a more dynamic datasource.
There are different approaches use but I'd generally do it this way:
- (void)viewDidLoad
{
[super viewDidLoad];
self.val2 = #"TEST";
//declare "NSMutableArray *arrDatasource;" globally
//this will be the soul of the tableView
arrDatasource = [[NSMutableArray alloc] init];
int i_numberOfCells = 10;
//populate beginning cells with default text
for (int i = 0; i < i_numberOfCells; i++) {
NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
[dictionary setObject:self.val2 forKey:#"displayText"];
[arrDatasource addObject:dictionary];
}
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
//return number of objects in arrDatasource
return arrDatasource.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"UITableViewCell" forIndexPath:indexPath];
//pick up value for key "displayText" and set it onto the cell's label
[cell.textLabel setText:arrDatasource[indexPath.row][#"displayText"]];
//this will be dynamic in nature because you can modify the contents
//of arrDatasource and simply tell tableView to update appropriately
return cell;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
//make indexPath of new cell to be created
NSIndexPath *indexPathNEXT = [NSIndexPath indexPathForItem:arrDatasource.count inSection:0];
//add the appropriate contents to a dictionary
NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
[dictionary setObject:#"NEWTHING" forKey:#"displayText"];
//add the dictionary object to the main array which is the datasource
[arrDatasource addObject:dictionary];
//add it to tableView
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:#[indexPathNEXT]
withRowAnimation:UITableViewRowAnimationAutomatic];
[self.tableView endUpdates];
//this ends up calling -cellForRowAtIndexPath for the newly created cell
//-cellForRowAtIndexPath shows the text (you put in the dictionary in this method above)
}
PS: -cellForRowAtIndexPath: is called whenever cell updates or refreshes or needs to be displayed and so this method needs to be implemented properly
I have a "UITableView", I am trying to handle selected row and use its data accordingly,
I have written necessary code to take the selected row, unfortunately it seems it does not work
If i select nothing,
NSIndexPath *path = [tableViewDoctorName indexPathForSelectedRow];
int rowSelected = path.row;
rowSelected's value is 0;
But, when i select the row it is again 0.
I have only one row in a table, i am not sure does it matter?
How can i accurately determine the selected row in a "UITableView"?
Set the UITableView delegate and implement this method:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
int rowSelected = indexPath.row;
}
indexPath.row start with 0 for first row, And you have only one row then it return always 0;
But if you want to get data of selected Row then you delegate method of UITableView.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// here you can get directly indexPath.row so you can get required data;
}
Of course how many rows you have in your tableView matters : if you only have 1, then its indexpath is (0 ,0) and this is the only one that can be (selected) in this case.
The selected row generally is highlighted (in blue) so you might want to store it in another property of your tableView delegate, if you don't want this blue selection to stay on-screen.
Typically, in your UITableViewDelegate :
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// deselect the row, to avoid the 'blue' selection to stay on-screen
[tableView deselectRowAtIndexPath:indexPath animated:YES];
// save your own copy of 'last' selected indexPath
self.mySavedIndexPath = indexPath;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
_selectedIndexPath = indexPath;
}
In outside the function,
use this to get selected row,
NSIndexPath *indexPath = [NSIndexPath indexPathForRow: _selectedIndexPath.row inSection:0];
int rowSelected = indexPath.row;
I have a tableView with sections, which could be opened and closed. So, when I tap on a section to open it, it is getting filled up with cells and -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) get called exactly as much times as I provided in -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section.
Is that correct? Shouldn't it be just number of visible cells?
Because in my case I have bad situation: I have a lot of custom cells (50~100 cells) and calling -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) for each cell slows down the opening of a section, cause each time reading from nib is performed and cell content is being populated with image.
I've check visibility of cell inside -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) like this:
if ([[self.tableView indexPathsForVisibleRows] containsObject:indexPath])
NSLog(#"visible %#", indexPath);
and it shows that from out of 45 cells, only 6 or 7 are visible. Others are out of visible area. But creating cells still performed.
Here is the code:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"IVCell";
IVCamera *camera = [server.cameras objectAtIndex:indexPath.row];
IVServerListViewCell *cell = (IVServerListViewCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:#"IVServerListCell" owner:self options:nil];
cell = (IVServerListViewCell*)_tableViewCell;
self.tableViewCell = nil;
}
[cell textLabel].text = camera.cameraName;
cell.preview = camera.preview;
cell.userData = camera;
cell.isEnabled = (server.isInactive)?NO:camera.isOnline;
return cell;
}
Is it still correct? Or am I missing something?
increase your
estimatedRowHeight of UITableview.
Well, I somehow dealt with my problem. Here are my ideas and thoughts how I came to the solution. Maybe it could be helpful to somebody.
I've instructed memory allocations and call stack using Instruments during opening section events. It showed me, that the majority of time is spent on loading cell from nib file.
Firstly, that I've done was reducing the size of nib file, i.e. minimizing the number of views used in custom tableview cell (now its only 2 views and 2 labels, instead of 6 views, 2 images and 2 labels before). It gave me some improve in cells loading. Apple documentation suggests to use as few as possible views and do not use transparency. So be attentive to these suggestions.
Secondly, as I discovered earlier, that not all cell are visible which are created by -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *), I decided to reduce somehow the number of loadings new cells from nib file. To achieve this, I've came to simple idea: return blank default cells for invisible rows, while load custom cells from nib for visible ones. Here is the piece of code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if ([self index:indexPath isInvisibleInTableView:tableView])
return [self getBlankCellForTableView:tableView];
// the rest of the method is the same
...
}
-(BOOL)index:(NSIndexPath*)indexPath isInvisibleInTableView:(UITableView*)tableView
{
NSMutableArray *visibleIndexPaths = [self getExtendedVisibleIndexPathsForTableView:tableView];
return ![visibleIndexPaths containsObject:indexPath];
}
-(UITableViewCell*)getBlankCellForTableView:(UITableView*)tableView
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"IVBlankCell"];
if (!cell)
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"IVBlankCell"] autorelease];
return cell;
}
As you can see, I'm not using just -(NSArray*)indexPathsForVisibleRows method of tableview for detecting visible cells. Instead, I've wrote my own method -(NSMutableArray*)getExtendedVisibleIndexPathsForTableView:(UITableView*)tableView. It was necessary because for some reason, when using -(NSArray*)indexPathsForVisibleRows the cells that are next to the last one visible cell or the cells that are previous to the first one visible cell were created as blank cells and looked like empty cells while scrolling. To overcome this, in -(NSMutableArray*)getExtendedVisibleIndexPathsForTableView: (UITableView*)tableView i'm adding border cells to the visible array cells:
-(NSMutableArray*)getExtendedVisibleIndexPathsForTableView:(UITableView*)tableView{
NSArray *visibleIPs = [tableView indexPathsForVisibleRows];
if (!visibleIPs || ![visibleIPs count])
return [NSMutableArray array];
NSIndexPath *firstVisibleIP = [visibleIPs objectAtIndex:0];
NSIndexPath *lastVisibleIP = [visibleIPs objectAtIndex:[visibleIPs count]-1];
NSIndexPath *prevIndex = ([firstVisibleIP row])?[NSIndexPath indexPathForRow:[firstVisibleIP row]-1 inSection:[firstVisibleIP section]]:nil;
NSIndexPath *nextIndex = [NSIndexPath indexPathForRow:[lastVisibleIP row]+1 inSection:[lastVisibleIP section]];
NSMutableArray *exVisibleIndexPaths = [NSMutableArray arrayWithArray:[tableView indexPathsForVisibleRows]];
if (prevIndex)
[exVisibleIndexPaths addObject:prevIndex];
[exVisibleIndexPaths addObject:nextIndex];
return exVisibleIndexPaths;
}
Thereby, I've reduced the time of opening sections with large number of custom cells, which was proved by Instruments tracing and felt while experiencing the app.
Simply add estimated height for UITableViewCell
Problem In my case was: cellforRowAtIndexPath was getting called array.count number of times, whereas, displayed cells where less than array.count.
To resolve this issue, I have just replaced,
(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
with,
(CGFloat)tableView:(UITableView )tableView estimatedHeightForRowAtIndexPath:(nonnull NSIndexPath )indexPath;
check your tableview size.
may be that your tableview height is very large that it keep loading cells until your cell fills all tableview size..
This seems correct yes. the idea about optimizing the loading itself lies within how "dequeueReusableCellWithIdentifier" works.
if u are loading the image from a remote location this is where u would want to optimize the code. but not from the loading of cells as this looks correct here.
I used some similar technique but since indexPathsForVisibleRows is sorted you don't need to use containsObject. Instead you can just do:
//
// Checks if indexPath is visible in current scroll state, we are expanding bounds by 1
// because the cells that are next to the last one visible or the cells that are previous
// to the first one visible could look empty while scrolling.
//
- (BOOL)isIndexPathVisible:(NSIndexPath *)indexPath
{
NSInteger row = [indexPath row];
NSArray *visible = [self.tableView indexPathsForVisibleRows];
NSInteger count = [visible count];
NSInteger first = (count > 0) ? MAX([visible[0] row] - 1, 0): 0;
NSInteger last = (count > 1) ? [visible[1] row] + 1: first + 2;
return row >= first && row <= last;
}
By the way; this assumes that you are using only one section. It won't work for more than one section.
Adding an else solved my problem.
Where I reseted any changes that were made to the cell.
if (! self.cell) {
self.cell = [[LanguageCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
self.cell.accessoryType = UITableViewCellAccessoryNone;
}
else
{
self.cell.checkImage.image = NO;
}