I have a UITableView with pagingEnabled. Each cell takes up the viewing area of the table. Meaning, each cell is the same height and width as the table. I'm using custom cells that have a name property. I'd like to display the name of the current (viewable) cell in a label. This works fine for the first and last cells but anything inbetween isn't so easy. The problem is that cellForRowAtIndexPath is called twice for these middle cells. Here's what it looks like scrolling from the first to last cell and then back. I've listed the indexes in order as cellForRowAtIndexPath fires for that row:
Row indexPath.row
0 0 //view loads and table appears
1 1,2 //user scrolls to second cell. cellForRowAtIndexPath fires twice. First time indexPath.row is one and second time it is two. This causes cell two's name to display in the label, rather than cell one.
2 2,3
3 3
//user starts scrolling back to first cell
2 1,2
1 1,0
0 0
I could set use an NSDate object to detect if I'm in a middle row. By diffing the previous time with current, I'll know. However, if the user scrolls really fast through the cells, that probably doesn't work. Is there another way to do it?
I've tried using variations of visiblecells properties but that didn't work. The UITableView will load the next cell even if it isn't visible, causing it to be part of the visible cells.
Well, on the off chance that you never figured out a solution, or for whoever comes to this question next, I'll provide you with the answer you were looking for. UITableView will provide you with the indexPaths you are looking for, and then UITableView will happily provide you with the cells that match those index paths:
UITableView *tableView = self.tableView; // Or however you get your table view
NSArray *paths = [tableView indexPathsForVisibleRows];
// For getting the cells themselves
NSMutableSet *visibleCells = [[NSMutableSet alloc] init];
for (NSIndexPath *path in paths) {
[visibleCells addObject:[tableView cellForRowAtIndexPath:path]];
}
// Now visibleCells contains all of the cells you care about.
Converted Douglas example to Swift:
let tableView = self.tableView // Or however you get your table view
let paths = tableView.indexPathsForVisibleRows
// For getting the cells themselves
let visibleCells : NSMutableSet = []
for path in paths! {
visibleCells.addObject(tableView.cellForRowAtIndexPath(path)!)
}
Rather than focusing on when the UITableView requests a cell, you should be focusing on when it displays the cell, which is indicated by the delegate method tableView:willDisplayCell:forRowAtIndexPath.
Simple and elegant way to retrieve visible cells of UITableView, no need to get visible cells by using indexpath values
NSArray * visibleCells = tableView.visibleCells;
NSLog(#"Total visible Cells: %i", [visibleCells count]);
If indexpath's of visible cells are needed
NSArray * paths = [tableView indexPathsForVisibleRows];
Swift 4+
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let firstVisibleIndexPath = self.tableView.indexPathsForVisibleRows?[0]
print("top visible cell section is \([firstVisibleIndexPath!.section])")
}
Related
I am new to iphone.I have a small doubt that is,I have a table view with 66 rows initially i placed a progress view to all rows but in viewdidload i set it to hidden for all those like below in tableViewClass(ShowProgressViewCont)
cell.progressView.hidden = YES;
here (cell) is the the reference of the CustomCell class.In this class i declare a progress view and setter and getter properties also be set here in this class
here in tableview there is a download button in each cell.If we click on that download button(for example in 66th cell).we have to remove the hidden property to the progress view for that particular 66th cell only.The remaining 65 cells should have the progress view in hidden only like that for all cells.
If any body know this please help me....
Are you familiar with the concept of table cells being reused?
viewDidLoad is not an appropriate place to manipulate the content of a single cell. It may work fine if the table is so small that all of its cells fit on the screen (in both orientations).
When there are more cells in the table than beeing displayed on the screen, then those cell that became invisible recently is being reused and displayed again.
So if there are 6 cells on the screen at a time then table cell no. 7 (sometimes 8) will be identical with cell no. 1.
cellForRowAtIndexPath would be a better place to hide/unhide certain views of a cell.
If it is a custom cell already then the cell's layoutSubViews could be appropriate, too. However, only in the tableViewController's cellForRowAtIndexPath you will have easy access to both, the table's data and the associated cell.
cellForRowAtIndexPath is called every time when a cell is about to become visible. Use the default reusing-mechanism to ensure that a proper cell object will be reused. It is pretty much straight forward.
Get the cell at index 65 and then cast it to your custom cell
UITableViewCell *cell = [tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:64 inSection:0]];
YourCustomCell *customCell = (YourCustomCell *)cell;
customCell.progressView.hidden = NO;
First set the row number in your download button in CellForRowAtInedexPath
downloadButton.tag = indexPath.row
[downloadButton addTarget:self action:#selector(actionDownload:) forControlEvents:UIControlEventTouchUpInside];
in actionDownload, make the IndexPath from button.tag and get the cell from "cellForRowAtIndexPath:",
finally update via reloadRowsAtIndexPaths: withRowAnimation:
Hide your progress view in your custom cell means make the default property of every progress view is hidden ,and then your button click method .
CutomeCell *cell = (CutomeCell *)[[button superview] superview];
[cell.progressView setHidden:NO];
NSIndexPath *rowToReload = [[self tableView] indexPathForCell:cell];
NSArray* rowsToReload = [NSArray arrayWithObjects:rowToReload, nil];
[UITableView reloadRowsAtIndexPaths:rowsToReload withRowAnimation:UITableViewRowAnimationNone];
may this help you ...
your model should be tracking the progress for every button clicked. for purposes of this answer, let's say the model is held in a property called modelInformationArray (which would contain an array of objects that relate to each cell in the table)
when the download button is clicked for a cell, modelInformationArray is modified in such a way that its object knows a download is being processed for it.
that object reports the downloading processing in a member called downloadingProcessingStarted. there are many other ways to do that part.
to get to the answer to your question … to then unhide the progress view, you would do something as follows in your UITableViewDataSource implementation of tableView:cellForRowAtIndexPath: .
- (UITableViewCell*)tableView:tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath {
YourCustomCell* cell = ...
if ([[self.modelInformationArray objectAtIndex:indexPath.row] downloadingProcessingStarted])
cell.progressView.hidden = NO;
}
I want my tableView to show 6 rows with text in it, in this case "Example." As far as I can tell, I have my numberOfSectionsInTableView: and numberOfRowsInSection: set properly. See example code below:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
// Return the number of rows in the section.
return 6;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
cell.textLabel.text = #"Example";
return cell;
}
The problem is when you see the image below showing lines for rows that shouldn't/don't exist.
How do I get rid of the lines showing past row 6?
The generally accepted way of doing this is to add a footer view with a frame size of CGRectZero, as such:
[tableView setTableFooterView:[[UIView alloc] initWithFrame:CGRectZero]]
What this does is tell the table that there is a footer, and so it stops displaying separator lines. However, since the footer has a CGRectZero as its frame, nothing gets displayed, and so the visual effect is that the separators simply stop.
Swift Version
The easiest method is to set the tableFooterView property:
override func viewDidLoad() {
super.viewDidLoad()
// This will remove extra separators from tableview
self.tableView.tableFooterView = UIView(frame: CGRect.zero)
}
This is Because of Your Table-view Height. Weather you have Write
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
// Return the number of rows in the section.
return 6;
}
But its show rows According to Table-view Size. If you Dont want to show This extra Lines then Make UITableView Style Plain To Grouped.
Short and simple answer..
self.tableView.tableFooterView = [UIView new];
You could do something along the lines of:
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:7 inSection:0];
[self.mytableView cellForRowAtIndexPath:indexPath].hidden = YES;
Im sure there are some better ways but this is the first thing that came to mind.
If you're referring to the light gray lines that appear below the last row, that's simply the default way a UITableView draws the row separator.
You could try changing the Separator style in Interface Builder (see the images below) to see if one of those might be more to your liking.
You didn't say what you do want to see past the last row. If you just want to see the window background, then just embed your table view in a UIView that's just tall enough to show the number of rows you want to see. If you want to see more rows without scrolling, then you would have to adjust the size of that containing view based on the number of rows.
To programmatically remove it, use this:
[yourTableView setSeparatorStyle:UITableViewCellSeparatorStyleNone];
It's a lot easier to:
return numberOfSections + 1
return 0 rows in the final section
This keeps it simple!
I have a UITableView where every cell either gets/loses a checkbox or goes to another table view when clicked. For every table, I want to add a check all button that checks off every cell in that table and all the ones inside it. How do I allow one UITableViewCell to toggle the checkbox of every one in it's TableView?
EDIT: Removing the last index in the index path, and replacing it by the new row number, I'm able to go through the entire table and check it off, like this:
for(int i = 0; i < [tableView numberOfRowsInSection:0]; i++){
UITableViewCell *newCell = [tableView cellForRowAtIndexPath:[[indexPath indexPathByRemovingLastIndex]
indexPathByAddingIndex: i]];
newCell.accessoryType = UITableViewCellAccessoryNone;
}
Oddly, it skips over every tenth cell or so - and it's not even consistent. For a list of years, sometimes it doesn't check off 2003 and 1993, sometimes 2003 and 1991, and and so on. It's always around every tenth cell or so, but I can't find a pattern.
When you click the cell didSelectRowAtIndexPath will be called, at that point all you gotta do is use tableView cellForRowAtIndexPath:indexPath method in order to get back all your cells one by one and set their accessory type to checkmark...hope this helps
EDIT: Another way to do it is, if you have maybe some sort of array (hard to tell you what to do exactly without looking at your code), but if you have some array that holds values as to which cells need have check marks on them, then you can use in cellForRowAtIndexPath to assign the checkmark accessory, so when your cell is selected, you can set all the values in the array to what you need them to be and just call UITableViews reloadData...hope that made sence :), heres a little snipet of code to try and make it more clear
lets assume you have 1 section and x amount of rows
NSMutableArray shouldHaveCheckmark; //this array will be of size x
//(one for each row) and hold NSNUmbers 0 means not checked 1 means checked you initialize
//this somewhere (viewDidLoad maybe) and should be declared in your .h file
//this is cellForRowAtIndex path
-(UITableViewCell)cellForRowAtIndexPath:(NSIndexPath*)path
{
UITableViewCell *cell=...
if([[shouldHaveCheckmark objectAtIndex:path.row] boolValue] )
//assign checkmark accesory
//other code
return cell;
}
So you can see in didSelectRowAtIndexPath you can just flip the numbers in the array and call reloadData on the tableView...that approach will work as well
The standard Grouped UITableView style allows UITableViewCells to be drawn with rounded corners at the top and bottom of each section. How is this accomplished? How does the cell know its own location within its section, and how does it know when to change its rounded edges?
I want to make my own rounded cells, and I have images to use, but don't know when to show which image
Note: I already know how the UITableView works, and I know how to use it. I just thought that since a UITableView is able to automatically draw rounded corners at the correct places, I should be able to as well, without needing to add anything to my data source or delegate.
NSIndexPath *indexPath = [(UITableView *)self.superview indexPathForCell: self];
int rows = [(UITableView *)self.superview numberOfRowsInSection:indexPath.section];
if (indexPath.row == 0 && rows == 1) {
// the one and only cell in the section
}
else if (indexPath.row == 0) {
//top
}
else if (indexPath.row != rows - 1) {
//middle
}
else {
//bottom
}
It's very simple. suppose cell is the object, whose position is to be found out.
UITableView* table = (UITableView *)[cell superview];
NSIndexPath* pathOfTheCell = [table indexPathForCell:cell];
NSInteger sectionOfTheCell = [pathOfTheCell section];
NSInteger rowOfTheCell = [pathOfTheCell row];
There is sectionLocation method of UITableViewCell that returns integer telling you what you need:
1 - middle cell
2 - top cell
3 - bottom cell
4 - single cell
I had no issues using this in several production apps since 2010.
UPDATE: one of our binaries was automatically rejected recently (end of 2018) because we were using 'sectionLocation' property, so it's not a good option anymore.
Add something like this into your header files and you can use it:
typedef NS_ENUM(NSInteger, MMMTableViewCellLocation) {
MMMTableViewCellLocationUndefined = 0,
MMMTableViewCellLocationMiddle = 1,
MMMTableViewCellLocationTop = 2,
MMMTableViewCellLocationBottom = 3,
MMMTableViewCellLocationSingle = 4
};
#interface UITableViewCell ()
/** Undocumented method of UITableViewCell which allows to know where within section the cell is located,
* so the cell can draw its borders properly. */
- (MMMTableViewCellLocation)sectionLocation;
/** Override this one to know when the value of sectionLocation changes. */
- (void)setSectionLocation:(MMMTableViewCellLocation)sectionLocation animated:(BOOL)animated;
#end
You can use
- (NSIndexPath *)indexPathForCell:(UITableViewCell *)cell
for this issue. In my example I am using this to scroll the cell (with custom content) to the top of the view.
If you need more robust and general stuff, take a look at http://cocoawithlove.com/2009/04/easy-custom-uitableview-drawing.html - Matt Gallagher shows what you need, pretty effectively. He basically recreates UITableViewController from UIViewController, while adding ability to use your own custom graphics. I'm just working on applying this to one my projects, so far it looks it would do the job.
Unfortunately, I have found no solution to this problem, and have resorted to subclassing UITableViewController and UITableViewCell into a generic solution that I can extend as necessary.
You don't do this in cell. Rounded corners are drawn in [tableView viewForHeaderInSection] and viewForFooterInSection.
The way I do it is to use Plain tableview style, then use these two views for roundness and cells are normal, no rounds.
Without getting into who draws what, you can know which cell is the last cell in its section inside of cellForRowAtIndexPath very easily.
You're passed in the indexPath of the cell you need to provide, right? You're also passed the tableView.
call [tableView numberofRowsInSection:indexPath.section] and if it's == ([indexPath.row]-1) you know you're being asked to supply the last cell in that section.
At the time that cellForRowAtIndexPath is being called, the cell is guaranteed to be at the indexPath passed in.
To expand upon Darren's answer (which I found most useful, thanks Darren!), what you can do is to iterate through all of the superviews' until you find the parent UITableView. This should be future proof since you do not rely on a fixed hierarchy of views.
I use a recursive method that will return the UITableView if it finds one or return nil if there is none.
- (UITableView *)parentTableViewOf:(UIView *)view {
Class class = [view.superview class];
NSLog(#"Class : %#", NSStringFromClass(class));
if([view.superview isKindOfClass:[UITableView class]]) {
return (UITableView *)view.superview;
} else {
return [self parentTableViewOf:view.superview];
}
return nil;
}
So far I've used this one and it seems to work without hiccups. Hope it helps! :)
The cells dont know where they go...The table view has cells, You are the one telling the table view WHAT goes in the cell. You do this in the DataSource where you implement cellForRowAtIndexPath...The way this works :
An index path has a row and a section
For a grouped table view
A section pertains to a group, and a row pertains to 1 entry in that section,
the way UITableView knows how many rows are in a section and how many sections there are is the DataSources methods numberOfSectionInTableView and the method numberOfRowsInSection, this will make the right calls to cellForRowAtIndexPath, it is up to you to recognize which section and row is being queried and you need to build your cell according to these specifications.
A good way to do this i s you can have a Dictionary with keys of section names and values of NSArray with the values that go in that section.
So you implementation for numberOfSectionsInRows would look like
return [[dictionary allKeys] count]
And the implmentation of numberOfRowsInSection would look like
NSString* key=[[dictionary allKeys] objectAtIndex:sectionNumber]
return [[dictionary objectForKey:key] count]
You can always refer to the UITableView programming guide at http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/TableView_iPhone/Introduction/Introduction.html
Hope that helps
Simply add a property to your custom UITableViewCell (depending on implementation) class that contains an int, NSNumber, or an NSIndexPath specifying which one it is. In you're using a data structure instead, then put it in you element in that data structure. Then you simply set the property when you create the data structure, something like elt.id=i, and then you access it in the cellForRowAtIndexPath, something like if (elt.id == 0 || elt.id == n-1) where n is the number of rows in your section.
I might have totally missed your question, but if I did, just comment and I'll post again.
I have a tableView that needs to be updated after information has been inserted from another view. If I perform a
[self.tableView reloadData];
The very next time I insert more information in another view and try to reload the table, all the currently visible rows are duplicated.
In other words, when I start up the app I have:
tableView:
Row 1
Row 2
Then I submit some information that will also show up in the table and suddenly I have:
tableView
Row 1
Row 2
Row 3 <- info I just added
Row 1
Row 2
My numberOfRowsInSection implementation looks like this:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [ItemsController sharedItemsController].count;
}
My cellForRowAtIndexPath implementation looks like this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
ItemsController* controller = [ItemsController sharedItemsController];
NSMutableArray* recentItems = controller.listOfRecentItems;
CustomCell *cell = nil;
NSUInteger row = [indexPath row];
if( row < recentItems.count )
{
Items* item = [recentItems objectAtIndex:row];
if( recentCellData == nil )
recentCellData = [[NSMutableDictionary alloc] initWithCapacity:[indexPath length]];
if( [recentCellData count] > 0 )
cell = [recentCellData objectForKey:[NSString stringWithFormat:#"%d", row]];
if (cell == nil) {
UIViewController * view1 = [[UIViewController alloc] initWithNibName:#"CustomCell" bundle:nil];
cell = (CustomCell*)[view1 view];
[recentCellData setObject:cell forKey:[NSString stringWithFormat:#"%d",row]];
}
// do some other stuff here
}
// Set up the cell
return cell;
}
What's the best way to update the table and avoid duplicating the currently visible rows.
Thank in advance for all the help!
The error isn't in how you're reloading the table, it's in how you're providing data to it. Set a breakpoint in the data source methods and the method that adds new rows to see where you're going wrong.
You'll only end up with five items if tableView:numberOfRowsinSection: returns 5. Thats the simple answer to your question, but I see other problems here. I'm wondering why you have this test: row < recentItems.count. Is that array the same thing as [ItemsController sharedItemsController].count? You really need to be using the same array for both methods.
(Also, it's not a syntax error, but you shouldn't use the property syntax for things that aren't declared as properties. You should write [recentItems count] instead.)
I'm also confused by the code you use to set up the cell. Cells are meant to be reusable. That is, you create one cell, then reconfigure it every time in your implementation of tableView:cellForRowAtIndexPath:. Your code creates a cell for each item in your list. This is very memory-inefficient, and will likely crash your program due to insufficient memory on the iPhone if you keep lots of cells in memory like this.
The recommended approach is to call dequeueReusableCellWithIdentifier:. If that returns nil, then you set up a cell using the initWithFrame:reuseIdentifier: initializer. The table view is very smart, and will only ask you to redraw the cell when it needs you to.
Your recentCellData dictionary looks really shaky to me, too. What if you insert an item after the item with key #"2"? All the items with key #"3" onward will need to be shifted one element to the right to work the way you expect. That's a ton of bookkeeping that seems rather unnecessary to me. If you really needed something like this -- and to be clear, I don't think you do -- why wouldn't you use an NSMutableArray, which is much easier to use?
I added a bit more info above.