In my app, I have a detailed view where the user can edit attributes of for example a person, their name, address etc.
In two cells, rather than being able to select them to edit their contents, they have a right accessory, a UISwitch, however sometimes, its inconsistent, but they replicate onto other cells in my last section.
I have been scanning my code dozens of times over with a fine comb and can't find the damn cause. What might cause this? Here is the code that I use to create the UISwitch on just a single cell:
if (indexPath.section == 0 && indexPath.row == 1)
{
cell.textLabel.text = #"Confirmed";
//Make the cell unselectable
[cell setSelectionStyle:UITableViewCellSelectionStyleNone];
//Create and add uiswitch
confirmedSwitch = [[UISwitch alloc] initWithFrame:CGRectZero];
[confirmedSwitch addTarget:self action:#selector(switchConfirmedStatus:) forControlEvents:UIControlEventValueChanged];
[confirmedSwitch setOn:[venue.isConfirmed boolValue]];
cell.accessoryView = confirmedSwitch;
}
So you expect it to only show up on that cell, see anything odd with that code? I have checked my if statements and all my brackets indexPath checks are correct.
Anyone see this before or have any clues?
The problem is because of reusability issues in the UITableView. You probably use the same identifier for all cells and this causes the cellForRowAtIndexPath to be implemented in other rows (when you scroll up and down).
This is a common problem when you are developing applications with tableView and there are plenty of questions like this on StackOverflow.
As a general solution, you will need to do either of these.
Use different identifiers when you assign dequeueReusableCellWithIdentifier for each cell. This is fairly simple, and you just need to assign different identifiers for them.
Subclass you UITableViewController, and create your own CustomTableViewController which will implement the necessary components in the cell. I believe you will need to override the set Layout Subviews method.
Take a array in view will appear and add object 0 for this row and 1 for all other rows and then in cellForRowAtIndexPath check if array has 0 at that index if it has then put switch otherwise nill..
for(int i =0;i<10;i++)
{
if(i==1)
{
[arrayForSwitch addObject:#"0"];
}
else
{
[arrayForSwitch addObject:#"1"];
}
}
then in cellForRowAtIndexPath write condition
if([arrayForSwitch objectAtIndex:indexPath.row isEqualToString:#"0"])
{
cell.accessoryView = confirmedSwitch;
}
else
{
cell.accessoryView =UITableViewCellAccessoryNone;
}
it will now remain same
Related
I'm trying to make a UITableView like the native calendar app:
but I'm trying to learn the best way to do this. I'm able to get this for the most part with a switch statement in the cellForRowAtIndexPath method, but I'm having troubles changing the textColor when a cell is selected.
For some reason cell.isSelected is always NO, and I have no way to reload the tableview after another cell is selected anyway.
Should I subclass UITableViewCell for something this simple and store an array of cells?
Any help would be appreciated, thanks.
There is no need to subclass, as stated in the app doc the delegation function:
tableView:willSelectRowAtIndexPath:
should do the trick
EDIT:
Below you find some code that should demonstrate the idea of using the delegate. Please note that this code is untested, as i am currently not in front of my xcode.
-(void)willSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if (prevIndexPath != nil) {
UITableViewCell* prevCell = [self.tableView cellForRowAtIndexPath: prevIndexPath];
prevCell.textLabel.textColor = [UIColor black]; // your initial color here
}
UITableViewCell* cell = [self.tableView cellForRowAtIndexPath: indexPath];
cell.textLabel.textColor = [UIColor green];
prevIndexPath = indexPath;
}
Make sure to set the UITableViewDelegate protocol to your controlling class that manages your TableView and set the tableViews.delegate to that.
To make this code run, you also have to define a property or variable with the name prevIndexPath. This ones holds the previously selected cell that is needed to revert to the cell to its initial color.
This is related to another question of mine which wasn't answered in a helpful way (message when a UITableView is empty).
I'm trying to show an UIImage graphic that says You haven't saved any bookmarks over an UITableView when it's empty. I have NSNotification set-up so that when bookmarks are added or deleted, a message is sent so that the UITableView can be updated.
I've been trying to do it with this code. Why won't this work?
- (void)bookmarksChanged:(NSNotification*)notification
{
[self.tableView reloadData];
UIImageView* emptyBookmarks = [[UIImageView alloc] initWithFrame:CGRectMake(75, 100, 160, 57)];
emptyBookmarks.alpha = 1;
emptyBookmarks.image = [UIImage imageNamed:#"emptyBookmark.png"];
[self.view addSubview:emptyBookmarks];
[emptyBookmarks release];
if ([self.dataModel bookmarksCount] == 0)
{
emptyBookmarks.alpha = 1;
}
else
{
emptyBookmarks.alpha = 0;
}
}
I'm probably approaching this the wrong way... But if salvageable, what am I doing wrong?
When I initially have an empty bookmarks tableview, there's no image displayed. After I add a bookmark and then delete it, the image shows. Grrh.
Another way (and IMO the correct way) to do this is to manipulate the backgroundView property on the UITableView.
While making a single cell with a custom image cell would certainly works, I think it overly complicates the logic of your UITableViewController's data source. It feels like a kludge.
According to UITableView documentation:
A table view’s background view is automatically resized to match the
size of the table view. This view is placed as a subview of the table
view behind all cells , header views, and footer views.
Assigning an opaque view to this property obscures the background color
set on the table view itself.
While you probably don't want to just set it to your UIImageView, it is very easy to make a UIView that contains the UIImageView that you want.
Well first off if you were going to do it that way, you would need to reload the tableView after updating the image or model etc. and not before.
But you are probably making things more complicated than they need to be!
Why not just check to see if the data for section 0 and indexPath.row 0 are empty and if so in cellForRowAtIndexPath display a text message accordingly.
// First make sure there is always one row returned even if the dataModel is empty.
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSInteger numRows = 0;
if ([self.dataModel lastObject]) {
// Return the number of rows in the section.
numRows = [self.dataModel count]; // etc.
}
if (numRows < 1) numRows = 1;
return numRows;
}
// Then display the data if there is some, otherwise a message if empty.
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
if ([self.dataModel lastObject]) {
// setup the cell the normal way here.
} else { // the datasource is empty - print a message
cell.textLabel.text = nil;
cell.detailTextLabel.text = NSLocalizedString(#"You haven't saved any bookmarks", #"");
cell.detailTextLabel.textColor = [UIColor colorWithRed:0/255.0 green:0/255.0 blue:0/255.0 alpha:0.7];
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell;
}
Are you sure [self.dataModel bookmarksCount] is equal to 0 ?
While I agree that you are probably going about this the wrong way,
your image is allocated and added in your bookmark changed, your notification does not trigger when there are no bookmarks initially. Hence you don't see the image. Call the bookmar changed when your table view inits or appears.
Probably the best way to achieve this is to perform a check in your numberOfRowsInSection method to return 1 if your data source is empty. Then in cellForRowAtIndexPath check if your data source is empty and if it is, create a custom cell that contains whatever you want. In heightForRowAtIndexPath you need to return your custom cell height if your datasource is empty, but only if you want the cell larger than the default. At least that is how I would approach it.
when bookmarks count is nil add one to your row method:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
int c;
c = bookmarks.count;
if(c == 0){
c = 1;
}
return c;
}
and then the same check again in your cellforrowatindexpath.
Another thing to be aware of in this situation is that if you're using core data and you're datasource is feeding off an entity, you will want to make sure your model matches. You can get some weird side-effect behavior in certain situations. This is especially true if you allow editing and core data has an empty model but you're tableview is still showing a cell.
If I have my data in an NSArray, and I can NSLog that data in my -cellForRowAtIndexPath method, would there be any reason why I wouldn't be able see the data in my UITableView using code like:
static NSString *simpleIdentifier = #"SimpleIdentifier";
UITableViewCell *simpleCell = [tableView dequeueReusableCellWithIdentifier:simpleIdentifier];
if (simpleCell == nil) {
simpleCell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleIdentifier];
}
NSUInteger row;
row = [indexPath row];
simpleCell.textLabel.textColor = [UIColor whiteColor];
simpleCell.selectionStyle = UITableViewCellSelectionStyleNone;
simpleCell.textLabel.text = [_categoriesArray objectAtIndex:row];
return simpleCell;
I'm wondering if I missed a "gotcha" or something. I have this data verbatim in one popover and it works fine. But then when I put it in another popover, it shows nothing. So I'm stumped! Any help would be great. Thanks.
How many rows and sections do you have defined for your table? If they are not defined correctly you won't have any data populating. I'm also assuming that your tableViewCell is not white, since you are setting the color of the text to white.
You're constructing your cell like this:
simpleCell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleIdentifier];
By default this creates a cell with an opaque white background. Then you're setting your text color to white:
simpleCell.textLabel.textColor = [UIColor whiteColor];
Try setting a different background color for your cell:
simpleCell.backgroundColor = [UIColor grayColor];
If you really need the table to be transparent you could set the color for both the cell and the tableView itself to [UIColor clearColor], but be aware that transparency really hurts your scrolling frame rate. You're better off using opaque views wherever possible.
Thank you everyone for trying to help me troubleshoot this problem. It was not a color issue. I finally got it to work, but I'm not quite sure why. Maybe someone else can chime in as why it works now. So in my cellForRowAtIndexPath method and other datasource methods, I have code like
if (tableView == tableView1 || tableView == _categoriesTableView || tableView == tableView2) {
...
if (tableView == tableView1) {
//do stuff
}
else if (tableView == _categoriesTableView) {
// do real stuff
}
else {
// do stuff
}
When I first had it working, I had a popover from a button that would show tableView1, then you would select a row in that table, to present another popover like _categoriesTableView. So this code worked fine. However, when I would try to change the first popover to show the _categoriesTableView, leaving all other code the same, no data would show correctly. Then instead of replacing the tableView1 initializing data for the popover, I still initialized it, but just did not present it in the popover, and now everything works. Not sure why the uninitialized memory of tableView1 would cause the problem since when I followed the code with breakpoints, my "do real stuff" was run, just wouldn't do what it was supposed to (display the data in the UITableView).
I'm extremely confused by the proper behavior of UITableView cell rendering. Here's the situation:
I have a list of 250 items that are loading into a table view, each with an image. To optimize the image download, I followed along with Apple's LazyTableImages sample code... pretty much following it exactly. Really good system... for reference, here's the cell renderer within the Apple sample code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// customize the appearance of table view cells
//
static NSString *CellIdentifier = #"LazyTableCell";
static NSString *PlaceholderCellIdentifier = #"PlaceholderCell";
// add a placeholder cell while waiting on table data
int nodeCount = [self.entries count];
if (nodeCount == 0 && indexPath.row == 0)
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:PlaceholderCellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:PlaceholderCellIdentifier] autorelease];
cell.detailTextLabel.textAlignment = UITextAlignmentCenter;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
cell.detailTextLabel.text = #"Loading…";
return cell;
}
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:CellIdentifier] autorelease];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
// Leave cells empty if there's no data yet
if (nodeCount > 0)
{
// Set up the cell...
AppRecord *appRecord = [self.entries objectAtIndex:indexPath.row];
cell.textLabel.text = appRecord.appName;
cell.detailTextLabel.text = appRecord.artist;
// Only load cached images; defer new downloads until scrolling ends
if (!appRecord.appIcon)
{
if (self.tableView.dragging == NO && self.tableView.decelerating == NO)
{
[self startIconDownload:appRecord forIndexPath:indexPath];
}
// if a download is deferred or in progress, return a placeholder image
cell.imageView.image = [UIImage imageNamed:#"Placeholder.png"];
}
else
{
cell.imageView.image = appRecord.appIcon;
}
}
return cell;
}
So – my implementation of Apple's LazyTableImages system has one crucial flaw: it starts all downloads for all images immediately. Now, if I remove this line:
//[self startIconDownload:appRecord forIndexPath:indexPath];
Then the system behaves exactly like you would expect: new images load as their placeholders scroll into view. However, the initial view cells do not automatically load their images without that prompt in the cell renderer. So, I have a problem: with the prompt in the cell renderer, all images load at once. Without the prompt, the initial view doesn't load. Now, this works fine in Apple sample code, which got me wondering what was going on with mine. It's almost like it was building all cells up front rather than just the 8 or so that would appear within the display. So, I got looking into it, and this is indeed the case... my table is building 250 unique cells! I didn't think the UITableView worked like this, I guess I thought it only built as many items as were needed to populate the table. Is this the case, or is it correct that it would build all 250 cells up front?
Also – related question: I've tried to compare my implementation against the Apple LazyTableImages sample, but have discovered that NSLog appears to be disabled within the Apple sample code (which makes direct behavior comparisons extremely difficult). Is that just a simple publish setting somewhere, or has Apple somehow locked down their samples so that you can't log output at runtime?
Thanks!
You certainly should not have an actual UITableViewCell instance for every row in the table. You should only see a few more instances than are visible in the UI. That is where your problem is. It doesn't have anything to do with the loading of images.
The only time I've seen a large number of cells instantiated when the cells where dequeued was when a coder had altered the frame of the tableview to make it much larger than the screen. The tableview retains enough cells from being dequeued to carpet its own frame regardless of what is visible. If the frame is to big then you get a lot of cells in queue.
NSLog does work in Apple examples so if you can't get NSLog output you've got something weird going on with the dev tools themselves.
You might want to shutdown Xcode and the simulator and restart and see if that clears up the odd behavior.
Oh my... mustISignUp is absolutely correct in saying "you definitely have a deeper underlying problem". I have variable-height table rows, and I was doing all height calculation and data storage on the rows themselves rather than on the data model that populated them. As a result, ALL cells were being created and populated by my heightForRowAtIndexPath method which was reading cell height from the cell objects. SO – lesson learned.
Thanks mustISignUp, and I love your username.
NSLog definitely isn't disabled within the Apple sample code. I don't know why you can't see it but you definitely have a deeper underlying problem.
Anyway, for your comparison:- if you have 6 rows on screen -tableView: cellForRowAtIndexPath: is called 6 times with index [0, 0] - [0, 5].
So, is that what you are seeing? How many times is -cellForRowAtIndexPath being called?
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.