Cost of iterating over cells in a UITableView - iphone

Inside each UITableViewCell of my UITableView, I have a UIScrollView. The scroll view is setup so that when the user swipes right a menu will appear. This is similar to the behavior of the cells in the iPhone Twitter app. When a user swipes upon another cell I iterate over all visible cells to tell the UIScrollView to scroll back to the cell content (i.e. its initial position). The iteration is done in the scrollViewWillBeginDragging method with the following code:
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
if( [scrollView tag] == 90 ) {
NSLog(#"Dragging a scroll view inside a cell!");
for (UITableViewCell *cell in self.tableView.visibleCells) {
[(UICellContentScrollView *)[cell viewWithTag:90] scrollRectToVisible:CGRectMake(0.0f, 0.0f, 320.0f, [cell frame].size.height) animated:YES];
}
}
}
In the method viewDidDisappear I iterate again over all cells to reset various things like so:
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
for( NSUInteger section = 0; section < [[self tableView] numberOfSections]; section++ ) {
for( NSUInteger row = 0; row < [[self tableView] numberOfRowsInSection:section]; row++ ) {
UITableViewCell *cell = [[self tableView] cellForRowAtIndexPath:[NSIndexPath indexPathForRow:row inSection:section]];
// resetting cell here
}
}
}
My question is if I am (a) going about this the right way and (b) does anyone have any recommendations on a better solution considering the table view may be storing up 50 (no more than 100) items.

Check out the NSNotification documentation. You could register all of your UITableViewCell objects to receive a notification you could call something like "cellWasSwiped" or "needToResetCells" or whatever. Then whenever you want to reset the cells you just post the notification. All of your UITableViewCell objects that are registered to receive it will get the notification and can then call whatever method you need.

Related

How to imitate rotation from the photos app on thumbnail view

I have an app that mimics the photos app in that it displays a table of thumbnails which represent an album that the user has clicked on. I'm having trouble imitating the animation of this window when rotation is occurred. For your reference the window I'm talking about is below:
I'm able to get the end result to turn out fine (ie after the animation is complete, everything works), however my rotation doesn't look as good as the photos app. The photos app actually looks like it's rotating the window and you can barely notice the photos resetting themselves. On mine, you can see the thumbnails sort of moving around and it doesn't look as good.
Does anyone have a clue as to what the photos app is doing? Is it possible that it's speeding up the animation, or maybe blurring it in the middle so you can't see what's going on? My code is listed below:
- (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] autorelease];
}
else
{
for (UIButton *photoButton in [cell subviews])
{
[photoButton removeFromSuperview];
}
}
NSInteger photosPerRow;
if (self.interfaceOrientation == UIInterfaceOrientationPortrait)
{
photosPerRow = 4;
}
else
{
photosPerRow = 6;
}
CGRect frame = CGRectMake(4, 2, 75, 75);
for (int i = [indexPath row] * photosPerRow; i < (([indexPath row] * photosPerRow) + photosPerRow) && i < [[self photos] count]; i++)
{
[[photos objectAtIndex:i] setFrame:frame];
[cell addSubview: [photos objectAtIndex:i]];
frame.origin.x = frame.origin.x + frame.size.width + 4;
}
return cell;
}
Then here is how I'm animating it in my tableview controller:
- (BOOL) shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
{
[self.tableView reloadData];
return (toInterfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
UPDATE: Well, I've tried a lot. So far switched all my code to a scroll view, then tried to have the thumbnails animated as follows when a rotation occurs: fade out the thumbnail, move it to it's new location, then fade it in. Of course I only did that with UIThumbViews that needed to be moved. I coming to the conclusion that apple must be using two views in order to pull them off. One view with the old set of thumbnail views, then rotating over the new set of thumbnail views. Any ideas?
UPDATED: This takes two lines of code, and you have to implement the thumbnails view in a tableview, not a scrollView:
[self.tableView reloadRowsAtIndexPaths: [self.tableView indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView reloadData];

Custom UITableViewCell button action?

I've been looking around to find a solution to this, but can't seem to find one that works for me. I have a custom cell with a button inside. My problem is how do I pass the indexPath to the action method?
Right now I'm doing
[cell.showRewards addTarget:self action:#selector(myAction:) forControlEvents:UIControlEventTouchUpInside];
In my cellForRowAtIndexPath method and my method is:
-(IBAction)myAction:(id)sender{
NSIndexPath *indexPath = [self.tableView indexPathForCell:(MyCustomCell *)[sender superview]];
NSLog(#"Selected row is: %d",indexPath.row);
}
Any tips? Thanks.
cell.showRewards.tag = indexPath.row;
-(IBAction)myAction:(id)sender
{
UIButton *btn = (UIButton *)sender;
int indexrow = btn.tag;
NSLog(#"Selected row is: %d",indexrow);
}
Just want to add what I believe is the best solution of all: a category on UIView.
It's as simple as this:
- (void)somethingHappened:(id)sender
{
NSIndexPath *indexPath = [self.tableView indexPathForCell:[sender parentCell]];
// Your code here...
}
Just use this category on UIView:
#interface UIView (ParentCell)
- (UITableViewCell *)parentCell;
#end
#implementation UIView (ParentCell)
- (UITableViewCell *)parentCell
{
UIView *superview = self.superview;
while( superview != nil ) {
if( [superview isKindOfClass:[UITableViewCell class]] )
return (UITableViewCell *)superview;
superview = superview.superview;
}
return nil;
}
#end
While I feel setting tag for the button is one way to go. You might need to write code to make sure each time the cell gets reused, the appropriate tag gets updated on the button object.
Instead I have a feeling this could work. Try this -
-(IBAction)myAction:(id)sender
{
CGPoint location = [sender locationInView:self.tableView];
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
UITableViewCell *swipeCell = [self.tableView cellForRowAtIndexPath:indexPath];
NSLog(#"Selected row: %d", indexPath.row);
//......
}
Essentially what you are doing is getting the coordinates of where the click happened with respect to your tableView. After getting the coordinates, tableView can give you the indexPath by using the method indexPathForRowAtPoint:. You are good to go after this...
Voila, you have not just the indexPath but also the actual cell where the click happened. To get the actual data from your datasource (assuming its NSArray), you can do -
[datasource objectAtIndex:[indexPath row]];
Try this one.
cell.showRewards.tag=indextPath.row
implement this in cellforrowatindexpath tableview's method.
-(IBAction)myAction:(id)sender{
UIButton* btn=(UIButton*)sender;
NSLog(#"Selected row is: %d",btn.tag);
}
You set the button tag value = indexpath and check it in function if tag value is this do what u want
In custom UITableViewCell class:
[self.contentView addSubview:but_you];
In cellForRowAtIndexPath method you can write:
[cell.showRewards addTarget:self action:#selector(myAction:) forControlEvents:UIControlEventTouchUpInside];
cell.showRewards.tag = indexPath.row;
You can assign indexpath to button tag and access in your method like
cell.showRewards.tag = indexPath.row;
-(IBAction)myAction:(id)sender
{
NSIndexPath *indexPath = [self.tableView indexPathForCell:[sender tag]];
NSLog(#"Selected row is: %d",indexPath.row);
}
I find it incredible that there isn't really a decent solution to this.
For whatever reason, I find the tagging methods and the 'using the visual location of the cell on the screen to identify the correct model object' outlined in the other answers a bit dirty.
Here are two different approaches to the problem:
Subclassing UITableViewCell
The solution I went with was to sub class UITableViewCell
#interface MyCustomCell : UITableViewCell
#property (nonatomic, strong) Model *myModelObject;
#end
When creating the cell in cellForRowAtIndexPath: you are likely to be using the model object to populate the cell data. In this method you can assign the model object to the cell.
And then in the button tap handler:
MatchTile *cell = (MatchTile *) sender.superview.superview;
if (cell && cell.myModelObject)
{
//Use cell.myModelObject
}
I'm not 100% happy with this solution to be honest. Attaching domain object to such a specialised UIKit component feels like bad practice.
Use Objective-C Associative Objects
If you don't want to subclass the cell there is a another bit of trickery you can use to associate the model object with the cell and retrieve it later.
To retrieve the model object from the cell, you will need a unique key to identify it. Define one like this:
static char* OBJECT_KEY = "uniqueRetrievalKey";
Add the following line to your cellForRowAtIndexPath: method when you are using the model object to populate the cell. This will associate your model object with the cell object.
objc_setAssociatedObject(cell, OBJECT_KEY, myModelObject, OBJC_ASSOCIATION_RETAIN);
And then anywhere you have a reference to that cell you can retrieve the model object using:
MyModelObject *myModelObject = (MyModelObject *) objc_getAssociatedObject(cell, OBJECT_KEY);
In reflection, although I opted for the first (because I'd already subclassed the cell), the second solution is probably a bit cleaner since it remains the responsibility of the ViewController to attach and retrieve the model object. The UITableViewCell doesn't need to know anything about it.
In [sender superview] you access not MyCustomCell, but it's contentView.
Read UITableViewCell Class Reference:
contentView
Returns the content view of the cell object. (read-only)
#property(nonatomic, readonly, retain) UIView *contentView
Discussion:
The content view of a UITableViewCell object is the default superview for content displayed by the cell. If you want to customize cells by simply adding additional views, you should add them to the content view so they will be positioned appropriately as the cell transitions into and out of editing mode.
Easiest way to modify your code is to use [[sender superview] superview].
But this will stop working if you later modify your cell and insert button in another view.
contentView appeared in iPhoneOS 2.0. Similar future modification will influence your code. That the reason why I don't suggest to use this way.
In - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath method write the code below:
[cell.zoomButton addTarget:self action:#selector(navigateAction:) forControlEvents:UIControlEventTouchUpInside];
cell.zoomButton.tag=indexPath.row;
Then write a method like this:
-(IBAction)navigateAction:(id)sender
{
UIButton *btn = (UIButton *)sender;
int indexrow = btn.tag;
NSLog(#"Selected row is: %d",indexrow);
currentBook = [[bookListParser bookListArray] objectAtIndex:indexrow];
KitapDetayViewController *kitapDetayViewController;
if(IS_IPHONE_5)
{
kitapDetayViewController = [[KitapDetayViewController alloc] initWithNibName:#"KitapDetayViewController" bundle:Nil];
}
else
{
kitapDetayViewController = [[KitapDetayViewController alloc] initWithNibName:#"KitapDetayViewController_iPhone4" bundle:Nil];
}
kitapDetayViewController.detailImageUrl = currentBook.detailImageUrl;
kitapDetayViewController.bookAuthor = currentBook.bookAuthor;
kitapDetayViewController.bookName = currentBook.bookName;
kitapDetayViewController.bookDescription = currentBook.bookDescription;
kitapDetayViewController.bookNarrator=currentBook.bookNarrator;
kitapDetayViewController.bookOrderHistory=currentBook.bookOrderDate;
int byte=[currentBook.bookSizeAtByte intValue];
int mb=byte/(1024*1024);
NSString *mbString = [NSString stringWithFormat:#"%d", mb];
kitapDetayViewController.bookSize=mbString;
kitapDetayViewController.bookOrderPrice=currentBook.priceAsText;
kitapDetayViewController.bookDuration=currentBook.bookDuration;
kitapDetayViewController.chapterNameListArray=self.chapterNameListArray;
// [[bookListParser bookListArray ]release];
[self.navigationController pushViewController:kitapDetayViewController animated:YES];
}
If you want the indexPath of the button Detecting which UIButton was pressed in a UITableView describe how to.
basically the button action becomes:
- (void)checkButtonTapped:(id)sender
{
CGPoint buttonPosition = [sender convertPoint:CGPointZero toView:self.tableView];
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:buttonPosition];
if (indexPath != nil)
{
...
}
}
Here is the "Simplest Way" to do it (Tested on IOS11):
NSIndexPath *indexPath = [myTable indexPathForRowAtPoint:[[[sender superview] superview] center]];

Getting reference of a UITextField which is on a UITableViewCell?

Actually i am using next and previous button for moving one to another cell and each cell has a textfield so when i am clicking on next button it moves me to the next cell and by getting this cell reference i can make the text field become first responder but when i am clicking on previous button it returns me no reference.
The code which i am using for next and previous is given below
- (IBAction)nextPrevious:(id)sender
{
NSIndexPath *indexPath ;
BOOL check = FALSE;
if([(UISegmentedControl *)sender selectedSegmentIndex] == 1){
if(sectionCount>=0 && sectionCount<8){
//for next button
check = TRUE;
sectionCount = sectionCount+1;
indexPath = [NSIndexPath indexPathForRow:0 inSection:sectionCount];
}
}else{
//for previous button
if(sectionCount>0 && sectionCount<=9){
check = TRUE;
sectionCount = sectionCount-1;
indexPath = [NSIndexPath indexPathForRow:0 inSection:sectionCount];
}
}
if(check == TRUE){
//[registrationTbl reloadData];
UITableViewCell *cell = [registrationTbl cellForRowAtIndexPath:indexPath];
for(UIView *view in cell.contentView.subviews){
if([view isKindOfClass:[UITextField class]]){
[(UITextField *)view becomeFirstResponder];
break;
}
}
[registrationTbl scrollToRowAtIndexPath:indexPath
atScrollPosition:UITableViewScrollPositionTop
animated:YES];
// UITextField *field = (UITextField *) [cell.contentView viewWithTag:indexPath.section];
// [field becomeFirstResponder];
}
Any small suggestion will be much appreciated. Thanks in advance
The problem lies in the scrolling. When you scroll to the top of the next row, the previous row gets removed and reused for the last visible row, meaning that the method cellForRowAtIndexPath: will probably return null, as the cell is not currently available.
The quick&dirty fix would involve scrolling to Middle or a little displaced so the cell is still visible. The not-so-quick-nor-dirty would involve making a procedure that scrolls the table to make sure the cell is visible, and then when the scrolling stops, set the textfield it as the first responder.
(Edit) To explain a little more this last approach. Let's say that you add a new variable NSIndexPath *indexPathEditing. The delegate method tableView:cellForRowAtIndexPath: would have:
if (indexPathEditing && indexPathEditing.row == indexPath.row && indexPathEditing.section == && indexPath.section)
{
// Retrieve the textfield with its tag.
[(UITextField*)[cell viewWithTag:<#Whatever#>] becomeFirstResponder];
indexPathEditing = nil;
}
This means that if indexPathEditing is set, and the current row that is being loaded is visible, it will automatically set itself as the firstResponder.
Then, for example (in your nextPrevious: method), all you need to do is:
indexPathEditing = [NSIndexPath indexPathForRow:0 inSection:sectionCount];
[registrationTbl scrollToRowAtIndexPath:indexPathEditing
atScrollPosition:UITableViewScrollPositionTop
animated:YES];
[registrationTbl reloadData];
The row will appear, the tableView:cellForRowAtIndexPath: called, and it will get automatically set as the firstResponder.
Also, notice that instead of doing a for with isKindOfClass, it's easier to set a tag number, and then retrieve the object with viewWithTag:, I incorporated this in the example.

How can I keep track of the index path of a button in a table view cell?

I have a table view where each cell has a button accessory view. The table is managed by a fetched results controller and is frequently reordered. I want to be able to press one of the buttons and obtain the index path of that button's table view cell. I've been trying to get this working for days by storing the row of the button in its tag, but when the table gets reordered, the row becomes incorrect and I keep failing at reordering the tags correctly. Any new ideas on how to keep track of the button's cell's index path?
If you feel uncomfortable relying on button.superview, this method should be a little more robust than some of the other answers here:
UIButton *button = (UIButton *)sender;
CGRect buttonFrame = [button convertRect:button.bounds toView:self.tableView];
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:buttonFrame.origin];
This stopped working with iOS 7; check out Mike Weller's answer instead
- (IBAction)clickedButton:(id)sender {
UIButton *button = (UIButton *)sender;
UITableViewCell *cell = (UITableViewCell *)button.superview;
UITableView *tableView = (UITableView *)cell.superview;
NSIndexPath *indexPath = [tableView indexPathForCell:cell];
}
Or shorter:
- (IBAction)clickedButton:(id)sender {
NSIndexPath *indexPath = [(UITableView *)sender.superview.superview indexPathForCell:(UITableViewCell *)sender.superview];
}
Both are untested!
Crawling up view hierarchies with .superview (like all of the existing answers demonstrate) is a really bad way to do things. If UITableViewCell's structure changes (which has happened before) your app will break. Seeing .superview.superview in your code should set off alarm bells.
The button and its handler should be added to a custom UITableViewCell subclass and layed out there. That's where it belongs.
The cell subclass can then delegate out the button event through a standard delegate interface, or a block. You should aim for something like this:
- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
MyCustomCell *cell = ...;
// ...
cell.onButtonTapped = ^{
[self buttonSelectedAtIndexPath:indexPath];
}
// OR
cell.delegate = self;
// ...
}
(Note: if you go the block route, you will need to use a __weak self reference to prevent retain cycles, but I thought that would clutter up the example).
If you take the delegate route you would then have this delegate method to implement:
- (void)cellButtonPressed:(UITableViewCell *)cell
{
NSIndexPath *indexPath = [self.tableView indexPathForCell:cell];
// ...
}
Your code now has full access to the appropriate context when it handles the event.
Implementing this interface on your cell class should be straightforward.
I don't know why I need to call the method superview twice to get the UITableViewCell.
Update:
Thank for Qiulang, now I got it.
"That's because SDK now has added a private class called UITableViewCellContentView for UITableViewCell, which is button's superview now." – Qiulang
UIButton *button = (UIButton *)sender;
UITableViewCell *cell = (UITableViewCell *)button.superview.superview;
UITableView *curTableView = (UITableView *)cell.superview;
NSIndexPath *indexPath = [curTableView indexPathForCell:cell];
I had this same issue also and built a simple recursive method that works no matter how many views deep you triggering control is.
-(NSIndexPath*)GetIndexPathFromSender:(id)sender{
if(!sender) { return nil; }
if([sender isKindOfClass:[UITableViewCell class]])
{
UITableViewCell *cell = sender;
return [self.tableView indexPathForCell:cell];
}
return [self GetIndexPathFromSender:((UIView*)[sender superview])];
}
-(void)ButtonClicked:(id)sender{
NSIndexPath *indexPath = [self GetIndexPathFromSender:sender];
}
I have created one Method for getting indexPath, Hope this will help you.
Create Button Action (aMethod:) in cellForRowAtIndexPath
-(void) aMethod:(UIButton *)sender
{
// Calling Magic Method which will return us indexPath.
NSIndexPath *indexPath = [self getButtonIndexPath:sender];
NSLog(#"IndexPath: %li", indexPath.row);
NSLog(#"IndexRow: %li", indexPath.section);
}
// Here is the Magic Method for getting button's indexPath
-(NSIndexPath *) getButtonIndexPath:(UIButton *) button
{
CGRect buttonFrame = [button convertRect:button.bounds toView:groupTable];
return [groupTable indexPathForRowAtPoint:buttonFrame.origin];
}
Use this Perfect working for me.
CGPoint center= [sender center];
CGPoint rootViewPoint = [[sender superview] convertPoint:center toView:_tableView1];
NSIndexPath *indexPath = [_tableView1 indexPathForRowAtPoint:rootViewPoint];
NSLog(#"%#",indexPath);
SWIFT 2 UPDATE
Here's how to find out which button was tapped
#IBAction func yourButton(sender: AnyObject) {
var position: CGPoint = sender.convertPoint(CGPointZero, toView: self.tableView)
let indexPath = self.tableView.indexPathForRowAtPoint(position)
let cell: UITableViewCell = tableView.cellForRowAtIndexPath(indexPath!)! as
UITableViewCell
print(indexPath?.row)
print("Tap tap tap tap")
}

First Tap on customcell of uitableview should expand it and second should contract it

In my application I have this requirement that first tap on custom cell of uitableview with a label in it should expand it and second should contract it. I'm able to expand and contract cell and expand label inside cell, but not able to contract the label on second tap.
I'm using this function
- (void)setSelected:(BOOL)selected animated:(BOOL)animated {
[super setSelected:selected animated:animated];
if( selected == YES ) {
[self expandRow];
}
else {
[self contractRow];
}
height = [lblFeed frame].size.height + 75;
}
expandRow expands the label and contractRow contracts it. I'm perplexed as for how many rows this function gets called. It doesn't get called only for the cell tapped, it gets called more number of times for single tap on single cell may be for other cells but I'm not getting which rows.
This' really urgent.
Can anybody please help?
Tapping a selected row doesn't cause it to be deselected. When a cell gets selected, it stays selected until deselectRowAtIndexPath:animated: gets called on its table. That's why your method isn't getting called for the second tap.
In an MVC architecture like UIKit, it's recommended that you handle user interactions in your controller classes. It would be appropriate to override -[UITableViewCell setSelected:animated:] if all you were doing was customizing the way the view represents a selected cell, but in this case your expand/contract toggle behavior would require a change in the way UITableView selects and deselects its cells.
You could subclass UITableView and implement this toggle behavior yourself, or you can leave UITableView alone and handle it all at the UIViewController level by doing something like this:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if ([self.expandedIndexPath isEqual:indexPath]) {
[(YourCustomCell *)[self tableView:tableView cellForRowAtIndexPath:indexPath] contractRow];
self.expandedIndexPath = nil;
}
else {
if (self.expandedIndexPath) {
[(YourCustomCell *)[self tableView:tableView cellForRowAtIndexPath:self.expandedIndexPath] contractRow];
}
[(YourCustomCell *)[self tableView:tableView cellForRowAtIndexPath:indexPath] expandRow];
self.expandedIndexPath = indexPath;
}
[tableView deselectRowAtIndexPath:indexPath animated:NO];
}
I would suggest that you don't add your functionality on top of the selected property of the cell, which has slightly different behaviour than you expect.
Just add your own BOOL expanded property, and see how that works. You should probably call it from the UITableView delegate methods, too.