I have UITableViewCell that contains UIView (lets call it CPView) which is created while cellForRowAtIndexPath is called. CPView is just a plain coloured view and for every cell its width is different (that's why needed to create in cellForRowAtIndexPath).
Problem is
1)The CPView 's colour gets darker every time cell loads (May be due to every time that cell creates the same view so overlapping effect).
2) The cell overlaps / inherits other cell's CPView (we can see this because of light and dark colour of two CPView).
How can I prevent cell to recreate if it already exist or creation of this CPView again?
Edit
- (void)configureCell:(CreditDebitCell *)cell atIndexPath:(NSIndexPath *)indexPath {
//other code
UIView * CPView;
if (CPView){
CPView =nil;
}
else
{
CPView = [[UIView alloc] initWithFrame:CGRectMake(cell.bounds.origin.x, cell.bounds.origin.y, cell.frame.size.width*[self.percentArray[indexPath.row] floatValue] ,cell.frame.size.height )];
[CPView setClipsToBounds:YES];
[CPView setBackgroundColor:[UIColor colorWithRed:107/255.0 green:15/255.0 blue:47/255.0 alpha:0.5]];
[cell addSubview: CPView];
}
}
The issue here is reuse of the cells - and therefore you get multiple views added to your cell view.
You can:
-remove subview
-check if subview exists and do/don't do anything.
You can check if the subview is there by going through subviews:
for (UIView *v in cell.contentView.subview) {
if ([v isKindOfClass:[CPView class]]) {
// remove or flag that it exists
}
}
But I think that you should handle this in your cell - not your view controller that implements table view delegate. Better tell cell to use some view/hide some view based on some kind of logic then to do that inside cellForRowAtIndexPath
According to your i question(without cellforRowAtIndexpath) i can assume that you should check every time something like in cellForRowAtIndexPath
if(cpView){
cpView = nil;
}
// alloc again with required size for particular row.
Make a subclass of your UITableViewCell and make a property of it that will reference your CPView. This will now let you have a better control whether your subclassed cell does / doesn't have any CPView that needs to be added.
Related
I'm using a button inside a tableView in which I get the indexPath.row when is pressed. But it only works fine when the cells can be displayed in the screen without scroll.
Once the tableView can be scrolleable and I scrolls throught the tableview, the indexPath.row returned is a wrong value, I noticed that initially setting 20 objects, for example Check is just printed 9 times no 20.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
lBtnWithAction = [[UIButton alloc] initWithFrame:CGRectMake(liLight1Xcord + 23, 10, liLight1Width + 5, liLight1Height + 25)];
lBtnWithAction.tag = ROW_BUTTON_ACTION;
lBtnWithAction.titleLabel.font = luiFontCheckmark;
lBtnWithAction.tintColor = [UIColor blackColor];
lBtnWithAction.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin;
[cell.contentView addSubview:lBtnWithAction];
}
else
{
lBtnWithAction = (UIButton *)[cell.contentView viewWithTag:ROW_BUTTON_ACTION];
}
//Set the tag
lBtnWithAction.tag = indexPath.row;
//Add the click event to the button inside a row
[lBtnWithAction addTarget:self action:#selector(rowButtonClicked:) forControlEvents:UIControlEventTouchUpInside];
//This is printed just 9 times (the the number of cells that are initially displayed in the screen with no scroll), when scrolling the other ones are printed
NSLog(#"Check: %li", (long)indexPath.row);
return cell;
}
To do something with the clicked index:
-(void)rowButtonClicked:(UIButton*)sender
{
NSLog(#"Pressed: %li", (long)sender.tag);
}
Constants.h
#define ROW_BUTTON_ACTION 9
What is the correct way to get the indexPath.row inside rowButtonClicked or setting a tag when I have a lot of of cells in my tableView?
My solution to this kind of problem is not to use a tag in this way at all. It's a complete misuse of tags (in my opinion), and is likely to cause trouble down the road (as you've discovered), because cells are reused.
Typically, the problem being solved is this: A piece of interface in a cell is interacted with by the user (e.g. a button is tapped), and now we want to know what row that cell currently corresponds to so that we can respond with respect to the corresponding data model.
The way I solve this in my apps is, when the button is tapped or whatever and I receive a control event or delegate event from it, to walk up the view hierarchy from that piece of the interface (the button or whatever) until I come to the cell, and then call the table view's indexPath(for:), which takes a cell and returns the corresponding index path. The control event or delegate event always includes the interface object as a parameter, so it is easy to get from that to the cell and from there to the row.
Thus, for example:
UIView* v = // sender, the interface object
do {
v = v.superview;
} while (![v isKindOfClass: [UITableViewCell class]]);
UITableViewCell* cell = (UITableViewCell*)v;
NSIndexPath* ip = [self.tableView indexPathForCell:cell];
// and now we know the row (ip.row)
[NOTE A possible alternative would be to use a custom cell subclass in which you have a special property where you store the row in cellForRowAt. But this seems to me completely unnecessary, seeing as indexPath(for:) gives you exactly that same information! On the other hand, there is no indexPath(for:) for a header/footer, so in that case I do use a custom subclass that stores the section number, as in this example (see the implementation of viewForHeaderInSection).]
I agree with #matt that this is not a good use of tags, but disagree with him slightly about the solution. Instead of walking up the button's superviews until you find a cell, I prefer to get the button's origin, convert it to table view coordinates, and then ask the table view for the indexPath of the cell that contains those coordinates.
I wish Apple would add a function indexPathForView(_:) to UITableView. It's a common need, and easy to implement. To that end, here is a simple extension to UITableView that lets you ask a table view for the indexPath of any view that lies inside one of the tableView's cells.
Below is the key code for the extension, in both Objective-C and Swift. There is a working project on GitHub called TableViewExtension-Obj-C that illustrates the uses of the table view extension below.
EDIT
In Objective-C:
Header file UITableView_indexPathForView.h:
#import <UIKit/UIKit.h>
#interface UIView (indexPathForView)
- (NSIndexPath *) indexPathForView: (UIView *) view;
#end
UITableView_indexPathForView.m file:
#import "UITableView_indexPathForView.h"
#implementation UITableView (UITableView_indexPathForView)
- (NSIndexPath *) indexPathForView: (UIView *) view {
CGPoint origin = view.bounds.origin;
CGPoint viewOrigin = [self convertPoint: origin fromView: view];
return [self indexPathForRowAtPoint: viewOrigin];
}
And the IBAction on the button:
- (void) buttonTapped: (UIButton *) sender {
NSIndexPath *indexPath = [self.tableView indexPathForView: sender];
NSLog(#"Button tapped at indexpPath [%ld-%ld]",
(long)indexPath.section,
(long)indexPath.row);
}
In Swift:
import UIKit
public extension UITableView {
func indexPathForView(_ view: UIView) -> IndexPath? {
let origin = view.bounds.origin
let viewOrigin = self.convert(origin, from: view)
let indexPath = self.indexPathForRow(at: viewOrigin)
return indexPath
}
}
I added this as a file "UITableView+indexPathForView" to a test project to make sure I got everything correct. Then in the IBAction for a button that is inside a cell:
func buttonTapped(_ button: UIButton) {
let indexPath = self.tableView.indexPathForView(button)
print("Button tapped at indexPath \(indexPath)")
}
I made the extension work on any UIView, not just buttons, so that it's more general-purpose.
The nice thing about this extension is that you can drop it into any project and it adds the new indexPathForView(_:) function to all your table views without having do change your other code at all.
You are running into the issue of cell-reuse.
When you create a button for the view you set a tag to it, but then you override this tag to set the row number to it.
When the cell get's reused, because the row number is longer ROW_BUTTON_ACTION, you don't reset the tag to the correct row number and things go wrong.
Using a tag to get information out of a view is almost always a bad idea and is quite brittle, as you can see here.
As Matt has already said, walking the hierarchy is a better idea.
Also, your method doesn't need to be written in this way. If you create your own custom cell, then the code you use to create and add buttons and tags isn't needed, you can do it in a xib, a storyboard, or even in code in the class. Furthermore, if you use the dequeue method that takes the index path, you will always get either a recycled cell, or a newly created cell, so there is no need to check that the cell returned is not nil.
I am learning about UITableview on iOS and following a course online. I get the table showing fine, but the images on my cells are not all the way to the left (whereas the instructor's ones are). Here is a screenshot of the cells in question:
I don't want that gap, I want the images to be positioned right at the beggining of the cell, all the way to the left. I have done some research and it seems Apple has changed the default look of the cells between ios6 and ios7 so that now the images in cells show a little gap at the left. To get rid of it, I have tried UIEdgeInsets:
[tableView setSeparatorInset:UIEdgeInsetsZero];
and that's not working. I also have tried this approach:
cell.imageView.frame = CGRectMake( 0, 0, 50, 55 );
Nothing happens. So how would I go about it? Thanks
edit-------------------------------------------------------------------------------------------------------------------------------
Still not have found the answer to this. The solutions posted here don't work. I found this piece of code:
self.tableView.contentInset = UIEdgeInsetsMake(0, -50, 0, 0);
Which besides completely puzzling me (as the parameter affected should be the y?) I thought solved the issue by making the image on the cell appear all the way to the left, until I realised it only moved the whole view to the left (as I should have expected I guess) leaving an equal gap on the other side of the screen. All I want is for my images in the cells to appear all the way to the left of the cell as it used to be the case on previous ios. Thanks
It happens because default table content offset from left is 15, you should change it with 0.
See this once, you get idea Remove empty space before cells in UITableView
If you create custom cells. UITableViewCell have owner imageView. Change title of image in your cell.
If you use default cell, use custom cell with constraint Leading space = 0.
It is better not use default imageView of the cell. Drag and drop UIImageView from objective library, create a custom table view cell (Child class of UITableViewCell) then create and outlet of the image view just dragged.
The spacing in the UITableViewCell is because of the default TRUE returned by shouldIndentWhileEditingRowAtIndexPath method of UITableViewDelegate.
I was able to reproduce your problem by the below scenario:
UITableView is in editable mode:
self.tableView.editing = true
And you have implemented:
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView
editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath {
return UITableViewCellEditingStyleNone;
}
To correct your code:
If you do not want to set Editing Style then you can turn off the editing mode by
self.tableView.editing = false
and remove editingStyleForRowAtIndexPath.
Else if you need editing mode then set the appropiate Editing style(UITableViewCellEditingStyleDeleteor UITableViewCellEditingStyleInsert) or simply turn the indentation off.
- (BOOL)tableView:(UITableView *)tableView
shouldIndentWhileEditingRowAtIndexPath:(NSIndexPath *)indexPath {
return FALSE;
}
You must create a custom cell, by adding a new class as a subclass of UITableViewCell. then you can design cell with autolayout and constraints which will resolve the issue.
there is a another concrete way to achieve this by creating subclass uitableviewcell (custom class).
steps to follow
create a class subclass of UITableViewCell.
in .h file create properties and outlets of UI components.
go to storyboard and add table view cell inside the tableview.
now add UI components like: imageview or button etc and set the x, y values according to.
make class of custom cell your className using identity inspector see image.
connect all outlets of UI components.
use below code uitableview
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
NSString *MyIdentifier = #"uniqueIdentifire";
yourCustomClassForCell *cell = (yourCustomClassForCell *)[tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil){
cell = [[yourCustomClassForCell alloc] initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:MyIdentifier];
}
cell.imageView.image = [imageAry objectAtIndex:indexPath.row];
}
Dont forget to give identifire by selecting your cell using storyboard Attribute inspector uniqueIdentifire to identifire property see image.
Also you can give some vertical space between cells by just to add this below code (Method only) inside customeCellClass.
- (void)setFrame:(CGRect)frame { // method to insert gap between table view cell
frame.origin.y += 6;
frame.size.height -= 2 * 6;
[super setFrame:frame];
}
You can not really change the frame of the inbuilt subviews of uitableviewcell like imageview, accessoryview. But if you create a custom tableviewcell class(even if you do not add any other subelement to it), you can change the frame of the inbuilt imageview by overriding the layoutSubviews method inside the UITableViewCell. I have tried it and it works.
#import "TableViewCell.h"
#implementation TableViewCell
- (void)awakeFromNib {
[super awakeFromNib];
// Initialization code
}
- (void)setSelected:(BOOL)selected animated:(BOOL)animated {
[super setSelected:selected animated:animated];
// Configure the view for the selected state
}
-(void) layoutSubviews{
[super layoutSubviews];
CGRect frame = self.imageView.frame;
frame.origin.x = 0;
self.imageView.frame = frame;
}
#end
I have a a custom UITableViewCell class and in it I have a UIImageView. This UIImageView is only displayed when the text of the UITableViewCell is equal to a certain string, eg "Home". When the method mapView:regionWillChangeAnimated: is called, I want to apply an animation on this UIImageView.
My question is how can I, when mapView:regionWillChangeAnimated: is called, go through my UITableView and custom UITableViewCells and perform an animation on the UIImageView within the cells which have the UIImageView set as visible?
I've been able to call methods on cells before using the UITableView delegate methods but I'm struggling to find a solution in this scenario because the the UITableView is not being directly called by the map panning method, it's not a didSelectRowAtIndex path issue?
Thank you.
If you have reference to table view in your map delegate method, you can get all visible cells using visibleCells method in UITableView and apply animation for them if needed. General structure may look like:
// Controller
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
...
[self applyCellsAnimation];
}
- (void)applyCellsAnimation {
for (CustomCell* cell in [self.tableView visibleCells]) {
[cell performImageAnimationIfNeeded];
}
}
// CustomCell
- (void)performImageAnimationIfNeeded {
if (!self.myImageView.hidden) {
// perform animation
}
}
You can get an array of all the visible rows in your table view using
[myTableView visibleCells]
You then just need to integrate through each cell and animate the image.
i.e.
for (MyCustomCell* cell in [myTableView visibleCells])
{
[cell animateImage];
}
The implementation of animateImage can then do whatever you want - just check the imageView.hidden property and animate it if the imageView is visible.
I'm having an issue,
I have a simple UICollectionView with a static 200 cells that load images from Flickr.
my CellForItemAtIndexPath looks like this:
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *cell = [cv dequeueReusableCellWithReuseIdentifier:#"FlickrCell" forIndexPath:indexPath];
cell.backgroundColor = [self generateRandomUIColor];
if(![[cell.subviews objectAtIndex:0] isKindOfClass:[PFImageView class]])
{
NSURL *staticPhotoURL = [self.context photoSourceURLFromDictionary:[self.photos objectAtIndex:indexPath.row] size:OFFlickrSmallSize];
PFImageView *imageView = [[PFImageView alloc] initWithFrame:CGRectMake(0, 0, cell.frame.size.height, cell.frame.size.width) andImageURL:staticPhotoURL andOwningCell:cell];
[cell addSubview:imageView];
}
return cell;
}
PFImageView is a subclass of UIImageView that loads a Flickr photo URL on a background thread and then updates it's own image on the main thread - this works fine.
The logic is really simple - I create a cell if there isn't one dequeueable.
If the cell (which I'm expecting to be dequeued and already have a PFImageView) doesn't have a PFImageView, I alloc and init an imageView for the cell and add it as a subview of the cell.
Thus I expect if the cell has been dequeued it should already have a PFImageView as a subview and as we should not get into the if statement to create a new imageView and kick off a new photo download request
Instead what I see is that the cells at the top and bottom of the UICollectionView that 'go off screen' momentarily - when they come back on screen they are not being reused and seemingly a new cell is created and the picture refreshed.
1) How can I achieve a static image once the cell has been created (i.e. not refreshing when the cell goes slightly off screen.
2) Why are the cells not being reused?
Many thanks for your time.
John
UICollectionView will reuse cells for maximum efficiency. It does not guarantee any particular reuse or population strategies. Anecdotally, it seems to place and remove cells based on integer power of two regions — e.g. on a non-retina iPad it might divide your scroll area up into regions of 1024x1024 and then populate and depopulate each of those regions as they transition into and out of the visible area. However you should not predicate any expectations on its exact behaviour.
In addition, your use of collection view cells is incorrect. See the documentation. A cell explicitly has at least two subviews — backgroundView and contentView. So if you add a subview it will be at index 2 at the absolute least and, in reality, the index will be undefined. In any case you should add subviews to contentView, not to the cell itself.
The most normal way of doing what you're doing would be to create a custom UICollectionView subclass that inherently has a PFImageView within it.
I see several potential issues:
You are looking specifically at index 0 of the cell for the child class that you are adding. The UICollectionViewCell may have other views as children, so you can't just assume that the only (or first) child is the one you added.
I don't see that you are calling registerClass:forCellWithReuseIdentifier: or registerNib:forCellWithReuseIdentifier:, one of which is required for proper use of dequeue (https://developer.apple.com/library/ios/documentation/uikit/reference/UICollectionViewCell_class/Reference/Reference.html).
You are only setting the URL of the PFImageView in the case that you have to construct the PFImageView. The idea with dequeuing reusable views is that you will only construct a small subset of the views needed, and the UITableView will recycle them as they move offscreen. You need to reset the value for the indexPath that is being requested, even when you don't construct the new content.
If your case is as simple as you describe, you can probably get away with adding your PFImageView to the contentView property of your dequeued UICollectionView.
In your controller:
// solve problem 2
[self.collectionView registerClass:[UICollectionViewCell class] forReuseIdentifer:#"FlickrCell"];
In collectionView:cellForItemAtIndexPath
UICollectionViewCell *cell = [cv dequeueReusableCellWithReuseIdentifier:#"FlickrCell" forIndexPath:indexPath];
cell.backgroundColor = [self generateRandomUIColor];
// solve problem 1 by looking in the contentView for your subview (and looping instead of assuming at 0)
PFImageView *pfImageView = nil;
for (UIView *subview in cell.contentView.subviews)
{
if ([subview isKindOfClass:[PFImageView class]])
{
pfImageView = (PFImageView *)subview;
break;
}
}
NSURL *staticPhotoURL = [self.context photoSourceURLFromDictionary:[self.photos objectAtIndex:indexPath.row] size:OFFlickrSmallSize];
if (pfImageView == nil)
{
// No PFImageView, create one
// note the use of contentView!
pfImageView = [[PFImageView alloc] initWithFrame:CGRectMake(0, 0, cell.contentView.frame.size.height, cell.frame.size.width) andImageURL:staticPhotoURL andOwningCell:cell.contentView];
[cell.contentView addSubview:pfImageView];
}
else
{
// Already have recycled view.
// need to reset the url for the pfImageView. (Problem 3)
// not sure what PFImageView looks like so this is an e.g. I'd probably remove the
// URL loading from the ctr above and instead have a function that loads the
// image. Then, you could do this outside of the if, regardless of whether you had
// to alloc the child view or not.
[pfImageView loadImageWithUrl:staticPhotoURL];
// if you really only have 200 static images, you might consider caching all of them
}
return cell;
For less simple cases (e.g. where I want to visually lay out the cell, or where I have multiple children in the content), I typically customize my UICollectionViewCell's using Interface Builder.
Create a subclass of UICollectionViewCell in the project (In your case, call it PFImageCell).
Add an IBOutlet property to that subclass for the view I want to change in initialization (In your case, a UIImageView).
#property (nonatomic, assign) IBOutlet UIImageView *image;
In Interface Builder, create a prototype cell for the UITableView.
In the properties sheet for that prototype cell, identify the UICollectionViewCell subclass as the class.
Give the prototype cell an identifier (the reuse identifier) in the property sheet.
Add the view child in interface builder to the prototype cell (here, a UIImageView).
Use IB to map the IBOutlet property to the added UIImageView
Then, on dequeue in cellForRowAtIndexPath, cast the dequeued result to the subclass (PFImageCell) and set the value of the IBOutlet property instance. Here, you'd load the proper image for your UIImageView.
I am not sure if the cell is being re-used or not. It may be being reused but the subview may not be there. My suggestion would be to create a PFImageViewCollectionViewCell Class (sub class of UICollectionViewCell) and register it as the CollectionView Cell and try. That's how I do and would do if I need a subview inside a cell.
Try adding a tag on this particular UIImageView
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath {
static int photoViewTag = 54353532;
UICollectionViewCell *cell = [cv dequeueReusableCellWithReuseIdentifier:#"FlickrCell" forIndexPath:indexPath];
cell.backgroundColor = [self generateRandomUIColor];
PFImageView *photoView = [cell.contentView viewWithTag:photoViewTag];
// Create a view
//
if (!photoView) {
photoView = [[PFImageView alloc] initWithFrame:CGRectMake(0, 0, cell.frame.size.height, cell.frame.size.width) andImageURL:staticPhotoURL andOwningCell:cell];
imageView.tag = photoViewTag;
[cell.contentView addSubview:imageView];
}
// Update the current view
//
else {
NSURL *staticPhotoURL = [self.context photoSourceURLFromDictionary:[self.photos objectAtIndex:indexPath.row] size:OFFlickrSmallSize];
photoView.imageURL = staticPhotoURL;
}
return cell;
}
I would really recommend to create your own UICollectionViewCell subclass though.
EDIT: Also, note that I used the contentView property instead of adding it directly to the cell.
I am adding a custom button into my cell.contentView, and I noticed that every time a cell is scrolled off the visible part of the screen and back on, the button gets re-added - the translucent parts of it get more and more solid. What is the correct way to handle it so that it does not keep stacking more objects on top when scrolling through the tableView? Note that custom content is different for each cell, so I cannot put it into the if (cell == nil) {...} block.
The code I have is:
UISegmentedControl *btn = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObject:btn_title]];
// set various other properties of btn
...
[cell.contentView addSubview:btn];
Every time the cell is dequeued, you have to remove the old subviews before adding new ones, or else you'll get that stacking effect. You can do this in one of two places:
a) In tableView:cellForRowAtIndexPath:, remove your old views after the dequeueReusableCellWithIdentifier: call and before adding your new ones.
b) If you're using a subclass of UITableViewCell, you can override prepareForReuse to remove unwanted views. prepareForReuse is called every time a cell is dequeued for reuse, so it's a good place to get rid of old views from the last time the cell was configured.
I'll post a sample fix for the code you posted. It can be extended to take care of more views.
The steps are:
Create a method in your CustomCell class that takes care of the whole setup (for example: setupWithItems:)
Once you have a cell in cellForRowAtIndexPath: (after dequeueing it or creating it), you should call setupWithItems: with the new list of items the cell should display.
In your setupWithItems: implementation, make sure you remove the UISegmentedControl from its parent view. You can easily do this it the segmented control is stored as a property of your custom cell.
In your setupWithItems: implementation, create a new UISegmentedControl and add it to the CustomCell's view hierarchy.
Sample code:
-(UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath
{
CustomCell* cell = [tableView dequeueReusableCellWithIdentifier:kSomeIdentifier];
if (!cell)
{
// Create a new cell
}
NSArray* currentCellItems = [self cellItemsForRow:indexPath.row];
[cell setupWithItems:currentCellItems];
return cell;
}
And in your CustomCell subclass:
- (void)setupWithItems:(NSArray*)items
{
if (self.segmentedControl)
{
[self.segmentedControl removeFromSuperView];
self.segmentedControl = nil;
}
// More setup...
UISegmentedControl *btn = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObject:btn_title]];
// set various other properties of btn
[cell.contentView addSubview:btn];
}