I have creating a excel view using collection view. Earlier I was facing an issue while scrolling the collection view listed at :
https://stackoverflow.com/questions/27036224/scrolling-disturbs-layout-of-collectionview
I fixed that issue with the after seeing Shivam's reply in:
Collection View,with custom layouts, cells misbehave on scrolling
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
NSString *cellID = [NSString stringWithFormat:#"%#%d", #"cCell",indexPath.row];
[myCollectionView registerClass: [CustomCell class] forCellWithReuseIdentifier:cellID];
CustomCell *cell = [self.collectionView dequeueReusableCellWithReuseIdentifier:cellID forIndexPath:indexPath];
[self configureCell:cell forIndexPath:indexPath];
return cell;
}
-(void)configureCell:(CustomCell*)cell forIndexPath:(NSIndexPath*)indexPath{
// configuration code
}
I don't know whether it is correct or not, but's its working.But now I am stuck in another problem related to reload of collection view.
Problem::: I have textfield in the cells for which I have implemented textFieldDidEndEditing delegate. I have also provided Next Button which provides proxy navigation to all cells in collection view as desired by me. In the clicked method of next button, I am saving the currentIndexpath, reloading the collection view, getting the next cell using saved index path, getting the textfield and making it as first responder. But next textfield never becomes first responder. I debugged the issue and find that after reload I am not able to retrieve the cell. If I remove the reload line then everything works fine.
NSIndexPath *reqIndexPath = [NSIndexPath indexPathForItem:colId inSection:currentSection];
CustomCell *cell = (CustomCell*)[self.collectionView cellForItemAtIndexPath:reqIndexPath];
I get this resolved by :
[self.collectionView reloadData];
[self.collectionView layoutIfNeeded];
Thanks to Lukewar reply in
Reloading a UICollectionView using reloadData method returns immediately before reloading data
Related
I have a tableview in a scrollview in a popover. When the view is presented, the bottom cell in tableview is not visible to the user. If I select all of the cells then deselect the fist cell, the out of view cell is deselected too. Has anyone come across this behaviour before? If so, how to approach it?
Now your job is to find all the visible cells in the tableview and then apply select/deselect to it.
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.
-(void) tableView:(UITableView *)tableView didDeselectRowAtIndexPath:
(NSIndexPath *)indexPath {
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
- (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:
(NSIndexPath *)indexPath {
//stuff
//as last line:
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
For that matter, deselectRowAtIndexPath can be called from anywhere at any time you want the row to be deselected.
[self.myTableView deselectRowAtIndexPath:[self.myTableView
indexPathForSelectedRow] animated: YES];
If you are using dequeueReusableCellWithIdentifier: change your cellForRowAtIndexPath: to use dequeueReusableCellWithIdentifier:forIndexPath:
In a UITableView cells get reused. That means it only produces as many as absolutely needed. As soon as a new one is coming onto the screen, the last one is "recycled" instead of initialising a whole new instance.
This makes your application run faster. It also means that you have to undo any changes you made, when recycling.
Selection status is one of them. The UITableView should manage this automatically for you, if it is dequeued with the relevant indexPath. If not, it wouldn't know whether that specific cell should be selected.
I'm trying to understand why awakeFromNib is being called twice in my code. I currently have a tableview that has a special compressible cell that appears once at the end of the table. The first awakeFromNib is being called when the tableview is scrolled to the special cell at the end (which is fine I believe,as the tableview is reusing cells). However, whenever I tap the cell to expand the cell, the awakeFromNib is being called again.
Could anyone explain to me why awakeFromNib is being called twice? And how I could only make it only be called once?
Thanks
EDIT** Code people have requested
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.section >= (NSInteger)[self.trip.destinations count]) {
GuestCell *cell = (GuestCell*)[tableView dequeueReusableCellWithIdentifier:GuestCellIdentifier forIndexPath:indexPath];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
[cell setupCellForGuests:self.trip.guests];
cell.guestExpanded = NO;
NSLog(#"RETURNING CELL");
return cell;
}
// For all other sections
return [self prepareCardCellForIndexPath:indexPath forHeightCalc:NO];
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.section >= (NSInteger)[self.trip.destinations count]) {
[self.tableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}
}
You're animating the reload of the expanding row. The table view implements this by creating another cell for the same index path, and animating a transition from the old cell to the new cell. It creates a second instance of your cell prototype, so the second instance also receives the awakeFromNib message. If you log self, you'll see that the address is different the second time.
I don't think you can avoid the creation of a second cell instance (and thus a second awakeFromNib) unless you get rid of the animation. Even then I'm not sure it will reuse the old cell.
If the cell with that nib is only one in the table, then my guess is that it has something to do with animations. I didn't check how tableview handles cells during animation, but for tableview header it asks for another instance and then performs animation (for example fade) - so the old instance is faded out and the new is faded in. At least that's what I think has the highest probability, if you are handling cells correctly.
What I have
1). Container has UITableView, which has two custom UITableViewCells.
2). Core Data has certain entity which has a text to be displayed at
UITableViewCell each time I get into the View.
What i am doing ?
1) I have chosen -viewWillAppear method which gets invoked each time the view is visible.
2) In -viewWillAppear, I retrieved the data from core data.
3) Retrieved particular cell from UITableView
NSUInteger idxArr[] ={2,0}; // 2 nd section, 0th Row.
NSIndexPath *cPath = [NSIndexPath indexPathWithIndexes:idxArr length:2];
myCell *tCell = (myCell *)[self.settings cellForRowAtIndexPath:cPath];
tCell.myLabel.text = rec.servername; // rec.servername is from DC.
When I checked in the lldb,
tCell was nil.
Questions:
1) It is the right way of getting the Cell ?
2) Or, By the time -viewWillAppear, does the UITableView not Ready ?
I am sure.
You should populate the cells by conforming to tableView dataSource protocol and then in your viewWillAppear you should call reloadData on your tableView.
After calling reloadData for tableview, We need to call -scrollToRowAtIndexPath: before getting cell from -cellForRowAtIndexPath:.
Because, As we are calling a row in section 2, it might not be in the visible area until we scroll. So, cellForRowAtIndexPath: returns nil.
Method -cellForRowAtIndexPath: shouldn't be called programically. It's a data source method for UITableView and it contain some cell reuse optimalizations. If you update the view after scrolling down and up -tableView:cellForRowAtIndexPath will be called again and your changes won't be visible.
If you want to update specific cell you should update make changes in:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
YourCell *cell = [tableView dequeueReusableCellWithIdentifier:#"CellId" forIndexPath:indexPath];
YourData *data = //Get your data here
if (data.isReady) {
cell.tf.text = data[indexPath.row].text;
} else {
cell.tf.text = #"Not ready yet. Need to reload this cell later";
}
return cell;
}
And then call method below when you finish fetch your data.
[self.tableView reloadRowsAtIndexPaths:(NSArray *) withRowAnimation:UITableViewRowAnimationFade];
If you want to reload whole tableView (usually it's not slow) as #salaman140 says you can call [self.tableView reloadData] to update all visible cells.
If I were you I wouldn't use:
NSUInteger idxArr[] ={2,0}; // 2 nd section, 0th Row.
NSIndexPath *cPath = [NSIndexPath indexPathWithIndexes:idxArr length:2];
I would (is much more clear):
NSIndexPath *cPath = [NSIndexPath indexPathForRow:0 inSection:2];
I'm using a CollectionView to display data. When the user presses a certain button, I am refreshing the CollectionViewCell to reflect the changes like this:
[self.collectionView reloadItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];
This works fine to reload the cell, except it doesn't reload it's footer view. I implemented the following method
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"FOOTER CALLED");
This doesn't get called when I reload the cell.
Eveything works if I reload the whole collection view with [self.collectionview reloadData], but this is not efficient.
How to make sure the Footer of my UICollectionViewCell at indexPath gets refreshed also?
You have to invalidate the layout or reload the section.
Invalidating the layout.
[[_collectionView collectionViewLayout] invalidateLayout]
Reloading the section. Use reloadSections: to update 1 or more sections in the UICollectionView.
[self.collectionView reloadSections:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, 3)]];
I need to detect when a tableview has finished reloading data. There was an older solution where you could subclass the tableview then overload the reloadData method, however apparently that no longer works because tables are handled on multiple threads now and reloadData is called before cellForRowAtIndexPath.
My question is, has there been any solution to this problem since the change?
My problem is I am losing the pointer to a textField when the table reloads its data, so the first responder I am trying to set to the next text field (to auto focus on the next data input field), is lost.
This is essentially a repeat of #wain 's answer, but I thought I would add a little code.
You can keep a reference to the index path of the cell that owns the active text field (as a property).
Then, in cellForRowAtIndexPath: something like this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
MyTableViewCell *cell = (MyTableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
//I would hold a reference to the text field as a property on a subclass of UITableViewCell so that you can check for whether it exists.
if (!cell.textField) {
cell.textField = [[UITextField alloc] initWithFrame:cell.contentView.frame];
[cell.contentView addSubview:cell.textField];
}
return cell;
}
- (void)textFieldDidBeginEditing:(UITextField *)textField
{
UITableViewCell *cell = (UITableViewCell *)textField.superview.superview;
NSIndexPath *indexPath = [self.tableView indexPathForCell:cell];
self.indexPathForActiveTextField = indexPath;
}
- (BOOL) textFieldShouldReturn:(UITextField *)textField
{
MyTableViewCell *cell = (MyTableViewCell *)textField.superview.superview;
NSIndexPath *ip = [self.tableView indexPathForCell:cell];
[self.tableView reloadData];
NSIndexPath *nextIndexPath = [NSIndexPath indexPathForRow:ip.row+1 inSection:ip.section];
MyTableViewCell *theNewCell = (MyTableViewCell *)[self.tableView cellForRowAtIndexPath:nextIndexPath];
if (theNewCell) {
[theNewCell.textField becomeFirstResponder];
}
return YES;
}
Store the NSIndexPath of the table cell that holds the text field that should be the first responder. When you want to change the first responder you can ask the table view for the cell at that index path, then find the text field and make it first responder.
If the table view gets reloaded, in cellForRowAtIndexPath: check the index path and make the 'new' text field the first responder.
In this way you can set the first responder at any time and you can't loose the reference to it as the reference is to a location, not an object (which will be reused or removed).
UITableView uses a pool to reuse displayed cell. The target cell is possibly reused in other row. Storing the NSIndexPath like Wain suggested is good untill you not reorder the cells or delete some entry from the datasource. Define a key in the model, that you set the firstResponder according to that. Hope i did not misunderstood the problem.