Is there a way to alter the frame of the "swipe" [DELETE] button used on UITableViewCells? Currently its centred vertically within the cell, but if possible I would like to move it down to the cyan guide show.
If you are looking for a strongly true way to solve this problem then you should to subclass of UITableViewCell and override the all state handling methods for correct drawing your own delete button (do not call super in those methods). But there is another easy way:
#implementation CustomCell
- (void)layoutSubviews {
[super layoutSubviews];
if (self.showingDeleteConfirmation) {
if ([self.subviews count] < 4) return;
UIView *delBtn = [self.subviews objectAtIndex:3];
delBtn.frame = CGRectOffset(delBtn.frame, 0, 10);
}
}
#end
Instead of didTransitionToState:,
How about using the -(void)willTransitionToState: and setting the frame of the editingAccessoryView?
- (void)willTransitionToState:(UITableViewCellStateMask)state
{
if (state == UITableViewCellEditingStyleDelete)
{
NSInteger num = 10;
UIView.frame = CGRectMake(UIView.frame.origin.x,UIView.frame.origin.y - num,
UIView.size.width,UIView.size.height);
}
}
Try changing the frame for Accessory View
Related
How do I do an infinite scrolling in a UITableView? I know how to do it using a UIScrollView, in which apple has demonstrated in one of the WWDC's video. I tried doing the following in tableView:cellForRowAtIndexPath::
if (indexPath.row == [self.newsFeedData_ count] - 1)
{
[self.newsFeedData_ addObjectsFromArray:self.newsFeedData_];
[self.tableView reloadData];
}
but this fails. Any other idea?
If you need to know when you hit the bottom of the UITableView, become it's delegate (because it is a subclass of UIScrollView), and use the -scrollViewDidScroll: delegate method to compare the table's content height and it's actual scroll position.
EDIT (something like this):
- (void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat actualPosition = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height - (someArbitraryNumber);
if (actualPosition >= contentHeight) {
[self.newsFeedData_ addObjectsFromArray:self.newsFeedData_];
[self.tableView reloadData];
}
}
You can support infinite scroll with pull to refresh at the top and/or scroll continuously at the bottom with a spinner wheel using:
https://github.com/samvermette/SVPullToRefresh
SVPullToRefresh handles the logic when UITableView reaches the bottom. A spinner is shown automatically and a callback block is fired. You add in your business logic to the callback block.
Here's an example:
#import "UIScrollView+SVInfiniteScrolling.h"
// ...
[tableView addInfiniteScrollingWithActionHandler:^{
// append data to data source, insert new cells at the end of table view
// call [tableView.infiniteScrollingView stopAnimating] when done
}];
This project can be added to your project using CocoaPods or directly compiled into your project.
Here's a very quick and complete demo of an infinite scrolling UITableView I put together...
#interface InfiniteScrollViewController ()
#property (nonatomic) NSMutableArray *tableViewData;
#property (nonatomic) BOOL loadingMoreTableViewData;
#end
#implementation InfiniteScrollViewController
- (void)viewDidLoad {
self.tableViewData = [[NSMutableArray alloc] init];
[self addSomeMoreEntriesToTableView];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return self.tableViewData.count + 1;
}
- (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];
}
if (indexPath.row < self.tableViewData.count) {
cell.textLabel.text = [self.tableViewData objectAtIndex:indexPath.row];
} else {
cell.textLabel.text = #"Loading more data...";
// User has scrolled to the bottom of the list of available data so simulate loading some more if we aren't already
if (!self.loadingMoreTableViewData) {
self.loadingMoreTableViewData = YES;
[self performSelector:#selector(addSomeMoreEntriesToTableView) withObject:nil afterDelay:5.0f];
}
}
return cell;
}
- (void)addSomeMoreEntriesToTableView {
int loopTill = self.tableViewData.count + 20;
while (self.tableViewData.count < loopTill) {
[self.tableViewData addObject:[NSString stringWithFormat:#"%i", self.tableViewData.count]];
};
self.loadingMoreTableViewData = NO;
[self.tableView reloadData];
}
#end
'UITableView' is same as 'UIScrollView' in 'scrollViewDidScroll' method.
So, its easy to emulate infinite scrolling.
double the array so that head and tail are joined together to emulate circular table
use my following code to make user switch between 1st part of doubled table and 2nd part of doubled table when they tend to reach the start or the end of the table.
:
/* To emulate infinite scrolling...
The table data was doubled to join the head and tail: (suppose table had 1,2,3,4)
1 2 3 4|1 2 3 4 (actual data doubled)
---------------
1 2 3 4 5 6 7 8 (visualising joined table in eight parts)
When the user scrolls backwards to 1/8th of the joined table, user is actually at the 1/4th of actual data, so we scroll instantly (we take user) to the 5/8th of the joined table where the cells are exactly the same.
Similarly, when user scrolls to 6/8th of the table, we will scroll back to 2/8th where the cells are same. (I'm using 6/8th when 7/8th sound more logical because 6/8th is good for small tables.)
In simple words, when user reaches 1/4th of the first half of table, we scroll to 1/4th of the second half, when he reaches 2/4th of the second half of table, we scroll to the 2/4 of first half. This is done simply by subtracting OR adding half the length of the new/joined table.
*/
-(void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat currentOffsetX = scrollView_.contentOffset.x;
CGFloat currentOffSetY = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height;
if (currentOffSetY < (contentHeight / 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY + (contentHeight/2)));
}
if (currentOffSetY > ((contentHeight * 6)/ 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY - (contentHeight/2)));
}
}
P.S. - I've used this code on one of my apps called NT Time Table (Lite). If you want the preview, you can check out the app: https://itunes.apple.com/au/app/nt-time-table-lite/id528213278?mt=8
If your table can sometimes be too short, at the beginning of the above method you can add a if logic to exit the method when data count is say for example less than 9.
For me worked better scrollViewDidEndDragging: than scrollViewDidScroll:.
The second approach will send you each position during scroll and cause, if you are fetching remote resources you will hit your endpoint several times, which is not good.
Complete example based on #codafi solution with comments from #danielgomezrico about how to calculate contentHeight:
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
willDecelerate:(BOOL)decelerate {
CGFloat actualPosition = scrollView.contentOffset.y;
CGFloat contentHeight = scrollView.contentSize.height - (self.tableView.frame.size.height);
if (actualPosition >= contentHeight) {
// fetch resources
[self.tableView reloadData];
}
}
Generally I override scrollViewDidEndDecelerating and inside it I put my code to request more data.
Example:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
float endScrolling = scrollView.contentOffset.y + scrollView.frame.size.height;
if (endScrolling >= scrollView.contentSize.height){
//put here your code
}
}
Recently I uploaded on GitHub a subclass of UITableView, that implements the infinite scroll.
You can download it here:
https://github.com/alchimya/iOS-LazyTableView
rather than overriding we can do this optimally in layoutSubviews.
Here's how I got it implemented. You can get to know more about the implementation here
- (void)layoutSubviews{
[super layoutSubviews];
if(self.delegateForViews){
CGPoint contentOffset = self.contentOffset;
if([self.delegateForViews noOfViews]>numOfReusableViews){
NSUInteger centerIndex=visibleViews.count/2;
NSUInteger noOfViews=[self.delegateForViews noOfViews];
UIView *centerView=[visibleViews objectAtIndex:centerIndex];
CGPoint centerViewOrigin=centerView.frame.origin;
CGSize centerViewSize=centerView.frame.size;
CGFloat offsetDifference=contentOffset.x-centerViewOrigin.x;
CGFloat offsetDifferenceAbs=fabs(contentOffset.x-centerViewOrigin.x);
if(offsetDifferenceAbs>=centerViewSize.width){
if(offsetDifference<0){
currentPosition--;
}else{
currentPosition++;
}
self.contentOffset=centerViewOrigin;
currentPosition=[self getPosition:currentPosition noOfViews:noOfViews];
[self.delegateForViews clearView:centerView];
[self.delegateForViews setupView:centerView forPosition:currentPosition];
for (int i=centerIndex-1; i>=0; i--) {
UIView* prevView=[visibleViews objectAtIndex:i];
[self.delegateForViews clearView:prevView];
[self.delegateForViews setupView:prevView forPosition:
[self getPosition:currentPosition-1 noOfViews:noOfViews]];
}
for (int i=centerIndex+1; i<visibleViews.count; i++) {
UIView* nextView=[visibleViews objectAtIndex:i];
[self.delegateForViews clearView:nextView];
[self.delegateForViews setupView:nextView forPosition:
[self getPosition:currentPosition+1 noOfViews:noOfViews]];
}
}
}
}
}
One of the simple and that offered me everything i need is this class:
https://github.com/jakemarsh/JMStatefulTableViewController
You just need to subclass JMStatefulTableViewController and the it has 3 methods that you need to overwrite:
one that is called on init, to get the initial data
statefulTableViewControllerWillBeginInitialLoading
one when the user pull to refresh
statefulTableViewControllerWillBeginLoadingFromPullToRefresh
one when is called for the infinite scroll (next page)
statefulTableViewControllerWillBeginLoadingNextPage
This can be used from Cocoapods too.
scrollviewDidScroll will call when you move through the rows in tableview
func scrollViewDidScroll(_ scrollView: UIScrollView) {
//check for the visible rows
let indexpath = self.tableView.indexPathsForVisibleRows?.last
//check if the visible row last is equal to the total number of counts
if(indexpath?.last == self.listCount){
//code for adding data to the tableview and reload the table view.
}
}
look in the link for more details about indexPathForVisibleRows
https://developer.apple.com/documentation/uikit/uitableview/1614885-indexpathsforvisiblerows
I am using UICollectionView with the minimum development target of iOS9 and found that can support drag and drop in terms of interactive movement. Everything works fine but the dropping the cell as the last cell in the target section is not working.
NB: I don't want the iOS11 drag and drop solution, because my App targets iOS9 onwards. Creating a dummy cell at the end of every section is not a straight forward solution.
Please see the image to get the problem visually.
Thanks in advance.
I have encountered the same issue, and finally managed to get it done. I used Apple documentation and multiple blog post about UICollectionView to build a fully functional Drag'N Drop feature between sections and even on invalid indexPaths.
Implementing default Drag'N Drop
First of all you have to disable the automatic Drag'N Drop feature offered by Apple, because you will be using your own GestureRecognizer.
So, add this in your viewDidLoad :
// deactivate default gesture recognizer for drag'n drop
self.installsStandardGestureForInteractiveMovement = NO;
Add a longPressGestureRecognizer to your collectionView, add the UIGestureRecognizerDelegate to your viewController protocols, and set the delegate in your viewDidLoad :
_longPressGestureRecognizer.delegate = self;
You now have to implement the longPressGestureRecognizer action :
// static variables to manage drag'n drop on invalid spaces
static NSIndexPath * longPressIndexPath = nil;
static CGPoint longPressLocation = (CGPoint) {0, 0};
- (IBAction)longPress:(UILongPressGestureRecognizer *)sender {
#autoreleasepool {
static BOOL isDragNDropping = NO;
longPressLocation = [sender locationInView:self.collectionView];
longPressIndexPath = [self.collectionView indexPathForItemAtPoint:longPressLocation];
// get the cell at indexPath (the one you long pressed)
UICollectionViewCell* cell = nil;
if (sender.state == UIGestureRecognizerStateChanged) {
NSLog(#"%s : STATE CHANGED", __FUNCTION__);
// Do stuff with cell
// Update the cell movement if the longPress location changes
if (isDragNDropping) {
[self.collectionView updateInteractiveMovementTargetPosition:longPressLocation];
} else {
// It's the first longPress movement, start the drag'n drop
if (longPressIndexPath) {
[self.collectionView beginInteractiveMovementForItemAtIndexPath:longPressIndexPath];
isDragNDropping = YES;
}
}
return;
}
if (sender.state == UIGestureRecognizerStateRecognized) {
NSLog(#"%s : STATE RECOGNIZED", __FUNCTION__);
// do stuff with the cell
// We were long pressing on a cell
if (isDragNDropping) {
[self.collectionView endInteractiveMovement];
}
isDragNDropping = NO;
return;
}
if (sender.state == UIGestureRecognizerStateBegan) {
NSLog(#"%s : STATE BEGAN", __FUNCTION__);
// do stuff with the newly selected cell
if (longPressIndexPath) {
cell = [self.collectionView cellForItemAtIndexPath: longPressIndexPath];
// You can add custom animations on the cell
[UIView animateWithDuration:0.35f animations:^{
[cell setTransform:CGAffineTransformMakeScale(1.2f, 1.2f)];
cell.layer.shadowColor = [UIColor blackColor].CGColor;
cell.layer.shadowRadius = 6.f;
cell.layer.shadowOpacity = 0.6f;
} completion:^(BOOL finished) {
}];
}
isDragNDropping = NO;
return;
}
}
}
Basically, at this point you have done the default Drag'N Drop that Apple was doing.
Bypassing the invalid indexPaths
The main thing is to implement this callback :
(NSIndexPath *)collectionView:(UICollectionView *)collectionView targetIndexPathForMoveFromItemAtIndexPath:(NSIndexPath *)originalIndexPath toProposedIndexPath:(NSIndexPath *)proposedIndexPath
It allows you to bypass the proposed indexPath to one of your choice.
You also have to implement this to keep track of the reordering :
(In case you are using CoreData and NSFetchedResultsController as your DataSource, you need to use a ranking to sort your items and this rank would have to be changed here)
-(void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
Now the main problem is that you want to insert in an invalid indexPath (since it does not exists yet).
To workaround that, you have to keep a record of the longPressGestureRecognizer location and indexPath. I have declared these 2 variables as static but ViewController's property would do as well.
The key here is to generate virtual indexPaths at your longPressGestureRecognizerlocation instead of the proposed indexPath like this :
- (NSIndexPath *)collectionView:(UICollectionView *)collectionView targetIndexPathForMoveFromItemAtIndexPath:(NSIndexPath *)originalIndexPath toProposedIndexPath:(NSIndexPath *)proposedIndexPath
{
NSLog(#"%s", __FUNCTION__);
NSLog(#"original idxPath : %li - %li | proposed idxPath : %li - %li", originalIndexPath.section, originalIndexPath.item, proposedIndexPath.section, proposedIndexPath.item);
// The longPressIndexPath is valid, we are drag'n dropping on an valid location, keep the proposedIndexPath
if (longPressIndexPath != nil) {
return proposedIndexPath;
}
// The longPressIndexPath is nil, which means we are drag'n dropping on a new location (at the end of a section in most cases)
if (longPressIndexPath == nil) {
NSLog(#"%s virtualIndexPath", __FUNCTION__);
// This part is not actually needed,
// I have added a way to accept drops on header/footer, and add the item to the corresponding section
// Build an set with each sectionIndexPaths
NSMutableSet<NSIndexPath*>* visiblesSectionIndexPaths = [NSMutableSet setWithArray:[self.collectionView indexPathsForVisibleSupplementaryElementsOfKind:UICollectionElementKindSectionHeader]];
[visiblesSectionIndexPaths addObjectsFromArray:[self.collectionView indexPathsForVisibleSupplementaryElementsOfKind:UICollectionElementKindSectionFooter]];
// Find the section containing the gesture location
// Custom method that return the index of the section containing the given point, -1 if no section were found
NSInteger sectionIndex = [self sectionIndexContainingPoint:longPressLocation];
if (sectionIndex > -1) {
// If so, generate a virtual indexPath, where we can drop this item
// The management of the indexPath in the dataSource will happen in the moveItemAtIndexPath callback
// We return a new indexPath
int itemIndex = [self.collectionView numberOfItemsInSection:sectionIndex];
if (itemIndex<0) {
itemIndex=0;
}
// Generate a virtual indexPath
NSIndexPath * virtualIndexPath;
virtualIndexPath = [NSIndexPath indexPathForItem:itemIndex inSection:sectionIndex];
NSLog(#"virtual idxPath : %li - %li", virtualIndexPath.section, virtualIndexPath.item);
return virtualIndexPath;
}
return proposedIndexPath;
}
}
And finally, you implement the moveItemAtIndexPath method
You have to change the section your item belongs to in your backing data container, and call a reloadDatato update your collectionView. This part is entirely dependent on your dataSource, I have done it myself with CoreData and NSFetchedResultsController.
Hope this will help.
N.B.: this is mostly chunks of code extracted from my own implementation, I'm not sure it will work as is, but you have the keys to make it roll.
The same behavior of UICollectionView as described here has been led to this question. Even though I decided to post my own one, because I did further investigations, I didn't want to post in a comment or in edit of the question mentioned above.
What happens?:
When large cells being displayed in a UICollectionView with a UICollectionViewFlowLayout, after scrolling the collection view to a certain offset, the cells will disappear.
When scrolling further until another cell comes into visible area, the vanished/hidden cell becomes visible again.
I tested with a vertical scrolling collection view and full-width-cells, but I'm rather sure, that it would also happen with similar setups for horizontal scrolling.
What are large cells?:
The described behavior happens with cells higher than twice the display height (960.f + 1.f on 3,5 inch displays, 1136.f + 1.f on 4 inch).
What exactly happens?:
When the scrolling offset of the collection view exceeds cell.frame.origin.y + displayHeightOfHardware the cells hidden property is set to YES and -collectionView:didEndDisplayingCell:forItemAtIndexPath: gets called (e.g. the first cell changes to hidden when scrollingOffset.y reaches 481.f on 3,5-inch-iPhone).
As described above, when scrolling until next cell comes into view, the hidden cell gets displayed again (i.e. hidden property changes to NO) and furthermore, when scrolling far enough the cell will never vanish again, when it shouldn't, no matter where you scroll to.
This changes when working with cells larger than triple-display-height (1441.f/1705.f). Those show the same behavior, but it stays the same, no matter how far they're being scrolled up and down.
What else?:
The situation can not be fixed by overriding -(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds to return YES.
The cells cannot being forced to display with setting the hidden property to NO programmatically after they were hidden (in didEndDisplayingCell for example)
So, whats the question?:
I'm pretty sure, that this is a bug in UICollectionView/Controller/Cell/Layout and I'll submit a TSI at Apple. But for the meantime: Has anyone any ideas for a quick hack solution?
i have a VERY dirty and internal solution for this problem:
#interface UICollectionView ()
- (CGRect)_visibleBounds;
#end
#interface MyCollectionView : UICollectionView
#end
#implementation MyCollectionView
- (CGRect)_visibleBounds {
CGRect rect = [super _visibleBounds];
rect.size.height = [self heightOfLargestVisibleCell];
return rect;
}
- (float)heightOfLargestVisibleCell {
// do your calculations for current max cellHeight and return it
return 1234;
}
#end
I have a workaround that seems to be working for me and should not run amok of Apple's rules for iOS applications.
The key is the observation that the large cells bounds are the issue. I've worked around that by ensuring that one edge of the cell is within the viewable area of the scrollable content region. You'll obviously need to subclass the UICollectionViewFlowLayout class or UICollectionViewLayout depending on your needs and make use of the contentOffset value to track where you are in the UIScrollView.
I also had to ensure:
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
returns YES or face a runtime exception indicating the layout was invalid. I keep the edge of the larger cell bound to the left edge in my case. This way you can avoid the erroneous bounds intersection detection for these larger cells.
This does create more work depending on how you would like the contents of the cell to be rendered as the width/height of the cell is being updated as you scroll. In my case, the subviews within the cell are relatively simple and do not require a lot of fiddling with.
As requested here is an example of my layoutAttributesInRect
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
NSMutableArray* attributes = [NSMutableArray array];
NSArray *vertical = myVerticalCellsStore.cells;
NSInteger startRow = floor(rect.origin.y * (vertical.count)/ (vertical.count * verticalViewHeight + verticalViewSpacing * 2));
startRow = (startRow < 0) ? 0 : startRow;
for (NSInteger i = startRow; i < vertical.count && (rect.origin.y + rect.size.height >= i * verticalViewHeight); i++) {
NSArray *horizontals = myHorizontalStore.horizontalCells;
UICollectionViewLayoutAttributes *verticalAttr = [self layoutAttributesForSupplementaryViewOfKind:#"vertical" atIndexPath:[NSIndexPath indexPathForItem:0 inSection:i]];
if (CGRectIntersectsRect(verticalAttr.frame, rect)) {
[attributes addObject:verticalAttr];
}
BOOL foundAnElement = NO;
for (NSInteger j = 0 ; j < horizontals.count; j++) {
MYViewLayoutAttributes *attr = (MyViewLayoutAttributes *)[self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:j inSection:i]];
if (CGRectIntersectsRect(rect, attr.frame)) {
[attributes addObject: attr];
foundAnElement = YES;
}
else if (foundAnElement) {
break;
}
}
}
return attributes;
}
This is my sanitized code. Basically I calculate about were the first cell should be based on the cell height. In my case that is fixed, so the calculation is pretty easy. But my horizontal elements have various widths. So the inner loop is really about figuring out the right number of horizontal cells to include in the attributes array. There I'm using the CGRectIntersectsRect to determine if the cell intersects. Then the loop keeps going until the intersection fails. And if at least one horizontal cell has been found the loop will break. Hope that helps.
My solution is basically the same as Jonathan's but in a category, so you don't have to use your own subclass.
#implementation UICollectionView (MTDFixDisappearingCellBug)
+ (void)load {
NSError *error = nil;
NSString *visibleBoundsSelector = [NSString stringWithFormat:#"%#isib%#unds", #"_v",#"leBo"];
if (![[self class] swizzleMethod:NSSelectorFromString(visibleBoundsSelector) withMethod:#selector(mtd_visibleBounds) error:&error]) {
FKLogErrorVariables(error);
}
}
- (CGRect)mtd_visibleBounds {
CGRect bounds = [self mtd_visibleBounds]; // swizzled, no infinite loop
MTDDiscussCollectionViewLayout *layout = [MTDDiscussCollectionViewLayout castedObjectOrNil:self.collectionViewLayout];
// Don`t ask me why, but there's a visual glitch when the collection view is scrolled to the top and the max height is too big,
// this fixes it
if (bounds.origin.y <= 0.f) {
return bounds;
}
bounds.size.height = MAX(bounds.size.height, layout.maxColumnHeight);
return bounds;
}
#end
I found that this issue only occurred when using a subclassed UICollectionViewLayoutAttributes and when that attribute class did not have a correct isEqual: method.
So for example:
#implementation COGridCollectionViewLayoutAttributes
- (id)copyWithZone:(NSZone *)zone
{
COGridCollectionViewLayoutAttributes *attributes = [super copyWithZone:zone];
attributes.isInEditMode = _isInEditMode;
return attributes;
}
- (BOOL)isEqual:(id)other {
if (other == self) {
return YES;
}
if (!other || ![[other class] isEqual:[self class]]) {
return NO;
}
if ([((COGridCollectionViewLayoutAttributes *) other) isInEditMode] != [self isInEditMode]) {
return NO;
}
return [super isEqual:other];
}
#end
Worked but originally I had:
return YES;
This is on iOS 7.
Because right now, viewWithTag actually search for itself first, and then all subviews recursively down the whole subtree, for a view with that tag.
But what if I set the tags of the subviews to 100, 101, etc, and later on, look for tag 100, but the parent of this current view sets the current view's tag to 100? Then viewWithTag will return the current view instead of any subview.
It is also strange that if the code is
[fooView viewWithTag: 123]
why would the code want to search the subtree including fooView itself? It is like, the code doesn't know fooView good enough to want to search for it too. Or put it another way, fooView is told to search itself... which is strange. A view doesn't know itself? (need to do a search to look for itself?)
So is there a way to search for subviews and grand-subviews only (without searching for self)?
Take advantage of the recursive nature of -viewWithTag:
- (UIView *)viewWithTagNotCountingSelf:(NSInteger)tag
{
UIView *toReturn = nil;
for (UIView *subView in self.subviews) {
toReturn = [subView viewWithTag:tag];
if (toReturn) {
break;
}
}
return toReturn;
}
Edit: this will drill down farther than "grand-subviews": it will get any view within the hierarchy that is not self. Also this is to be implemented in a category on UIView.
let result = view.subviews.filter{$0.tag == tag}.first
After reviewing the documentation for -viewWithTag: and running a few tests, it appears the answer to OP's question is - This behavior is already provided.
Return Value
The view in the receiver’s hierarchy whose tag property matches the
value in the tag parameter.
Discussion
This method searches the current view and all of its subviews for the
specified view.
I am concluding this to mean that 'view' is also a 'subview', thus limiting the scope of the search.
do this:
NSMutableArray *arrSameViewTag = [NSMutableArray array];
for(UIView *subview in [yourView subviews]) //your view to find subview
{
if(subview.tag == 123) //specific tah here
{
[arrSameViewTag addObject:subview]; //view found add in array
}
}
NSlog(#"arrSameViewTag : %#",arrSameViewTag);
To find specific like UIButton or any UIElement then like this:
NSMutableArray *arrSameViewTag = [NSMutableArray array];
for(id *subview in [yourView subviews]) //your view to find subview
{
if([subview isKindofClass[UIButton class]) //any UIElement of specific type here
{
UIButton *btn = (UIButton *)subview; //same UIElement mentioned for checking it
if(btn.tag == 123) //specific tah here
{
[arrSameViewTag addObject:subview]; //view found add in array
}
}
}
NSlog(#"arrSameViewTag : %#",arrSameViewTag)
For 1 level:
UIView *view;
for (int i = 0; i < viewToSearch.subviews.count; i++){
UIView *subview = viewToSearch.subviews[i];
if (subview.tag == tagToSeach){
view = subview;
break;
}
}
To search a view hierarchy with multiple levels:
__block UIView *view;
BOOL (^__block searchViewForTag)(UIView *,NSInteger) = ^(UIView *aView, NSInteger tag){
for (UIView *subview in aView.subviews){
if (subview.tag == tag){
view = subview;
return YES;
}
if (searchViewForTag(subview,tag)) return YES;
}
return NO;
};
NSInteger tagToSearchFor = 1;
searchViewForTag(viewToSearch,tagToSearchFor);
//Do something with view
How do I do an infinite scrolling in a UITableView? I know how to do it using a UIScrollView, in which apple has demonstrated in one of the WWDC's video. I tried doing the following in tableView:cellForRowAtIndexPath::
if (indexPath.row == [self.newsFeedData_ count] - 1)
{
[self.newsFeedData_ addObjectsFromArray:self.newsFeedData_];
[self.tableView reloadData];
}
but this fails. Any other idea?
If you need to know when you hit the bottom of the UITableView, become it's delegate (because it is a subclass of UIScrollView), and use the -scrollViewDidScroll: delegate method to compare the table's content height and it's actual scroll position.
EDIT (something like this):
- (void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat actualPosition = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height - (someArbitraryNumber);
if (actualPosition >= contentHeight) {
[self.newsFeedData_ addObjectsFromArray:self.newsFeedData_];
[self.tableView reloadData];
}
}
You can support infinite scroll with pull to refresh at the top and/or scroll continuously at the bottom with a spinner wheel using:
https://github.com/samvermette/SVPullToRefresh
SVPullToRefresh handles the logic when UITableView reaches the bottom. A spinner is shown automatically and a callback block is fired. You add in your business logic to the callback block.
Here's an example:
#import "UIScrollView+SVInfiniteScrolling.h"
// ...
[tableView addInfiniteScrollingWithActionHandler:^{
// append data to data source, insert new cells at the end of table view
// call [tableView.infiniteScrollingView stopAnimating] when done
}];
This project can be added to your project using CocoaPods or directly compiled into your project.
Here's a very quick and complete demo of an infinite scrolling UITableView I put together...
#interface InfiniteScrollViewController ()
#property (nonatomic) NSMutableArray *tableViewData;
#property (nonatomic) BOOL loadingMoreTableViewData;
#end
#implementation InfiniteScrollViewController
- (void)viewDidLoad {
self.tableViewData = [[NSMutableArray alloc] init];
[self addSomeMoreEntriesToTableView];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return self.tableViewData.count + 1;
}
- (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];
}
if (indexPath.row < self.tableViewData.count) {
cell.textLabel.text = [self.tableViewData objectAtIndex:indexPath.row];
} else {
cell.textLabel.text = #"Loading more data...";
// User has scrolled to the bottom of the list of available data so simulate loading some more if we aren't already
if (!self.loadingMoreTableViewData) {
self.loadingMoreTableViewData = YES;
[self performSelector:#selector(addSomeMoreEntriesToTableView) withObject:nil afterDelay:5.0f];
}
}
return cell;
}
- (void)addSomeMoreEntriesToTableView {
int loopTill = self.tableViewData.count + 20;
while (self.tableViewData.count < loopTill) {
[self.tableViewData addObject:[NSString stringWithFormat:#"%i", self.tableViewData.count]];
};
self.loadingMoreTableViewData = NO;
[self.tableView reloadData];
}
#end
'UITableView' is same as 'UIScrollView' in 'scrollViewDidScroll' method.
So, its easy to emulate infinite scrolling.
double the array so that head and tail are joined together to emulate circular table
use my following code to make user switch between 1st part of doubled table and 2nd part of doubled table when they tend to reach the start or the end of the table.
:
/* To emulate infinite scrolling...
The table data was doubled to join the head and tail: (suppose table had 1,2,3,4)
1 2 3 4|1 2 3 4 (actual data doubled)
---------------
1 2 3 4 5 6 7 8 (visualising joined table in eight parts)
When the user scrolls backwards to 1/8th of the joined table, user is actually at the 1/4th of actual data, so we scroll instantly (we take user) to the 5/8th of the joined table where the cells are exactly the same.
Similarly, when user scrolls to 6/8th of the table, we will scroll back to 2/8th where the cells are same. (I'm using 6/8th when 7/8th sound more logical because 6/8th is good for small tables.)
In simple words, when user reaches 1/4th of the first half of table, we scroll to 1/4th of the second half, when he reaches 2/4th of the second half of table, we scroll to the 2/4 of first half. This is done simply by subtracting OR adding half the length of the new/joined table.
*/
-(void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat currentOffsetX = scrollView_.contentOffset.x;
CGFloat currentOffSetY = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height;
if (currentOffSetY < (contentHeight / 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY + (contentHeight/2)));
}
if (currentOffSetY > ((contentHeight * 6)/ 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY - (contentHeight/2)));
}
}
P.S. - I've used this code on one of my apps called NT Time Table (Lite). If you want the preview, you can check out the app: https://itunes.apple.com/au/app/nt-time-table-lite/id528213278?mt=8
If your table can sometimes be too short, at the beginning of the above method you can add a if logic to exit the method when data count is say for example less than 9.
For me worked better scrollViewDidEndDragging: than scrollViewDidScroll:.
The second approach will send you each position during scroll and cause, if you are fetching remote resources you will hit your endpoint several times, which is not good.
Complete example based on #codafi solution with comments from #danielgomezrico about how to calculate contentHeight:
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
willDecelerate:(BOOL)decelerate {
CGFloat actualPosition = scrollView.contentOffset.y;
CGFloat contentHeight = scrollView.contentSize.height - (self.tableView.frame.size.height);
if (actualPosition >= contentHeight) {
// fetch resources
[self.tableView reloadData];
}
}
Generally I override scrollViewDidEndDecelerating and inside it I put my code to request more data.
Example:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
float endScrolling = scrollView.contentOffset.y + scrollView.frame.size.height;
if (endScrolling >= scrollView.contentSize.height){
//put here your code
}
}
Recently I uploaded on GitHub a subclass of UITableView, that implements the infinite scroll.
You can download it here:
https://github.com/alchimya/iOS-LazyTableView
rather than overriding we can do this optimally in layoutSubviews.
Here's how I got it implemented. You can get to know more about the implementation here
- (void)layoutSubviews{
[super layoutSubviews];
if(self.delegateForViews){
CGPoint contentOffset = self.contentOffset;
if([self.delegateForViews noOfViews]>numOfReusableViews){
NSUInteger centerIndex=visibleViews.count/2;
NSUInteger noOfViews=[self.delegateForViews noOfViews];
UIView *centerView=[visibleViews objectAtIndex:centerIndex];
CGPoint centerViewOrigin=centerView.frame.origin;
CGSize centerViewSize=centerView.frame.size;
CGFloat offsetDifference=contentOffset.x-centerViewOrigin.x;
CGFloat offsetDifferenceAbs=fabs(contentOffset.x-centerViewOrigin.x);
if(offsetDifferenceAbs>=centerViewSize.width){
if(offsetDifference<0){
currentPosition--;
}else{
currentPosition++;
}
self.contentOffset=centerViewOrigin;
currentPosition=[self getPosition:currentPosition noOfViews:noOfViews];
[self.delegateForViews clearView:centerView];
[self.delegateForViews setupView:centerView forPosition:currentPosition];
for (int i=centerIndex-1; i>=0; i--) {
UIView* prevView=[visibleViews objectAtIndex:i];
[self.delegateForViews clearView:prevView];
[self.delegateForViews setupView:prevView forPosition:
[self getPosition:currentPosition-1 noOfViews:noOfViews]];
}
for (int i=centerIndex+1; i<visibleViews.count; i++) {
UIView* nextView=[visibleViews objectAtIndex:i];
[self.delegateForViews clearView:nextView];
[self.delegateForViews setupView:nextView forPosition:
[self getPosition:currentPosition+1 noOfViews:noOfViews]];
}
}
}
}
}
One of the simple and that offered me everything i need is this class:
https://github.com/jakemarsh/JMStatefulTableViewController
You just need to subclass JMStatefulTableViewController and the it has 3 methods that you need to overwrite:
one that is called on init, to get the initial data
statefulTableViewControllerWillBeginInitialLoading
one when the user pull to refresh
statefulTableViewControllerWillBeginLoadingFromPullToRefresh
one when is called for the infinite scroll (next page)
statefulTableViewControllerWillBeginLoadingNextPage
This can be used from Cocoapods too.
scrollviewDidScroll will call when you move through the rows in tableview
func scrollViewDidScroll(_ scrollView: UIScrollView) {
//check for the visible rows
let indexpath = self.tableView.indexPathsForVisibleRows?.last
//check if the visible row last is equal to the total number of counts
if(indexpath?.last == self.listCount){
//code for adding data to the tableview and reload the table view.
}
}
look in the link for more details about indexPathForVisibleRows
https://developer.apple.com/documentation/uikit/uitableview/1614885-indexpathsforvisiblerows