Related
So most of the problems people have with this particular event is to have scrollViewDidScroll fire when there is animation happening. My case is just the opposite. I feel that scrollViewDidScroll should NOT be firing in my case.
Let me further explain.
I am animating things in scrollViewDidScroll and this was working perfectly until I moved UITableView into a UIView class.
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
// Animation code here.
NSLog(#"scrollViewDidScroll");
}
- (void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
NSLog(#"scrollViewDidEndDecelerating");
NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
[_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
}
What this provides is a smooth scrolling experience that snaps back to a previous table row. The console can verify that scrollViewDidScroll event is firing because of scrollToRowAtIndexPath.
Console:
2014-03-31 22:21:43.346 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.379 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.429 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.462 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.479 Project[45843:a0b] scrollViewDidEndDecelerating
2014-03-31 22:21:43.496 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.513 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.529 Project[45843:a0b] scrollViewDidScroll
Onto the questions:
1. How can I ensure that the event scrollViewDidScroll only fires due to user interaction and not automation from code?
2. Is there another method that provides the same functionality as scrollToRowAtIndexPath without triggering scrollViewDidScroll?
I know this is a very old question. I just have been in a similar situation that I need to run some code only when the user is scrolling but not when I call scrollToRowAtIndexPath. I have found an easier solution for this using the scrollView variables dragging and decelerating.
we have 3 cases of scrolling here.
user is dragging
user just ended dragging and the tableview is decelrating
programmatically called scrollForRowAtIndexPath:
All of the cases above will trigger scrollViewDidScroll: but
user is dragging dragging is True and decelerating is False
user just ended dragging and the tableview is decelrating dragging is False and decelerating is True
programmatically called scrollForRowAtIndexPath: dragging is False and decelerating is False
So your code will be like something like this:
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView.dragging)
{
// Do what you want when user is dragging
} else if (scrollView.decelerating)
{
// Do what you want when table is decelerating after finished dragging
} else
{
// Do what you want when table is scrolling programmatically.
}
}
Or if you want to just distinguish the scrolling progammatically
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView.dragging || scrollView.decelerating)
{
// Scrolling by the user
} else
{
// Scrolling by the code
}
}
Soon after I posted the question, I took a small break, came back to the problem and figured it out. Should of done that sooner instead of wasting a few hours. bleh!
The solution is simple, set a bool flag that gets set before any progammatic scrolling and then change that after the animation is done using the event scrollViewDidEndScrollingAnimation.
bool performingAutomatedScroll = false;
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
// If we are scrolling because of code, don't use any animations.
if (performingAutomatedScroll) return;
// Animation code here.
}
- (void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
performingAutomatedScroll = true;
NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
[_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
[_myTableView reloadRowsAtIndexPaths:[_timeCarousel indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationNone];
}
- (void) scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
if (!decelerate) {
performingAutomatedScroll = true;
NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
[_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
[_myTableView reloadRowsAtIndexPaths:[_timeCarousel indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationNone];
}
}
-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
performingAutomatedScroll = false;
}
My UI structure is as follow:
UITabBarController (TBC) -> UINavigationController (NC) -> UITableViewController (TVC)
(for the simplicity of the example lets say the TBC has only one controller on its viewControllers array - the NC)
My TVC has UISearchBar as its table header, and when the TVC appear I hide the search bar beneath the NC navigation bar by settings the table view content offset.
When user tap a cell in the TVC another view controller is pushed (VC) and hides the tab bar with VC.hidesBottomBarWhenPushed = YES;
Now there is a very annoying behavior that I dont know how to solve:
When the user tap the back button from VC back to TVC, the search bar jumps to be visible even if it was hidden (beneath the navigation bar) before the VC was pushed.
This effect happens only if the TVC doesn't have enough rows to fill the screen, its like the search bar force itself to be visible if there is a place on screen. but its really looks bad and buggy.
I uploaded a simple project that demonstrates the problem, it has the same structure as I described in my question.
I added two bar buttons for your convenience, the "hide bar" button hides the search bar for you, and the "toggle count" button toggle the table view rows count to demonstrate that the issue happens only if there are few items.
Okay.. It looks to me like you've stumbled upon a bug. It should be reported through apples bugreporter (here).
I've made a fairy simple working work-around, but keep in mind that it is a work-around. This will work, but you might have to review it if you have/add other controls to the tableView. It should be safe to use(not acting randomly), and it's not the ugliest of work-arounds, so I think it's fine to use in a release. I've uploaded the same project with the fix here, and you can just go ahead and download it, and you'll probably understand what I've done. I'll explain (in extreme detail) what I've actually thought and done here, in case the download links dies in the future:
Train of thought:
As simalone also said, the problem is that when hidesBottomBarWhenPushed is set to YES, then it will call an additional viewDidLayoutSubviews which somehow resets your current state. We need to override viewDidLayoutSubviews, and check if we are laying out subviews because we are coming from ViewController, or if it's just a regular call. When we establish that the call is indeed because we are returning from ViewController, we need to hide the search bar (only if it was hidden before).
When we return from ViewController, three calls are made to viewDidLayoutSubviews in TableViewController. I'm guessing the first is for tableView, and it seems that the second call is 'for'(or rather from) the tabBar. This second one is the one moving the searchBar down. I have no idea what the third call is, but we can ignore it.
So now there are three things we need to check inside viewDidLayoutSubviews: We need to check if we are returning from ViewController, we need to check if the searchBar was hidden before we pushed(if it should hidden be now), and we need to check that it's the second call to this method.
First things first.
In TableViewController, I added a property #property BOOL backPush; to the header(.h)-file. Now I need to change this variable from ViewController.
In ViewController, I put this:
#import "TableViewController"
...
-(void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
if(self.isMovingFromParentViewController)
{
if([self.navigationController.topViewController isKindOfClass:[TableViewController class]])
[((TableViewController*)self.navigationController.topViewController) setBackPush:YES];
}
}
In the code above, when the view is disappearing (I.E pushing forward, back, closing, whatever), I'm checking if we are disappearing because it was removed from the parent. If it is(which it is when the back-button is called), I check if the now-current top view controller is of class TableViewController, which it also is if we go back. Then I set the property backPush to YES. That's the only thing we need in ViewController.
Now, to the TableViewController. I added a counter next to your row-count:
#interface TableViewController () {
NSInteger _rows;
int count;
}
This is to keep track of how many calls have been made to viewDidLayoutSubviews later. I set count = 0; in viewDidLoad.
Now to the magic:
-(void)viewDidLayoutSubviews
{
[super viewDidLayoutSubviews];
if((self.backPush && count == 0 && self.tableView.contentOffset.y ==
self.tableView.tableHeaderView.frame.size.height) ||
(self.backPush && count == 1 &&
self.tableView.contentOffset.y == 0))
{
if(count == 0)
count++;
else
{
count = 0;
self.backPush = NO;
[self hideSearchBar];
}
}
else if((count == 0 || count == 1) || self.tableView.tableHeaderView.isFirstResponder)
{
count = 0;
self.backPush = NO;
}
}
The first if-statement wants either of these situations:
backPush is YES, count is 0, and searchBar is already hidden.
backPush is YES, count is 1, and searchBar is visible.
If 1. is true, then we increment count by 1.
If 2. is true, then 1. has already happened, and we now know that we are in the second round of viewDidLayout.. when we are coming back from VC AND that the searchBar WAS hidden (because 1. happened) but now isn't hidden. It probably happens in the super-method or something.
Now we can finally push the searchBar out again. I also reset count and set backPush back to NO.
The else if is also pretty important. It checks if count is 0 or 1, or if the searchBar has the keyboard showing. If count is 0 or 1 when it reaches here, it means that the first if-statement failed, e.g that the searchBar wasn't hidden, or that it was scrolled far up.
(When I think of it, the else-if should check if backPush is YES as well. Now it sets those variables repeatedly)
Let me know if you find a better way!
I think this one is simple solution. Thanks to
Sti
for giving some ideas to solve this bug.
Initialize variable var hideSearchBar = false
and inside viewDidLayoutSubviews add this code for maintain same content offset.
if hideSearchBar == true {
self.tableView.contentOffset = CGPointMake(0, self.tableView.tableHeaderView!.bounds.height - self.tableView.contentInset.top)
}
Finally implement below methods.
override func scrollViewDidScroll(scrollView: UIScrollView) {
if self.tableView.tableHeaderView!.bounds.height - self.tableView.contentInset.top == self.tableView.contentOffset.y && self.tableView.dragging == false {
hideSearchBar = true
}
else if self.tableView.dragging == true {//Reset hiding process after user dragging
hideSearchBar = false
}
}
func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
if self.tableView.contentOffset.y + self.tableView.contentInset.top <= self.tableView.tableHeaderView!.bounds.height
{
self.tableView.contentOffset = CGPointMake(0, self.tableView.tableHeaderView!.bounds.height - self.tableView.contentInset.top)
}
}
Try to set for TVC
self.automaticallyAdjustsScrollViewInsets = NO
This is a problem caused by hidesBottomBarWhenPushed = YES , if you uncheck Hide Bottom Bar On Push, the searchBar will not appear when VC back to TVC.
Try this in TableViewController.m:
- (void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
[self hideSearchBar];
}
I can't explain why but I know that if hidesBottomBarWhenPushed = YES for UITabBarController to push vc, viewDidLayoutSubviews will be called more than once when the view appears again. First time subviews keep the same position, whereas the second time be called, subviews will be adjusted for some reason to relayout with the most original position, which is very weird. Do your custom layout in viewDidLayoutSubviews will prevent this to happen even after viewDidAppear.
My solution is a little stupid.
Add this method to the sample code.
- (void)viewWillLayoutSubviews
{
[self hideSearchBar];
}
It seems the tableView will redraw the scrollView inside it.
Since the tableView reset the contentOffset, I made a custom tableView has property to save the hidden status of search bar.Below is the code.Hope it helps.
//
// TableViewController.m
// SearchBarJump
//
// Created by Eyal Cohen on 3/9/14.
// Copyright (c) 2014 Eyal. All rights reserved.
//
#import "TableViewController.h"
#interface CustomTableView : UITableView
#property (nonatomic, assign, getter = isSearchBarHidden)BOOL searchBarHidden;
#end
#implementation CustomTableView
#synthesize searchBarHidden = _searchBarHidden;
- (void)layoutSubviews
{
[super layoutSubviews];
if (self.isSearchBarHidden) {
[self hideSearchBar:NO];
}
}
- (void)setSearchBarHidden:(BOOL)searchBarHidden
{
_searchBarHidden = searchBarHidden;
if (_searchBarHidden && self.contentOffset.y != self.tableHeaderView.frame.size.height) {
[self hideSearchBar:YES];
}
}
- (void)hideSearchBar:(BOOL)animated {
// hide search bar
[self setContentOffset:CGPointMake(0.0, self.tableHeaderView.frame.size.height) animated:animated];
}
#end
#interface TableViewController () {
NSInteger _rows;
}
#property (nonatomic, weak) IBOutlet CustomTableView *mainTable;
#end
#implementation TableViewController
#synthesize mainTable = _mainTable;
- (id)initWithStyle:(UITableViewStyle)style
{
self = [super initWithStyle:style];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.view = _mainTable;
[_mainTable setDelegate:self];
[_mainTable setDataSource:self];
_rows = 3;
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.mainTable setSearchBarHidden:YES];
}
- (void)hideSearchBar {
// hide search bar
[_mainTable setContentOffset:CGPointMake(0.0, self.tableView.tableHeaderView.frame.size.height) animated:NO];
}
- (IBAction)toggleCount:(UIBarButtonItem *)sender {
if (_rows == 20) {
_rows = 3;
} else {
_rows = 20;
}
[_mainTable reloadData];
}
- (IBAction)hideBar:(UIBarButtonItem *)sender {
[self hideSearchBar];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return _rows;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
cell.textLabel.text = #"cell";
return cell;
}
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
[_mainTable setSearchBarHidden:NO];
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
if (_mainTable.contentOffset.y == _mainTable.tableHeaderView.bounds.size.height) {
[_mainTable setSearchBarHidden:YES];
}
}
#end
UITableViewController always modifies its UITableviews content offset in its viewDidAppear to make sure that its all rows are visible. So your hacky methods don't work here.
There are several solution to this problem. The one I selected is shown below
First delete that searchBar from your storyboard.
#interface TableViewController () {
NSInteger _rows;
}
#end
#implementation TableViewController
- (id)initWithStyle:(UITableViewStyle)style
{
self = [super initWithStyle:style];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
_rows = 4; // +1 for searchBar
}
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
}
- (void)hideSearchBar {
// hide search bar
[[self tableView] scrollToRowAtIndexPath:[NSIndexPath indexPathWithIndex:1] atScrollPosition:UITableViewScrollPositionTop animated:NO];
}
- (IBAction)toggleCount:(UIBarButtonItem *)sender {
if (_rows == 20) {
_rows = 4;
} else {
_rows = 20;
}
[self.tableView reloadData];
}
- (IBAction)hideBar:(UIBarButtonItem *)sender {
[self hideSearchBar];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return _rows;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if(indexPath.row == 0){
UITableViewCell *cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
UISearchBar *searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, tableView.frame.size.width,44)];
[cell addSubview:searchBar];
return cell;
}
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
cell.textLabel.text = #"cell";
return cell;
}
#end
The above solution just ensures that automatic scrolling magic is disabled.
If you want your default searchBar to be hidden override UITableView and call hideSearchBar when tableview is initially loaded for the first time.
I fix the bug just like this:
#interface NTTableView : UITableView
#end
#implementation NTTableView
-(void)setContentOffset:(CGPoint)contentOffset{
if (self.contentOffset.y==-20&&
contentOffset.y==-64) {
NSLog(#"iOS7 bug here, FML");
}else{
[super setContentOffset:contentOffset];
}
}
#end
Fix for my somewhat similar situation with a UISearchBar as the tableHeaderView. Not sure if this falls into the same exact scenario, but it hides the search bar when the view appears. (Being unconcerned with the amount of rows in the table view)
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:NO];
}
Setting edgesForExtendedLayout to [.top, .bottom] instead of just .top on TVC fixed problem for me.
Of course, automaticallyAdjustsScrollViewInsets is set to false
EDIT: seems that it only works if tvc.tabBar is translucent
As a weird hack I can only suggest to add an empty cell to the end of cells with height about 400
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return _rows + 1;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
if(indexPath.row == _rows)
{
//cellEmpty - cell identifier in storyboard
cell = [tableView dequeueReusableCellWithIdentifier:#"cellEmpty" forIndexPath:indexPath];
}
else
{
cell.textLabel.text = #"cell";
}
// Configure the cell...
return cell;
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
if(indexPath.row == _rows)
{
return 400;
}
else
{
return 44;
}
}
your output file
https://github.com/iDevAndroid/SearchBarJump
simply use this code don't make do complex for that
-(void)viewDidDisappear:(BOOL)animated{
[self.tableView setContentInset:UIEdgeInsetsMake(-0.3, 0, 0, 0)];
[super viewDidAppear:animated];
}
here is one problem if you are set UIEdgeInsetsMake(0, 0, 0, 0) the searchBar jumping as in original mode
When I call insertItemsAtIndices on an AQGridView, the items are overlapping, rather than being displayed in their relevant grid. It works fine if I call reloadData on the GridView, but I'd like to just add one cell at a time.
I have portraitGridCellSizeForGridView implemented, but it doesn't seem to be getting called after an insert call.
Here's the relevant code to insert:
[self.cartItemArray addObject:cartItem];
[self.cartGridView beginUpdates];
[self.cartGridView insertItemsAtIndices:[NSIndexSet indexSetWithIndex:self.cartItemArray.count - 1] withAnimation:AQGridViewItemAnimationNone];
[self.cartGridView endUpdates];
Here's the AQGridView delegate methods:
- (NSUInteger)numberOfItemsInGridView:(AQGridView *)gridView {
return _cartItemArray.count;
}
- (AQGridViewCell *)gridView:(AQGridView *)gridView cellForItemAtIndex:(NSUInteger)index {
static NSString * GridCellIdentifier = #"CartItemListViewCell";
CartItemListViewCell_iPad * cell = (CartItemListViewCell_iPad *)[gridView dequeueReusableCellWithIdentifier:GridCellIdentifier];
if (!cell) {
CGRect cellFrame = CGRectMake(0, 0, _cellWidth, _cellHeight);
cell = [[CartItemListViewCell_iPad alloc] initWithFrame:cellFrame reuseIdentifier:GridCellIdentifier];
}
CartItem *cartItem = [_cartItemArray objectAtIndex:index];
[(CartItemListViewCell_iPad*)cell updateCartItem:cartItem];
return cell;
}
- (CGSize)portraitGridCellSizeForGridView:(AQGridView *)gridView {
return CGSizeMake(_cellWidth, _cellHeight);
}
- (void)gridView:(AQGridView *)gridView didSelectItemAtIndex:(NSUInteger)index {
if (index >= _cartItemArray.count){
return;
}
self.selectedItemIndex = index;
[[NSNotificationCenter defaultCenter] postNotificationName:NotificationEditPrintSizeCartItem object:[_cartItemArray objectAtIndex:index]];
}
And here's what it looks like:
As you can see I'm using two AQGridView's on the screen. I wonder if that's causing the problem? Any help is appreciated. Thanks!
Ok, just solved it. Searching through the code, I noticed the following was called in reloadData:
[_gridData setDesiredCellSize: [_dataSource portraitGridCellSizeForGridView: self]];
So, now I'm calling reloadData before I add anything to it.
Is there some way to find out when a UITableView has finished asking for data from its data source?
None of the viewDidLoad/viewWillAppear/viewDidAppear methods of the associated view controller (UITableViewController) are of use here, as they all fire too early. None of them (entirely understandably) guarantee that queries to the data source have finished for the time being (eg, until the view is scrolled).
One workaround I have found is to call reloadData in viewDidAppear, since, when reloadData returns, the table view is guaranteed to have finished querying the data source as much as it needs to for the time being.
However, this seems rather nasty, as I assume it is causing the data source to be asked for the same information twice (once automatically, and once because of the reloadData call) when it is first loaded.
The reason I want to do this at all is that I want to preserve the scroll position of the UITableView - but right down to the pixel level, not just to the nearest row.
When restoring the scroll position (using scrollRectToVisible:animated:), I need the table view to already have sufficient data in it, or else the scrollRectToVisible:animated: method call does nothing (which is what happens if you place the call on its own in any of viewDidLoad, viewWillAppear or viewDidAppear).
This answer doesn't seem to be working anymore, due to some changes made to UITableView implementation since the answer was written. See this comment : Get notified when UITableView has finished asking for data?
I've been playing with this problem for a couple of days and think that subclassing UITableView's reloadData is the best approach :
- (void)reloadData {
NSLog(#"BEGIN reloadData");
[super reloadData];
NSLog(#"END reloadData");
}
reloadData doesn't end before the table has finish reload its data. So, when the second NSLog is fired, the table view has actually finish asking for data.
I've subclassed UITableView to send methods to the delegate before and after reloadData. It works like a charm.
I did have a same scenario in my app and thought would post my answer to you guys as other answers mentioned here does not work for me for iOS7 and later
Finally this is the only thing that worked out for me.
[yourTableview reloadData];
dispatch_async(dispatch_get_main_queue(),^{
NSIndexPath *path = [NSIndexPath indexPathForRow:yourRow inSection:yourSection];
//Basically maintain your logic to get the indexpath
[yourTableview scrollToRowAtIndexPath:path atScrollPosition:UITableViewScrollPositionTop animated:YES];
});
Swift Update:
yourTableview.reloadData()
dispatch_async(dispatch_get_main_queue(), { () -> Void in
let path : NSIndexPath = NSIndexPath(forRow: myRowValue, inSection: mySectionValue)
//Basically maintain your logic to get the indexpath
yourTableview.scrollToRowAtIndexPath(path, atScrollPosition: UITableViewScrollPosition.Top, animated: true)
})
So how this works.
Basically when you do a reload the main thread becomes busy so at that time when we do a dispatch async thread, the block will wait till the main thread gets finished. So once the tableview has been loaded completely the main thread will gets finish and so it will dispatch our method block
Tested in iOS7 and iOS8 and it works awesome;)
Update for iOS9: This just works fine is iOS9 also. I have created a sample project in github as a POC.
https://github.com/ipraba/TableReloadingNotifier
I am attaching the screenshot of my test here.
Tested Environment: iOS9 iPhone6 simulator from Xcode7
EDIT: This answer is actually not a solution. It probably appears to work at first because reloading can happen pretty fast, but in fact the completion block doesn't necessarily get called after the data has fully finished reloading - because reloadData doesn't block. You should probably search for a better solution.
To expand on #Eric MORAND's answer, lets put a completion block in. Who doesn't love a block?
#interface DUTableView : UITableView
- (void) reloadDataWithCompletion:( void (^) (void) )completionBlock;
#end
and...
#import "DUTableView.h"
#implementation DUTableView
- (void) reloadDataWithCompletion:( void (^) (void) )completionBlock {
[super reloadData];
if(completionBlock) {
completionBlock();
}
}
#end
Usage:
[self.tableView reloadDataWithCompletion:^{
//do your stuff here
}];
reloadData just asking for data for the visible cells. Says, to be notified when specify portion of your table is loaded, please hook the tableView: willDisplayCell: method.
- (void) reloadDisplayData
{
isLoading = YES;
NSLog(#"Reload display with last index %d", lastIndex);
[_tableView reloadData];
if(lastIndex <= 0){
isLoading = YES;
//Notify completed
}
- (void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
if(indexPath.row >= lastIndex){
isLoading = NO;
//Notify completed
}
That is my solution. 100% works and used in many projects. It's a simple UITableView subclass.
#protocol MyTableViewDelegate<NSObject, UITableViewDelegate>
#optional
- (void)tableViewWillReloadData:(UITableView *)tableView;
- (void)tableViewDidReloadData:(UITableView *)tableView;
#end
#interface MyTableView : UITableView {
struct {
unsigned int delegateWillReloadData:1;
unsigned int delegateDidReloadData:1;
unsigned int reloading:1;
} _flags;
}
#end
#implementation MyTableView
- (id<MyTableViewDelegate>)delegate {
return (id<MyTableViewDelegate>)[super delegate];
}
- (void)setDelegate:(id<MyTableViewDelegate>)delegate {
[super setDelegate:delegate];
_flags.delegateWillReloadData = [delegate respondsToSelector:#selector(tableViewWillReloadData:)];
_flags.delegateDidReloadData = [delegate respondsToSelector:#selector(tableViewDidReloadData:)];
}
- (void)reloadData {
[super reloadData];
if (_flags.reloading == NO) {
_flags.reloading = YES;
if (_flags.delegateWillReloadData) {
[(id<MyTableViewDelegate>)self.delegate tableViewWillReloadData:self];
}
[self performSelector:#selector(finishReload) withObject:nil afterDelay:0.0f];
}
}
- (void)finishReload {
_flags.reloading = NO;
if (_flags.delegateDidReloadData) {
[(id<MyTableViewDelegate>)self.delegate tableViewDidReloadData:self];
}
}
#end
It's similar to Josh Brown's solution with one exception. No delay is needed in performSelector method. No matter how long reloadData takes. tableViewDidLoadData: always fires when tableView finishes asking dataSource cellForRowAtIndexPath.
Even if you do not want to subclass UITableView you can simply call [performSelector:#selector(finishReload) withObject:nil afterDelay:0.0f] and your selector will be called right after the table finishes reloading. But you should ensure that selector is called only once per call to reloadData:
[self.tableView reloadData];
[self performSelector:#selector(finishReload) withObject:nil afterDelay:0.0f];
Enjoy. :)
This is an answer to a slightly different question: I needed to know when UITableView had also finished calling cellForRowAtIndexPath(). I subclassed layoutSubviews() (thanks #Eric MORAND) and added a delegate callback:
SDTableView.h:
#protocol SDTableViewDelegate <NSObject, UITableViewDelegate>
#required
- (void)willReloadData;
- (void)didReloadData;
- (void)willLayoutSubviews;
- (void)didLayoutSubviews;
#end
#interface SDTableView : UITableView
#property(nonatomic,assign) id <SDTableViewDelegate> delegate;
#end;
SDTableView.m:
#import "SDTableView.h"
#implementation SDTableView
#dynamic delegate;
- (void) reloadData {
[self.delegate willReloadData];
[super reloadData];
[self.delegate didReloadData];
}
- (void) layoutSubviews {
[self.delegate willLayoutSubviews];
[super layoutSubviews];
[self.delegate didLayoutSubviews];
}
#end
Usage:
MyTableViewController.h:
#import "SDTableView.h"
#interface MyTableViewController : UITableViewController <SDTableViewDelegate>
#property (nonatomic) BOOL reloadInProgress;
MyTableViewController.m:
#import "MyTableViewController.h"
#implementation MyTableViewController
#synthesize reloadInProgress;
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
if ( ! reloadInProgress) {
NSLog(#"---- numberOfSectionsInTableView(): reloadInProgress=TRUE");
reloadInProgress = TRUE;
}
return 1;
}
- (void)willReloadData {}
- (void)didReloadData {}
- (void)willLayoutSubviews {}
- (void)didLayoutSubviews {
if (reloadInProgress) {
NSLog(#"---- layoutSubviewsEnd(): reloadInProgress=FALSE");
reloadInProgress = FALSE;
}
}
NOTES:
Since this is a subclass of UITableView which already has a delegate property pointing to MyTableViewController there's no need to add another one. The "#dynamic delegate" tells the compiler to use this property. (Here's a link describing this: http://farhadnoorzay.com/2012/01/20/objective-c-how-to-add-delegate-methods-in-a-subclass/)
The UITableView property in MyTableViewController must be changed to use the new SDTableView class. This is done in the Interface Builder Identity Inspector. Select the UITableView inside of the UITableViewController and set its "Custom Class" to SDTableView.
I had found something similar to get notification for change in contentSize of TableView. I think that should work here as well since contentSize also changes with loading data.
Try this:
In viewDidLoad write,
[self.tableView addObserver:self forKeyPath:#"contentSize" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld | NSKeyValueObservingOptionPrior context:NULL];
and add this method to your viewController:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if ([keyPath isEqualToString:#"contentSize"]) {
DLog(#"change = %#", change.description)
NSValue *new = [change valueForKey:#"new"];
NSValue *old = [change valueForKey:#"old"];
if (new && old) {
if (![old isEqualToValue:new]) {
// do your stuff
}
}
}
}
You might need slight modifications in the check for change. This had worked for me though.
Cheers! :)
Here's a possible solution, though it's a hack:
[self.tableView reloadData];
[self performSelector:#selector(scrollTableView) withObject:nil afterDelay:0.3];
Where your -scrollTableView method scrolls the table view with -scrollRectToVisible:animated:. And, of course, you could configure the delay in the code above from 0.3 to whatever seems to work for you. Yeah, it's ridiculously hacky, but it works for me on my iPhone 5 and 4S...
I had something similar I believe. I added a BOOL as instance variable which tells me if the offset has been restored and check that in -viewWillAppear:. When it has not been restored, I restore it in that method and set the BOOL to indicate that I did recover the offset.
It's kind of a hack and it probably can be done better, but this works for me at the moment.
It sounds like you want to update cell content, but without the sudden jumps that can accompany cell insertions and deletions.
There are several articles on doing that. This is one.
I suggest using setContentOffset:animated: instead of scrollRectToVisible:animated: for pixel-perfect settings of a scroll view.
You can try the following logic:
-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"MyIdentifier"];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:#"MyIdentifier"];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
if ( [self chkIfLastCellIndexToCreate:tableView :indexPath]){
NSLog(#"Created Last Cell. IndexPath = %#", indexPath);
//[self.activityIndicator hide];
//Do the task for TableView Loading Finished
}
prevIndexPath = indexPath;
return cell;
}
-(BOOL) chkIfLastCellIndexToCreate:(UITableView*)tableView : (NSIndexPath *)indexPath{
BOOL bRetVal = NO;
NSArray *visibleIndices = [tableView indexPathsForVisibleRows];
if (!visibleIndices || ![visibleIndices count])
bRetVal = YES;
NSIndexPath *firstVisibleIP = [visibleIndices objectAtIndex:0];
NSIndexPath *lastVisibleIP = [visibleIndices objectAtIndex:[visibleIndices count]-1];
if ((indexPath.row > prevIndexPath.row) && (indexPath.section >= prevIndexPath.section)){
//Ascending - scrolling up
if ([indexPath isEqual:lastVisibleIP]) {
bRetVal = YES;
//NSLog(#"Last Loading Cell :: %#", indexPath);
}
} else if ((indexPath.row < prevIndexPath.row) && (indexPath.section <= prevIndexPath.section)) {
//Descending - scrolling down
if ([indexPath isEqual:firstVisibleIP]) {
bRetVal = YES;
//NSLog(#"Last Loading Cell :: %#", indexPath);
}
}
return bRetVal;
}
And before you call reloadData, set prevIndexPath to nil. Like:
prevIndexPath = nil;
[mainTableView reloadData];
I tested with NSLogs, and this logic seems ok. You may customise/improve as needed.
finally i have made my code work with this -
[tableView scrollToRowAtIndexPath:scrollToIndex atScrollPosition:UITableViewScrollPositionTop animated:YES];
there were few things which needed to be taken care of -
call it within "- (UITableViewCell *)MyTableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath"
just ensure that "scrollToRowAtIndexPath" message is sent to relevant instance of UITableView, which is definitely MyTableview in this case.
In my case UIView is the view which contains instance of UITableView
Also, this will be called for every cell load. Therefore, put up a logic inside "cellForRowAtIndexPath" to avoid calling "scrollToRowAtIndexPath" more than once.
You can resize your tableview or set it content size in this method when all data loaded:
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
tableView.frame =CGRectMake(tableView.frame.origin.x, tableView.frame.origin.y, tableView.frame.size.width, tableView.contentSize.height);
}
I just run repeating scheduled timer and invalidate it only when table's contentSize is bigger when tableHeaderView height (means there is rows content in the table). The code in C# (monotouch), but I hope the idea is clear:
public override void ReloadTableData()
{
base.ReloadTableData();
// don't do anything if there is no data
if (ItemsSource != null && ItemsSource.Length > 0)
{
_timer = NSTimer.CreateRepeatingScheduledTimer(TimeSpan.MinValue,
new NSAction(() =>
{
// make sure that table has header view and content size is big enought
if (TableView.TableHeaderView != null &&
TableView.ContentSize.Height >
TableView.TableHeaderView.Frame.Height)
{
TableView.SetContentOffset(
new PointF(0, TableView.TableHeaderView.Frame.Height), false);
_timer.Invalidate();
_timer = null;
}
}));
}
}
Isn't UITableView layoutSubviews called just before the table view displays it content? I've noticed that it is called once the table view has finished load its data, maybe you should investigate in that direction.
Since iOS 6 onwards, the UITableview delegate method called:
-(void)tableView:(UITableView *)tableView willDisplayHeaderView:(UIView *)view forSection:(NSInteger)section
will execute once your table reloads successfully. You can do customisation as required in this method.
The best solution I've found in Swift
extension UITableView {
func reloadData(completion: ()->()) {
self.reloadData()
dispatch_async(dispatch_get_main_queue()) {
completion()
}
}
}
Why no just extend?
#interface UITableView(reloadComplete)
- (void) reloadDataWithCompletion:( void (^) (void) )completionBlock;
#end
#implementation UITableView(reloadComplete)
- (void) reloadDataWithCompletion:( void (^) (void) )completionBlock {
[self reloadData];
if(completionBlock) {
completionBlock();
}
}
#end
scroll to the end:
[self.table reloadDataWithCompletion:^{
NSInteger numberOfRows = [self.table numberOfRowsInSection:0];
if (numberOfRows > 0)
{
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:numberOfRows-1 inSection:0];
[self.table scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:NO];
}
}];
Not tested with a lot of data
I have an application that works some what similar to how iPhone's Contact application works. When we add a new Contact user is directed to a view only screen with Contact information. If we select "All Contacts" from the navigation bar, user is navigated to list of all contacts where the recently added contact is in view.
We can move the view to a particular row using:
[itemsTableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionBottom];
... but it's not working. I'm calling this right after calling:
[tableView reloadData];
I think I'm not suppose to call selectRowAtIndexPath:animated:scrollPosition method here. But if not here, then where?
Is there any delegate method that gets called after the following method?
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;
I think I've got a similar app: A list of item., tap '+' -> new screen, come back and see the updated list, scrolled to show the added item at the bottom.
In summary, I put reloadData in viewWillAppear:animated: and scrollToRowAtIndexPath:... in viewDidAppear:animated:.
// Note: Member variables dataHasChanged and scrollToLast have been
// set to YES somewhere else, e.g. when tapping 'Save' in the new-item view.
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
if (dataHasChanged) {
self.dataHasChanged = NO;
[[self tableView] reloadData];
} else {
self.scrollToLast = NO; // No reload -> no need to scroll!
}
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if (scrollToLast) {
NSIndexPath *scrollIndexPath = [NSIndexPath indexPathForRow:([dataController count] - 1) inSection:0];
[[self tableView] scrollToRowAtIndexPath:scrollIndexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];
}
}
I hope this helps. If you add something in the middle of the list, you could easily scroll to that position instead.
You can try this , my application in some kind of similar to you when i click on a button scroll of uitableview is up.
[tableviewname setContentOffset:CGPointMake(0, ([arrayofcontact count]-10)*cellheight) animated:YES];
10 is for how many cell you want to scroll up
Hope this will help you:-)
Scrolling animation is inevitable when offset is set from viewDidAppear(_:). A better place for setting initial scroll offset is viewWillAppear(_:). You'll need to force the layout of a table view, because it's content size is not defined at that point.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
tableView.setNeedsLayout()
tableView.layoutIfNeeded()
if let selectedIndexPath = selectedIndexPath, tableView.numberOfRows(inSection: selectedIndexPath.section) > 0 {
tableView.scrollToRow(at: selectedIndexPath, at: .top, animated: false)
}
}
Do you have enough dummy contacts added to test the scrolling? It seems that only when your tableView is of a certain size the iPhone finds the inputus to scroll.
This is the code that works for me in my project. I use a previous button and therefore I scroll the tableview a little bit further down that it usually would go with UITABLEVIEWSCROLLPOSITION. (my previous button won't work if it can't "see" the previous cell.
Ignore some of the custom method calls.
- (void)textFieldDidBeginEditing:(UITextField *)textField {
//Show the navButtons
[self navButtonAnimation];
DetailsStandardCell *cell = (DetailsStandardCell *)textField.superview.superview.superview;
self.parentController.lastCell = cell;
//Code to scroll the tableview to the previous indexpath so the previous button will work. NOTE previous button only works if its target table cell is visible.
NSUInteger row = cell.cellPath.row;
NSUInteger section = cell.cellPath.section;
NSIndexPath *previousIndexPath = nil;
if (cell.cellPath.row == 0 && cell.cellPath.section != 0) //take selection back to last row of previous section
{
NSUInteger previousIndex[] = {section -1, ([[self.sections objectForKey:[NSNumber numberWithInt:section - 1]]count] -1)};
previousIndexPath = [[NSIndexPath alloc] initWithIndexes:previousIndex length:2];
}
else if (cell.cellPath.row != 0 && cell.cellPath.section != 0)
{
NSUInteger previousIndex[] = {section, row - 1};
previousIndexPath = [[NSIndexPath alloc] initWithIndexes:previousIndex length:2];
}
[self.theTableView scrollToRowAtIndexPath: cell.cellPath.section == 0 ? cell.cellPath : previousIndexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
}