I have a for loop in my project like this:
for (int i = 0; i < 2; i++) {
[array addObject:randomObject];
[self.tableView reloadData];
}
I have my dataSource methods like this:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSLog(#"Count: %lu",(unsigned long)array.count);
return [array count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"Reloading Data");
static NSString *CellIdentifier = #"Random";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
return cell;
}
But for some strange reason only numberOfRowsInSection is getting called and cellForRowAtIndexPath is not.
Also cellForRowAtIndexPath DOES get called in the last time of the loop(when x is = to 1)
the tableview only asks for cells when it updates its view hierarchy. Not when reloading its data. That will only cause it to update its internal size information.
Updating cells only happens when the runloop is pogressed. When you are in a loop, the main thread is blocked and then runloop is not progressed.
Only after your loop the OS runs the runloop and the table calls for Cells.
All the datasource methods are called on the same thread. By calling reloadData you start the "queue" of datasource methods, by calling it again you cancel the previous "queue". This mechanics protects datasource from being inconsistent as if you have the data changed (hence the next reloadData call), the first "queue" operations would have outdated state.
Related
I'm experiencing pretty mysterious glitch:
After endUpdates was called all removed updated cells becoming just hidden and new cell will created, without reusing existing ones.
Usually even -tableView:didEndDisplayingCell:forRowAtIndexPath: not called, but not always.
Result looks like this:
I have no any clue about reasons of this behavior and will appreciate any ideas how to debug and fix this.
Unfortunately, source code it pretty complex and I'm unable to extract something intergal. if you ask me about related code - i will copy it to there.
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
id item = [self.presenter.mediator itemAtIndexPath:indexPath];
NSString *reuseIdentifier = [self.reuseIdentifierMatcher reuseIdentifierForItem:item];
UITableViewCell<ViewItemProtocol>* cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier
forIndexPath:indexPath];
cell.item = item;
return cell;
}
- (void)applyChangesSet:(TableChangesSet*)changes
{
LOG_VALUE(#([[NSThread currentThread] isMainThread]));
[self.tableView beginUpdates];
for (TableChange *change in changes.changes)
{
[self applyChange:change];
}
[self.tableView endUpdates];
}
applyChange does not contains any UI manipulations, except deleteRowsAtIndexPaths/insertRowsAtIndexPaths/reloadRowsAtIndexPaths;
Debug output is #([[NSThread currentThread] isMainThread]) is 1
I've got my cellForRowAtIndexPath delegate method defined as so:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
PLOTCheckinTableViewCell *cell = (PLOTCheckinTableViewCell *)[tableView dequeueReusableCellWithIdentifier:CheckinCellIdentifier forIndexPath:indexPath];
if([self.items count] == 0){
return cell;
}
NSDictionary *checkin = self.items[indexPath.row];
// configure and return custom cell
}
I'm using a custom cell class (PLOTCheckinTableViewCell).
I faced an issue where the user would pull to refresh and then attempt to pull again before the first request had completed (on completion of the request, I reload the table data). When they did this, the app would crash and say that indexPath.row was basically out of bounds, ie. the array was empty.
By putting in this IF check above, I mitigated the crash.
However,
Why exactly does my IF check "work", I see no visual implications of returning the cell before it's been configured. This is confusing
Are there any better ways to guard against this happening (ie. the table data being reloaded with an empty array)? Surely the numberOfRowsInSection would have returned array count which would be 0? (if it was an empty array)
EDIT (further code)
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
float count = [self.items count];
return count;
}
- (void)resetData {
self.items = [NSMutableArray array];
}
-(void) refreshInvoked:(id)sender forState:(UIControlState)state {
[self resetData];
[self downloadHomeTimeline];
[self.refreshControl endRefreshing];
}
- (void)downloadHomeTimeline {
[self.apiClient homeTimeline:self.page completionBlock:^(NSDictionary *data){
for (NSDictionary *obj in data[#"items"]) {
[self.items addObject:obj];
}
[self.itemsTableView reloadData];
}];
}
I couple of things that i would suggest to do. Make sure that the [self.itemsTableView reloadData] is executed on the main thread and also i would put the [self.refresControl endRefreshing] in the completion block. This way it will stop the refresh when its done and you should not let the user more then once simultaneously.
- (void)downloadHomeTimeline {
[self.apiClient homeTimeline:self.page completionBlock:^(NSDictionary *data){
for (NSDictionary *obj in data[#"items"]) {
[self.items addObject:obj];
}
dispatch_async(dispatch_get_main_queue(), ^{
[self.itemsTableView reloadData];
[self.refreshControl endRefreshing];
});
}];
}
Also in the numberOfRowsInSection just return count
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [self.items count];
}
To add to the answer. You should not reset the array before you receive new data. While getting new data the user can still scroll the table and that means new cells will be created but your NSMutableArray doesn't have any data. That is when you get the error and app crashes. You would have to [tableView reloadData] to clear the table so that the tableView would know that there are 0 rows, which i don't think is your intent.
Let me know if that's solves the issue.
I took approach of the UITableview to get cell click ExpandView. I want something like this to be implement.
So, UITableView would be best approach for this or suggest me any good way of implementing, also I am not able to get subview to adjust according to screenSize.
Could be there are another ways to accomplish this but this is how I am expand UITableViewCell on the fly. This could give the idea and you can implement your solution.
I keep row heights in my data model:
- (void)viewDidLoad {
[super viewDidLoad];
//Data source
datasource = [[NSMutableArray alloc] init];
NSMutableDictionary *aDicti = [[NSMutableDictionary alloc] init];
[aDicti setValue:#"a TEXT" forKey:#"text"];
[aDicti setValue:#(50) forKey:#"cellheight"]; // here
}
When selection changed, just updating related key in data source.
-(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView beginUpdates];
[[datasource objectAtIndex:indexPath.row] setObject:#(50) forKey:#"cellheight"];
[tableView endUpdates];
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView beginUpdates];
[[datasource objectAtIndex:indexPath.row] setObject:#(200) forKey:#"cellheight"];
[tableView endUpdates];
}
Once [tableView endUpdates]; executed heightForRowAtIndexPath and numberOfRowsInSection delegate methods fired and automatically adjust cell height with the value from data source.
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
return [[[datasource objectAtIndex:indexPath.row] objectForKey:#"cellheight"] intValue];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return datasource.count;
}
If you do not want to keep row height in your data source you can basically apply this.
-(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView beginUpdates];
[tableView endUpdates];
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView beginUpdates];
[tableView endUpdates];
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
if (tableView.indexPathForSelectedRow.row == indexPath.row) {
return 100;
}
return 50;
}
That's call, accordion, this site having good examples (with demos) for it, here's the link.
Basically when you are working with TableView you should play with number of section headers and cells.
In case of using section headers you should set numberOfRowsInSection to 0 (roll up) to X when you want to expand it. After that call
tableView.reloadData
I implemented this behavior here, with animation, with different heights:
https://github.com/rudald/expandedTableViewIOSSwift/
There are numerous open source projects regarding this feature. I've downloaded a few projects and the most customizable and issue-less, for me, was SLExpandableTableView
SDNestedTable does exactly what you want.
The module concept is that of having all the default functionality of
a UITableView and its cells while at the same time adding for each
cell a child UITableView. Each cell (SDGroupCell) in the main
SDNestedTableViewController tableview acts as controller for its own
sub table. The state, population and behavior of the table and
subtable is instead mostly controlled by
SDNestedTableViewController.
If you’re looking for a straight forward easy-to-setup library for expandable views, HVTableView is your choice. It provides an acceptable performance which is sufficient for using in regular projects.
I am a beginner in Objective-C & iPhone development.
I add dynamically cells in a TableView. I want to set labels's text properties with an array. I saw many tutorials, and I searched during several hours but labels are never filled.
My code is :
- (void)insertNewObject
{
for (NSInteger ic=0; ic<((pages.count)); ++ic) {
NSLog(#"%d", ic);
NSDictionary *monDico = pages[ic];
menu = [monDico objectForKey:#"Name"];
NSIndexPath *indexPathTable = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView insertRowsAtIndexPaths:#[indexPathTable] withRowAnimation:UITableViewRowAnimationAutomatic];
[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]]; // I try include & exclude : never call
}
[self.tableView reloadData];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
cell.textLabel.text = menu[indexPath.row];
NSLog(#"%#%#", #"Cell Label = ", cell.textLabel.text);
return cell;
}
Please note that insertNewObject method is called during viewDidLoad execution.
I use a breakpoint in the cellForRowAtIndexPath method : it never calls ! I try with :
explicit calling
forcing reloadData method
but did not work too.
Can you please tell me why ?
Thanks in advance.
If cellForRowAtIndexPath is not being called then most likely you have not set:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [menu count]; // indicates the number of rows in your table view
}
This method needs to return the number of rows you expect to render within your table view. The default is 0 = no rows. I'm assuming you want to show all the items in your menu array so simply return [menu count].
Check this: UITableViewDataSource Protocol Reference
If you want to access to textLabel property of your cell, then it must be style of: UITableViewCellStyleDefault. Or, if you use storyboard, then set Cell's style to Basic.
And, of course, make sure that you have set delegate and datasource properties of your tableView.
- (void)viewDidLoad
{
[super viewDidLoad];
//...
self.tableView.delegate = self;
self.tableView.dataSource = self;
}
------------------EDIT------------------
If you're using UITableViewController, then no more need to set delegate and dataSource properties manually, because they will automatically set by UITableViewController when your view did load.
If cellForRowAtIndexPath: method still not being called, then make sure that following methods that you implemented, both returns value >0:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView;
and
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
Set a breakpoint before return and see returning values, or just NSLog them before returning.
I´m quite new to iOS development and I´m having a terrible time by trying something that should be easy; to add an extra row in a TableView everytime the user clicks on one of the existing rows. There is no real purpose on that action, I´m just wanting to understand the behaviour of TableView.
So I did the following:
I used a Split View-based template and changed the number of rows to 30 in the RootViewController.
- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
return 30;
}
The method tableView:didSelectRowAtIndexPath looks in the following manner:
- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
/*
When a row is selected, set the detail view controller's detail item to the item associated with the selected row.
*/
NSMutableArray* paths = [[NSMutableArray alloc] init];
NSIndexPath *indice = [NSIndexPath indexPathForRow:30 inSection:0];
[paths addObject:indice];
detailViewController.detailItem = [NSString stringWithFormat:#"Second Story Element %d with all its information and bla bla bla", indexPath.row];
[[self tableView] beginUpdates];
[self.tableView insertRowsAtIndexPaths:(NSArray *) paths withRowAnimation:UITableViewRowAnimationNone];
[[self tableView] endUpdates];
}
When I execute the program and click on one of the elements, I receive the following error:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (30) must be equal to the number of rows contained in that section before the update (30), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted).'
I did not change any other part of the code that the template provides.
I read quite extensively the documentation from Apple and the responses to the following questions:
Add a row dynamically in TableView of iphone
and
how to properly use insertRowsAtIndexPaths?
The second question seems to address the same problem, but I´m not capable to understand what is happening. What do they mean with dataSource? The response that I understand better says the following:
It's a two step process:
First update your data source so numberOfRowsInSection and cellForRowAtIndexPath will return the correct values for your post-insert data. You must do this before you insert or delete rows or you will see the "invalid number of rows" error that you're getting.
What does this update of the data source implies?
Sample code would be HIGHLY appreciated, because I´m totally frustrated.
By the way, all that I´m trying has nothing to do with entering the editing mode, has it?
You need to keep the count returned by tableView:numberOfRowsInSection: in sync!
So when you have 30 rows and then tell the tableview to insert a new row you need to make sure tableView:numberOfRowsInSection: will now return 31.
- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section
{
return self.rowCount;
}
- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
self.rowCount++;
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:(NSArray *) paths withRowAnimation:UITableViewRowAnimationNone];
[self.tableView endUpdates];
}
In practice you would probably use an array to track your rows return [self.rows count]; etc
The answer is quite simple. When you want to modify a table view you need to perform two simple steps:
Deal with the model
Deal with table animation
You already perform the second step. But you have missed the first one. Usually when you deal with a table you pass it a data source. In other words some data to display within it.
A simple example is using a NSMutableArray (it's dynamic as the name suggests) that contains dummy data.
For example, create a property like the following in .h
#property (nonatomic, strong) NSMutableArray* myDataSource;
and in .m synthesize it as:
#synthesize myDataSource;
Now, you can alloc-init that array and populate it as the following (for example in viewDidLoad method of your controller).
self.myDataSource = [[NSMutableArray alloc] init];
[self.myDataSource addObject:#"First"];
[self.myDataSource addObject:#"Second"];
Then, instead of hardcoding the number of rows you will display (30 in your case), you can do the following:
- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section {
return [self.myDataSource count];
}
Now, in you didSelectRowAtIndexPath delegate you can add a third element.
- (void)tableView:(UITableView *)aTableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[self.myDataSource addObject:#"Third"];
[[self tableView] beginUpdates];
[self.tableView insertRowsAtIndexPaths:(NSArray *) paths withRowAnimation:UITableViewRowAnimationNone];
[[self tableView] endUpdates];
}
It looks like one big problem is with tableView:numberOfRowsInSection:. You need to return the correct number of rows in that method.
To do that, it's usually best to maintain an NSArray or NSMutableArray of items for the table view so in that function, you can say: return [arrayOfValues count];. Keep the array as a property of your view controller class so that it's readily accessible in all methods.
The array can also be used in cellForRowAtIndexPath:. If you have an array of NSString, you can say cell.text = [arrayOfValues objectAtRow:indexPath.row];.
Then, when you want to add an item to the table view, you can just add it to the array and reload the table, e.g. [tableView reloadData];.
Try implementing this concept and let me know how it goes.
You can Also do that for dayanamic table cell
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [arrayStationStore count];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIndentyfire;
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIndentyfire];
if (cell == nil)
{
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIndentyfire];
}
cell.textLabel.text = [arrayStationStore objectAtIndex:indexPath.row];
return cell;
}
-(NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// Check if current row is selected
BOOL isSelected = NO;
if([tblStationName cellForRowAtIndexPath:indexPath].accessoryType == UITableViewCellAccessoryCheckmark)
{
isSelected = YES;
}
if(isSelected)
{
[tblStationName cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone;
[arrayReplace removeObject:indexPath];
NSLog(#"array replace remove is %# ",arrayReplace);
}
else
{
[tblStationName cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark;
[arrayReplace addObject:indexPath];
NSLog(#"array replace add is %# ",arrayReplace);
}
return indexPath;
}