CODEWITHSUNDEEP
iosobjective-ciphoneuitableview
EnriMR
EnriMR

Reputation: 3970

How to know if a UITableViewCell is not being showed at UITableView

I have developed a UITableView with some cells that could have subcells.

Example:

enter image description here

My app allows users to move cells position but, when a table has got one or more cell with subcells, I collapse all of them in order to allow only move cells with the same identation (or in the same level)

If the table is pretty long, when I collapse cells with subelements, I use indexPath of that cell to remove the subelements from the table. My problem is that some of that cells are not in memory so I get a crash.

How can I detect that a cell is not being showed in order only remove the element from the dataSource?

This is my method to collapse/expand elements:

- (void)expandCollapseSubtasks:(UIButton *)sender
{
    CGPoint buttonPosition = [sender convertPoint:CGPointZero toView:_taskTableView]; //when CGPoint = 0,0 not remove cells?
    NSIndexPath *indexPath = [_taskTableView indexPathForRowAtPoint:buttonPosition];

    if (indexPath != nil)
    {
        Task *task = [_tasks objectAtIndex:indexPath.row];
        TaskTitleCell *cell = (TaskTitleCell *)[_taskTableView cellForRowAtIndexPath:indexPath];
        UILabel *subtasksNumberLabel = (UILabel *)[cell viewWithTag:107];
        UIButton *subtasksButton = (UIButton *)[cell viewWithTag:108];

        NSMutableArray *subtasksIndexPaths = [[NSMutableArray alloc] init];

        NSNumber *hidden;
        //Expand
        if (!subtasksButton.selected){
            hidden = @0;
            subtasksNumberLabel.textColor = [UIColor colorWithRed:72.0/255.0 green:175.0/255.0 blue:237.0/255.0 alpha:1.0];

            NSDictionary *subtasksAndIndexesDictionary = [task getSubtasksIndexesInTaskCollection:_tasks ofList:task.list];

            NSIndexSet *indexes = [subtasksAndIndexesDictionary objectForKey:@"indexes"];
            NSArray *subtasks = [subtasksAndIndexesDictionary objectForKey:@"subtasks"];

            [_tasks insertObjects:subtasks atIndexes:indexes];

            [indexes enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
                NSIndexPath *subtaskIndexPath = [NSIndexPath indexPathForRow:idx inSection:0];
                [subtasksIndexPaths addObject:subtaskIndexPath];
            }];

            [_taskTableView insertRowsAtIndexPaths:subtasksIndexPaths withRowAnimation:UITableViewRowAnimationTop];

        //Collapse
        }else{
            hidden = @1;
            subtasksNumberLabel.textColor = [UIColor whiteColor];

            NSArray *subtasks = [task getSubtasks];

            [_tasks removeObjectsInArray:subtasks];

            for (int i=1;i<=subtasks.count; i++){
                NSIndexPath *subtaskIndexPath = [NSIndexPath indexPathForRow:indexPath.row+i inSection:0];
                [subtasksIndexPaths addObject:subtaskIndexPath];
            }

            [_taskTableView deleteRowsAtIndexPaths:subtasksIndexPaths withRowAnimation:UITableViewRowAnimationBottom];

        }

        subtasksButton.selected = !subtasksButton.selected;
        task.hidesubtasks = hidden;

        [[NSManagedObjectContext defaultContext] saveToPersistentStoreAndWait];
    }
}

And the call

NSIndexPath *indexPath = [NSIndexPath indexPathForRow:idx inSection:0];
UITableViewCell *cell = [_taskTableView cellForRowAtIndexPath:indexPath];
UIButton *subtasksButton = (UIButton *)[cell viewWithTag:108];
[self expandCollapseSubtasks:subtasksButton];

Where idx is the position of the element in the dataSource

Upvotes: 0

Views: 52

Answers (1)

Greg
Greg

Reputation: 25459

You can get array of NSIndexPath for all visible cells:

NSArray *array = [self.tableView indexPathsForVisibleRows];

You can also get array of cells itself instead of NSIndexPath:

[tableView visibleCells]

That what you need to find out the invisible cells.

Upvotes: 1

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