我开发了一个 UITableView
,其中包含一些可以包含子单元的单元格。
例子:
我的应用程序允许用户移动单元格位置,但是,当一个表格有一个或多个带有子单元格的单元格时,我会折叠所有这些单元格,以便只允许移动具有相同标识(或同一级别)的单元格
如果表格很长,当我折叠带有子元素的单元格时,我使用该单元格的 indexPath 从表格中删除子元素。我的问题是其中一些单元格不在内存中,所以我遇到了崩溃。
如何检测未显示单元格以便仅从数据源中删除元素?
这是我折叠/展开元素的方法:
- (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];
}
}
和电话
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:idx inSection:0];
UITableViewCell *cell = [_taskTableView cellForRowAtIndexPath:indexPath];
UIButton *subtasksButton = (UIButton *)[cell viewWithTag:108];
[self expandCollapseSubtasks:subtasksButton];
其中idx
是元素在dataSource中的位置
最佳答案
您可以获得所有可见单元格的 NSIndexPath 数组:
NSArray *array = [self.tableView indexPathsForVisibleRows];
您还可以获取单元格数组本身而不是 NSIndexPath:
[tableView visibleCells]
这就是您找出不可见细胞所需要的。
关于ios - 如何知道 UITableViewCell 是否未显示在 UITableView 上,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32460511/