objective c - How to reload and animate just one UITableView cell/row?

Question

how can I reload and animate just one cell/row ? Right now i download some files. Everytime a file finished downloading, i call it's finished delegate and call [tableview reload]. But then the whole table reloads. And how can i animate the table, so that it doesn't blink in. For example a fade effect or so.

greets Max

Answer 1

Use the following UITableView instance method:

- (void)reloadRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation

You have to specify an NSArray of NSIndexPaths that you want to reload. If you just want to reload. If you only want to reload one cell, then you can supply an NSArray that only holds one NSIndexPath. For example:

NSIndexPath* rowToReload = [NSIndexPath indexPathForRow:3 inSection:0];
NSArray* rowsToReload = [NSArray arrayWithObjects:rowToReload, nil];
[myUITableView reloadRowsAtIndexPaths:rowsToReload withRowAnimation:UITableViewRowAnimationNone];

You can see the UITableViewRowAnimation enum for all the possible ways of animating the row refresh. If you don't want any animation then you can use the value UITableViewRowAnimationNone, as in the example.

Reloading specific rows has a greater advantage than simply getting the animation effect that you'd like. You also get a huge performance boost because only the cells that you really need to be reloaded are have their data refreshed, repositioned and redrawn. Depending on the complexity of your cells, there can be quite an overhead each time you refresh a cell, so narrowing down the amount of refreshes you make is a necessary optimization that you should use wherever possible.