Animating UITableView update, succeeded but needs more detail

I want to show animation when add cells to UITableView.

Here's is what I implemented (pseudo code)

[self.tableView beginUpdates];

// remove row exists
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:(rows exists)  withRowAnimation:UITableViewRowAnimationFade];

(chang data source here, for me, it's NSFetchedResultsController)

// insert new rows
[self.tableView insertRowsAtIndexPaths:(new rows) withRowAnimation:UITableViewRowAnimationFade];

[self.tableView endUpdates];

This code shows animation well, but it has a small开发者_运维百科 problem.

The cells are shows moving animation from frame rect (0, 0, 0, 0) to it's actual position, not only fading animation.

I think problem is that initial frame of cells are (0, 0, 0, 0), so I set up initial frame property of cell in cellForRowAtIndexPath, but it does not work.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    ....
    cell.frame = CGRectMake(0, indexPath.row * 64, 320, 64);
    NSLog(@"set frame");
    ....
}

How can I show shade anmation only, with no cell moving animation?

The code is untested, but the idea should work:

BOOL animateRowsAlpha = NO;

- (void)reloadData {
    [UIView animateWithDuration:0.2 
                     animations:^{
                         for (UITableViewCell *cell in self.tableView.visibleCells) {
                             cell.alpha = 0.0f;
                         }
                     } completion:^(BOOL finished) {
                         animateRowsAlpha = YES;
                         [self.tableView reloadData];
                     }
     ];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *cellIdentifier = @"Cell";
    UITableViewCell *cell = (UITableViewCell *)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (!cell) 
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];

    if(animateRowsAlpha)
        cell.alpha = 0.0;

    return cell;
}

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (!animateRowsAlpha) {
        return;
    }

    [UIView animateWithDuration:0.2 
                     animations:^{
                         cell.alpha = 1.0f;
                     }];

    NSArray *indexPaths = [tableView indexPathsForVisibleRows];
    NSIndexPath *lastIndexPath = [indexPaths lastObject];
    if(!lastIndexPath || [lastIndexPath compare:indexPath] == NSOrderedSame) {
        animateRowsAlpha = NO;
    }
}