iPad 2和iPhone 4s具有不同的UITableView滚动性能

Question

Solved

There was a shadow on the self.view layer. After removed it, the tableview scrolls smoothly (56-59fps).

The problem I got is so weird.

I am building a UITableView based Twitter like App. After optimized the table view loading and scrolling, I tested the App (same code & same UI) on both iPad 2 and iPhone 4S. On the iPad 2, I got 56-59fps smooth scrolling animation. But on the iPhone 4S, I got only 43-49fps scrolling animation, which is awful.

This seems not caused by the Retina display. After I remove all images from cells, the problem is still there. The following is the code of cellForRowAtIndexPath

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    // fetch note from the fetched results controller
    Note *note = [self.fetchedResultsController objectAtIndexPath:indexPath];

    if ([note.photos count] > 0) {

        static NSString *CellIdentifier = @"Photo Cell";
        PhotoCell *cell = (PhotoCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

        if (cell == nil){
            cell = [[PhotoCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        } else {
            [cell clearContents];
        }

        NSNumber *currentRowNumber = [NSNumber numberWithInt:indexPath.row];
        // check if the photos of this cell has been pre loaded
        NSDictionary *coverImages = [self.coverImagesForNotes objectForKey:currentRowNumber];

        if (coverImages == nil) {
            if (self.tableView.dragging == NO && self.tableView.decelerating == NO) {
                coverImages = [self loadCoverImagesForCell:indexPath photos:note.photos];
                [self.coverImagesForNotes setObject:coverImages forKey:currentRowNumber];
            } 
        }

        // assign contents to the cell
        [self compositeContentView:cell forNote:note rowNumber:indexPath.row];

        // refine
        unsigned textContentHeight = [[self.cellTextHeightDict objectForKey:currentRowNumber] integerValue];
        unsigned currentPageNumber = [self currentPageNumberAtRow:indexPath.row];
        [cell initPhotoVideoView:textContentHeight photos:note.photos coverImages:coverImages showPage:currentPageNumber rowNumber:indexPath.row];

        cell.delegate = self;

        return cell;

    } else {
        static NSString *CellIdentifier = @"Simple Cell";
        BaseCell *cell = (BaseCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

        if (cell == nil){
            cell = [[OneViewBaseCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        }

        // assign contents to the cell
        [self compositeContentView:cell forNote:note rowNumber:indexPath.row];

        return cell;
    }
}

Thanks for answers.

Answer 1

Are you using images in your table view cells? This will be more expensive on a retina display. Also if you are using images, try to load them in on a background thread which will reduce the latency.

If you're not using images then you should really look at how you are creating your cells, please post tableView:cellForRowAtIndexPath: method implementation