Disabling UITableView due to shadows and borders

Question

I have the following code to add border color and shadow for the background of my UITableViewCell. My problem is that this code causes a huge lag behind the tableView itself.

Please tell me how I can optimize my code by preventing a UITableView from lagging?

if ([cell viewWithTag:012] == nil && comment.isReply == NO) {
    UIImageView *iv = [[[UIImageView alloc] initWithFrame:frame] autorelease];
    [iv setImage:[UIImage imageNamed:@"paper"]];
    [iv setTag:012];
    [cell insertSubview:iv atIndex:0];

    [iv.layer setBorderWidth:1.0];
    [iv.layer setBorderColor:[[UIColor whiteColor] CGColor]];

    [iv.layer setShadowColor:[[UIColor blackColor] CGColor]];
    [iv.layer setShadowOffset:CGSizeMake(0, 1)];
    [iv.layer setShadowOpacity:0.75];

}

else if ([cell viewWithTag:012] == nil && comment.isReply == YES) {

    frame.origin.x += 35;

    UIImageView *iv = [[[UIImageView alloc] initWithFrame:frame] autorelease];
    [iv setImage:[UIImage imageNamed:@"paper"]];
    [iv setTag:012];
    [cell insertSubview:iv atIndex:0];

    UIImage *arrow = [UIImage imageNamed:@"arrow"];
    UIImageView *ivs = [[[UIImageView alloc] initWithFrame:CGRectMake(-12, ([cell frame].size.width / 2) + ([arrow size].width/2) , arrow.size.width, arrow.size.height)] autorelease];
    [cell addSubview:ivs];

    [iv.layer setBorderWidth:1.0];
    [iv.layer setBorderColor:[[UIColor whiteColor] CGColor]];

    [iv.layer setShadowColor:[[UIColor blackColor] CGColor]];
    [iv.layer setShadowOffset:CGSizeMake(0, 0)];
    [iv.layer setShadowOpacity:0.75];

}

Answer 1

You should avoid manipulating the cell with every load, instead you should configure the user interface when the cell is initialized / created.

, , ( ), cellForRowAtIndexPath:, , , (, , ). , , . .

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    // Reuse id
    static NSString *identifier1 = @"identifer-1";
    static NSString *identifier2 = @"identifier-2";
    static NSString *regular = @"regular";

    UITableViewCell *cell;

    if (comment.isReply == NO) {
        cell = [tableView dequeueReusableCellWithIdentifier: identifier1];

        if (cell == nil) {
            cell = [[[UITableViewCell alloc] initWithStyle: UITableViewCellStyleDefault reuseIdentifier: identifier1] autorelease];

            // Do the UI modification here
        }
    } else if (comment.isReply == YES) {
        cell = [tableView dequeueReusableCellWithIdentifier: identifier2];

        if (cell == nil) {
            cell = [[[UITableViewCell alloc] initWithStyle: UITableViewCellStyleDefault reuseIdentifier: identifier2] autorelease];

            // Do the UI modification here
        }
    } else {
        // Regular cell
        cell = [tableView dequeueReusableCellWithIdentifier: regular];

        if (cell == nil) {
            cell = [[[UITableViewCell alloc] initWithStyle: UITableViewCellStyleDefault reuseIdentifier: regular] autorelease];
        }
    }

    // Load the data into the cell

    return cell;
}

, , , , UITableView .

Answer 2

shadowPath CALayer . - ...

iv.layer.shadowPath = [UIBezierPath bezierPathWithRect:iv.bounds].CGPath;

shouldRasterize CALayer. . , , .

cell.layer.shouldRasterize = YES;
cell.layer.rasterizationScale = [UIScreen mainScreen].scale;