根据UITableView iOS中的可见单元格加载内容

Question

In my app am trying to load a NSMutableArray with total 80,000 text "name" and its working perfectly but when we scroll the entire scroll get lagged(not smooth scroll).

So am looking for any way to load contents to only those visible cells in UITableView (in asychronously).

This is my current code

    - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;    //count of section
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    // return [[copyGenericDetails valueForKey:@"name"]count];    //count number of row from counting array hear cataGorry is An Array

    return [[bigArray valueForKey:@"Name"]count];
}



- (UITableViewCell *)tableView:(UITableView *)tableView
         cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *MyIdentifier = @"cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];

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


    cell.textLabel.text=[[bigArray valueForKey:@"Name"] objectAtIndex:indexPath.row];
    return cell;
}


- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{

    return 40;

}

Please help me with scrolling of this list.

Answer 1

Assuming bigArray is what is says, ie NSArray, then this line:

cell.textLabel.text=[[bigArray valueForKey:@"Name"] objectAtIndex:indexPath.row];

might be what's slowing you down. The [bigArray valueForKey:@"Name"] causes all 80,000 entries to be scanned, and the valueForKey obtained and stored. Only then do you select the correct row. I would switch them round:

cell.textLabel.text=[[bigArray objectAtIndex:indexPath.row] valueForKey:@"Name"];

That way it's just a lookup on the 80,0000 items, and obtain the Name property for just the one item. Likewise:

return [[bigArray valueForKey:@"Name"]count];

can be replaced with:

return [bigArray count];

Answer 2

if your big array is loaded means array is ready completely or no background task is running then scrolling should be fast. Check some thing extra is not effecting the scrolling like loading some thing else or any background task ?

Answer 3

As UITableView only loads visible cells it cannot be the tableView that is slowing you down. But as NSArray is not really one of the fastest access structures it might be the array that is slowing you down. Have you tried splitting your data into several smaller arrays ( lets say always 10k values into one array) and implement some logic to access the different arrays according to the indexPath.row?

Oh and by the way: What device are you testing on?