Alternating TableView Cell Colors

[iSDK]

Hi, I have completed a grouped tableview project, and i am just stuck on alternating cell colors.

I would like to have the first cell blue and then the second cell white. And when the second cell is white, i would like the background of the cell to be black. This would then carry on throughout the tableview.

Thanks in advance.

[kelvinkao]

In your data source class, when you are create the cells for the table view, you can just change what you returned according to the row number, right?

[iSDK]

Surely there is an easier way than typing it in for every cell.

[[cell detailTextLabel] setText:@"Example"];
}[/code]

Originally Posted by kelvinkao

In your data source class, when you are create the cells for the table view, you can just change what you returned according to the row number, right?

[kelvinkao]

You don't need to type it in for every cell, per se. Just do calculations based on the row number, figure out if it's odd or even, and color accordingly.

[iSDK]

Would you mind giving some example code?

Originally Posted by kelvinkao

You don't need to type it in for every cell, per se. Just do calculations based on the row number, figure out if it's odd or even, and color accordingly.

[lynngobin]

Try some thing like this:

- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
if (indexPath.row == 0 || indexPath.row%2 == 0) {
UIColor *altCellColor = [UIColor colorWithRed:256/256.0 green:237/256.0 blue:227/256.0 alpha:1.0];
cell.backgroundColor = altCellColor;
}
}

[iSDK]

thanks!

Originally Posted by lynngobin

Try some thing like this:

- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
if (indexPath.row == 0 || indexPath.row%2 == 0) {
UIColor *altCellColor = [UIColor colorWithRed:256/256.0 green:237/256.0 blue:227/256.0 alpha:1.0];
cell.backgroundColor = altCellColor;
}
}

[iSDK]

I have just implemented it into my application, and all the cells are red/white but in no particular order. Also if i scroll up and down all of the cells change to red.

Originally Posted by iSDK

thanks!

[kelvinkao]

Post your code.

[iSDK]

    
if (indexPath.row%2 == 0) 
{
    UIColor *altCellColor = [UIColor colorWithRed:256/256.0 green:237/256.0 blue:227/256.0 alpha:1.0];
    cell.backgroundColor = altCellColor;
    }

Originally Posted by kelvinkao

Post your code.

[kelvinkao]

What method is this in? Where is the other color set?

My guess is that you are not setting the odd and even numbers equal number of times.

[iSDK]

The other color set is white! Its in the method cellforrowatindex path.

Originally Posted by kelvinkao

What method is this in? Where is the other color set?
My guess is that you are not setting the odd and even numbers equal number of times.

[kelvinkao]

Originally Posted by iSDK

The other color set is white! Its in the method cellforrowatindex path.

My guess is that you are not setting colors correctly when you re-use the cells. You can either set BOTH colors in that cellWillDisplay method, or post the cellForRowAtIndexPath method for us to have a look.

[iSDK]

- (UITableViewCell *)tableView:(UITableView *)tableView 
		 cellForRowAtIndexPath:(NSIndexPath *)indexPath {
	static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
	
	NSArray *listData =[self.tableContents objectForKey:[self.sortedKeys objectAtIndex:[indexPath section]]];
	
	UITableViewCell * cell = [tableView 
							  dequeueReusableCellWithIdentifier:SimpleTableIdentifier];
	
	if(cell == nil) {
		
		 cell = [[[UITableViewCell alloc] 
		 initWithStyle:UITableViewCellStyleValue1 
		 reuseIdentifier:SimpleTableIdentifier] autorelease];
		 
		
		/*cell = [[[UITableViewCell alloc] 
				 initWithStyle:UITableViewCellStyleSubtitle
				 reuseIdentifier:SimpleTableIdentifier] autorelease];
		*/
	}
	if (indexPath.row%3 == 0)
	{
		UIColor *altCellColor = [UIColor colorWithRed:256/256.0 green:237/256.0 blue:227/256.0 alpha:1.0];
		cell.backgroundColor = altCellColor;
		}

Originally Posted by kelvinkao

My guess is that you are not setting colors correctly when you re-use the cells. You can either set BOTH colors in that cellWillDisplay method, or post the cellForRowAtIndexPath method for us to have a look.

[kelvinkao]

It shouldn't say %3. This is why your colors appear random. Take that block of code out and set both colors in cellWillDisplay

Or instead you can set ALL cells to white in that method. And then in cellWillDisplay, use the %2 logic to set half of them to red. You can also set both colors in the cellForRowAtIndexPath method. As long as you don't do that %3 calculation (which changes cells 0, 3, 6, 9, etc.), it should be fine.

[iSDK]

How can i set the color to white?

Originally Posted by kelvinkao

It shouldn't say %3. This is why your colors appear random. Take that block of code out and set both colors in cellWillDisplay

Or instead you can set ALL cells to white in that method. And then in cellWillDisplay, use the %2 logic to set half of them to red. You can also set both colors in the cellForRowAtIndexPath method. As long as you don't do that %3 calculation (which changes cells 0, 3, 6, 9, etc.), it should be fine.

[iSDK]

I have tried

- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
	if (indexPath.row%2 == 0) {
		UIColor *altCellColor = [UIColor colorWithRed:200/256.0 green:237/256.0 blue:255/256.0 alpha:1.0];
		UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		cell.backgroundColor = altCellColor, altCellColor2;
	}
}

But when i scroll all of the cells turn blue, but they all start off as blue and white.

Originally Posted by iSDK

How can i set the color to white?

[BrianSlick]

What do you think this does?

cell.backgroundColor = altCellColor, altCellColor2;

[iSDK]

Hehe i know! I managed to get it to work by:

- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
	if (indexPath.row == 0) {
		UIColor *altCellColor = [UIColor colorWithRed:200/256.0 green:237/256.0 blue:255/256.0 alpha:1.0];
		UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		cell.backgroundColor = altCellColor;
}
	if (indexPath.row == 1) {
		UIColor *altCellColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		cell.backgroundColor = altCellColor2;
	}
}

Originally Posted by BrianSlick

What do you think this does?

cell.backgroundColor = altCellColor, altCellColor2;

[BrianSlick]

Uh, something isn't right there.

For your colors, be sure to use float values. 1.0, etc. For the white one, just use whiteColor.

[iSDK]

Ok, thanks

Originally Posted by BrianSlick

Uh, something isn't right there.

For your colors, be sure to use float values. 1.0, etc. For the white one, just use whiteColor.

[kelvinkao]

Originally Posted by iSDK

Hehe i know! I managed to get it to work by:

- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
	if (indexPath.row == 0) {
		UIColor *altCellColor = [UIColor colorWithRed:200/256.0 green:237/256.0 blue:255/256.0 alpha:1.0];
		UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		cell.backgroundColor = altCellColor;
}
	if (indexPath.row == 1) {
		UIColor *altCellColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0];
		cell.backgroundColor = altCellColor2;
	}
}

By the way, you are declaring altCellColor and altCellColor2 twice (and only use it once for each). You probably got compiler warnings for those.

[Kalimba]

Originally Posted by kelvinkao

By the way, you are declaring altCellColor and altCellColor2 twice (and only use it once for each). You probably got compiler warnings for those.

Technically, those are two different declarations for each variable (each set is contained within its own scope), but you should indeed be getting some "declared but unused variable" warnings.

[iSDK]

Soz i forgot to take them out. It havent declared both of them in my full code.

Originally Posted by Kalimba

Technically, those are two different declarations for each variable (each set is contained within its own scope), but you should indeed be getting some "declared but unused variable" warnings.