UITableViewCell with alternate background color in customized cells - objective-c

Question

I'd like the background to of my UITableViewCells to have a different color every two cells displayed, but when I scroll down and back, they all get the same color. How can I get this effect knowing that my cells have different contentView size (according to their content) ?
#define FONT_SIZE 14.0f
#define CELL_CONTENT_WIDTH 320.0f
#define CELL_CONTENT_MARGIN 20.0f
#define NAME_CELL_HEIGHT 20.0f
#import "CartCell.h"
#implementation CartCell
#synthesize nameLabel = _nameLabel;
#synthesize ingredientsLabel = _ingredientsLabel;
#synthesize myStore;
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
myStore = [Store sharedStore];
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
self.nameLabel = nil;
self.ingredientsLabel = nil;
// SET "NAME" CELL
self.nameLabel = [[UILabel alloc] initWithFrame:CGRectZero];
[self.nameLabel setLineBreakMode:UILineBreakModeWordWrap];
[self.nameLabel setMinimumFontSize:FONT_SIZE];
[self.nameLabel setNumberOfLines:1];
[self.nameLabel setTag:1];
self.nameLabel.font = [UIFont fontWithName:#"Helvetica-Bold" size:18];
[self.nameLabel sizeToFit];
self.nameLabel.backgroundColor = [UIColor clearColor];
[[self contentView] addSubview:self.nameLabel];
// SET "INGREDIENTS" CELL
self.ingredientsLabel = [[UILabel alloc] initWithFrame:CGRectZero];
[self.ingredientsLabel setLineBreakMode:UILineBreakModeWordWrap];
[self.ingredientsLabel setMinimumFontSize:FONT_SIZE];
[self.ingredientsLabel setNumberOfLines:0];
[self.ingredientsLabel setFont:[UIFont systemFontOfSize:FONT_SIZE]];
[self.ingredientsLabel setTag:2];
self.ingredientsLabel.backgroundColor = [UIColor clearColor];
[[self contentView] addSubview:self.ingredientsLabel];
if (myStore.cellBackgroundShouldBeLight == YES) {
NSLog(#"clear [in] ? %#", myStore.cellBackgroundShouldBeLight ? #"Yes" : #"No");
self.contentView.backgroundColor = [[UIColor alloc]initWithRed:87.0/255.0 green:168.0/255.0 blue:229.0/255.0 alpha:1];
myStore.cellBackgroundShouldBeLight = NO;
} else {
NSLog(#"clear [in] ? %#", myStore.cellBackgroundShouldBeLight ? #"Yes" : #"No");
self.contentView.backgroundColor = [[UIColor alloc]initWithRed:187.0/255.0 green:268.0/255.0 blue:229.0/255.0 alpha:1];
myStore.cellBackgroundShouldBeLight = YES;
}
}
return self;
}
- (void)setSelected:(BOOL)selected animated:(BOOL)animated
{
[super setSelected:selected animated:animated];
// Configure the view for the selected state
}
#end
UPDATE:
I'm know trying to set it in cellForRowAtIndexPath as it was suggested, but I get the same result: scrolling down worked fine the first time, but then scrolling up again messed up the cells background color.
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"CartCell";
CartCell *cell = (CartCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
Recipes *info = [_fetchedResultsController objectAtIndexPath:indexPath];
if (cell == nil)
{
cell = [[CartCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// if (!cell.nameLabel) {
// cell.nameLabel = (UILabel*)[cell viewWithTag:1];
// // cell.nameLabel = (UILabel*)[cell viewWithTag:1];
// }
// if (!cell.ingredientsLabel)
// cell.ingredientsLabel = (UILabel*)[cell viewWithTag:2];
CGSize constraint = CGSizeMake(CELL_CONTENT_WIDTH - (CELL_CONTENT_MARGIN * 2), 20000.0f);
CGSize size = [info.ingredients sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE] constrainedToSize:constraint lineBreakMode:UILineBreakModeWordWrap];
[cell.nameLabel setFrame:CGRectMake(10, 10, CELL_CONTENT_WIDTH - (CELL_CONTENT_MARGIN * 2), NAME_CELL_HEIGHT)];
[cell.ingredientsLabel setFrame:CGRectMake(CELL_CONTENT_MARGIN, CELL_CONTENT_MARGIN + NAME_CELL_HEIGHT, CELL_CONTENT_WIDTH - (CELL_CONTENT_MARGIN * 2), MAX(size.height, 44.0f))];
// SETTING TEXT CONTENT
cell.nameLabel.text = info.name;
cell.ingredientsLabel.text = info.ingredients;
// SETTING BACKGROUND COLOR
// UIView *lab = [[UIView alloc] initWithFrame:cell.frame];
// [lab setBackgroundColor:[UIColor blueColor]];
if (myStore.cellBackgroundShouldBeLight == YES) {
NSLog(#"clear? %#", myStore.cellBackgroundShouldBeLight ? #"Yes" : #"No");
cell.contentView.backgroundColor = [[UIColor alloc]initWithRed:87.0/255.0 green:84.0/255.0 blue:229.0/255.0 alpha:1];
// cell.backgroundView = lab;
// ingredientsLabel.backgroundColor = [UIColor clearColor];
// nameLabel.backgroundColor = [[UIColor alloc]initWithRed:87.0/255.0 green:168.0/255.0 blue:229.0/255.0 alpha:1];
// [cell setBackgroundColor: [[UIColor alloc]initWithRed:87.0/255.0 green:168.0/255.0 blue:229.0/255.0 alpha:1]];
// [cell setBackgroundColor:[UIColor colorWithRed:.8 green:.8 blue:1 alpha:1]];
myStore.cellBackgroundShouldBeLight = NO;
} else {
// cell.contentView.tag = 2;
NSLog(#"clear? %#", myStore.cellBackgroundShouldBeLight ? #"Yes" : #"No");
cell.contentView.backgroundColor = [[UIColor alloc]initWithRed:187.0/255.0 green:184.0/255.0 blue:229.0/255.0 alpha:1];
myStore.cellBackgroundShouldBeLight = YES;
}
return cell;
}

Answer 1

It is very simple, the indexPath tells you everything you need to know. If the indexPath.row is even then use one color. If the indexPath.row is odd use a different color.
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
…
// SETTING BACKGROUND COLOR
// UIView *lab = [[UIView alloc] initWithFrame:cell.frame];
// [lab setBackgroundColor:[UIColor blueColor]];
if (indexPath.row % 2) {
cell.contentView.backgroundColor = [[[UIColor alloc]initWithRed:87.0/255.0 green:84.0/255.0 blue:229.0/255.0 alpha:1] autorelease];
} else {
cell.contentView.backgroundColor = [[[UIColor alloc]initWithRed:187.0/255.0 green:184.0/255.0 blue:229.0/255.0 alpha:1] autorelease];
}
…
return cell;
}
Your method is having problems because blindly assuming cells will be asked for in alternating pairs is a bad assumption. The tableView could ask for cells in any order is chooses. In your example, I believe cells could be asked for as follows. First, 0, 1,…, 9 are asked for. Next, you scroll down and 10, 11, and 12 are fetched. At this point, 0, 1, and 2 have gone off the screen. You scroll back up and 2 is asked for, but oh no, your model is on an odd number alternation, so you get the wrong color.

Answer 2

Use the -willDisplayCell method.
- (void)tableView: (UITableView *)tableView willDisplayCell: (UITableViewCell *)cell forRowAtIndexPath: (NSIndexPath *)indexPath {
if (indexPath.row %2) { //change the "%2" depending on how many cells you want alternating.
UIColor *altCellColor = [UIColor colorWithRed:255/255.0 green:237/255.0 blue:227/255.0 alpha:1.0]; //this can be changed, at the moment it sets the background color to red.
cell.backgroundColor = altCellColor;
}
else if (indexPath.row %2) {
UIColor *altCellColor2 = [UIColor colorWithRed:1 green:1 blue:1 alpha:1.0]; //this can be changed, at the moment it sets the background color to white.
cell.backgroundColor = altCellColor2;
}
}

Answer 3

The appropriate place to change your cell's background color would be the "cellForRowAtIndexPath:" method, where the cells data gets filled out and returned to the table view.
One way to do this would be: When the data goes into the cell, change the background color depending on what row you're on.

Answer 4

Put the color on the cellForRowAtIndexPath: don't set on custom cell.

Answer 5

Take a look what I use to customize my table
- (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
#if USE_CUSTOM_DRAWING
const NSInteger TOP_LABEL_TAG = 1001;
const NSInteger BOTTOM_LABEL_TAG = 1002;
UILabel *topLabel;
UILabel *bottomLabel;
#endif
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
//
// Create the cell.
//
cell =
[[[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]
autorelease];
#if USE_CUSTOM_DRAWING
UIImage *indicatorImage = [UIImage imageNamed:#"indicator.png"];
cell.accessoryView =
[[[UIImageView alloc]
initWithImage:indicatorImage]
autorelease];
const CGFloat LABEL_HEIGHT = 20;
UIImage *image = [UIImage imageNamed:#"imageA.png"];
//
// Create the label for the top row of text
//
topLabel =
[[[UILabel alloc]
initWithFrame:
CGRectMake(
image.size.width + 2.0 * cell.indentationWidth,
0.5 * (aTableView.rowHeight - 2 * LABEL_HEIGHT),
aTableView.bounds.size.width -
image.size.width - 4.0 * cell.indentationWidth
- indicatorImage.size.width,
LABEL_HEIGHT)]
autorelease];
[cell.contentView addSubview:topLabel];
//
// Configure the properties for the text that are the same on every row
//
topLabel.tag = TOP_LABEL_TAG;
topLabel.backgroundColor = [UIColor clearColor];
topLabel.textColor = [UIColor colorWithRed:0.25 green:0.0 blue:0.0 alpha:1.0];
topLabel.highlightedTextColor = [UIColor colorWithRed:1.0 green:1.0 blue:0.9 alpha:1.0];
topLabel.font = [UIFont systemFontOfSize:[UIFont labelFontSize]];
//
// Create the label for the top row of text
//
bottomLabel =
[[[UILabel alloc]
initWithFrame:
CGRectMake(
image.size.width + 2.0 * cell.indentationWidth,
0.5 * (aTableView.rowHeight - 2 * LABEL_HEIGHT) + LABEL_HEIGHT,
aTableView.bounds.size.width -
image.size.width - 4.0 * cell.indentationWidth
- indicatorImage.size.width,
LABEL_HEIGHT)]
autorelease];
[cell.contentView addSubview:bottomLabel];
//
// Configure the properties for the text that are the same on every row
//
bottomLabel.tag = BOTTOM_LABEL_TAG;
bottomLabel.backgroundColor = [UIColor clearColor];
bottomLabel.textColor = [UIColor colorWithRed:0.25 green:0.0 blue:0.0 alpha:1.0];
bottomLabel.highlightedTextColor = [UIColor colorWithRed:1.0 green:1.0 blue:0.9 alpha:1.0];
bottomLabel.font = [UIFont systemFontOfSize:[UIFont labelFontSize] - 2];
//
// Create a background image view.
//
cell.backgroundView =
[[[UIImageView alloc] init] autorelease];
cell.selectedBackgroundView =
[[[UIImageView alloc] init] autorelease];
#endif
}
#if USE_CUSTOM_DRAWING
else
{
for (UIView *sub in [cell.contentView subviews]) {
// if([sub class] == [UITableViewCellContentView class])
NSLog(#"this is uilabel %#",[sub class]);
}
topLabel = (UILabel *)[cell viewWithTag:TOP_LABEL_TAG];
bottomLabel = (UILabel *)[cell viewWithTag:BOTTOM_LABEL_TAG];
}
topLabel.text = [NSString stringWithFormat:#"Cell at row %ld.", [indexPath row]];
bottomLabel.text = [NSString stringWithFormat:#"Some other information.", [indexPath row]];
//
// Set the background and selected background images for the text.
// Since we will round the corners at the top and bottom of sections, we
// need to conditionally choose the images based on the row index and the
// number of rows in the section.
//
UIImage *rowBackground;
UIImage *selectionBackground;
NSInteger sectionRows = [aTableView numberOfRowsInSection:[indexPath section]];
NSInteger row = [indexPath row];
if (row == 0 && row == sectionRows - 1)
{
rowBackground = [UIImage imageNamed:#"topAndBottomRow.png"];
selectionBackground = [UIImage imageNamed:#"topAndBottomRowSelected.png"];
}
else if (row == 0)
{
rowBackground = [UIImage imageNamed:#"topRow.png"];
selectionBackground = [UIImage imageNamed:#"topRowSelected.png"];
}
else if (row == sectionRows - 1)
{
rowBackground = [UIImage imageNamed:#"bottomRow.png"];
selectionBackground = [UIImage imageNamed:#"bottomRowSelected.png"];
}
else
{
rowBackground = [UIImage imageNamed:#"middleRow.png"];
selectionBackground = [UIImage imageNamed:#"middleRowSelected.png"];
}
((UIImageView *)cell.backgroundView).image = rowBackground;
((UIImageView *)cell.selectedBackgroundView).image = selectionBackground;
// cell.backgroundView.backgroundColor = [UIColor colorWithPatternImage:rowBackground];
// cell.selectedBackgroundView.backgroundColor = [UIColor colorWithPatternImage:selectionBackground];
//
// Here I set an image based on the row. This is just to have something
// colorful to show on each row.
//
if ((row % 3) == 0)
{
cell.imageView.image = [UIImage imageNamed:#"imageA.png"];
}
else if ((row % 3) == 1)
{
cell.imageView.image = [UIImage imageNamed:#"imageB.png"];
}
else
{
cell.imageView.image = [UIImage imageNamed:#"imageC.png"];
}
#else
cell.text = [NSString stringWithFormat:#"Cell at row %ld.", [indexPath row]];
#endif
return cell;
}
past it after all #import lines
#define USE_CUSTOM_DRAWING 1

Answer 6

Heading ##Simplest way of changing alternate colors
if(indexPath.row%2) {
cell.backgroundColor=[UIColor nameUrColor] //brownColor, yellowColor, blueColor
} else {
cell.backgroundColor=[UIColor nameAnotherColor]
}

Answer 7

if(cell.contentView)
{
[cell.nameLbl setFont:[UIFont systemFontOfSize:24]];
int red_value = arc4random() % 210;
int green_value = arc4random() % 210;
int blue_value = arc4random() % 210;
cell.contentView.backgroundColor = [UIColor colorWithRed:red_value/255.0 green:green_value/255.0 blue:blue_value/255.0 alpha:0.6];
}