ios - UITableViewCell display wrong data when scrolling - ios

Question

Here's my code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifierNormal = #"CellNormal";
static NSString *CellIdentifierTracking = #"CellTracking";
switch (self.mapState) {
case MapStateNormal:
{
// UITableViewCell *cell = [self.table dequeueReusableCellWithIdentifier:CellIdentifierNormal];
// if (cell == nil) {
UITableViewCell *cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifierNormal];
// }
[cell.textLabel setText:#"abc"];
return cell;
}
case MapStateTracking:
{
// UITableViewCell *cell = [self.table dequeueReusableCellWithIdentifier:CellIdentifierTracking];
// if (cell == nil) {
UITableViewCell *cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifierTracking];
// }
if (indexPath.row == 0) {
[cell.textLabel setText:#"Lorem ipsum"];
} else {
NSURL *url = [LoremIpsum URLForPlaceholderImageFromService:LoremIpsumPlaceholderImageServicePlaceKittenCom
withWidth:1024
height:1024];
[cell.imageView setImageWithURL:url
placeholderImage:[UIImage imageNamed:#"MenuButton"]];
}
return cell;
}
default:
break;
}
return nil;
}
This piece of code works fine but not the best practice because I re-create UITableViewCell everytime. It display like this:
However, when I uncomment those lines above to enable dequeueReusableCell then the table shows its cells with errors like this (the yellow part is my code):
You can see that there's an UIImage in first row and text in some rows below while I clearly didn't set it in my code.
What could I do to fix this ? or should I stick with the first method ?
Thanks.

Answer 1

You should really re-use the table view cells, because it is a lot of overhead if you recreate them all the time, i.e. the out-commented code is right.
Next, the docs say: "The table view's delegate in tableView:cellForRowAtIndexPath: should always reset all content when reusing a cell."
If you do not reset the content, it will be shown again.
So I suggest that you set
cell.imageView.image = nil;
in your -(UITableViewCell *)tableView:cellForRowAtIndexPath:(NSIndexPath *)indexPath method.

Answer 2

Simply set [cell.textLabel setText:#""]; for each cell you dont't want to display any text. Cells are reused with the previous text, so you need to clear it.

Answer 3

Try this, clear the cell if it cell != nil
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifierNormal = #"CellNormal";
static NSString *CellIdentifierTracking = #"CellTracking";
switch (self.mapState) {
case MapStateNormal:
{
UITableViewCell *cell = [self.table dequeueReusableCellWithIdentifier:CellIdentifierNormal];
if (cell == nil) {
UITableViewCell *cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifierNormal];
} else {
[cell.textLabel setText:#""];
[cell.imageView setImage:nil];
}
...
return cell;
}
case MapStateTracking:
{
UITableViewCell *cell = [self.table dequeueReusableCellWithIdentifier:CellIdentifierTracking];
if (cell == nil) {
UITableViewCell *cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifierTracking];
} else {
[cell.textLabel setText:#""];
[cell.imageView setImage:nil];
}
....
return cell;
}
default:
break;
}
return nil;
}