As I scroll back and forth in the UICollectionView, I notice that the content changes in the cells that appear and disappear on the screen.
Is there any way to prevent this from happening?
I just want to load all of the content to each cell appropriately and then prevent it from changing as I scroll.
Here's some of the code related to this:
- (UICollectionViewCell *) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
cell.backgroundColor = [UIColor clearColor];
UILabel *label = (UILabel *)[cell viewWithTag:100];
if (!label) {
label = [[UILabel alloc] initWithFrame:cell.bounds];
label.tag = 100;
label.text = [self.array objectAtIndex:indexPath.row];
label.textAlignment = NSTextAlignmentCenter;
label.textColor = [UIColor blackColor];
[cell.contentView addSubview:label];
}
return cell;
}
The problem is that you are not supplying the content for the label in your cellForRowAtIndexPath:. Remember, these cells are being reused. So even if the label already exists, you need to supply the label text, because the cell is now being used in a different row and therefore needs different text!
So just move this line:
label.text = [self.array objectAtIndex:indexPath.row];
...down and outside the if block, to just before you return the cell.
Related
I want to add 2 imageViews on the Left and Right and a cell textLabel on the Center on TableView.
The 2 imageViews has different role and action.
(Being able to touch, hidden and not hidden)
Now the left side imageView is on the top of the center textLabel.
So I want to change the textLabel's width and x position not to be on the top of imageViews.
I tried this code but it didn't work.
CGRect frame = CGRectMake(40, 0, 200, 40);
cell.textLabel.frame = frame;
and I also tried to add UILabel on the tableView.
But I will implement TableViewCell animation and if I add UILabel, it doesn't work.
So I don't use this way.
How can I solve it?
here is the code.
- (void)viewDidLoad {
tableView = [[UITableView alloc]initWithFrame:rect style:UITableViewStylePlain];
tableView.delegate = self;
tableView.dataSource = self;
self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
[self.view addSubview: self.tableView];
self.tableView.backgroundColor = [UIColor clearColor];
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"Cell"];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
[self updateCell:cell atIndexPath:indexPath];
return cell;
}
- (void)updateCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
NSMutableArray *set = [self.section objectAtIndex:indexPath.row];
cell.backgroundColor = [UIColor blueColor];
cell.textLabel.textColor = [UIColor blackColor];
cell.textLabel.font = [UIFont fontWithName:#"HiraKakuProN-W3" size:15];
cell.textLabel.adjustsFontSizeToFitWidth = YES;
cell.textLabel.minimumScaleFactor = 10.0f;
cell.textLabel.numberOfLines = 0;
}
you need to override the layoutSubviews for your UItableviewCell class
- (void)layoutSubviews {
[super layoutSubviews];
CGSize size = self.bounds.size;
self.textLabel.frame = CGRectMake(2.0f, 4.0f, size.width, size.height); // or customize
self.textLabel.contentMode = UIViewContentModeScaleAspectFit;
}
Choice-2
crate the UILabel and subview to cell.contentView
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(4, 4, 200, 30)];
label.text = #"Test";
[cell.contentView addSubview:label];
Update
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
[self updateCell:cell atIndexPath:indexPath];
if (cell == nil){
myCellView = [[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:#"Cell"];
UILabel *orderLbl = [[UILabel alloc] initWithFrame:CGRectMake(1, 13, 176, 21)];
[orderLbl setTag:1];
orderLbl.textColor = [UIColor whiteColor];
[orderLbl setBackgroundColor:[UIColor clearColor]];
[orderLbl setTextAlignment:NSTextAlignmentCenter];
[cell.contentView addSubview:orderLbl];
}
[(UILabel *)[cell.contentView viewWithTag:1] setText:[NSString stringWithFormat:#"test"]];
return cell;
}
Better you can use Custom Textlabel with your desired frame requirement.
Give a tag for the textlabel and find out the label in cellForRowAtIndexPath as following :
UILabel *myLabel = (UILabel *)[cell.contentView viewWithTag:givenTagValue];
Then apply your required behaviour for this label as you want.
Hope it helps..
In such cases I prefer creating custom subclass and apply layout as I wanted so if I get any autolayout warning I always know it's because layout is not correct.
Actually, changing the frame the textLabel in cell is NOT allowed in TableView. The width of frame for the textlabel of each cell relates to the cell, developer couldn't set it programmatically. However, I worked out a feasible solution: we may not change the frame of the textLabel, but we may change the source text alternatively. If we can truncate the source string in advance, this problem is overcome.
//Assign each element in the array a row in table view
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var myCell = myTableView.dequeueReusableCell(withIdentifier: "The Cell")
if myCell == nil {
myCell = UITableViewCell(style: UITableViewCellStyle.value1, reuseIdentifier: "The Cell")
}
myCell?.accessoryType = UITableViewCellAccessoryType.none
// If the text is too long (longer than 25 chars), the text will be truncated
// The lenght of label cannot be set effectively here, so I truncate the source string alternatively
var myString: String = sectionArray[indexPath.row]
if myString.characters.count > 25 {
let myIndex = myString.index(myString.startIndex, offsetBy: 25)
myString = myString.substring(to: myIndex)
myString += "..."
}
myCell?.textLabel?.text = myString
myCell?.detailTextLabel?.text = "\(NSDate())"
return myCell!
}
That supports to work.
I am using table view using custom coding with tag method to save memory.
I was successful to show data in the view but the problem is if 10 cells are showing and then if I scroll down like for one cell then it should show 2-11 cell data but it switches to 1-10 again.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"cellID";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
UILabel *cellNAMElabl = nil;
UILabel *cellDetaillabl = nil;
UIImageView *imgView = nil;
if (cell == nil) {
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
cellNAMElabl = [[UILabel alloc] initWithFrame:CGRectMake(88, 10, 150, 20)];
[cellNAMElabl setTag:1];
cellNAMElabl.text = [name5 objectAtIndex:indexPath.row];
UIFont *myFont1 = [ UIFont fontWithName: #"Arial" size: 20.0 ];
cellNAMElabl.font = myFont1;
[cell.contentView addSubview:cellNAMElabl];
cellDetaillabl = [[UILabel alloc] initWithFrame:CGRectMake(88, 28, 150, 20)];
[cellDetaillabl setTag:2];
cellDetaillabl.text = [email5 objectAtIndex:indexPath.row];
UIFont *myFont = [ UIFont fontWithName: #"Arial" size: 13.0 ];
cellDetaillabl.font = myFont;
[cell.contentView addSubview:cellDetaillabl];
imgView=[[UIImageView alloc] initWithFrame:CGRectMake(25, 5, 52, 50)];
[imgView setTag:3];
imgView.image = [imagepath5 objectAtIndex:indexPath.row];
[cell.contentView addSubview:imgView];
}
cellNAMElabl = (UILabel *)[cell viewWithTag:1];
cellDetaillabl = (UILabel*)[cell viewWithTag:2];
imgView = (UIImageView*)[cell viewWithTag:3];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}
You are not assigning new content to subviews, if they have been already created. After the case if(cell == nil), these you have just got references.
cellNAMElabl = (UILabel *)[cell viewWithTag:1];
cellDetaillabl = (UILabel*)[cell viewWithTag:2];
imgView = (UIImageView*)[cell viewWithTag:3];
Here when cell is not nil, you are just getting references to labels and imageview, but you are not setting new text and image from data source. Add following lines and remove them from the if (cell == nil) part:
cellNAMElabl.text = [name5 objectAtIndex:indexPath.row];
cellDetaillabl.text = [email5 objectAtIndex:indexPath.row];
imgView.image = [imagepath5 objectAtIndex:indexPath.row];
[cell.contentView addSubview:imgView];
The way this dequeueReusableCellWithIdentifier works: If iOS detects that a cell is not displayed anymore, then dequeueReusableCellWithIdentifier will return that cell. If there is no unused cell, it returns nil. So what you need to do:
If dequeueReusableCellWithIdentifier returns nil, then you create a new cell, and you do all the setup that is required for all cells with the same identifier. For example, add view tags like you did, set fonts, colors etc.
Then, whether you use a cell returned by dequeueReusableCellWithIdentifier or one that you just created yourself, you add all the information that is used for the specific section/row that you want to display. So if row 1, row2, and so on display different text, then you set the text here. That's what you didn't do, so when a cell was reused, you didn't set the new text for it.
So the idea is that all the work that is the same for all rows is only done once when a cell is created, and only as many cells are created as is needed to display them on the screen. The work that is different from row to row is done for each row, as it is needed.
If you set a breakpoint in the if cell == nil block its probably only being hit for the first set if your reuseID is correct. Thats why its never getting a chance to set any new data into the cell.
You should not look for a nil cell, rather use a correct reuseID and a prototype cell in IB that is set to a custom UITableViewCell subclass you create.
Its also good practice to implement prepareForReuse on custom cells, where you clear any cell data e.g. label.text = nil, imageview.image = nil
This way you dont get invalid data from previously dequeued cells. It might not solve the question directly, but it would have wiped the fixed data set in your if cell == nil block to help debug.
What you want to do is..
add/setup the tableViewCell UI if the cell is nil..
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"cellID";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
UILabel *cellNAMElabl = [[UILabel alloc] initWithFrame:CGRectMake(88, 10, 150, 20)];
cellNAMElabl.tag = 1;
cellNAMElabl.font = [UIFont fontWithName: #"Arial" size: 20.0 ];
[cell.contentView addSubview:cellNAMElabl];
UILabel *cellDetaillabl = [[UILabel alloc] initWithFrame:CGRectMake(88, 28, 150, 20)];
cellDetaillabl.tag = 2;
cellDetaillabl.font = [UIFont fontWithName: #"Arial" size: 13.0 ];
[cell.contentView addSubview:cellDetaillabl];
UIImageView *imgView=[[UIImageView alloc] initWithFrame:CGRectMake(25, 5, 52, 50)];
imgView.tag = 3;
[cell.contentView addSubview:imgView];
}
//and just update your data if the cell is currently exist and not nil..
//you already called the view using tag so, you dont need those:
// UILabel *cellNAMElabl = nil;
// UILabel *cellDetaillabl = nil;
// UIImageView *imgView = nil;
((UILabel *)[cell viewWithTag:1]).text = [name5 objectAtIndex:indexPath.row]; // cellNAMElabl
((UILabel*)[cell viewWithTag:2]).text = [email5 objectAtIndex:indexPath.row]; // cellDetaillabl
((UIImageView*)[cell viewWithTag:3]).image = [imagepath5 objectAtIndex:indexPath.row]; // imgView
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}
hope this have help you, happy coding cheers!
I am using UICollectionView. in collection view label is overload every time i am using this code
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(5.0, 90.0,90.0, 21.0)];
[label setTag : indexPath.row];
label.text = [NSString stringWithFormat:#"%#",[arrImages objectAtIndex:indexPath.row]];
label.textColor = [UIColor redColor];
label.backgroundColor = [UIColor clearColor];
label.font = [UIFont boldSystemFontOfSize:12];
label.textColor = [UIColor colorWithRed:46.0/255.0 green:63.0/255.0 blue:81.0/255.0 alpha:1.0];
[cell.contentView addSubview:label];
return cell;
}
any one help me ?
The cell will get dequeued using UICollectionView's recycler - the label itself stays at the recycled cell, so there's no need in re-allocating it, you just need to find where you placed it:
#define LABEL_TAG 100001
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
UILabel *label = (UILabel*)[cell.contentView viewWithTag:LABEL_TAG];
if (!label) {
label = [[UILabel alloc] initWithFrame:CGRectMake(5.0, 90.0,90.0, 21.0)];
label.textColor = [UIColor redColor];
label.backgroundColor = [UIColor clearColor];
label.font = [UIFont boldSystemFontOfSize:12];
label.textColor = [UIColor colorWithRed:46.0/255.0 green:63.0/255.0 blue:81.0/255.0 alpha:1.0];
label.tag = LABEL_TAG;
[cell.contentView addSubview:label];
}
label.text = [NSString stringWithFormat:#"%#",[arrImages objectAtIndex:indexPath.row]];
return cell;
}
You have to generate the instance of your label just once, for the life - time of the cell.
But as I see in your method, you will get a new instance of the label every time the method is called.
Basically, you can subclass a UICollectionViewCell and then generate the required label only once. In the delegate method shown here, you should only update them with required information.
I am having two labels created manually for displaying it in the tableviewcell named title and detail, code for displaying it are,
dealarray = [[NSMutableArray alloc]initWithObjects:#"1",#"2",#"3",#"4",nil];
detailarray = [[NSMutableArray alloc]initWithObjects:#"oneoneoneoneone oneoneoneoneoneoneoooooooo",#"two",#"three",#"fouronefouronefouronefouronefouronefouronefouron",nil];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
for(UILabel *lbl in [cell.contentView subviews])
{
[lbl removeFromSuperview];
}
cell.accessoryType= UITableViewCellAccessoryNone;
UILabel* title;
title= [[UILabel alloc] initWithFrame:CGRectMake(5,5,300,20)];
[cell.contentView addSubview:title];
[cell.contentView bringSubviewToFront:title];
[title setFont:[UIFont boldSystemFontOfSize:14]];
title.tag = 1001;
title.backgroundColor = [UIColor clearColor];
title.textColor = [UIColor blackColor];
title.text =[dealarray objectAtIndex:indexPath.row];
UILabel* detail;
detail= [[UILabel alloc] initWithFrame:CGRectMake(5,30,300,10)];
[cell.contentView addSubview:detail];
[cell.contentView bringSubviewToFront:detail];
[detail setFont:[UIFont systemFontOfSize:12]];
detail.tag = 1002;
detail.backgroundColor = [UIColor clearColor];
detail.textColor = [UIColor blackColor];
detail.text = [detailarray objectAtIndex:indexPath.row];
return cell
}
No problem in displaying those 2 labels and no problem in hiding all the 'detail' label and displaying the 'title' alone, the problem arises when I try to display the 'detail' label of the resp selective of cells.
Code tried:
// conti of cellforrowatindexpath
detail.numberOfLines = 3;
detail.lineBreakMode = NSLineBreakByWordWrapping;
if (a==-1)// declared 'a' in viewdidload as -1
{
((UILabel*)detail).hidden = YES;
}
else if(a==indexPath.row)
{
((UILabel*)detail).hidden = NO;
}
((UILabel*)detail).hidden = YES;
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView deselectRowAtIndexPath:indexPath animated:YES];
a=indexPath.row;
[tableview reloadData];
}
Sorry for posting large amount of codes, it may help any one who is searching for the wholesome data of my doubt.
Whats the mistake am doing, I can't hide the detail label for resp selecting of cells. Can anybody help in this regard?
May I suggest you to use xcode functionnality to design your cell content? (as easy as drag and drop of UILabel on your cell for example) Then you will be able to access them from your code using their respective "tag" id.
A correct way of doing is detail here : http://www.appcoda.com/customize-table-view-cells-for-uitableview/
I think it's a better way than programmatically creating content for your cell, because using xcode interface you will be able to flawlessly define your interface.
Anyway to respond precisely to your question you should try to hide the detail label from "didSelectRowAtIndexPath" :
// Retrieve the corresponding cell
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
// Get the detail label (using its tag) you set it to 1002
UILabel *detail = (UILabel *)[cell viewWithTag:1002];
// Hide it
detail.hidden = true;
Hope this help.
There is an error in your logic. You code as written will always set detail.hidden to YES, the 2 preceding if are ignored, thus this (BTW you don't need the type coercion and extra brackets):
if(a==-1) detail.hidden = YES;
else if (a==indexPath.row) detail.hidden = NO;
else detail.hidden = YES;
I'm trying to create a tableview where the height of the cells are dynamic.
So far I manage to set the height of the cells depending on the custom UILabel I've added inside.
With the regular cell.textLabel it works fine, but when I use my own label something goes wrong. I only see half the label, but when I scroll up and down, sometimes the label extends and shows all the text... You can see where the label should end in the image.
Image
This is the text inside the cellForRowAtIndexPath:
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// Configure the cell.
Car *carForCell = [cars objectAtIndex:indexPath.row];
UILabel *nameLabel = [[UILabel alloc] init];
nameLabel = (UILabel *)[cell viewWithTag:100];
nameLabel.numberOfLines = 0;
nameLabel.text = carForCell.directions;
[nameLabel sizeToFit];
[nameLabel setBackgroundColor:[UIColor greenColor]];
return cell;
Unless you have typos in the code you posted, you don't seem to be adding the label to the cell at all. You also seem to be creating a new label every time, and then replacing the contents of your nameLabel pointer with the cell's view (which will always be nil).
Try doing something like this first and then see how it looks:
static NSString *CellIdentifier = #"Cell";
UILabel *nameLabel;
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
nameLabel = [[UILabel alloc] init];
nameLabel.tag = 100;
nameLabel.numberOfLines = 0;
[nameLabel setBackgroundColor:[UIColor greenColor]];
[cell.contentView addSubview:nameLabel];
}
else {
nameLabel = (UILabel *)[cell viewWithTag:100];
}
// Configure the cell.
Car *carForCell = [cars objectAtIndex:indexPath.row];
nameLabel.text = carForCell.directions;
[nameLabel sizeToFit];
return cell;
You will also need to tell the tableView what size each cell needs to be using the tableView:heightForRowAtIndexPath: delegate method. That will mean getting the relevant Car object again and calculating the height using sizeWithFont:sizeWithFont:forWidth:lineBreakMode:
How are you setting the height of the cell? It should be done in - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
You should calculate and return the height of the UITableViewCell in the following method:
- (CGFloat) tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath;
Here you should do your initial calculation of how high your cell should be.
For example:
CGSize textSize = [myString sizeWithFont:[UIFont systemFontOfSize:16] constrainedToSize:CGSizeMake(320, 9999)];
return textSize.height;