I have TableViewController and ViewController. In 3 cells change pictures depending on the index and intForString in ViewController.
In the first session I work with all cells. In the second I work with one cell. When I go to the third session image stay only to the cell in which I worked the second session. And the other two images disappear. How to make that all the images were displayed?
I don't understand what you are asking when you say "How to make that all the images were displayed?"
However, this bit is very wrong:
(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell *cell1 = [tableView cellForRowAtIndexPath:indexPath];
The table view data source method tableView:cellForRowAtIndexPath: is supposed to configure and return a new (or recycled) table view cell.
The method you're calling in the first line is the table view instance method cellForRowAtIndexPath. That method only returns a cell if there is a cell on-screen for the specified indexPath.
That won't work.
You want to use code that calls dequeueReusableCellWithIdentifier:forIndexPath. If you've defined a class for your identifier, that method will always return a valid cell. If not, you need to add code that checks for nil and creates a new cell using the UITableViewCell method initWithStyle:reuseIdentifier:
Related
Hello guys i think almost everyone who is in ios development may come across the issue of reuse of the UITableCell by using following code line.
RZRestaurantListingCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
I have search lot about this but not getting any desire answer so please help me out in this case.
I have the same issue as most of iPhone developer having after reusing the cell.
I have the UIProgressView inside my cell and one button is there for downloading the video and i am showing the progress there in progress view how much is left.
So Now what i have problem is when i have more data and going out of the screen at that time i am press the download button on very first row of the UITableviewCell then i am scrolling down so the progress also shown in bottom random one cell so the UI changes in two cell rather then one.
You need to implement -prepareForReuse method in your custom cell class and set all cell properties to default value.
- (void)prepareForReuse
If a UITableViewCell object is reusable—that is, it has a reuse
identifier—this method is invoked just before the object is returned
from the UITableView method dequeueReusableCellWithIdentifier:. For
performance reasons, you should only reset attributes of the cell that
are not related to content, for example, alpha, editing, and selection
state. The table view's delegate in tableView:cellForRowAtIndexPath:
should always reset all content when reusing a cell. If the cell
object does not have an associated reuse identifier, this method is
not called. If you override this method, you must be sure to invoke
the superclass implementation.
Refer here for more, https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewCell_Class/#//apple_ref/occ/instm/UITableViewCell/prepareForReuse
You need to assign a progress value inside the - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
RZRestaurantListingCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// If the cell is reused, the `-prepareForReuse:` of `UITableViewCell` will be called.
//!! Assign current progress value to this cell, otherwise, the progressBar.value may look like a random value.
//!! Because the current cell is reused from a disappeared cell.
cell.progressBar.value = ... ;
return cell;
}
The design may be complex, because the progress may be updated continuously when the cell is on the screen.
Use prepareforreuse method to clear content of cell before using it... e.g.
-(void)prepareForReuse
{
[super prepareForReuse];
self.textLabel.text = #"";
self.detailTextLabel.text = #"";
self.imageView.image = nil;
}
I've got a subclass of UITableViewCell. I want to create a shadow on the labels dependent on the brightness of the image on the background. However, this image is set in the TableViewController. When awakeFromNib is called, self.backImage.iamge is nil. I tried implementing initWithStyle in the subclass itself but it logged nil as well.
When the cell is eventually loaded tho, the image is displayed.
Is there an event that happends when the cell is updated trough
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
?
So your table view controller is setting the background image for the cell? I assume it does this in cellForRowAtIndexPath after dequeueing the cell?
If so, try creating a method on your custom cell that sets the label shadow. Call the method after dequeueing the cell and setting the background image. If necessary, pass a parameter in the method that tells how dark to make the shadow.
I want to change the background of my content view inside the cell while showing delete button like in the following image;
I tried using willTransitionToState in my custom tableview cell class. But i cannot find a way to access current cell. Is there any other method I can access the cell?
I solve it by using "willBeginEditingRowAtIndexPath" method inside the table view controller implementation.
I access to the current cell instance. And I'm done.
Code Sample:
- (void)tableView:(UITableView *)tableView willBeginEditingRowAtIndexPath:(NSIndexPath *)indexPath{
TYMyCustomTableViewCell *cell = (TYMyCustomTableViewCell *)[tableView cellForRowAtIndexPath:indexPath];
cell.viewContainer.backgroundColor=[UIColor grayColor];
}
At my experiment I need to have reference to first UITableViewCell in tableView. By some action I need to set image and some other cell properties and to keep this state of this only cell even if the tableView will be scrolled. All of this properties can be potentially nulled via scrolling (and they actually are) because of reusing. For set this properties every time cell appears on screen, inside of `-cellForRowAtIndexpath' I tried to catch first cell using:
UITableViewCell *firstCell = (UITableViewCell *)[atableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]];
but looks like this way I can only catch every next first cell on next scrollable "screen".
So, how can I get ref to first UITableView cell?
If I understand you correctly, you are trying to do something special if the cell at (0, 0) is about to be displayed, right? If that's the case, you can easily implement UITableViewDelegate's tableView:willDisplayCell:forRowAtIndexPath: method as follows:
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath) {
// Do something special
}
}
There is also a corresponding tableView:didEndDisplayingCell:forRowAtIndexPath: method if you need to undo things.
Hope it helps!
There is no "first" table view cell. The entire table view typically uses a single cell to improve performance.
You can change that, by implementing your own cell reuse system (search for reuse in the documentation). But generally the cell is the wrong place to store any data related to a specific index in the table view.
I have a UITableViewController with UITextfield inside the tableview cells. If I scroll the table view, the user entered data in the textfields disappears. I tried to add the textfield data to a NSMutableArray but it still didn't work. Any help please.
When cellForRowAtIndexPath: is called, the cell you return has to be completely filled in with whatever data you want to show. So, if the cell includes a UITextfield, you'll need to set it's text property to the right value for that row in your data.
When a table cell disappears off the top or bottom of the screen, the UITableViewCell itself becomes available for re-use. (As you scroll, cells disappear, and new cells appear, but the UITableView class is re-using the UITableViewCell objects.) In cellForRowAtIndexPath: when you get a cached cell to use, you have to be sure to setup everything you want it to show for the row in question, otherwise you might see some odd behavior in your table.
Does this help?
EDIT:
Here's an example of the typical pattern used in cellForRowAtIndexPath:. Notice the use of dequeueReusableCellWithIdentifier:. That method returns a previously allocated but not in use UITableViewCell, if there is one. Notice further that if no cached cell is returned, the code creates a new one, and sets it up (with stuff that is independent of anything that might be row specific). Following that, you'd setup the cell as you need it for the row in question.
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *SearchResultsCellIdentifier = #"SearchResultsCellIdentifer";
UITableViewCell *cell = [tableView
dequeueReusableCellWithIdentifier:SearchResultsCellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:SearchResultsCellIdentifier] autorelease];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}
// Your row-specific setup of the cell here
// ...
return cell;
}
Check the docs for specifics about these methods. There are LOTS of examples from Apple and elsewhere about how to implement tableViews.