I have a UITableView which makes use of cells with custom backgroundViews. I'm assigning the backgroundViews in tableView:cellForRowAtIndexPath:indexPath: as suggested here. In a nutshell, dependent upon the position of a UITableViewCell within its UITableView, I want to assign certain backgroundView images. Here's the code in question:
UIImage *rowBackground = nil;
if (row == 0 && row == sectionRows - 1) {
rowBackground = [UIImage imageNamed:#"row_bg_start_and_end.png"];
} else if (row == 0) {
rowBackground = [UIImage imageNamed:#"row_bg_start.png"];
} else if (row == sectionRows - 1) {
rowBackground = [UIImage imageNamed:#"row_bg_end.png"];
} else {
rowBackground = [UIImage imageNamed:#"row_bg.png"];
}
((UIImageView *)cell.backgroundView).image = rowBackground;
This works fine, and I see the results I'm expecting. I have issues, however, when it comes to the removal or addition of rows, which invariably means certain rows retain their previous backgroundViews, rather than recalculating their placement and updating the view in question.
I understand the purpose of dequeueReusableCellWithIdentifier and why this is happening. But I'm not sure how to go about fixing it correctly. I can tell that the rows are recalculated correctly when tableView:cellForRowAtIndexPath:indexPath: is called by scrolling them off screen, which results in their backgroundView being reset correctly.
Should I be setting the backgroundView property in willDisplayCell:forRowAtIndexPath: also? How should I handle this situation?
The easiest approach to fix the problem you're having is to reprocess the background images of all visible rows when you add new rows to a section.
i.e.
for (UITableViewCell *cell in aTableView.visibleCells)
{
NSIndexPath *cellIndexPath = [aTableView indexPathForCell:cell];
/* look at the cell.backgroundImage and if it's not appropriate
for the indexPath, update it */
}
You could carefully override all the UITableView methods that insert new rows and only check perform this work for the specific rows that need to be updated but I don't think this would be worth the effort.
Related
I have UITableView where I want design as below.
For this I have images as below.
bottomRow.png
middleRow.png
topAndBottomRow.png
topRow.png
For this I have used below code inside -(UITableViewCell *) tableView:(UITableView *) tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UIImage *selectedImage;
if (indexPath.row==0) {
selectedImage = [UIImage imageNamed:#"topRow.png"];
} else if (indexPath.row == ([products count]-1)) {
selectedImage = [UIImage imageNamed:#"bottomRow.png"];
} else {
selectedImage = [UIImage imageNamed:#"middleRow.png"];
}
if ([products count]==1) {
selectedImage = [UIImage imageNamed:#"topAndBottomRow.png"];
}
UIImageView *selectedBackgroundImageView = [[UIImageView alloc] initWithImage:selectedImage];
cell.selectedBackgroundView = selectedBackgroundImageView;
selectedBackgroundImageView = [[UIImageView alloc] initWithImage:selectedImage];
cell.backgroundView = selectedBackgroundImageView;
Now, everything works perfect.
BUT my designer is insisting on below point.
On tableview, I can have 4 cells at one time. Now let's say I have 6 rows.
Now when I have 6 rows (and tableview can show only 4), the 4th row shows bottomRow.png which is obvious. But my designer is insisting, even the tableview is scrolled, you should have same design for all 4 rows.
Edit 1
First of all, sorry for not being clear.
Well when the UITableView loads, I can only see first 4 cells even there are 6 cells because I have set the height of tableview accordingly. To see rest 2 cells, I have to scroll down. I believe this is how table view works.
Now let's say there are only 4 records. For 4 records, table view looks like image I have.
Now when I have tableview size as 6 (with id as 1-6), the fourth row gets image middleRow.png. Here what my designer wanted is to see bottomRow.png.
Now let's say I scroll down. Now I see row with cell id as 3-6. Now cell with id 3 have middleRow.png, but my designer wanted to see topRow.png.
I know this is ugly, but this is what my designer wanted to see.
Any suggestions to get this done?
One way to achieve your goal: Use numberOfRows to find out if this cell is the last cell.
In your cellForRowAtIndexPath:
if (indexPath.row==0) {
selectedImage = [UIImage imageNamed:#"topRow.png"];
.....
else if (indexPath.row == [tableView numberOfRowsInSection:indexPath.section]-1){
selectedImage = [UIImage imageNamed:#"bottomRow.png"];
}
EDIT:
Sorry, I misunderstood your question, I have another proposal that I think you may try...
customCell, with a custom method to set its image. For example,
[customCell setSelectedImage: [UIImage imageNamed:#"middleRow.png"];
2.
In cellForRowAtIndexPath, you can set all cells to be: middleRow.png
3.
After loading of tableView, run a checking method using [self.tableView visibleCells];
eg
- (void) setImageForTopAndBottomCells{
CustomCell *topCell = [[self.tableView visibleCells] objectAtIndex: 0];
CustomCell *bottomCell = [[self.tableView visibleCells] objectAtIndex: self.tableView.visibleCells.count-1];
[topCell setSelectedImage: [UIImage imageNamed:#"topRow.png"];
[bottomCell setSelectedImage: [UIImage imageNamed:#"bottomRow.png"];
}
If your tableView is scrollable, set your ViewController as a UIScrollView delegate, in your delegate method scrollViewDidScroll, run the setImageForTopAndBottomCells method again.
There could be better ways for achieving what you want than the one I proposed, let me know if you found one.
What about using a combination of scrollViewDidScroll:, indexPathsForVisibleRows and reloadRowsAtIndexPaths:withRowAnimation: with something like this:
Every time the table view scrolls you get the list of visible rows using the UIScrollViewDelegate method scrollViewDidScroll:
If it scrolled enough to change the background, call the UITableView's reloadRowsAtIndexPaths:withRowAnimation: passing all the index paths that needs new background
Instead of using indexPath.row == 0 to find the top you would use [indexPath isEqual:[tableView indexPathsForVisibleRows][0]] and the same thing for the other rows
Hope this helps.
You can use middlerow.png as background view of your UITableViewCell in CellForRowAtIndexPath method. Below is the code
cell.backgroundView = [[UIImageView alloc] initWithImage[[UIImageimageNamed:#"middlerow.png"]stretchableImageWithLeftCapWidth:0.0 topCapHeight:5.0]];
And after this you can change the Corner radius (add border color/width) of your table view. But for this first you will have to add QuartzCore framework.
self.table.layer.borderColor=[[UIColor colorWithRed:209.0/255 green:209.0/255 blue:209.0/255 alpha:1.0] CGColor];
self.table.layer.borderWidth =3.0;
self.table.layer.cornerRadius =10.0;
Hope this helps.
You can Use this:
NSArray *visible = [tableView indexPathsForVisibleRows];
NSIndexPath *indexpath = (NSIndexPath*)[visible objectAtIndex:0];
-(NSArray *)indexPathsForVisibleRows returns an array of index paths each identifying a visible row in the receiver.So once you get the visible rows, you can use the required image according to indexpath.row.
This is related to another question of mine which wasn't answered in a helpful way (message when a UITableView is empty).
I'm trying to show an UIImage graphic that says You haven't saved any bookmarks over an UITableView when it's empty. I have NSNotification set-up so that when bookmarks are added or deleted, a message is sent so that the UITableView can be updated.
I've been trying to do it with this code. Why won't this work?
- (void)bookmarksChanged:(NSNotification*)notification
{
[self.tableView reloadData];
UIImageView* emptyBookmarks = [[UIImageView alloc] initWithFrame:CGRectMake(75, 100, 160, 57)];
emptyBookmarks.alpha = 1;
emptyBookmarks.image = [UIImage imageNamed:#"emptyBookmark.png"];
[self.view addSubview:emptyBookmarks];
[emptyBookmarks release];
if ([self.dataModel bookmarksCount] == 0)
{
emptyBookmarks.alpha = 1;
}
else
{
emptyBookmarks.alpha = 0;
}
}
I'm probably approaching this the wrong way... But if salvageable, what am I doing wrong?
When I initially have an empty bookmarks tableview, there's no image displayed. After I add a bookmark and then delete it, the image shows. Grrh.
Another way (and IMO the correct way) to do this is to manipulate the backgroundView property on the UITableView.
While making a single cell with a custom image cell would certainly works, I think it overly complicates the logic of your UITableViewController's data source. It feels like a kludge.
According to UITableView documentation:
A table view’s background view is automatically resized to match the
size of the table view. This view is placed as a subview of the table
view behind all cells , header views, and footer views.
Assigning an opaque view to this property obscures the background color
set on the table view itself.
While you probably don't want to just set it to your UIImageView, it is very easy to make a UIView that contains the UIImageView that you want.
Well first off if you were going to do it that way, you would need to reload the tableView after updating the image or model etc. and not before.
But you are probably making things more complicated than they need to be!
Why not just check to see if the data for section 0 and indexPath.row 0 are empty and if so in cellForRowAtIndexPath display a text message accordingly.
// First make sure there is always one row returned even if the dataModel is empty.
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSInteger numRows = 0;
if ([self.dataModel lastObject]) {
// Return the number of rows in the section.
numRows = [self.dataModel count]; // etc.
}
if (numRows < 1) numRows = 1;
return numRows;
}
// Then display the data if there is some, otherwise a message if empty.
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
if ([self.dataModel lastObject]) {
// setup the cell the normal way here.
} else { // the datasource is empty - print a message
cell.textLabel.text = nil;
cell.detailTextLabel.text = NSLocalizedString(#"You haven't saved any bookmarks", #"");
cell.detailTextLabel.textColor = [UIColor colorWithRed:0/255.0 green:0/255.0 blue:0/255.0 alpha:0.7];
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell;
}
Are you sure [self.dataModel bookmarksCount] is equal to 0 ?
While I agree that you are probably going about this the wrong way,
your image is allocated and added in your bookmark changed, your notification does not trigger when there are no bookmarks initially. Hence you don't see the image. Call the bookmar changed when your table view inits or appears.
Probably the best way to achieve this is to perform a check in your numberOfRowsInSection method to return 1 if your data source is empty. Then in cellForRowAtIndexPath check if your data source is empty and if it is, create a custom cell that contains whatever you want. In heightForRowAtIndexPath you need to return your custom cell height if your datasource is empty, but only if you want the cell larger than the default. At least that is how I would approach it.
when bookmarks count is nil add one to your row method:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
int c;
c = bookmarks.count;
if(c == 0){
c = 1;
}
return c;
}
and then the same check again in your cellforrowatindexpath.
Another thing to be aware of in this situation is that if you're using core data and you're datasource is feeding off an entity, you will want to make sure your model matches. You can get some weird side-effect behavior in certain situations. This is especially true if you allow editing and core data has an empty model but you're tableview is still showing a cell.
I'm making an iPhone app with a Table View, and I'm trying to place a different icon / image next to each cell on a table.
I know that you set the image in (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath with code that looks like this:
UIImage *image = [UIImage imageNamed:#"image.png"];
cell.imageView.image = image;
What I'm trying to figure out is, how do I target a specific cell, so that it has a unique image? Like:
if (cell.number == 0) {
//Use a specific image
}
else if (cell.number == 1) {
//Use a different image
Thanks!
The indexPath variable contains information about the cell's position. Modifying your example:
if (indexPath.row == 0) {
// Use a specific image.
}
See the NSIndexPath Class Reference and NSIndexPath UIKit Additions Reference for more information. It's also important to note that cell numbers reset in each section.
Use the row (and possibly also section) properties in the NSIndexPath passed to your tableView:cellForRowAtIndexPath: method to identify which cell is being queried.
this function is passed an index path, which has a section and a row. indexPath.row will pass back an integer you can check.
When cellForRowAtIndexPath is executed you have access to the indexPath variable, so if you want to customize the cell style depending on the cell index you can do something like this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.row == 0) {
// code for cell 0
}
else {
if (indexPath.row == 1) {
// code for cell 1
}
}
}
This is just an example, I don't think that customizing your cells by using if conditions is the best idea, but it shows you how to do what you need.
Remember that indexPath contains the section of the table too. If you are using a Grouped table view, you need to manager the section too. For example:
if (indexPath.section == 0) {
// section 0
if (indexPath.row == 0) {
// code for section 0 - cell 0
}
else {
if (indexPath.row == 1) {
// code for section 0 - cell 1
}
}
}
else {
if (indexPath.section == 1) {
// section 1
if (indexPath.row == 0) {
// code for section 1 - cell 0
}
else {
if (indexPath.row == 1) {
// code for section 1 - cell 1
}
}
}
}
For a slightly nicer looking approach I would put all the images you want to use into an array:
_iconArray = #[#"picture1.png", #"picture2.png", #"picture3.png"];
This means that when you come to the cellForRowAtIndex function you can say only:
cell.imageView.image = [UIImage imageNamed:_iconArray[indexPath.row]];
This is also easier if you have more than one section, this time you can make an array of arrays, each containing the required pictures for the different sections.
_sectionsArray = #[_iconArray1, _iconArray2, _iconArray3];
cell.imageView.image = [UIImage imageNamed:_sectionsArray[indexPath.section][indexPath.row];
This immediately makes it very easy to modify the pictures (as you are only dealing with the arrays. And much easier if you have more rows and sections (imagine doing it manually for 100 rows)
I'm extremely confused by the proper behavior of UITableView cell rendering. Here's the situation:
I have a list of 250 items that are loading into a table view, each with an image. To optimize the image download, I followed along with Apple's LazyTableImages sample code... pretty much following it exactly. Really good system... for reference, here's the cell renderer within the Apple sample code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// customize the appearance of table view cells
//
static NSString *CellIdentifier = #"LazyTableCell";
static NSString *PlaceholderCellIdentifier = #"PlaceholderCell";
// add a placeholder cell while waiting on table data
int nodeCount = [self.entries count];
if (nodeCount == 0 && indexPath.row == 0)
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:PlaceholderCellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:PlaceholderCellIdentifier] autorelease];
cell.detailTextLabel.textAlignment = UITextAlignmentCenter;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
cell.detailTextLabel.text = #"Loading…";
return cell;
}
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:CellIdentifier] autorelease];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
// Leave cells empty if there's no data yet
if (nodeCount > 0)
{
// Set up the cell...
AppRecord *appRecord = [self.entries objectAtIndex:indexPath.row];
cell.textLabel.text = appRecord.appName;
cell.detailTextLabel.text = appRecord.artist;
// Only load cached images; defer new downloads until scrolling ends
if (!appRecord.appIcon)
{
if (self.tableView.dragging == NO && self.tableView.decelerating == NO)
{
[self startIconDownload:appRecord forIndexPath:indexPath];
}
// if a download is deferred or in progress, return a placeholder image
cell.imageView.image = [UIImage imageNamed:#"Placeholder.png"];
}
else
{
cell.imageView.image = appRecord.appIcon;
}
}
return cell;
}
So – my implementation of Apple's LazyTableImages system has one crucial flaw: it starts all downloads for all images immediately. Now, if I remove this line:
//[self startIconDownload:appRecord forIndexPath:indexPath];
Then the system behaves exactly like you would expect: new images load as their placeholders scroll into view. However, the initial view cells do not automatically load their images without that prompt in the cell renderer. So, I have a problem: with the prompt in the cell renderer, all images load at once. Without the prompt, the initial view doesn't load. Now, this works fine in Apple sample code, which got me wondering what was going on with mine. It's almost like it was building all cells up front rather than just the 8 or so that would appear within the display. So, I got looking into it, and this is indeed the case... my table is building 250 unique cells! I didn't think the UITableView worked like this, I guess I thought it only built as many items as were needed to populate the table. Is this the case, or is it correct that it would build all 250 cells up front?
Also – related question: I've tried to compare my implementation against the Apple LazyTableImages sample, but have discovered that NSLog appears to be disabled within the Apple sample code (which makes direct behavior comparisons extremely difficult). Is that just a simple publish setting somewhere, or has Apple somehow locked down their samples so that you can't log output at runtime?
Thanks!
You certainly should not have an actual UITableViewCell instance for every row in the table. You should only see a few more instances than are visible in the UI. That is where your problem is. It doesn't have anything to do with the loading of images.
The only time I've seen a large number of cells instantiated when the cells where dequeued was when a coder had altered the frame of the tableview to make it much larger than the screen. The tableview retains enough cells from being dequeued to carpet its own frame regardless of what is visible. If the frame is to big then you get a lot of cells in queue.
NSLog does work in Apple examples so if you can't get NSLog output you've got something weird going on with the dev tools themselves.
You might want to shutdown Xcode and the simulator and restart and see if that clears up the odd behavior.
Oh my... mustISignUp is absolutely correct in saying "you definitely have a deeper underlying problem". I have variable-height table rows, and I was doing all height calculation and data storage on the rows themselves rather than on the data model that populated them. As a result, ALL cells were being created and populated by my heightForRowAtIndexPath method which was reading cell height from the cell objects. SO – lesson learned.
Thanks mustISignUp, and I love your username.
NSLog definitely isn't disabled within the Apple sample code. I don't know why you can't see it but you definitely have a deeper underlying problem.
Anyway, for your comparison:- if you have 6 rows on screen -tableView: cellForRowAtIndexPath: is called 6 times with index [0, 0] - [0, 5].
So, is that what you are seeing? How many times is -cellForRowAtIndexPath being called?
i'm using a default style table (UITableViewCellStyleSubtitle)
i want to add more then one detailTextLabel in each row,
how can i customize it?
code:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:CellIdentifier] autorelease];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
// Leave cells empty if there's no data yet
if (nodeCount > 0)
{
// Set up the cell...
ARecord *aRecord = [self.entries objectAtIndex:indexPath.row];
cell.textLabel.text = aRecord.lDate;
cell.detailTextLabel.text = aRecord.WNum;
// Only load cached images; defer new downloads until scrolling ends
//(!aRecord.appIcon) - use icon
if (!aRecord.appIcon)
{
if (self.tableView.dragging == NO && self.tableView.decelerating == NO)
{
[self startIconDownload:aRecord forIndexPath:indexPath];
}
// if a download is deferred or in progress, return a placeholder image
cell.imageView.image = [UIImage imageNamed:#"Placeholder.png"];
}
else
{
cell.imageView.image = aRecord.appIcon;
}
}
return cell;
}
The best way of doing this is to add a UILabel to the cell.contentView. You would do this when you initially create the cell. I've found two things to be especially helpful: to lay out the label on a table cell in a throwaway document in Interface Builder to determine the initial frame. It's also especially helpful to set the autoresizingMask so that the label will be resized appropriately when the cell is resized (due to autorotation, going into edit mode, etc.).
Finally, you'll need to set the table view's rowHeight to a higher value to accommodate the larger cells, otherwise you'll end up with overlapping cells.
Also, set a tag on your label to make it easy to retrieve with viewWithTag: when you go to update the text.
You could add the labels to cell.contentView.