I'm having a funky problem with drawing a custom view in a UITableView. The drawRect function of my custom view, called ChatBubbleView, is just drawing a rectangle of a constant size.
I have an NSLog debugging statement in the drawRect function of ChatBubbleView. The first 5 times I add a cell to the UITableView, everything draws nicely, and I see the NSLog statement trigger. After 5 however, the drawing becomes garbled, and I no longer see the debugging statement.
I'm totally baffled, and I'd appreciate any help you might provide. Thanks in advance!
Here is the function that is called when reloadData is called on the UITableView.
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (forumMode) {
//This part works, ignore
} else {
ChatBubbleView* chatBubble = nil;
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero
reuseIdentifier:CellIdentifier] autorelease];
// Add the bubble
chatBubble = [[[ChatBubbleView alloc] init] autorelease];
chatBubble.tag = BUBBLEVIEW_TAG;
[cell.contentView addSubview:chatBubble];
} else {
// Reuse old views
chatBubble = (ChatBubbleView*)[cell.contentView viewWithTag: BUBBLEVIEW_TAG];
}
chatBubble.labelSize = CGSizeMake(50, 18);
chatBubble.frame = CGRectMake(0, 0, chatBubble.labelSize.width, chatBubble.labelSize.height);
}
return cell;
}
EDIT: I should add that the function that reloads the UITableView looks like this:
-(IBAction) btnAdd:(id) sender {
[listOfMessages addObject:textView.text];
[self.tableView reloadData];
}
EDIT 2: I've discovered that the custom views in the cells sometimes redraw themselves when I scroll the cells in and out of view. It seems that the tableview refreshing changes the parameters of the custom view.
You say //This part works, ignore but if you are reusing the CellIdentifier it might not work as the cell that will get dequeued could be a different type of cell (that happens to have the same CellIdentifier). Make sure each cell type has a unique CellIdentifier.
To be sure, put some debugging in your if / else block to see what cell you're getting back...
Related
I have a problem, setting a button to a UITableviewCell.
After viewDidLoad, the button is on the right place. But when I am scrolling down, the button is anyplace else.
Here is my code, I hope you can help me.
Thanks In Advance.
- (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 (indexPath.section == 0 && indexPath.row == 0 && _isAddImageViewLoad == NO) {
// Add Image Button
UIButton *addImage = [UIButton buttonWithType:UIButtonTypeCustom];
UIImage* image = [UIImage imageNamed:#"AddImage#2x"];
addImage.frame = CGRectMake(110.0f, 10.0f, 110.0f, 110.0f);
[addImage setImage:image forState:UIControlStateNormal];
[cell.contentView addSubview:addImage];
_isAddImageViewLoad = YES;
} else {
NSDictionary *dictionary = [_items objectAtIndex:indexPath.section];
NSArray *array = [dictionary objectForKey:#"data"];
NSString *cellValue = [array objectAtIndex:indexPath.row];
cell.textLabel.text = cellValue;
}
return cell;
}
It is because you are reusing the cells, and the button is getting placed when it shouldn't an easy solution in your else section. Write addImage.hidden = YES; and in your if statement put addImage.hidden = NO;
Just a couple things. If you use "AddImage" it will use the "AddImage#2x" automatically if it's a retina display. I don't think that will solve your issue but it could be causing weirdness.
When a table view cell is scrolled off the view it is "recycled" in a sense. It appears like you are using a bool to exclude the original cell from being loaded again with a button. You may want to use a header to hold your button if you always want it at the "top". You may also want to verify that the button is being removed when the cell is reused. if its not it will show up in the next row that reuses that cell.
On a side note... Buttons don't usually work very well in table view cells because they handle touches in very different ways. It's quite a bit of modification to get them to feel natural but that's another matter.
Hope that helps!
The problem is because of cell reuse. You need to put some code in the else clause to delete the button if it exits. One way to do this, would be to give your button a tag, like:
addImage.tag = 10;
Then in your else clause:
}else{
if (cell viewWithTag:10) [[cell viewWithTag: 10] removeFromSuperview];
...
The problem is because of the dequeue for the cells. The first time the tableview creates the cells, all the cells run through the
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
code. But when the section 0 row 0 is moved off the screen, that cell is pushed into the cell reusable queue.
Now when your tableview needs to display section 0 row 0, it will get a cell from the reuse queue. you will not get the same cell as the first time. So now you might have 2 cells with the button.
What you should do is have different CellIdentifier for section 0 row 0 , and all other sections and rows. Also create the button when creating the cell. So after the first time the tableView creates the cell, you will not be creating the the button everything.
Look at this line of code:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
This line of code means the UITableViewCells are not created every time. They are re-used as you scroll up and down. Using the code you have above, the UIButton will be created in the correct spot, but then as the cells are re-used, it will create the button in random spots.
One quick way to solve the problem, change the above line of code to simply
UITableViewCell *cell;
When I scroll down and up again my text in tableView will disappear.
And my code is:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [screenDefBuild.elementsToTableView count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *MyIdentifier = #"MyIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:MyIdentifier];
}
ScreenListElements *currentScreenElement = [screenDefBuild.elementsToTableView objectAtIndex:indexPath.row];
cell.textLabel.text = currentScreenElement.objectName;
currentRow++;
return cell;
}
- (void)viewDidLoad
{
[super viewDidLoad];
tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
[tableView setDataSource:self];
[self.view addSubview:tableView];
}
I also want to fill my table view to entire screen. (grey strap on the top).
I don't know what you're doing with this variable
currentRow++;
But whatever you use that for, i'd wager its breaking your code.
the UITableView will call cellForRowAtIndexPath every time a cell is about to appear on screen regardless of whether it has been on screen before or not. When you scroll down and then scroll back up this variable will have increased beyond the bounds of your data, hence you get empty cells.
You need to design this method in such a way that it can create any cell in the table view at any time. You can't rely on the order that the cells will be made and with scrolling you will have to make the same cell over and over again. Only use indexPath to figure out which cell you are currently supposed to be making.
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UITableView_Class/Reference/Reference.html
Answer for the second part of the question- grey strap. You are adding the table view to current view, so you should use the size property of self.view.frame but not the origin. You want this to be set to 0,0.
Change
tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
to
CGRect viewFrame=self.view.frame;
viewFrame.origin=CGPointZero;
tableView = [[UITableView alloc] initWithFrame:viewFrame];
As for the first part of your question- it's strange, as you seem to do everything properly. One thing i may suggest is to add [tableView reloadData]; in the end of viewDidLoad.
Below is code for UITableView, But when i scroll its behaves weirdly (too annoying)... This problem is due to reuseIdentifier.... but dont know how to solve..
- (UITableViewCell *)tableView:(UITableView *)tableView1 cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView1 dequeueReusableCellWithIdentifier:CellIdentifier];
NSInteger imgTag = 1;
NSInteger lblTag = 2;
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(2, 2, 52, 52)];
// Image:[UIImage imageNamed:[self.glassType objectAtIndex:indexPath.row]]];
imgView.tag = imgTag;
[cell.contentView addSubview:imgView];
[imgView release];
UILabel *lblName = [[UILabel alloc] initWithFrame:CGRectMake(60, cell.frame.size.height/4, 200, 21)];
// lblName.text = [self.glassName objectAtIndex:indexPath.row];
lblName.tag = lblTag;
[cell addSubview:lblName];
[lblName release];
}
NSInteger imgIndex = 2;
NSInteger lblIndex = 3;
((UIImageView *)[cell viewWithTag:imgTag]).image = [[self.glassType objectAtIndex:indexPath.row] objectAtIndex:imgIndex];
((UILabel *)[cell viewWithTag:lblTag]).text = [[self.glassName objectAtIndex:indexPath.row] objectAtIndex:lblIndex];
return cell;
}
- (void)tableView:(UITableView *)tableView1 didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView1 cellForRowAtIndexPath:indexPath];
cell.accessoryType = UITableViewCellAccessoryCheckmark;
}
How to make Cell for row at index so that it remains constant even when scrolled??? Also how to make single selection in UITableView??
The answer is that you should not add subviews to your table cells outside of the "if (cell == nil) { ..." clause or they get added over and over again to the same cell when it gets re-used.
See my answer to this question for a more detailed explanation, including code for how to fix it:
cellForRowAtIndexPath memory management
You also cannot store state in table cells because as soon as they scroll offscreen they are recycled and re-appear at a different index in your table. You need to set up an array of model objects to store state for your table cells (such as what their accessory type should be). A more detailed explanation can be found in my answer to this question:
Looping through UITableViewCells of a UITableView
If you fix how you are adding subviews to the cells, and store your "ticked" state in an array of model objects as well as setting the cell.accessoryType (so that it can be restored when the cell is dequeued), then your approach to row selection is otherwise correct.
So put this in your tableView:cellForRowAtIndexPath: method, just before the return cell;:
MyModelObject *object = [self.arrayOfModelObjects objectAtIndex:indexPath.row];
BOOL isChecked = object.checked;
cell.accessoryType = isChecked? UITableViewCellAccessoryCheckmark: UITableViewCellAccessoryNone;
And in your tableView: didSelectRowAtIndexPath: method, get rid of the current logic and replace it with:
- (void)tableView:(UITableView *)tableView1 didSelectRowAtIndexPath:(NSIndexPath *)indexPath
for (int i = 0; i < [self.arrayOfModelObjects count]; i++)
{
MyModelObject *object = [self.arrayOfModelObjects objectAtIndex:i];
object.checked = (i == indexPath.row); // only check the one we just tapped
}
//refresh table to update the accessory views for all rows
[tableView1 reloadData];
}
Obviously replace the arrayOfModelObjects with your own model implementation. You could just use an array of NSNumber objects containing bools if you don't want to create a custom class for this purpose.
The recycling queue is like a pool where previously created Cells are stored before to reuse them. For example when you scrolls up, at the moment the cell disappears above, it is stored in the queue and becomes available for the cell that will appear at the bottom. Ok ?
Actually the number of cells really created is exactly the max simultaneous cell you can display in your table (in most cases from 3 to 8). In other words your if (cell == nil) code is executed (more or less from 3 to 8 times) at the first reloadData to create the pool of cells your table needs.
Then all you make on a cell is kept as it and appears again when you dequeue it. It's now easy to understand that, in your code, you have to make all strictly row-dependant settings outside the if (cell == nil) block. The same way, do not add subViews outside the if (cell == nil) block, you can imagine the thousands of subview you will add each time you reset a dequeued cell !
Tip: if you need some custom cleanup before reusing a cell (like to set an image to blank), you can create a custom UITableviewCell class and implements the prepareForReuse method.
Is it clear ?
Always reload your tableView in viewWillAppear method instead of viewDidLoad.
(void) viewWillAppear:(BOOL)animated{
[self.tableView reloadData];
}
This avoids most of all unexpected and annoying problems. :)
UITableView not scrolling smoothly...(iPhone SDK) ..!!
I have implemented UITableView DataSource and Delegate methods in an individual separate classes.(one for delegate and one for datasource) in main program i write only:
//assume that all objects are allocated
ObjTableView.dataSource=ObjDataSource;
ObjTableView.delegate = ObjDelegate;
[self.view addSubView: ObjTableView];
when i run this code , UITable view appears but when i try to scroll it, it doesn't scroll smoothly.
I have also checked that UITableViewCell doesn't redraw once the cell is initialized.
can any one tell me why this happens ? How can i solve this problem ??
From comments:
ListDataSource *ObjListDataSource = [[ListDataSource alloc]initWithArray:[[sender object] valueForKey:#"List"]];
ListDelegate *ObjListDelegate = [[ListDelegate alloc]initWithArray:[[sender object] valueForKey:#"List"]];
tblList = [[UITableView alloc]initWithFrame:CGRectMake(0, 0, 320, 460)];
tblList.dataSource = ObjListDataSource; tblList.delegate = ObjListDelegate;
[self.view addSubview:tblList]; [tblShopList release];
More from comments:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *CellIdentifier = [NSString stringWithFormat:#"%i",indexPath.row];
UITableViewCell *cell = (UITableViewCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectMake(0,0,320,100) reuseIdentifier:CellIdentifier] autorelease];
//custom cell code
}
return cell;
}
More Information:
I have used NSNotification which notifies to current class when parsing is complete, after receiving notification , current class method calls DataSource, Delegate methods (which is defined in a separate class file).
So UItableViewCell customization (which is in ListDataSource) and table view(in current class) both are in different classes.
A problem is
NSString *CellIdentifier = [NSString stringWithFormat:#"%i",indexPath.row];
The id needs to be the same for all cells of the same class, otherwise you never reuse them. As you can see in most examples, it is indeed a constant in most (all?) cases.
Little explaination on the reuseIdentifier: every time a cell gets out of screen, you can reuse it instead of creating a new one. To reuse it, you need a cell in queue with the same identifier as the one you pass to dequeueReusableCellWithIdentifier. The way you did, the cells are never reused, because each id is unique (they may or may not be reused in case a row reappears on screen, depending on queue size, which is not configurable AFAIK). This is why personalization of the cell should happen OUTSIDE the "cell == nil" block. Long story short, you are using the reuseIdentifier not as intendend.
I think Michele is correct, but I would also add that it looks like you are doing your cell customization where the cell gets created. What you should be doing is something more like this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *CellIdentifier = #"CellIdentifier";
UITableViewCell *cell = (UITableViewCell)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectMake(0,0,320,100) reuseIdentifier:CellIdentifier] autorelease];
//custom REUSABLE cell code here, e.g. text color, etc.
}
NSString *cellText = [dataArray objectAtIndex:indexPath.row]; //assuming you have a simple array for your data
cell.textLabel.text = cellText;
return cell;
}
I would also add that I'm not sure why you are able to run the app with the code you have here, since UITableViewCell cell = ... is an invalid initializer. It should be UITableViewCell *cell = ....
It would be helpful to see how you are customizing your cell, since without that it's hard to see what's happening.
We couldn't find a way to animate UIViews inside a UITableCell as an action from a callback.
Suppose in a scenario where you click on a button on the UITableViewCell and it fires off an asynchronous action to download a picture. Suppose further that when the picture is downloaded we want a UIView in the cell to animate the picture to give user a visual feedback that something new is about to be presented.
We couldn't find a way to track down the UIVIew to invoke beginAnimation on because the original cell that the user clicked on might now be used for another row due to the nature of cells being reused when you scroll up and down in the table. In other words we can't keep a pointer to that UITableViewCell. We need to find another way to target the cell and animate it if that row is visible and don't animate if the row is scrolled out of range.
Keep the cell object different from the object being animated so the cell holds a UIView. When the animation callback occurs check to make sure that the UIView still exists and, if it does, animate the changes.
When the cell object gets bumped off the screen and recycled, release the UIView that would have been animated and create a new one. When the animation callback occurs it will have nothing to do because the UIView no longer exists.
A modification of the above is to keep some sort of object in the UIView that your callback can check to see if the animation is still appropriate. This could be some sort of unique identifier for the picture being downloaded. If the identifier changes, no animation is needed. If it matches, do the animation.
EDIT:
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *MyIdentifier = #"MyTableCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:MyIdentifier] autorelease];
} else {
UIView *oldViewToAnimate = [cell.contentView viewWithTag:1];
[oldViewToAnimate removeFromSuperview];
}
UIView *viewToAnimate = [[UIView alloc] initWithFrame:CGRectZero]; //replace with appropriate frame
viewToAnimate.tag = 1;
[cell.contentView addSubview:viewToAnimate];
return cell;
}
When you spawn your download process you pass in [cell.contentView viewWithTag:1]. When the download is done, it will update the appropriate view. If the table cell was reused the view will no longer have a superview and will not update the wrong cell.
There are things you can do to make this more efficient but this is the basic idea. If you have a custom UITableViewCell than this will probably look a bit different.
EDIT 2:
To reuse the viewToAnimate objects to make sure that they get updated if their parent cells were recycled, do something like the following:
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *MyIdentifier = #"MyTableCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:MyIdentifier] autorelease];
} else {
UIView *oldViewToAnimate = [cell.contentView viewWithTag:1];
[oldViewToAnimate removeFromSuperview];
}
UIView *viewToAnimate = [self viewToAnimateForIndexPath:indexPath];
viewToAnimate.tag = 1;
[cell.contentView addSubview:viewToAnimate];
return cell;
}
viewToAnimateForIndexPath will need to:
Check to see if a viewToAnimate has been created for this indexPath
Create a viewToAnimate if there isn't one
Save a reference to the view that can be looked up by indexPath
Return the viewToAnimate so the table cell can use it
I don't know enough about your data structure to do this for you. Once the download process completes it can call this same method to get the view and animate it.