I've made a subclass of UITableViewCell and added a MapView. Everytime I scroll the map of the screen and scroll back to that cell it loads again. (As you all know it's the default behaviour for cell reusing)
Is there anyway to prevent that? Or do you know any other tricks for that case? thanks a lot!
One possible solution:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
NSInteger row = [indexPath row];
UITableViewCell *cell = nil;
if( row != kMapCellRow ) { // defined value to whatever value it may be
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
}
else {
// use an ivar to track the map cell, should be set to nil in class init
cell = _mapCell;
}
if (cell == nil) {
if( row != kMapCellRow ) { // defined value to whatever value it may be
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
else {
// create your map cell here
cell = [[[MyTableViewMapCell alloc] init...
}
}
// configure it here
You could replace the defined kMapCellRow with an instance variable if it makes sense for your app.
Related
In my app, i add a slider in Table view i.e. each row contains a slider & It also works fine.
But when i scroll the table view the slider get reload i.e. each shows me starting position rather than slider value.
//My code is as follow for slider in table cell:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier=[NSString stringWithFormat:#"CellIdentifier%d",indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
return cell;
}
UISlider* theSlider = [[[UISlider alloc] initWithFrame:CGRectMake(174,12,120,23)] autorelease];
theSlider.maximumValue=99;
theSlider.minimumValue=0;
[cell addSubview:theSlider];
return cell;
}
How can i solve this??
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *CellIdentifier=[NSString stringWithFormat:#"CellIdentifier%d",indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier]; UISlider* theSlider = [[[UISlider alloc] initWithFrame:CGRectMake(174,12,120,23)] autorelease];
theSlider.maximumValue=99;
theSlider.minimumValue=0;
[cell addSubview:theSlider];
} return cell;
This way the slider gets created only when cell is nil i.e cell gets created. and use tableView:willDisplayCell:forRowAtIndexPath: method to set the slider value like slider.value = yourvalue;
You need to store values of slider view and set the values of sliderview in cellForRowAtIndexPath slider.value = yourvalue;
The problem is that cellForRowAtIndexPath is called not just once, but every time that the tableView need to render that cell... So you have to be sure that only initialize theSlider the first time is called...
The best approach is to define a custom UITableViewCell and put there a property that would store theSlider, then, when cellForRowAtIndexPath is called, check if it is already initialized or not, see:
// If the slider is not yet initialized, then do it
if(cell.theSlider == nil)
{
// Init...
}
This is really from "cellForRowAtIndexPath" method . Every time when you are scrolling every cell is getting nil and reinitialise it. Better you can try with creating custom cell class(BY creating sub class of UITableViewCell) and also the defining slider in condition "if (cell == nil)".
I am creating a table with three different types of custom cell, One of them, one custom cell is having UITextField. I create two rows using this custom cell. I set tag and delegate for textfields of both row.
My problem is, when I scroll the table, these rows with textfields move up and disappear from the screen, when scroll down, that time my app gets crash.
I get an error like
-[CellImageViewController txtField]: unrecognized selector sent to instance 0xa0ea5e0
Here is my code for cellForRowAtIndexPath:
if (indexPath.row == 0 )
{
if (cell == nil) {
cell = [[[CellWithTextFieldViewController alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID] autorelease];
}
cell.txtField.tag =1;
cell.txtField.delegate = self;
cell.txtField.text = #"kjfkd";
}
return cell;
}
else if(indexPath.row==1)
{
if (cell == nil) {
cell = [[[CellWithTextFieldViewController alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID] autorelease];
}
cell.txtField.tag = 2;
cell.txtField.text = #"glk";
cell.txtField.delegate = self;
return cell;
}
Any one have idea about this issue?
you have different type of cells, so you need to use a cellIdentifier different for each one.
Try this:
customOrNormalCell *cell [tableView dequeueReusableCellWithIdentifier:CellIdentifier]
if(!cell){
cell = [[CellWithTextFieldViewController alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:[NSString stringWithFormat:#"%i", indexPath.row]];
}
With this code, each cellIdentifier will be 1,2,3,4... (All different)
I'm pretty sure that it will solves the problem
create UITextField before create UITableView and Add your Textfield object in cell Content view
[cell.contentView addSubview:yourTxtFieldOblect];
It looks like you might be reusing a cell of a different type.
Try making sure which kind of class the cell you are reusing is before trying to access it's properties.
why you are define cell for each row?
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier = [NSString stringWithFormat:#"Cell%d",indexPath.row];
CellWithTextFieldViewController *cell = (CellWithTextFieldViewController *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil)
{
cell =[[[CellWithTextFieldViewController alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]autorelease];
cell.txtField.tag = indexPath.row;
cell.txtField.text = [SET TEXT FROM ARRAY];
cell.txtField.delegate = self;
}
}
I had also faced this problem in my project.
just try this:
Disabled the scrolling property in Tableview and create a scrollview.Then add your Tableview in your scrollview.
UITableView *table=[[UITableView alloc]initWithFrame:CGRectMake(0, 0, 976, 395) style:UITableViewStylePlain];
[table setSeparatorStyle:UITableViewCellSelectionStyleNone];
UIScroll *scroll=[[UIScrollView alloc]initWithFrame:CGRectMake(24, 168, 978, 395)];
[table setScrollEnabled:NO];
[scroll addSubview:table];
[self.view addSubview:scroll];
[scroll sendSubviewToBack:table];
Try this
static NSString *cellIdentifier= #"Cell";
CellWithTextFieldViewController *cell = (CellWithTextFieldViewController *)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (cell == nil) {
cell = [[CellWithTextFieldViewController alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
}
cell.txtField.tag =indexPath.row+1;
cell.txtField.delegate = self;
cell.txtField.text = #"kjfkd";
return cell;
While scrolling tableView your cell is getting reused. Thats why textField is disappearing. Try to use different cell id for different custom cells. Dont forget to give the same id in nib file for cell identifier
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *customCellOne = #"customCell1";
static NSString *customCellTwo = #"customCell2";
UITableViewCell *cell =nil;
if (0 == indexPath.row)
{
cell = (CustomCellOne *)[tableView dequeueReusableCellWithIdentifier:customCellOne];
if (nil == cell)
{
// Create custom cell one and do what ever you want
}
}
else if (1 == indexPath.row)
{
cell=(CustomCellTwo *)[tableView dequeueReusableCellWithIdentifier:customCellTwo];
if (nil == cell)
{
// Create custom cell two and do what ever you want
}
}
return cell;
}
I don't know,may be when reused the cell,the textfield delegate was released.
may be you can set the
textfield.deleagate = self;
in CellWithTextFieldViewController.m
When scrolling my UITableView (tends to be when I scroll it fast) the data for my cells gets mixed up, so labels might be repeated etc.
I understand that reusing the cells probably causes this, but what if the user scrolls down the list really quickly and all the cells get mixed up, how am I supposed to avoid this?
Thanks.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"VideoListCell";
VideoListCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[VideoListCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// Configure the cell...
if (isPlaylistView)
{
//Fill cell with data
}
else if (isPlaylistDetailView || isSearchResultsView)
{
//Fill cell with data
}
else
{
//Playlist button and uploads
if (indexPath.section == 0)
{
//Fill cell with data
}
else
{
//Fill cell with data
}
}
return cell;
}
You generally use this kind of code:
cell = dequeReusableCell;
if (cell == nil) {
create cell;
initialize cell;
}
fill cell with actual data from current row
return cell;
If you will move code "fill cell with actual data from current row" into "if" — you will get the kind of behavior you get right now.
So the answer will be "fill cell with data after you initialize it, outside of "if (cell == nil)" block.
UITableView will ever only dequeue a cell for reuse if the position that the cell was in is currently off-screen. So you don't have to worry about "mix-ups".
static NSString *cellIdentifier=#"cell";
UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if(cell==nil)
{
cell=[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:nil];
}
I think it will be helpful to you.
set dequeueReusableCellWithIdentifier to nil for example..
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:nil];
UPDATE:
See this Example... i load many data in the cell with also my custom Gridview...
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString* cellIdentifier = #"gridCell";
UITableViewCell *gridCell = [tableView dequeueReusableCellWithIdentifier:nil];
if(gridCell == nil)
{
gridCell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
}
return gridCell;
}
hope this help you....
In your custom cell class override prepareForReuse method. In this method set text of your labels to nil and set imageview's image to nil also. This function is called everytime when a cell is reused so your problem will be solved by this. May be like this
- (void)prepareForReuse{
[super prepareForReuse];
self.titleLabel.text = nil;
self.unitImageView.image = nil;
}
How can I store a boolean value in each row of a UITableview. I need to retrieve the boolean value stored in the cell, when that particular cell is selected.
There are so many ways:
1. You can use UITableViewCell.tag property
2. You can create your own cell class inherited from UITableViewCell and add there normal property for you BOOL value
3. You can use array associated with your tableview and when you get cell selected, just use indexPath to find associated value in your array
etc.
I recommend to use tag property in UITableViewCell.
- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath;
// returns nil if cell is not visible or index path is out of range
{
static NSString *identifier = #"MyIndetifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
//make sure tu put here, or before return cell.
cell.tag = 0; //0 =NO, 1=YES;
return cell;
}
-(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
BOOL boolean = cell.tag; // return 0 or 1. based on what boolean you set on this particular row.
}
You probably have some other storage, where you keep things like the table cell title or subtitle. Store the boolean there. Use this to convert the bool to something you can put in an array or dictionary.
[NSNumber numberWithBool:YES]
For example, if you're using an NSArray of strings to store the titles, instead use an array of dictionaries. Each dictionary would have a "title" and (for example) "isActive" boolean (stored as an NSNumber).
NSMutableArray *tableData;
every table cell associate with a NSMutableDictionary store in tableData,
you can set a NSNumber(store bool) to the Dictionary.
You need to implement method of UITableView
- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath;
// returns nil if cell is not visible or index path is out of range
{
//create cell here
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
return cell;
}
(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
//by using indexpath.row you can access the cell on which user clicked.
}
I have a UITableView, and I am showng data based on indexPath.section, however, when I scroll my table view very quickly, its data keep overlapping. How to fix this?
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
}
switch(indexPath.section)
{
// case 0 to 10;
//values change if I scroll my table
}
}
I think you are allocating some labels inside the cellForRowAtIndex delegate method. Thats why you got this problem. You can solve this in 2 ways:
Alloc the labels outside the delegate
method. set tags for your labels and
use it inside the cellForRowAtIndex
by refering the tags.
use custom cell view controller.
i fixed the issues
here is the solution if any one need
NSString *CellIdentifier=nil ;
NSMutableArray *Array= [[[NSMutableArray alloc] initWithObjects: #"One",#"Two", #"Three",#"Ad",#"Ae",#"Ah",#"Aj" ,nil]autorelease];
CellIdentifier = [Array objectAtIndex:indexPath.section];
///302-1021-9244-4658-1994-3384
UITableViewCell * cell = [tabelView dequeueReusableCellWithIdentifier:CellIdentifier];
Thanks