Uislider in a tableView Cell - objective-c

Question

hi everyone i'm new in iOS programming ! I have a custom table view controller with custom table view cell ! one of those cell have a uislider and a label ! I want to change label text when slider change value ! this is my code :
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSDictionary *cellInfo = [[self.sections objectAtIndex:currentTab] objectAtIndex:indexPath.row];
HLNotificheCell *cell = [tableView dequeueReusableCellWithIdentifier:[cellInfo objectForKey:#"cell"] forIndexPath:indexPath];
UIImageView *radioIndicator = (UIImageView *)[cell.contentView viewWithTag:200];
radioIndicator.image = (currentBullet != indexPath.row) ? [UIImage imageNamed:#"RadioOff"] : [UIImage imageNamed:#"RadioOn"];
UIImageView *av = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 80)];
av.backgroundColor = [UIColor clearColor];
av.opaque = NO;
av.image = [UIImage imageNamed:#"NewsSeparetor.png"];
cell.backgroundView = av;
cell.slider.maximumValue = 100;
cell.slider.minimumValue = 1;
cell.slider.continuous = TRUE;
//set a method which will get called when a slider in a cell changes value
[cell.slider addTarget:self action:#selector(sliderChanged:) forControlEvents:UIControlEventValueChanged];
//Keep a reference to each slider by assigning a tag so that we can determine
//which slider is being changed
cell.slider.tag = indexPath.row;
//Grab the value from the sliderValuesArray and set the slider knob to that position
return cell;
}
-(void)sliderChanged:(UISlider*)sender{
HLNotificheCell *cell = [[HLNotificheCell alloc]init];
if (sender == cell.slider) {
cell.label.text = [NSString stringWithFormat:#"%0.3f", cell.slider.value];
}
}

Answer 1

Actually there is a lot of bad practices in your code. Please let me explain.
Let's begin with your HLNotificheCell class. I think header file should look like this:
#import <UIKit/UIKit.h>
#define HLNotificheCellIdentifier #"HLNotificheCellIdentifier"
#interface HLNotificheCell : UITableViewCell
- (instancetype)initWithReuseIdentifier:(NSString *)reuseIdentifier;
#property (strong, nonatomic) UISlider *slider;
#property (strong, nonatomic) UIImageView *radioIndicator;
#end
and implementation file:
#import "HLNotificheCell.h"
#implementation HLNotificheCell
- (instancetype)initWithReuseIdentifier:(NSString *)reuseIdentifier {
self = [super initWithStyle:UITableViewCellStyleDefault reuseIdentifier:reuseIdentifier];
if (self) {
_slider = [[UISlider alloc] init];
_slider.maximumValue = 100;
_slider.minimumValue = 1;
_slider.continuous = YES; //YES is more natural in objc rather than TRUE.
[self addSubview: _slider];
_radioIndicator = [[UIImageView alloc] init];
[self addSubview:_radioIndicator];
UIImageView *av = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 80)];
av.backgroundColor = [UIColor clearColor];
av.opaque = NO;
av.image = [UIImage imageNamed:#"NewsSeparetor.png"];
self.backgroundView = av;
//it's better to use built-in textLabel instead of creating your own. Trust me when you will have 20 different customized cells you will get lost with their names.
self.textLabel.textColor = [UIColor redColor];
}
return self;
}
- (void)layoutSubviews {
[super layoutSubviews];
// layout your self.slider and self.radioIndicator here or use xib for it.
// e.g. this will layout slider to fit whole cell:
self.slider.frame = self.bounds;
}
#end
Ok, lets go now to cellForRowAtIndexPath method:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// try to dequeue cell if exist
HLNotificheCell *cell = (HLNotificheCell *)[tableView dequeueReusableCellWithIdentifier:HLNotificheCellIdentifier];
// if doesn't, create new one.
if (!cell) { // is enough to set slider target only once when cell is created. When reuse is not needed.
cell = [[HLNotificheCell alloc] initWithReuseIdentifier:HLNotificheCellIdentifier];
[cell.slider addTarget:self action:#selector(sliderChanged:) forControlEvents:UIControlEventValueChanged];
}
//set image as you wish:
cell.radioIndicator.image = (currentBullet != indexPath.row) ? [UIImage imageNamed:#"RadioOff"] : [UIImage imageNamed:#"RadioOn"];
//Keep a reference to each slider by assigning a tag so that we can determine
//which slider is being changed
cell.slider.tag = indexPath.row;
//Grab the value from the sliderValuesArray and set the slider knob to that position
NSNumber *sliderValue = sliderValuesArray[indexPath.row];
[cell.slider setValue:sliderValue.floatValue animated:NO]
return cell;
}
and sliderChanged: method:
-(void)sliderChanged:(UISlider*)sender{
// You cannot do this:
// HLNotificheCell *cell = [[HLNotificheCell alloc]init];
// because you have to restore reference from sender.tag as you wrote in cellForRowAtIndexPath method:
HLNotificheCell *cell = (HLNotificheCell *)[tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:slider.tag inSection:0]] // I assume you have only 1 section
cell.textLabel.text = [NSString stringWithFormat:#"%0.3f", cell.slider.value];
//save new value to the sliderValuesArray
self.sliderValuesArray[indexPath.row] = #(cell.slider.value);
}
Assumptions:
when you will use this part of code please do not use registerClass:forCellReuseIdentifier:
yours sliderValuesArray is kind of NSMutableArray class.
sliderValuesArray has been initialized with size same as number of cells, like:
self.sliderValuesArray = [[NSMutableArray alloc] initWithCapacity:<#numberOfCels#>];
for (int i = 0; i < sliderValuesArray.count; i++) {
sliderValuesArray[i] = #(0);
}
your table view contains only one type of cells (HLNotificheCell)
There could be some typos and/or lack of semicolons because I wrote it without compiler.

Answer 2

I doing this easier. Apple write that you can use IBActions for static rows. (You can read about it here in The Technique for Static Row Content. But I already tested it on iOS 9 with dynamic cells and it's just works :)
At first - Custom cell with IBAction
#interface SliderTableViewCell ()
#property (weak, nonatomic) IBOutlet UILabel *sliderValueLabel;
#property (weak, nonatomic) IBOutlet UISlider *slider;
#end
#implementation SliderTableViewCell
- (void)awakeFromNib {
self.slider.minimumValue = 1;
self.slider.maximumValue = 1000;
}
- (IBAction)sliderValueChanged:(id)sender {
self.sliderValueLabel.text = [NSString stringWithFormat:#"1_%.f", self.slider.value];
}
#end
Second - TableView Delegate
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
SliderTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kReuseIdentifierSliderCell];
cell.slider.value = 142;
cell.sliderValueLabel.text = #"1_142";
return cell;
}
Third - Run your app and enjoy yourself ;)