multiple checkmarks from - objective-c

Question

Tutorial I am following: http://www.appcoda.com/ios-programming-tutorial-create-a-simple-table-view-app/
I have created a tableview with 16 cells. When I select a row, it will show checkmark on it.
But when I scroll the tableview, there is also a checkmark showing on another cell further down the list. This repeats for any cell selected.
#import "FlightChecklistViewController.h"
#interface FlightChecklistViewController ()
#end
#implementation FlightChecklistViewController
{
NSArray *tableData;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
// Initialize table data
tableData = [NSArray arrayWithObjects:#"Egg Benedict", #"Mushroom Risotto", #"Full Breakfast", #"Hamburger", #"Ham and Egg Sandwich", #"Creme Brelee", #"White Chocolate Donut", #"Starbucks Coffee", #"Vegetable Curry", #"Instant Noodle with Egg", #"Noodle with BBQ Pork", #"Japanese Noodle with Pork", #"Green Tea", #"Thai Shrimp Cake", #"Angry Birds Cake", #"Ham and Cheese Panini", nil];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [tableData count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *simpleTableIdentifier = #"SimpleTableItem";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
}
cell.textLabel.text = [tableData objectAtIndex:indexPath.row];
return cell;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UIAlertView *messageAlert = [[UIAlertView alloc]
initWithTitle:#"Row Selected" message:#"You've selected a row" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
// Display Alert Message
[messageAlert show];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
cell.accessoryType = UITableViewCellAccessoryCheckmark;
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
#end
Any suggestions?

Answer 1

You need to store the information about the rows indexpaths, that were selected, somehow.
And populate your cell according to it.
#import "ViewController.h"
#interface ViewController ()
#property (nonatomic, strong) NSMutableArray *selectedCells;
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.selectedCells = [NSMutableArray array];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 100;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *unifiedID = #"aCellID";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:unifiedID];
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:unifiedID];
}
cell.textLabel.text = [NSString stringWithFormat:#"%u", indexPath.row];
//if the indexPath was found among the selected ones, set the checkmark on the cell
cell.accessoryType = ([self isRowSelectedOnTableView:tableView atIndexPath:indexPath]) ? UITableViewCellAccessoryCheckmark : UITableViewCellAccessoryNone;
return cell;
}
//if a row gets selected, toggle checkmark
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
if([self isRowSelectedOnTableView:tableView atIndexPath:indexPath]){
[self.selectedCells removeObject:indexPath];
cell.accessoryType = UITableViewCellAccessoryNone;
} else {
[self.selectedCells addObject:indexPath];
cell.accessoryType = UITableViewCellAccessoryCheckmark;
}
}
-(BOOL)isRowSelectedOnTableView:(UITableView *)tableView atIndexPath:(NSIndexPath *)indexPath
{
return ([self.selectedCells containsObject:indexPath]) ? YES : NO;
}
#end
you will find the complete example code on github

Answer 2

The problem is that cells are reused. So, if you add a checkmark accessory view to a cell further up it'll appear again when the cell is reused further down. You should save which ones are checkmarked in an array somewhere that correlates to the rows of the table when you add/remove a checkmark. Then, when you give the table view a new cell you can determine whether or not it needs a checkmark and set that up.

Answer 3

I had the same issue recently with one of my apps, and I fixed it by doing this:
#property (nonatomic, strong) NSArray *list;
- (void)viewDidLoad
{
[super viewDidLoad];
self.list = [[NSArray alloc] initWithObjects:#"foo", #"bar", nil];
}
- (NSString *)SettingsPlist
{
NSString *paths = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *PlistPath = [paths stringByAppendingPathComponent:#"Settings.plist"];
return PlistPath;
}
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
{
return [[self list] count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *contentForThisRow = [[self list] objectAtIndex:[indexPath row]];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
if(cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"Cell"];
}
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:[self SettingsPlist]];
NSString *row = [NSString stringWithFormat:#"%d",indexPath.row];
if([[dict objectForKey:row]isEqualToString:#"0"])
{
cell.accessoryType = UITableViewCellAccessoryNone;
}
else
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
}
[[cell textLabel] setText:contentForThisRow];
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSMutableDictionary *plist = [NSMutableDictionary dictionaryWithContentsOfFile:[self SettingsPlist]];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
NSString *row = [NSString stringWithFormat:#"%d",indexPath.row];
if(cell.accessoryType == UITableViewCellAccessoryNone)
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
NSString *on = #"1";
[plist setObject:on forKey:row];
[plist writeToFile:[self SettingsPlist] atomically:YES];
}
else if(cell.accessoryType == UITableViewCellAccessoryCheckmark)
{
cell.accessoryType = UITableViewCellAccessoryNone;
NSString *off = #"0";
[plist setObject:off forKey:row];
[plist writeToFile:[self SettingsPlist] atomically:YES];
}
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}