保留UITableViewCell选择状态 [英] Retaining UITableViewCell selection statuses

问题描述

为什么 UITableViewCell 在选择，滚动，然后向后滚动后不重新加载复选标记？

Why the UITableViewCells don't reload the checkmarks after selecting, scrolling away, then scrolling back?

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    #define CHECK_NULL_STRING(str) ([str isKindOfClass:[NSNull class]] || !str)?@"":str

    static NSString *CellIdentifier = @"inviteCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    cell.accessoryType = UITableViewCellAccessoryCheckmark;
    cell.textLabel.highlightedTextColor = [UIColor colorWithHexString:@"#669900"];
    cell.selectionStyle = UITableViewCellSelectionStyleGray;
    cell.backgroundColor = [UIColor blackColor];
    cell.textLabel.textColor = [UIColor whiteColor];
    [[UITableViewCell appearance] setTintColor:[UIColor colorWithHexString:@"#669900"]];

    if (cell == nil) {
        cell = [[UITableViewCell alloc] init];
    }

    if (cell == nil) {cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; }

    BOOL isSearching = tableView != self.tableView;
    NSArray *arrayToUse = (isSearching ? searchResults : contactsObjects);
    id p = arrayToUse[indexPath.row];

    NSString *fName = (__bridge_transfer NSString *)(ABRecordCopyValue((__bridge ABRecordRef)(p), kABPersonSortByFirstName));
    NSString *lName = (__bridge_transfer NSString *)(ABRecordCopyValue((__bridge ABRecordRef)(p), kABPersonSortByLastName));
    cell.textLabel.text = [NSString stringWithFormat:@"%@ %@", CHECK_NULL_STRING(fName), CHECK_NULL_STRING(lName)];

    BOOL showCheckmark = [[stateArray objectAtIndex:indexPath.row] boolValue];
    if (showCheckmark == YES)
    {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
        NSLog(@"It hit showCheckmark = YES, and stateArray is %@",stateArray[indexPath.row]);
    }
    else
    {
        cell.accessoryType = UITableViewCellAccessoryNone;
        NSLog(@"It hit showCheckmark = NO, and stateArray is %@",stateArray[indexPath.row]);
    }

    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;
{
    id object = contactsObjects[indexPath.row];
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

    if (cell.accessoryType == UITableViewCellAccessoryNone)
    {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
        [stateArray insertObject:[NSNumber numberWithBool:YES] atIndex:indexPath.row];
        [selectedObjects addObject:object];
    }
    else
    {
        cell.accessoryType = UITableViewCellAccessoryNone;
        [stateArray insertObject:[NSNumber numberWithBool:NO] atIndex:indexPath.row];
        [selectedObjects removeObject:object];
    }

    //slow-motion selection animation.
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

推荐答案

细胞选择问题不是解决了，即使 insertObject 替换为 replaceWithObject ，但是，不应该浪费时间设置 BOOL 在 NSMutableArray 中包含 NSInteger 的对象。相反，对于单元格选择内存，应该使用 NSDictionary ，如下所示：

The cell selection problem was not solved, even when insertObject was replaced with replaceWithObject, however, one should not waste time setting BOOL objects with an NSInteger inside an NSMutableArray. Instead, for cell selection memory, one should use NSDictionary like this:

@property (nonatomic, strong) NSMutableDictionary * selectedRowCollection;

- (void)viewDidLoad{

    self.selectedRowCollection = [[NSMutableDictionary alloc] init];
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;
{    
    id object = contactsObjects[indexPath.row];
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

    if (cell.accessoryType == UITableViewCellAccessoryNone)
    {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
        [self.selectedRowCollection setObject:@"1" forKey:[NSString stringWithFormat:@"%d",indexPath.row]]; 
    }
    else
    {
        cell.accessoryType = UITableViewCellAccessoryNone;
        [self.selectedRowCollection removeObjectForKey:[NSString stringWithFormat:@"%d",indexPath.row]];
    }

    //slow-motion selection animation.
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

   - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    BOOL showCheckmark =  [[self.selectedRowCollection valueForKey:[NSString stringWithFormat:@"%d",indexPath.row]] boolValue];

    if (showCheckmark == YES)
    {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    }
    else
    {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }
}

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