重新加载tableview的活动单元格

Question

I'm developing an application on iOS targeting iOS 7.0 and later. Now, my question is that how to reload the rows of a UITableView which are visible on screen. I'm using dynamic cells.

Actually while selecting an option I'm changing some colors like title color of each cell but those cells which are already loaded on screen are not changed and if I'm loading whole table then its taking a long time.

Waiting for your kind reply.

Code

//on clicking this button color is updating

- (IBAction)btnDone:(id)sender {

appDel.selectedMood=_moodDetView.str;

appDel.barColor=_moodDetView.backgroundColor;

self.navigationController.navigationBar.barTintColor = _moodDetView.backgroundColor;

//[self.mainTblView reloadData];

[self.menuView setBackgroundColor:appDel.barColor];

[_moodDetView setHidden:YES];

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath     *)indexPath
  {
    //For menu contents
    if (tableView.tag==2) {
        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"];
        if (cell == nil) {
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
            cell.textLabel.textColor = [UIColor whiteColor];
            cell.textLabel.font = [UIFont fontWithName:@"Futura" size:14.0];
            cell.textLabel.textAlignment = NSTextAlignmentCenter;
            cell.backgroundColor = [UIColor clearColor];
        }

        switch (indexPath.row) {
            case 0:
            {
                cell.textLabel.text=@"Select Mood";
            }
                break;
            case 1:
            {
                cell.textLabel.text=@"Search by Author";
            }
                break;
            case 2:
            {
               cell.textLabel.text=@"Search by Category";
            }
                break;
            case 3:
            {
                  cell.textLabel.text=@"Favorites";
            }
                break;
            case 4:
            {
                    cell.textLabel.text=@"Feeds";
            }
                break;

            default:
                break;
        }
        return cell;
    }

    //for main table
    else{

    // Configure the cell...

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    FeedCustomCell* CELL=( FeedCustomCell *)cell;

    CELL.cellImageView.layer.cornerRadius=CELL.cellImageView.frame.size.width/2;

    CELL.cellImageView.clipsToBounds=YES;

    CELL.gesRec=[[CustomTapGestureRecognizer alloc]initWithTarget:self action:@selector(authorBtnTouched:)];

    [CELL.lblAuthName setTextAlignment:NSTextAlignmentJustified];

    [CELL.lblAuthName setTextColor:[AppDelegate invertColor:appDel.barColor]];

        NSString * str=[NSString stringWithFormat:@"%@",[[dataArray objectAtIndex:indexPath.row] objectForKey:@"authorId"]];

    UIImage * img=[UIImage imageNamed:str];

    CELL.cellImageView.image=img?img:[UIImage imageNamed:@"n3"];

    [CELL.lblAuthName addGestureRecognizer:CELL.gesRec];

    CELL.gesRec.authorImage=CELL.cellImageView.image;

    NSString * authName=[[dataArray objectAtIndex:indexPath.row] objectForKey:@"authorName"];

    [CELL.lblAuthName setText:authName];

    [CELL.gesRec setAuthorId:(int)str.integerValue];

    [CELL.gesRec setAuthorName:authName];

    [CELL.txtViewQuote setTextColor:appDel.barColor];

    CELL.txtViewQuote.text=[[dataArray objectAtIndex:indexPath.row] objectForKey:@"quoteTxt"];

    CGSize sizeThatShouldFitTheContent = [CELL.txtViewQuote sizeThatFits:CELL.txtViewQuote.frame.size];

    CELL.heightConstraintOfTxtView.constant = sizeThatShouldFitTheContent.height;

    [CELL.contentView sizeToFit];

    return CELL;

    }


}

regards: Syed Meesum Ali

Junior Software Developer

Answer 1

If you implement custom cell subclassing UITableViewCell, you can implement prepareForReuse method. You can reset some properties example, alpha, selection state in that method.

Answer 2

The simplest possible way to do it would be:

[myTable reloadRowsAtIndexPaths:myTable.indexPathsForVisibleRows withRowAnimation:UITableViewRowAnimationAutomatic];

However since you are looking for a more optimized way, The following would be better:

On button click, in the target method, iterate over visible cells, and make relevant changes in each cell.

- (IBAction)btnDone:(id)sender {

    for (UITableViewCell* cell in yourTable.visibleCells) {

        if ([cell isKindOfClass:[FeedCustomCell  class]]) {

            [((FeedCustomCell*)cell).lblAuthName setTextColor:[AppDelegate invertColor:appDel.barColor]];
        }
    }
}

This should be way faster that reloading (drawing) all visible cells.

ALSO , a word of advice. Use different reuseIdentifer s for different types of cells, or your table might cause app crashes.