UITableViewCell调整大小以适合详细文本

Question

I am trying to resize a UITableViewCell to show/hide parts of the detail text on selection. All cells show the first line of the detail text. when the user taps a cell, the entire detail text should be displayed without moving the currently visible part of the text.

Currently, I am doing the following:
In cellForRowAtIndexPath:

cell.textLabel.text = ...;
cell.detailTextLabel.text = ...;

if ([indexPath isEqual:self.currentSelection])
{
    cell.detailTextLabel.numberOfLines = CGFLOAT_MAX;
}
else
{
    cell.detailTextLabel.numberOfLines = 1;
}

In didSelectRowAtIndexPath:

if ([self.currentSelection isEqual:indexPath])
{
    self.currentSelection = nil;
}
else
{
    self.currentSelection = indexPath;
}

[tableView reloadData];

And in heightForRowAtIndexPath

float minHeight = 60;

if ([indexPath isEqual:self.currentSelection])
{
    KPLexiconEntry *lexiconEntry = ...;

    UIFont *cellFont = [UIFont fontWithName:@"Helvetica" size:14.0];
    CGSize constraintSize = CGSizeMake(320.0f, MAXFLOAT);

    NSMutableParagraphStyle * paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
    paragraphStyle.alignment = NSTextAlignmentLeft;

    NSDictionary * attributes = @{NSFontAttributeName : cellFont, NSParagraphStyleAttributeName : paragraphStyle};
    CGSize labelSize = [lexiconEntry.explanation boundingRectWithSize:constraintSize options:NSStringDrawingUsesLineFragmentOrigin attributes:attributes context:nil].size;

    float height = labelSize.height + 44;
    return height > minHeight ? height : minHeight;
}

return minHeight;

This shows or hides the detail text as i wanted to, but the text inside the cell (including the textLabel.text ) jumps up or down a few pixels.
How can I prevent this and get a smooth appearance?

Answer 1

You Can do it :-

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifire = @"CellIdentifire";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifire];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifire];
      [cell.textLabel sizeToFit];
    }
    cell.textLable.text= @"";
    return cell;
}

Answer 2

You can add height constraint for details text (hiding element) and outlet him. Then set when that element is hidden his constraint == 0;

Answer 3

I figured out a way to solve this:
Instead of using the detailLabel , I created a NSAttributedString and used textLabel.attributedText . The attributed string simply shows the title (previously in the textLabel ) in a larger font than the rest (previously ind the detailLabel ). I created a method to create the attributed string:

- (NSAttributedString*)attributedTextForIndexPath:(NSIndexPath*)indexPath {
    id itemForIndexPath = ...;
    NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] init];

    UIFont *titleFont = [UIFont systemFontOfSize:16];
    NSDictionary *titleAttributes = @{NSForegroundColorAttributeName: [UIColor whiteColor], NSBackgroundColorAttributeName: [UIColor clearColor], NSFontAttributeName: titleFont};
    NSString *titleRaw = [NSString stringWithFormat:@"%@\n", @"itemForIndexPath.title"];
    NSAttributedString *title = [[NSAttributedString alloc] initWithString:titleRaw attributes:titleAttributes];
    [attrString appendAttributedString:title];

    UIFont *textFont = [UIFont systemFontOfSize:14];
    NSDictionary *textAttributes = @{NSForegroundColorAttributeName: [UIColor whiteColor], NSBackgroundColorAttributeName: [UIColor clearColor], NSFontAttributeName: textFont};;
    NSString *textRaw = itemForIndexPath.text;
    if (![indexPath isEqual:self.currentSelection] && textRaw.length >= 30)
    {
        textRaw = [NSString stringWithFormat:@"%@...", [textRaw substringToIndex:27]];
    }

    NSAttributedString *text = [[NSAttributedString alloc] initWithString:textRaw attributes:textAttributes];
    [attrString appendAttributedString:text];

    return attrString;
}

As you can see, I manually restrict the length of the text for all but the selected cell.

Then, in cellForRowAtIndexPath , I assign it like this:

cell.textLabel.attributedText = [self attributedTextForIndexPath:indexPath];

and in heightForRowAtIndexPath :

NSAttributedString *text = [self attributedTextForIndexPath:indexPath];
CGSize constraintSize = CGSizeMake(255, CGFLOAT_MAX);
CGSize size = [text boundingRectWithSize:constraintSize options:NSStringDrawingUsesLineFragmentOrigin context:nil].size;
return ceil(size.height + 22); // adding 22 for padding