Ios 为什么UITableViewCell的高度小于其文本的高度？

我有一个

UITableView

和

UITableView单元格

s，我在函数

heightForRowAtIndexPath

中以休闲方式设置每个单元格的高度：

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
    UITableViewCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath];
    NSStringDrawingOptions opts = (NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading);
    CGSize boundingRect = CGSizeMake(450.f, CGFLOAT_MAX);
    CGSize size = [cell.detailTextLabel.text boundingRectWithSize:boundingRect
                                                      options:opts
                                                   attributes:[cell.detailTextLabel.attributedText attributesAtIndex:0 effectiveRange:nil]
                                                      context:nil].size;
    CGFloat height = size.height;
    size = [cell.textLabel.text boundingRectWithSize:boundingRect
                                         options:opts
                                      attributes:[cell.textLabel.attributedText attributesAtIndex:0 effectiveRange:nil]
                                         context:nil].size;
    height += size.height;
    return height;
}

NSString *nickName = @"some nickname"; // gets the nickname
NSString title = [NSString stringWithFormat:@"%@ wrote:", nickName];
NSString *detail = @"some text"; // gets the content of the message

[cell.textLabel setText: title];
[cell.detailTextLabel setText: detail];
cell.detailTextLabel.numberOfLines = 0;
cell.detailTextLabel.lineBreakMode = NSLineBreakByWordWrapping;

但是我得到的单元格对于文本来说太小了，较长的文本不适合：

在单元格中写入的文本按以下方式设置：

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
    UITableViewCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath];
    NSStringDrawingOptions opts = (NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading);
    CGSize boundingRect = CGSizeMake(450.f, CGFLOAT_MAX);
    CGSize size = [cell.detailTextLabel.text boundingRectWithSize:boundingRect
                                                      options:opts
                                                   attributes:[cell.detailTextLabel.attributedText attributesAtIndex:0 effectiveRange:nil]
                                                      context:nil].size;
    CGFloat height = size.height;
    size = [cell.textLabel.text boundingRectWithSize:boundingRect
                                         options:opts
                                      attributes:[cell.textLabel.attributedText attributesAtIndex:0 effectiveRange:nil]
                                         context:nil].size;
    height += size.height;
    return height;
}

NSString *nickName = @"some nickname"; // gets the nickname
NSString title = [NSString stringWithFormat:@"%@ wrote:", nickName];
NSString *detail = @"some text"; // gets the content of the message

[cell.textLabel setText: title];
[cell.detailTextLabel setText: detail];
cell.detailTextLabel.numberOfLines = 0;
cell.detailTextLabel.lineBreakMode = NSLineBreakByWordWrapping;

---

为什么单元格的高度太短？

来自方法

boundingRectWithSize:options:attributes:context:

:

“此方法返回字符串中glyph的实际边界”

缺少的是单元格的边距，可以使用

单元格访问。layoutMargins

：

height += cell.layoutMargins.top + cell.layoutMargins.bottom;

---

尝试使用

NSAttributedString

的boundingRect方法（Swift 3）

在目标C中：

// change this value with the width of your UITableViewCell
CGFloat availableWidth = 355;

NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:@"your string"];
CGRect stringBoundingRect = [attrStr boundingRectWithSize:CGSizeMake(availableWidth, CGFLOAT_MAX) options: NSStringDrawingUsesLineFragmentOrigin| NSStringDrawingUsesDeviceMetrics context:nil];

CGFloat height = stringBoundingRect.size.height;

---

为什么要设置行高？？为什么不使用EstimateDrowEight？也许可以使用自动布局：