在iOS 6中，苹果为UILabel添加了一个属性，极大地简化了标签的动态垂直大小调整:preferredmaxlayoutidth。

将此属性与lineBreakMode = nslinebreakbywordwrapped和sizeToFit方法结合使用，可以轻松地调整UILabel实例的大小，以容纳整个文本的高度。

引用iOS文档:

preferredMaxLayoutWidth 多行标签的首选最大宽度(以点为单位)。 讨论 当对标签应用布局约束时，此属性将影响标签的大小。在布局过程中，如果文本扩展到超出此属性指定的宽度，则附加文本将流动到一个或多个新行，从而增加标签的高度。

一个示例:

...
UILabel *status = [[UILabel alloc] init];
status.lineBreakMode = NSLineBreakByWordWrapping;
status.numberOfLines = 5; // limits to 5 lines; use 0 for unlimited.

[self addSubview:status]; // self here is the parent view

status.preferredMaxLayoutWidth = self.frame.size.width; // assumes the parent view has its frame already set.

status.text = @"Some quite lengthy message may go here…";
[status sizeToFit];
[status setNeedsDisplay];
...

NSString *str = @"Please enter your text......";
CGSize lblSize = [str sizeWithFont:[UIFont systemFontOfSize:15] constrainedToSize: CGSizeMake(200.0f, 600.0f) lineBreakMode: NSLineBreakByWordWrapping];

UILabel *label = [[UILabel alloc]init];
label.frame = CGRectMake(60, 20, 200, lblSize.height);
label.numberOfLines = 0;
label.lineBreakMode = NSLineBreakByWordWrapping;
label.font = [UIFont systemFontOfSize:15];
label.text = str;
label.backgroundColor = [UIColor clearColor];
[label sizeToFit];
[self.view addSubview:label];

你可以使用下面的代码得到高度

你必须通过

文本2。字体3。标签宽度 func hightforlabel (text: String, font: UIFont, width: CGFloat) -> CGFloat { let label:UILabel = UILabel(frame: CGRect(x: 0, y: 0, width: width, height: CGFloat.greatestFiniteMagnitude)) 标签。numberolines = 0 标签。lineBreakMode = nslinebreakmode . bywordwrapped 标签。Font = Font 标签。Text = Text label.sizeToFit () 返回label.frame.height ｝

你可以通过以下方式实现TableViewController的(UITableViewCell *)tableView:cellForRowAtIndexPath方法(例如):

#define CELL_LABEL_TAG 1

- (UITableViewCell *)tableView:(UITableView *)tableView  cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSString *text = @"my long text";

    static NSString *MyIdentifier = @"MyIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero  reuseIdentifier:identifier] autorelease];
    }

    CGFloat width = [UIScreen mainScreen].bounds.size.width - 50;
    CGFloat height = [self textHeight:text] + 10;
    CGRect frame = CGRectMake(10.0f, 10.0f, width, height);

    UILabel *cellLabel = [[UILabel alloc] initWithFrame:frame];
    cellLabel.tag = CELL_LABEL_TAG;
    cellLabel.textColor = [UIColor blackColor];
    cellLabel.backgroundColor = [UIColor clearColor];
    cellLabel.textAlignment = UITextAlignmentLeft;
    cellLabel.font = [UIFont systemFontOfSize:12.0f];
    [cell.contentView addSubview:cellLabel];
    [cellLabel release];

    return cell;
}

UILabel *label = (UILabel *)[cell viewWithTag:CELL_LABEL_TAG];
label.text = text;
label.numberOfLines = 0;
[label sizeToFit];
return cell;

也可以使用NSString的sizeWithFont:constrainedToSize:lineBreakMode:方法来计算文本的高度。

我计算UILabel动态高度的方法。

    let width = ... //< width of this label 
    let text = ... //< display content

    label.numberOfLines = 0
    label.lineBreakMode = .byWordWrapping
    label.preferredMaxLayoutWidth = width

    // Font of this label.
    //label.font = UIFont.systemFont(ofSize: 17.0)
    // Compute intrinsicContentSize based on font, and preferredMaxLayoutWidth
    label.invalidateIntrinsicContentSize() 
    // Destination height
    let height = label.intrinsicContentSize.height

包装功能:

func computeHeight(text: String, width: CGFloat) -> CGFloat {
    // A dummy label in order to compute dynamic height.
    let label = UILabel()

    label.numberOfLines = 0
    label.lineBreakMode = .byWordWrapping
    label.font = UIFont.systemFont(ofSize: 17.0)

    label.preferredMaxLayoutWidth = width
    label.text = text
    label.invalidateIntrinsicContentSize()

    let height = label.intrinsicContentSize.height
    return height
}

sizeWithFont constrainedToSize:lineBreakMode:是使用的方法。如何使用它的例子如下:

//Calculate the expected size based on the font and linebreak mode of your label
// FLT_MAX here simply means no constraint in height
CGSize maximumLabelSize = CGSizeMake(296, FLT_MAX);

CGSize expectedLabelSize = [yourString sizeWithFont:yourLabel.font constrainedToSize:maximumLabelSize lineBreakMode:yourLabel.lineBreakMode];   

//adjust the label the the new height.
CGRect newFrame = yourLabel.frame;
newFrame.size.height = expectedLabelSize.height;
yourLabel.frame = newFrame;