迅速回答: 下面的代码计算textView的高度。

                let maximumLabelSize = CGSize(width: Double(textView.frame.size.width-100.0), height: DBL_MAX)
                let options = NSStringDrawingOptions.TruncatesLastVisibleLine | NSStringDrawingOptions.UsesLineFragmentOrigin
                let attribute = [NSFontAttributeName: textView.font!]
                let str = NSString(string: message)
                let labelBounds = str.boundingRectWithSize(maximumLabelSize,
                    options: NSStringDrawingOptions.UsesLineFragmentOrigin,
                    attributes: attribute,
                    context: nil)
                let myTextHeight = CGFloat(ceilf(Float(labelBounds.height)))

现在你可以设置你的textView的高度为myTextHeight

我回顾了所有的答案，所有都保持固定的宽度和调整只有高度。如果你想调整宽度，你可以很容易地使用这个方法:

当配置文本视图时，将滚动设置为禁用

textView.isScrollEnabled = false

然后在委托方法func textViewDidChange(_ textView: UITextView)添加以下代码:

func textViewDidChange(_ textView: UITextView) {
    let newSize = textView.sizeThatFits(CGSize(width: CGFloat.greatestFiniteMagnitude, height: CGFloat.greatestFiniteMagnitude))
    textView.frame = CGRect(origin: textView.frame.origin, size: newSize)
}

输出:

我们可以用约束来做。

为UITextView设置高度约束。

2.为高度限制创建IBOutlet。

 @property (weak, nonatomic) IBOutlet NSLayoutConstraint *txtheightconstraints;

3.不要忘记为你的textview设置委托。

4.

-(void)textViewDidChange:(UITextView *)textView
{
    CGFloat fixedWidth = textView.frame.size.width;
    CGSize newSize = [textView sizeThatFits:CGSizeMake(fixedWidth, MAXFLOAT)];
    CGRect newFrame = textView.frame;
    newFrame.size = CGSizeMake(fmaxf(newSize.width, fixedWidth), newSize.height);
    NSLog(@"this is updating height%@",NSStringFromCGSize(newFrame.size));
    [UIView animateWithDuration:0.2 animations:^{
                  _txtheightconstraints.constant=newFrame.size.height;
    }];

}

然后像这样更新你的约束:

从iOS 8开始，可以使用UITableView的自动布局功能来自动调整UITextView的大小，而不需要任何自定义代码。我在github上放了一个项目，演示了这一点，但关键是:

UITextView必须禁用滚动，这可以通过编程或通过接口构建器来实现。如果启用滚动，它将不会调整大小，因为滚动可以让您查看较大的内容。 在UITableViewController的viewDidLoad中，你必须为estimatedRowHeight设置一个值，然后将rowHeight设置为UITableViewAutomaticDimension。

- (void)viewDidLoad {
    [super viewDidLoad];
    self.tableView.estimatedRowHeight = self.tableView.rowHeight;
    self.tableView.rowHeight = UITableViewAutomaticDimension;
}

项目部署目标必须是iOS 8或更高版本。

The easiest way to ask a UITextView is just calling -sizeToFitit should work also with scrollingEnabled = YES, after that check for the height and add a height constraint on the text view with the same value. Pay attention that UITexView contains insets, this means that you can't ask the string object how much space it want to use, because this is just the bounding rect of the text. All the person that are experiencing wrong size using -sizeToFit it's probably due to the fact that the text view has not been layout yet to the interface size. This always happen when you use size classes and a UITableView, the first time cells are created in the - tableView:cellForRowAtIndexPath: the comes out with the size of the any-any configuration, if you compute you value just now the text view will have a different width than the expected and this will screw all sizes. To overcome this issue I've found useful to override the -layoutSubviews method of the cell to recalculate textview height.

迅速回答: 下面的代码计算textView的高度。

                let maximumLabelSize = CGSize(width: Double(textView.frame.size.width-100.0), height: DBL_MAX)
                let options = NSStringDrawingOptions.TruncatesLastVisibleLine | NSStringDrawingOptions.UsesLineFragmentOrigin
                let attribute = [NSFontAttributeName: textView.font!]
                let str = NSString(string: message)
                let labelBounds = str.boundingRectWithSize(maximumLabelSize,
                    options: NSStringDrawingOptions.UsesLineFragmentOrigin,
                    attributes: attribute,
                    context: nil)
                let myTextHeight = CGFloat(ceilf(Float(labelBounds.height)))

现在你可以设置你的textView的高度为myTextHeight