这是@jhibberd的快速版本

    let cell:MsgTableViewCell! = self.tableView.dequeueReusableCellWithIdentifier("MsgTableViewCell", forIndexPath: indexPath) as? MsgTableViewCell
    cell.msgText.text = self.items[indexPath.row]
    var fixedWidth:CGFloat = cell.msgText.frame.size.width
    var size:CGSize = CGSize(width: fixedWidth,height: CGFloat.max)
    var newSize:CGSize = cell.msgText.sizeThatFits(size)
    var newFrame:CGRect = cell.msgText.frame;
    newFrame.size = CGSizeMake(CGFloat(fmaxf(Float(newSize.width), Float(fixedWidth))), newSize.height);
    cell.msgText.frame = newFrame
    cell.msgText.frame.size = newSize        
    return cell

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.

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:

以下是步骤

解决方案适用于所有版本的iOS。Swift 3.0及以上版本。

添加你的UITextView到View。我用代码添加它，你可以通过界面生成器添加。 添加约束。我在代码中添加约束，你也可以在接口生成器中这样做。 使用UITextViewDelegate方法func textViewDidChange(_ textView: UITextView)来调整textView的大小

代码:

//1. Add your UITextView in ViewDidLoad let textView = UITextView() textView.frame = CGRect(x: 0, y: 0, width: 200, height: 100) textView.backgroundColor = .lightGray textView.text = "Here is some default text." //2. Add constraints textView.translatesAutoresizingMaskIntoConstraints = false [ textView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor), textView.leadingAnchor.constraint(equalTo: view.leadingAnchor), textView.trailingAnchor.constraint(equalTo: view.trailingAnchor), textView.heightAnchor.constraint(equalToConstant: 50), textView.widthAnchor.constraint(equalToConstant: 30) ].forEach{ $0.isActive = true } textView.font = UIFont.preferredFont(forTextStyle: .headline) textView.delegate = self textView.isScrollEnabled = false textViewDidChange(textView) //3. Implement the delegate method. func textViewDidChange(_ textView: UITextView) { let size = CGSize(width: view.frame.width, height: .infinity) let estimatedSize = textView.sizeThatFits(size) textView.constraints.forEach { (constraint) in if constraint.firstAttribute == .height { print("Height: ", estimatedSize.height) constraint.constant = estimatedSize.height } } }

看起来这个家伙为NSTextView找到了答案，他的答案也适用于iOS。事实证明，intrinsicContentSize并不与布局管理器同步。如果一个布局发生在intrinsicContentSize之后，你可能会有一个差异。

他有一个简单的解决办法。

NSOutlineView中的NSTextView与IntrinsicContentSize设置错误的高度

这个方法似乎适用于ios7

 // Code from apple developer forum - @Steve Krulewitz, @Mark Marszal, @Eric Silverberg
- (CGFloat)measureHeight
{
    if ([self respondsToSelector:@selector(snapshotViewAfterScreenUpdates:)])
    {
    CGRect frame = internalTextView.bounds;
    CGSize fudgeFactor;
    // The padding added around the text on iOS6 and iOS7 is different.
    fudgeFactor = CGSizeMake(10.0, 16.0);

    frame.size.height -= fudgeFactor.height;
    frame.size.width -= fudgeFactor.width;

    NSMutableAttributedString* textToMeasure;
    if(internalTextView.attributedText && internalTextView.attributedText.length > 0){
        textToMeasure = [[NSMutableAttributedString alloc] initWithAttributedString:internalTextView.attributedText];
    }
    else{
        textToMeasure = [[NSMutableAttributedString alloc] initWithString:internalTextView.text];
        [textToMeasure addAttribute:NSFontAttributeName value:internalTextView.font range:NSMakeRange(0, textToMeasure.length)];
    }

    if ([textToMeasure.string hasSuffix:@"\n"])
    {
        [textToMeasure appendAttributedString:[[NSAttributedString alloc] initWithString:@"-" attributes:@{NSFontAttributeName: internalTextView.font}]];
    }

    // NSAttributedString class method: boundingRectWithSize:options:context is
    // available only on ios7.0 sdk.
    CGRect size = [textToMeasure boundingRectWithSize:CGSizeMake(CGRectGetWidth(frame), MAXFLOAT)
                                              options:NSStringDrawingUsesLineFragmentOrigin
                                              context:nil];

    return CGRectGetHeight(size) + fudgeFactor.height;
}
else
{
    return self.internalTextView.contentSize.height;
}
}