iOS自动布局：表格视图单元格的动态高度

Question

I have a table view with a bunch of cells (custom cell, which only has its content view).

In tableView:cellForRowAtIndexPath: I'm adding a predefined UIView (which has several subviews) to the content view of the custom cell. I set up all constraints for the UIView and its subviews before.

Last but not least, I set the vertical and horizontal constraints for the content view of my custom cell (superview) and the UIView, which was added before (subview).

The constraint strings look like this:

    H:|[view]|
    V:|[view]|

Unfortunately, I still get the default height for all table view cells. I'm wondering If there's a way to let auto layout do the calculation of the height automatically according to content size.

Answer 1

Check out my detailed answer to this question here: https://stackoverflow.com/a/18746930/796419

It takes a bit of work to set up, but you can absolutely have Auto Layout constraints driving a completely dynamic table view without a single hardcoded height (and let the constraint solver do the heavy lifting and provide you with the row height).

Answer 2

Auto Layout won't help with the cell height. You'll need to set that in tableView:heightForRowAtIndexPath . I guess you're probably asking this because your cell heights are variable, not fixed. ie, they depend on the content.

To resolve that, pre-calculate the cell heights and store them in an array. Return the value for the appropriate indexPath in the tableView:heightForRowAtIndexPath method.

Be sure to calculate content sizes on the main thread, using sizeThatFits of UILabel classes and such like.

If your calculation is intensive, do the majority of it off main apart from the view related methods such as sizeThatFits .

Answer 3

I solved the problem by using CGSize size = [view systemLayoutSizeFittingSize:UILayoutFittingCompressedSize]; in tableView:heightForRowAtIndexPath: .

Answer 4

To set automatic dimensions for row height, ensure following steps to make, auto dimension effective for cell/row height layout.

• Assign and implement dataSource and delegate
• Assign UITableViewAutomaticDimension to rowHeight & estimatedRowHeight
• Implement delegate/dataSource methods (ie heightForRowAt and return a value UITableViewAutomaticDimension to it)

Swift:

@IBOutlet weak var table: UITableView!

override func viewDidLoad() {
    super.viewDidLoad()

    // Don't forget to set dataSource and delegate for table
    table.dataSource = self
    table.delegate = self

    // Set automatic dimensions for row height
    // Swift 4.2 onwards
    table.rowHeight = UITableView.automaticDimension
    table.estimatedRowHeight = UITableView.automaticDimension


    // Swift 4.1 and below
    table.rowHeight = UITableViewAutomaticDimension
    table.estimatedRowHeight = UITableViewAutomaticDimension

}



// UITableViewAutomaticDimension calculates height of label contents/text
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    // Swift 4.2 onwards
    return UITableView.automaticDimension

    // Swift 4.1 and below
    return UITableViewAutomaticDimension
}

For label instance in UITableviewCell

• Set number of lines = 0 (& line break mode = truncate tail)
• Set all constraints (top, bottom, right left) with respect to its superview/ cell container.
• Optional : Set minimum height for label, if you want minimum vertical area covered by label, even if there is no data.