Hide UITableviewcell which contains UITextview (Autolayout)

2
votes

I have a cell in a tableview which contains UITextView. UITextview has a constraints of top, leading, trailing and bottom to the uitableviewcell content view. I want to hide the uitableviewcell if a textview contains empty text. For that, i reduce cell height to 0. Since the textview has constraint set with respect to UITableViewCell. 

  UITableViewCell
---------------------------
|           -T-           |
| -L-   UITextView  -R-   |
|_________-B-_____________|

L,T,B,R - Left, Top, Bottom, Right Constraints

i am getting the constraints issue. 

Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x7fe5d58753a0 UITableViewCellContentView:0x7fe5d5874fe0.bottomMargin == UITextView:0x7fe5d399c000.bottom>",
    "<NSLayoutConstraint:0x7fe5d58753f0 UITableViewCellContentView:0x7fe5d5874fe0.topMargin == UITextView:0x7fe5d399c000.top>",
    "<NSLayoutConstraint:0x7fe5d5888a20 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x7fe5d5874fe0(0.5)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fe5d58753a0 UITableViewCellContentView:0x7fe5d5874fe0.bottomMargin == UITextView:0x7fe5d399c000.bottom>

How can i hide the cell without having any issue with autolayout.

3
iosuitableviewautolayoutnslayoutconstraint
You can change the Top and bottom constraints constants to 0 – Reinier Melian
But the cell is repeatable content. How can i change the constraint? Could you explain more – iPhone Guy
How do you set the height to 0,by autolayout or by heightForRow:atIndexPath? – 7vikram7

3 Answers

1
votes

I would turn the constraints off and on using the active property. This is the simplest approach, but note that it will only work on iOS 8+, because the active property on NSLayoutConstraint was only added in iOS 8.

First ensure that you have an IBOutletCollection array containing all the constraints you need:

@IBOutlet var allConstraints : [NSLayoutConstraint]!

You can hook them up in your xib/storyboard, if you have one. Otherwise just set them up in code.

Then, in the case where you want to hide the cell, do:

cell.allConstraints.forEach { $0.active = false }

in the tableview datasource method -cellForRowAtIndexPath:.

Also, override the -prepareForReuse: method on the cell subclass as follows:

override func prepareForReuse() {
  super.prepareForReuse()
  allConstraints.forEach { $0.active = true }
}

This turns the constraints back on, so things behave correctly if a hidden cell is reused to create a non-hidden cell.

You may also need to add calls to setNeedsLayout and layoutIfNeeded, but I'd try without them to start with - hopefully the layout pass triggered in the table view's reloadData should take care of things for you - it's always best not to call those functions if you don't need to.

0
votes

You can save value of the string in a global variable, then in the cellForRowAtIndexPath you can check if var is null, if not you can return cell.

Like this:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
    if (your global var != nil) {
        let cell: MyCell? = tableView.dequeueReusableCellWithIdentifier("myCell", forIndexPath: indexPath) as? MyCell

        cell?.label.text = your value

        return cell!
   }

}
0
votes

Try to change the relation of the constraints. Instead of equal use less or equal

Contraints Settings