Create a dropdown swift for ios . It receives an array of strings and forms a drop-down list from them. It has a reference UIView , which is always visible, the currently selected value is displayed there. If the array of strings passed by Dropdown has more than one value, then there is an arrow down icon in the reference UIView , if there is only one value, then only text is shown in the UIView , while the text is placed in the center of the reference UIView , and the arrow icon is hidden .

Most often, in the array of strings passed to Dropdown, there is more than one value, so in .xib I created a variant for the text with the icon. Set the following constraints . The text and icon have small indents from the parent view, respectively, leading and trailing . The text ( UILabel ) is stretched over the entire parent view and has a small trailing indent. The text and icon have constraint CenterVertically and the icon has constraints width and height .

Therefore, for the variant when the dropdown has only one value, we need to hide the icon, change the constraints the text and change its alignment . There is a lot of free space, so we reduce the width of the dropdown to 5/8 of the previous one. For a start, I went the simplest way, working with points:

  switch appearance { case .Text: icon.hidden = true let nw = w < (UIScreen.mainScreen().bounds.width / 2) ? (w * 5 / 8) : w self.width = nw self.x += (w - nw) / 2 if (type == .Dropdown) { label.textAlignment = .Center label.center = self.center }

The desired result is not received. Text crawls out of view . I tried to change the width, but to no avail, it seems that constraints from .xib still .xib , which attracted it for leading and trai l ing to the parent view (although it’s also not completely clear, because the width of the parent view changes in the code) returned to constraints :

  switch appearance { case .Text: icon.hidden = true let nw = w < (UIScreen.mainScreen().bounds.width / 2) ? (w * 5 / 8) : w self.width = nw self.x += (w - nw) / 2 if (type == .Dropdown) { label.textAlignment = .Center var cs : [NSLayoutConstraint] = [] for const in label.constraints { cs.append(const) } label.removeConstraints(cs) let cx = NSLayoutConstraint(item: label, attribute: .CenterX, relatedBy: .Equal, toItem: self, attribute: .CenterX, multiplier: 1, constant: 1) let cy = NSLayoutConstraint(item: label, attribute: .CenterY, relatedBy: .Equal, toItem: self, attribute: .CenterY, multiplier: 1, constant: 1) label.width = nw self.addConstraint(cx) self.addConstraint(cy) }

As a result, the text completely disappears from the dropdown ! Assumed that the fact is that there are no constraints for the width and height text.

  switch appearance { case .Text: icon.hidden = true let nw = w < (UIScreen.mainScreen().bounds.width / 2) ? (w * 5 / 8) : w self.width = nw self.x += (w - nw) / 2 if (type == .Dropdown) { label.textAlignment = .Center var cs : [NSLayoutConstraint] = [] for const in label.constraints { cs.append(const) } label.removeConstraints(cs) let cx = NSLayoutConstraint(item: label, attribute: .CenterX, relatedBy: .Equal, toItem: self, attribute: .CenterX, multiplier: 1, constant: 1) let cy = NSLayoutConstraint(item: label, attribute: .CenterY, relatedBy: .Equal, toItem: self, attribute: .CenterY, multiplier: 1, constant: 1) // 6 просто потому что 6 )) чтобы убедиться что оно работает let cw = NSLayoutConstraint(item: label, attribute: .Width, relatedBy: .Equal, toItem: label, attribute: .Width, multiplier: 1, constant: 6) let ch = NSLayoutConstraint(item: label, attribute: .Height, relatedBy: .Equal, toItem: label, attribute: .Height, multiplier: 1, constant: 6) label.width = nw self.addConstraint(cx) self.addConstraint(cy) label.addConstraint(cw) label.addConstraint(ch) }

In which direction can you move to achieve the desired result?

  • From the easiest - place all the necessary constraints in the interface builder and then change their values ​​in the code - VAndrJ
  • But how can I remove everything from the question that is not directly related to the problem? type here the inscription with the picture works, the inscription without the picture does not work - Max Mikheyenko
  • Then there will be advice to ask everything in .xib, and I have either for one .xib mode of operation or for another - iamthevoid

1 answer 1

Greetings.

  1. From the written it is not very clear how the Label is attached with the text on the left to the parent View. If you do not specify Leading or Width constraint, it will run away.

  2. To modify constraint, it’s best to use the following approach:

    • Create a property for NSLayoutConstraint
    • Snap an appropriate constraint element from xib / storyboard

    • In the code change for example as follows

       self.textLabelLeadingConstraint.constant = 0; self.textLabelLeadingConstraint.multiplier = 1;

    • Send to redraw

       self.textLabel.setNeedsLayout();