带有约束的iOS自定义UIControl，UITextView：无法同时满足约束

Question

I created a custom UITextView that does some syntax highlighting and it works very well. When I create a regular UITextView and add constraints, I get no errors or warnings. When I use my custom UITextView (which inherits from UITextView ) I get all sorts of constraint warnings that say it can't satisfy the constraints I've added. For example:

(
    "<NSLayoutConstraint:0x7b9c8750 MyApp.MyCodeAppTextView:0x7c280200.width == UIView:0x7bc621c0.width>",
    "<NSAutoresizingMaskLayoutConstraint:0x7bc68be0 h=--& v=--& H:[MyApp.MyCodeAppTextView:0x7c280200(0)]>",
    "<NSLayoutConstraint:0x7bc6a720 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7bc621c0(320)]>"
)

Is there something I have to add to my custom UIControl/UITextView in order for it to be able to respond to constraints properly?

Answer 1

Apparently you need to put these three things in your custom class.

1. setTranslatesAutoresizingMaskIntoConstraints(false)
2. intrinsicContentSize
3. requiresConstraintBasedLayout

   ---

With that in mind this is the code I added to my custom class to make it work.

import UIKit

public class YourCustomUIControl:UIView {
    required public init(coder aDecoder: NSCoder) {
        super.init()
        setTranslatesAutoresizingMaskIntoConstraints(false)
    }

    override public func intrinsicContentSize() -> CGSize {
        return CGSizeMake(100, 70)
    }

    override class public func requiresConstraintBasedLayout() -> Bool {
        return true
    }
}