Swift 中的 UIButton 未注册触摸

Question

I'm trying to create a UIButton using Swift. It compiles fine and I can see my button in the simulator, but when I click it, nothing happens. This is the code I am using:

let settings = UIButton()
settings.addTarget(self, action: "touchedSet:", forControlEvents: UIControlEvents.TouchUpInside)
settings.setTitle("Settings", forState: .Normal)
settings.frame = CGRectMake(0, 530, 150, 50)
scrollView.addSubview(settings)

In the same class, here is the function 'touchedSet':

func touchedSet(sender: UIButton!) {
    println("You tapped the button")
}

I'm using the simulator as I don't have an iOS 8.0 device, could that be the problem?

Thanks!

Answer 1

I see it is an old question but I just faced very similar problem yesterday. My buttons were highlighted on touch but not firing the action.

I have two view controllers. One view covers the others view and button is on the top view.

eg.

• Rootviewcontroller has back view

• Topviewcontroller has top view

The button on top view does not call the action if I don't add the topviewcontroler as childviewcontroller of the rootviewcontroller. After adding the topviewcontroller as childviewcontroller it started to working.

So in short: just try to add the view controller of buttons superview as childviewcontroller to the parent views viewcontroller with the following method

func addChildViewController(_ childController: UIViewController)

Answer 2

Selectors are a struct that have to be created.

Do it this way...

Updated for Swift 4

settingsButton.addTarget(self, action: #selector(showSettings), for: .touchUpInside)

That should do it.

Answer 3

In the simulator, sometimes it doesn't recognise the selector. There is a bug it seems. I just changed the action name (selector), and it worked.

let buttonPuzzle:UIButton = UIButton(frame: CGRectMake(100, 400, 100, 50))
buttonPuzzle.backgroundColor = UIColor.greenColor()
buttonPuzzle.setTitle("Puzzle", forState: UIControlState.Normal)
buttonPuzzle.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)
buttonPuzzle.tag = 22;
self.view.addSubview(buttonPuzzle)

Selector Function is Here:

func buttonAction(sender:UIButton!)
{
    var btnsendtag:UIButton = sender
    if btnsendtag.tag == 22 {
        //println("Button tapped tag 22")
    }   
}

Answer 4

For those who are also stuck in the tutorial:

I ran in to the same problem, when I was following Apple's "Start Developing iOS Apps (Swift)". It turned out that I had overlooked these code lines in the tutorial:

override var intrinsicContentSize : CGSize {
    return CGSize(width: 240, height: 44)
}

Adding them to my RatingControl fixed the problem.

Answer 5

For anyone else doing manual view layout running into this issue, you might have defined your subview like such:

let settingsButton: UIButton = {
    let button = UIButton(type: .system)
    // do some more setup
    button.addTarget(self, selector: #selector(openSettings), for: .touchUpInside)
    return button
}()

The error lies with the fact that you are adding a target and passing self before it is actually available.

This can be fixed in two ways

1. Making the variable lazy and still adding the target in the initialization block:

    lazy var button: UIButton = { let button = UIButton(type: .system) // since this variable is lazy, we are guaranteed that self is available button.addTarget(self, selector: #selector(openSettings), for: .touchUpInside) return button }()

2. Adding the target after your parent view has been initialized:

    init() { self.settingsButton = .init(type: .system) super.init(frame: .zero) self.settingsButton.addTarget(self, selector: #selector(openSettings), for: .touchUpInside) }

Answer 6

I have had this problem when parent view of my button has isUserInteractionEnabled == false . All subviews will have the same userInteraction as their parent view. So I have just added this line parentView.isUserInteractionEnabled = true and the problem disappeared. Hope this helps someone.

Answer 7

I had a similar problem when i had a subViewController with buttons and tapHandlers to match, and I wanted to place this to a stack in a separate superViewController..

This cause none of the tapHandlers to to trigger, and the solution was to instead of only using addArrangedSubview(subViewController.view), I also used addChildViewController(subViewController) in the superview to allow the childViewController to continue to operate as a viewController and not just a view.

Answer 8

所以你应该使用以下行

settings.userInteractionEnabled = true

Answer 9

I had the same issue when implementing UIButton and SearchBar on container view(UIView). In my case, the cause was the constraint issue. Constraint to searchBar had issue and because of this, function set had never been called.

You can see if there's any from "Debug View Hierarchy" button. (constraint problem is shown as purple warning)

(env: iOS12, xcode10.1)

Answer 10

Interestingly enough, I just ran into the same issue on the very latest versions of iOS/Xcode (v12.4 / v10.3). Turns out the issue for me was a LayoutConstraint! No joke. I had a leading label with the uiSwitch to the right, and found that I needed to change the constraints between the two such that it wasn't a fixed constant value of 8 points (Label-8-Switch-0-|).

As soon as I changed this to a ">=" the Switch was able to change states between on/off. Laughably, it's almost like it wasn't able to change because it needs "room" (that apparently varies) to make the change with.

Not sure, but file it away as one of those "hummmm?" items in your memory.

One other item (that really shouldn't matter, frankly) is the valueChanged and tappedUpInside were both not firing (true on both an actual handset and on the simulators). Also, they were hooked up through a storyboard. But, this shouldn't matter as far as I know.

Answer 11

I had the same issue. The problem was the view had top constraint, but not left/right and height constraints. So, the view was shrinking to 1x1 and it was not passing the touch event to children.

By adding more constraints, the children now getting the touch event and working ...

let guide = view.safeAreaLayoutGuide
viewHeader.topAnchor.constraint(equalTo: guide.topAnchor).isActive = true
viewHeader.rightAnchor.constraint(equalTo: guide.rightAnchor).isActive = true
viewHeader.leftAnchor.constraint(equalTo: guide.leftAnchor).isActive = true
let heightConstraint = NSLayoutConstraint(item: viewHeader,
                                          attribute: NSLayoutConstraint.Attribute.height,
                                          relatedBy: NSLayoutConstraint.Relation.equal,
                                          toItem: nil,
                                          attribute: NSLayoutConstraint.Attribute.notAnAttribute,
                                          multiplier: 1,
                                          constant: 44)
viewHeader.addConstraints([heightConstraint])

Answer 12

Old question, but I also found myself stuck with an unresponding button. I simply changed my initialisation from

let button = UIButton(frame: .zero)

to

let button = UIButton(type: .system)

Answer 13

如果您使用故事板，请确保将按钮与代码中的 IBOutlet 实例变量链接起来。

Answer 14

I can see only one problem: You have to set the action with Selector as following:

settings.addTarget(self, action: Selector("touchedSet:"), forControlEvents: UIControlEvents.TouchUpInside)

Don't forget to insert : if you need to pass parameters to the function.

Answer 15

You said within the same class. Make sure that the button code itself is in the viewDidLoad() and the action be outside of it but inside the class if you are working with a view.

Answer 16

The problem with that tutorial from Apple is the way they put the UIView (RatingControl) inside the StackView, which is incorrect. The UIView (RatingControl) should be outside of the StackView. So, the solution is: 1. Drag the UIView (RatingControl) outside of the StackView 2. Set the constraints for the new position of the RatingControl - Leading margin to the Container equal zero - Trailing margin to the Container equal zero - Top margin to the StackView equal zero

With this new constraints, now the RatingControl will have the same with as the Container, no matter what is the device screen size, and always will be just behind of the StackView where the photo selector will appear.

I hope this help you guys.

Answer 17

Old question, but thought I'd give some help to other looking for this issue. First off, I'm not entire sure this is correct so please correct me if I'm wrong.

But if you set the selector wrongly the application would crash when you press the button since it's subscribed to a selector which doesn't exist. Which means that your selector is working. My guess is that something else is blocking the touch event, assuming UIButton.enabled = true and UIButton.userInteractionEnabled = true . Usually you could check this by long pressing the button and see if it hits. If it does then you have a UIGestureRecognizer added somewhere which takes up the hits first. Could also be the UIScrollView which is delaying the touch input (there's a checkbox for this in the Inspector).

Hope this helps someone, and hope it's accurate.

Answer 18

I've found similar example for Swift 2 and adapted for Swift 3. Tested it is working very well. I hope it helps.

// http://lab.dejaworks.com/ios-swift-3-playground-uibutton-action
// Trevor D. Beydag

import UIKit
import PlaygroundSupport
class Responder : NSObject {
    func action() {
        print("Button pressed!")
    }
}

let containerView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 300.0,    height: 600.0))
PlaygroundPage.current.liveView = containerView
let responder = Responder()

let button = UIButton(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
button.backgroundColor = UIColor.green
button.setTitle("TEST", for: .normal)
button.addTarget(responder, action: #selector(Responder.action), for: .touchUpInside)
containerView.addSubview(button)

Answer 19

我已将高度和宽度约束更改为 0，出于某种原因，我需要这样做，以便它在一个用例的多用途视图上正确显示，按钮可见，但触摸停止工作。

Answer 20

In my case, I had a transparent UIView above the UIButton in the view hierarchy, which is why when I was "clicking on the UIButton ", I was actually clicking on the transparent UIView on top of it.

Sending the transparent UIView back using parentUIView.sendSubviewToBack(transparentUIView) worked for me, because after doing this the UIButton came on top of the view hierarchy. Click on the "Debug View Hierarchy" button in Xcode to check if the UIButton is on top or not.

Answer 21

If you're using Autolayout to build your UI, make sure to declare all your constraints in your view and parent views.

Some times we forget to set all of them and the system complains about it, drawing your UI but not responding correctly in your touch events.

In my case, i've forgot to set my bottom constraint in my view so i'm here to set this comment as a reminder.

Answer 22

When a view like a button is placed next to another view like an image view etc. especially if if the image view is on top of another view Xcode sometimes thinks that your button is underneath that image view even though it is not. Sometimes you need to clear all the constraints and reset all constraints in order for the button to work.