点击时如何反复更改按钮？

Question

Using Swift, how do I make a:

1. Button with words "start", that changes to "pause" and vice versa when tapped? Not just once, but can be done infinitely? (eg in a stopwatch app)
2. Custom image button that changes between 2 image when tapped, that can also be done (tapped & change) infinitely?

Answer 1

In your storyboard, set the Default state title to "Start" and the Selected state title to "Pause"

Or alternatively, if you're doing it in code:

startPauseButton.setTitle("Start", forState: .Normal)
startPauseButton.setTitle("Pause", forState: .Selected)

In your IBAction func , toggle the button.selected property between true & false

@IBAction func toggleStopwatch(button:UIButton) {
    if button.selected {
        // Pause the stopwatch
    } else {
        // Start the stopwatch
    }
    button.selected = !button.selected
}

You can also set different images for different states: Default , Highlighted , Selected , Disabled

Answer 2

Step 1: Create a Bool variable

var isPlaying:Bool = false

Step 2: Connect your button with this IBAction method:

@IBAction func btnStartStop(sender: UIButton) {
    if isPlaying{

        isPlaying = false
        sender.setTitle("Pause", forState: UIControlState.Normal)
        sender.setImage(pauseImage, forState: .Normal)
        //Pause Stopwatch
    }
    else{

        isPlaying = true
        sender.setTitle("Play", forState: UIControlState.Normal)
        sender.setImage(playImage, forState: .Normal)
      //Play Stopwatch
    }
  }

Answer 3

In the @IBAction of the button (assuming you are using storyboards), you change the title or image of the button to what you want. You can also check for the title or image and perform an action based on what you have.

@IBAction func pressbutton(sender: UIButton) {
    switch sender.titleLabel?.text {
        case "Play":
        play()
        case "Pause":
        pause()
    default:
        other()
    }
    sender.titleLabel?.text = "Whatever you want"
}

Or with images (assuming you have an images array somewhere that stores the images, which you should):

@IBAction func pressbutton(sender: UIButton) {
    switch sender.imageView!.image! {
        case images[0]:
            play()
        case images[1]:
            pause()
    default:
        other()
    }
    sender.imageView?.image = UIImage(...)
}

Answer 4

Try this....

@IBAction func btnStopWatch(sender: UIButton) {
        if btnStopWatch.selected == true  {
            btnStopWatch.setTitle("stop", forState: UIControlState.Normal)
            btnStopWatch.setImage(stopImage, forState: UIControlState.Normal)
            btnStopWatch.selected = false
        } else {
            btnStopWatch.setTitle("start", forState: UIControlState.Normal)
            btnStopWatch.setImage(startImage, forState: UIControlState.Normal)
            btnStopWatch.selected = true
        }
    }

Answer 5

#1. Toggle a UIButton title

With Swift 3, UIButton has a method called setTitle(_:for:) . setTitle(_:for:) has the following declaration:

func setTitle(_ title: String?, for state: UIControlState)

Sets the title to use for the specified state.

The following Playground code shows how to use setTitle(_:for:) in order to toggle the title of a button according to its state:

import PlaygroundSupport
import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.white

        let button = UIButton(type: UIButtonType.system)
        button.addTarget(self, action: #selector(toggle(sender:)), for: UIControlEvents.touchUpInside)

        // Set button's states
        button.setTitle("Start", for: UIControlState.normal)
        button.setTitle("Pause", for: UIControlState.selected)

        // set layout
        view.addSubview(button)
        button.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = button.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = button.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])
    }

    /// trigger action when button is tapped
    func toggle(sender: UIButton) {
        sender.isSelected = !sender.isSelected
        print("Button state: \(sender.isSelected)")
    }

}

let vc = ViewController()
PlaygroundPage.current.liveView = vc

Preview your view controller in the Playground assistant editor using View > Assistant Editor > Show Assistant Editor

---

#2. Toggle a UIButton image

UIButton has a method called setImage(_:for:) . setImage(_:for:) has the following declaration:

func setImage(_ image: UIImage?, for state: UIControlState)

Sets the image to use for the specified state.

The following Playground code shows how to use setImage(_:for:) in order to toggle the title of a button according to its state:

import PlaygroundSupport
import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.white

        let button = UIButton()
        button.addTarget(self, action: #selector(toggle(sender:)), for: UIControlEvents.touchUpInside)

        // Set button's states
        button.setImage(UIImage(named: "on.png"), for: UIControlState.normal)
        button.setImage(UIImage(named: "off.png"), for: UIControlState.selected)

        // set layout
        view.addSubview(button)
        button.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = button.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = button.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        let heightConstraint = button.heightAnchor.constraint(equalToConstant: 100)
        let widthConstraint = button.widthAnchor.constraint(equalToConstant: 100)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, heightConstraint, widthConstraint])
    }

    /// trigger action when button is tapped
    func toggle(sender: UIButton) {
        sender.isSelected = !sender.isSelected
        print("Button state: \(sender.isSelected)")
    }

}

let vc = ViewController()
PlaygroundPage.current.liveView = vc

Preview your view controller in the Playground assistant editor using View > Assistant Editor > Show Assistant Editor