React on drag over view - swift

Question

I have a view that I want to change whenever long press or drag occurs over it. It can start outside of the view, but also inside.
struct ContentView: View {
#State var active: Bool = false
var body: some View {
Rectangle()
.fill(self.active ? Color.red : Color.secondary)
}
}
An example of this behaviour is the iPhone keyboard: when you long press on a key it pops up (active = true). When you move outside it, it pops down (active = false) but the next key is then active.
I have tried using LongPressGesture but cannot figure out how to make it behave as I want.

Answer 1

I made example for you in playgrounds to display how to use a LongPressGestureRecognizer.
You add the gesture recognizer to the view you want long pressed, with target being the parent controller handling the gesture recognition (ContentView in your case) and action being what happens with a long press.
In my implementation, a long press to the view bodyView changes its color from clear to red. This happens inside the didSet of the showBody property, which calls showBodyToggled(). I'm checking the state of the gesture, because the gesture recognizer will send messages for each state (I'm only performing the action if the state is .began).
Let me know if you have any questions:
//: A UIKit based Playground for presenting user interface
import UIKit
import PlaygroundSupport
class MyViewController : UIViewController {
var bodyView: UIView!
var showBody = false {
didSet {
showBodyToggled()
}
}
override func viewDidLoad() {
super.viewDidLoad()
configureSubviews()
configureLongPressRecognizer()
}
func configureSubviews() {
bodyView = UIView()
bodyView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(bodyView)
NSLayoutConstraint.activate([
bodyView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
bodyView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
bodyView.heightAnchor.constraint(equalToConstant: 200),
bodyView.widthAnchor.constraint(equalToConstant: 300)
])
}
func configureLongPressRecognizer() {
bodyView.addGestureRecognizer(
UILongPressGestureRecognizer(
target: self,
action: #selector(longPressed(_:))
)
)
}
#objc func longPressed(_ sender: UILongPressGestureRecognizer) {
// the way I'm doing it: only acts when the long press first happens.
// delete this state check if you'd prefer the default long press implementation
switch sender.state {
case .began:
showBody = !showBody
default:
break
}
}
func showBodyToggled() {
UIView.animate(withDuration: 0.4) { [weak self] in
guard let self = self else { return }
self.bodyView.backgroundColor = self.showBody ? .red : .clear
}
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()
EDIT:
Here's an example in SwiftUI where a long press of 0.5 seconds toggles the color of a circle between red and black
struct ContentView: View {
#State var active = false
var longPress: some Gesture {
LongPressGesture()
.onEnded { _ in
withAnimation(.easeIn(duration: 0.4)) {
self.active = !self.active
}
}
}
var body: some View {
Circle()
.fill(self.active ? Color.red : Color.black)
.frame(width: 100, height: 100, alignment: .center)
.gesture(longPress)
}
}