SWIFTUI 键盘快捷键 键盘监听
房时铭
方法❶
使用NSEvent.addLocalMonitorForEvents(matching: [.keyDown])
不细述
方法❷
Using some additional convenience sugar methods, I can just write like this:
.commands {
CommandMenu("Input") {
keyInput(.leftArrow)
keyInput(.rightArrow)
keyInput(.upArrow)
keyInput(.downArrow)
keyInput(.space)
}
}
And forward key inputs to all subviews like this:
.environmentObject(keyInputSubject)
And then a child view, here GameView can listen to the events with onReceive, like so:
struct GameView: View {
@EnvironmentObject private var keyInputSubjectWrapper: KeyInputSubjectWrapper
@StateObject var game: Game
var body: some View {
HStack {
board
info
}.onReceive(keyInputSubjectWrapper) {
game.keyInput($0)
}
}
}
The keyInput method used to declare the keys inside CommandMenu builder is just this:
private extension ItsRainingPolygonsApp {
func keyInput(_ key: KeyEquivalent, modifiers: EventModifiers = .none) -> some View {
keyboardShortcut(key, sender: keyInputSubject, modifiers: modifiers)
}
}
Full Code
extension KeyEquivalent: Equatable {
public static func == (lhs: Self, rhs: Self) -> Bool {
lhs.character == rhs.character
}
}
public typealias KeyInputSubject = PassthroughSubject<KeyEquivalent, Never>
public final class KeyInputSubjectWrapper: ObservableObject, Subject {
public func send(_ value: Output) {
objectWillChange.send(value)
}
public func send(completion: Subscribers.Completion<Failure>) {
objectWillChange.send(completion: completion)
}
public func send(subscription: Subscription) {
objectWillChange.send(subscription: subscription)
}
public typealias ObjectWillChangePublisher = KeyInputSubject
public let objectWillChange: ObjectWillChangePublisher
public init(subject: ObjectWillChangePublisher = .init()) {
objectWillChange = subject
}
}
// MARK: Publisher Conformance
public extension KeyInputSubjectWrapper {
typealias Output = KeyInputSubject.Output
typealias Failure = KeyInputSubject.Failure
func receive<S>(subscriber: S) where S : Subscriber, S.Failure == Failure, S.Input == Output {
objectWillChange.receive(subscriber: subscriber)
}
}
@main
struct ItsRainingPolygonsApp: App {
private let keyInputSubject = KeyInputSubjectWrapper()
var body: some Scene {
WindowGroup {
#if os(macOS)
ContentView()
.frame(idealWidth: .infinity, idealHeight: .infinity)
.onReceive(keyInputSubject) {
print("Key pressed: \($0)")
}
.environmentObject(keyInputSubject)
#else
ContentView()
#endif
}
.commands {
CommandMenu("Input") {
keyInput(.leftArrow)
keyInput(.rightArrow)
keyInput(.upArrow)
keyInput(.downArrow)
keyInput(.space)
}
}
}
}
private extension ItsRainingPolygonsApp {
func keyInput(_ key: KeyEquivalent, modifiers: EventModifiers = .none) -> some View {
keyboardShortcut(key, sender: keyInputSubject, modifiers: modifiers)
}
}
public func keyboardShortcut<Sender, Label>(
_ key: KeyEquivalent,
sender: Sender,
modifiers: EventModifiers = .none,
@ViewBuilder label: () -> Label
) -> some View where Label: View, Sender: Subject, Sender.Output == KeyEquivalent {
Button(action: { sender.send(key) }, label: label)
.keyboardShortcut(key, modifiers: modifiers)
}
public func keyboardShortcut<Sender>(
_ key: KeyEquivalent,
sender: Sender,
modifiers: EventModifiers = .none
) -> some View where Sender: Subject, Sender.Output == KeyEquivalent {
guard let nameFromKey = key.name else {
return AnyView(EmptyView())
}
return AnyView(keyboardShortcut(key, sender: sender, modifiers: modifiers) {
Text("\(nameFromKey)")
})
}
extension KeyEquivalent {
var lowerCaseName: String? {
switch self {
case .space: return "space"
case .clear: return "clear"
case .delete: return "delete"
case .deleteForward: return "delete forward"
case .downArrow: return "down arrow"
case .end: return "end"
case .escape: return "escape"
case .home: return "home"
case .leftArrow: return "left arrow"
case .pageDown: return "page down"
case .pageUp: return "page up"
case .return: return "return"
case .rightArrow: return "right arrow"
case .space: return "space"
case .tab: return "tab"
case .upArrow: return "up arrow"
default: return nil
}
}
var name: String? {
lowerCaseName?.capitalizingFirstLetter()
}
}
public extension EventModifiers {
static let none = Self()
}
extension String {
func capitalizingFirstLetter() -> String {
return prefix(1).uppercased() + self.lowercased().dropFirst()
}
mutating func capitalizeFirstLetter() {
self = self.capitalizingFirstLetter()
}
}
extension KeyEquivalent: CustomStringConvertible {
public var description: String {
name ?? "\(character)"
}
}
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answered Jul 1, 2020 at 12:03
8,32755 gold badges6060 silver badges9090 bronze badges
-
1
Code is not complete without the following two lines: ``` import SwiftUI import Combine ``` Apr 9, 2021 at 17:06 -
1
Thanks for this! I had trouble adding support for characters such as keyInput("a"). I was able to solve this by changing your code slightly. If you change default: return nil for lowerCaseName to return String(self.character).lowercased(), then you will be able to use characters.– Matt54
Mar 12, 2022 at 19:04 - @Sajjon Adding to Command
.taband.escapedon't seem to work.– Joannes
Mar 24, 2022 at 8:39 -
2
How about if a key is released? May 21, 2022 at 21:58 - This is excellent code, but I want to alert the readers this is code that publishes the given menu click (eg: Input->left arrow) to any interested child views through the environment. Dec 5, 2022 at 3:01
方法❸
There is no built-in native SwiftUI API for this, so far.
Here is just a demo of a possible approach. Tested with Xcode 11.4 / macOS 10.15.4
struct KeyEventHandling: NSViewRepresentable {
class KeyView: NSView {
override var acceptsFirstResponder: Bool { true }
override func keyDown(with event: NSEvent) {
print(">> key \(event.charactersIgnoringModifiers ?? "")")
}
}
func makeNSView(context: Context) -> NSView {
let view = KeyView()
DispatchQueue.main.async { // wait till next event cycle
view.window?.makeFirstResponder(view)
}
return view
}
func updateNSView(_ nsView: NSView, context: Context) {
}
}
struct TestKeyboardEventHandling: View {
var body: some View {
Text("Hello, World!")
.background(KeyEventHandling())
}
}
Output:
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answered Apr 11, 2020 at 10:25
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- thanks - unfortunately this locks up because I need to create multiple shapes and attach to shapes. The keyboard event handling should only be activated if the shape has been selected (longPress). What would be the best way to achieve this? Apr 11, 2020 at 22:34
- Ignore this I just realised I need to do this on the main layout window and send commands to the selected objects because more than one object may be selected. However there is still an issue with focus handling - how does one detect when a window loses focus ? Apr 11, 2020 at 22:55
-
4
The code works in Xcode 11.6 and macOS 10.15.6. However, there is an error sound for each key press detected.– Dummy
Aug 17, 2020 at 7:12 - The solution works but it just detects the alphas and arrow keys, those mods like fn, control, option, command keys does not work and whatever key pressed there was an error sound Aug 21, 2020 at 17:15
-
5
About the error sound: if you removesuper.keyDown(with: event)(which tells the rest responder chain that the key stroke was not handled) then the sound should no longer be emitted.– Milos
方法❹
There's another solution that is very simple but only works for particular types of keys - you'd have to experiment. Just create Buttons with .keyboardShortcut modifier, but hide them visually.
Group {
Button(action: { goAway() }) {}
.keyboardShortcut(.escape, modifiers: [])
Button(action: { goLeft() }) {}
.keyboardShortcut(.upArrow, modifiers: [])
Button(action: { goDown() }) {}
.keyboardShortcut(.downArrow, modifiers: [])
}.opacity(0)
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