Swift-4 MacOS 检测鼠标滚轮在 NSTextField 上滚动？

Question

我在使用 Swift-4 的 MacOS 应用程序上有一个 NSTextField

它的目的是让用户输入一个数字。有没有办法根据鼠标滚轮的向上滚动或向下滚动来更改数字？

Answer 1

您可以覆盖 scrollWheel(with event: NSEvent) 方法并检查 event.deltaY 是正数还是负数并增加或减少 textField 值:

import Cocoa
class ViewController: NSViewController {
    @IBOutlet weak var textField: NSTextField!
    override func viewDidLoad() {
        super.viewDidLoad()
        textField.stringValue = "0"
    }
    override func scrollWheel(with event: NSEvent) {
        super.scrollWheel(with: event)
        if var value = Int(textField.stringValue) {
            if event.deltaY > 0 { value += 1 }
            if event.deltaY < 0 { value -= 1 }
            textField.stringValue = String(value)
            print(value)
        }
    }
}

如果您只想更改具有焦点的字段，您可以使用 View 窗口字段编辑器:

if let text = view.window?.fieldEditor(false, for: nil) {
    if var value = Int(text.string) {
        if event.deltaY > 0 { value += 1 }
        if event.deltaY < 0 { value -= 1 }
        text.string = String(value)
        print(value)
    }
}

如果您想将滚动限制为仅特定字段，您需要将 View Controller 设置为它的委托(delegate)并将其委托(delegate)与文本字段对象进行比较:

import Cocoa
class ViewController: NSViewController, NSTextFieldDelegate {
    @IBOutlet weak var textField1: NSTextField!
    @IBOutlet weak var textField2: NSTextField!
    override func viewDidAppear() {
        super.viewDidAppear()
        textField1.delegate = self
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        textField1.stringValue = "0"
        textField2.stringValue = "0"
    }
    override func scrollWheel(with event: NSEvent) {
        super.scrollWheel(with: event)
        NSSound(named: "Tink")?.stop
        if view.window?.firstResponder?.textView?.delegate === textField1,
            let text = view.window?.fieldEditor(false, for: nil),
            var value = Int(text.string) {
            if event.deltaY < 0 { value += 1 }
            if event.deltaY > 0 { value -= 1 }
            NSSound(named: "Tink")?.play()
            text.string = String(value)
            print(value)
        }
    }
}

---

extension NSResponder {
    var textView: NSTextView? { return self as? NSTextView }
}