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

Question

我在带有 Swift-4

的 MacOS 应用程序上有一个 NSTextField

它的用途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

您可以重写 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，您可以使用视图 window fieldEditor:

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，您需要将视图控制器设置为它的委托并将其委托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 }
}

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

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