Base on macOS 10.15, Xcode 11.7.

异常描述

1、当程序运行在非活跃状态时，且 NSWindow 为默认样式（可关闭、缩放、有标题栏等）。

此时如果点击 NSWindow 中的按钮，一般情况下会将该 NSWindow 变成活跃状态，同时触发按钮的 action 一次。但对于 PlainButtonStyle 样式的按钮，却无法触发其事件函数！

2、当程序运行在非活跃状态时，且 NSWindow 为空样式（styleMask = []），且允许拖动（isMovableByWindowBackground = true）。

此时如果点击 NSWindow 中的按钮，一般情况下会将该 NSWindow 变成活跃状态，同时触发按钮的 action 一次。但对于 PlainButtonStyle 样式的按钮，却会触发其事件函数两次！

测试代码

ContentView.swift

AppDelegate.swift

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EnlighterJS 3 Syntax Highlighter

import SwiftUI

struct ContentView: View {

var body: some View {

VStack {

Button("Normal") {

NSLog("normal Button clicked")

}

Button(action: {

NSLog("LinkButton clicked")

}){

Text("LinkButton")

}.buttonStyle(LinkButtonStyle())

Button(action: {

NSLog("BorderedButton clicked")

}){

Text("BorderedButton")

}.buttonStyle(BorderedButtonStyle())

Button(action: {

NSLog("BorderlessButton clicked")

}){

Text("BorderlessButton")

}.buttonStyle(BorderlessButtonStyle())

Button(action: {

NSLog("PlainButton clicked")

}){

Text("PlainButton")

}.buttonStyle(PlainButtonStyle())

}.frame(width: 400, height: 300)

}

}

import SwiftUI struct ContentView: View { var body: some View { VStack { Button("Normal") { NSLog("normal Button clicked") } Button(action: { NSLog("LinkButton clicked") }){ Text("LinkButton") }.buttonStyle(LinkButtonStyle()) Button(action: { NSLog("BorderedButton clicked") }){ Text("BorderedButton") }.buttonStyle(BorderedButtonStyle()) Button(action: { NSLog("BorderlessButton clicked") }){ Text("BorderlessButton") }.buttonStyle(BorderlessButtonStyle()) Button(action: { NSLog("PlainButton clicked") }){ Text("PlainButton") }.buttonStyle(PlainButtonStyle()) }.frame(width: 400, height: 300) } }

import Cocoa

import SwiftUI

@NSApplicationMain

class AppDelegate: NSObject, NSApplicationDelegate {

var window: NSWindow!

func applicationDidFinishLaunching(_ aNotification: Notification) {

// Create the SwiftUI view that provides the window contents.

let contentView = ContentView()

// When App runs in backend, PlainButtonStyle Button could be triggered

window = NSWindow(

contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),

styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],

backing: .buffered, defer: false)

// When App runs in backend, PlainButtonStyle Button trigger twice

// window = NSWindow(

// contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),

// styleMask: [],

// backing: .buffered, defer: false)

// window.isMovableByWindowBackground = true

window.center()

window.setFrameAutosaveName("Main Window")

window.contentView = NSHostingView(rootView: contentView)

window.makeKeyAndOrderFront(nil)

}

func applicationWillTerminate(_ aNotification: Notification) {

// Insert code here to tear down your application

}

}

import Cocoa import SwiftUI @NSApplicationMain class AppDelegate: NSObject, NSApplicationDelegate { var window: NSWindow! func applicationDidFinishLaunching(_ aNotification: Notification) { // Create the SwiftUI view that provides the window contents. let contentView = ContentView() // When App runs in backend, PlainButtonStyle Button could be triggered window = NSWindow( contentRect: NSRect(x: 0, y: 0, width: 480, height: 300), styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView], backing: .buffered, defer: false) // When App runs in backend, PlainButtonStyle Button trigger twice // window = NSWindow( // contentRect: NSRect(x: 0, y: 0, width: 480, height: 300), // styleMask: [], // backing: .buffered, defer: false) // window.isMovableByWindowBackground = true window.center() window.setFrameAutosaveName("Main Window") window.contentView = NSHostingView(rootView: contentView) window.makeKeyAndOrderFront(nil) } func applicationWillTerminate(_ aNotification: Notification) { // Insert code here to tear down your application } }

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Button("Normal") {
                NSLog("normal Button clicked")
            }
            
            Button(action: {
                NSLog("LinkButton clicked")
            }){
                Text("LinkButton")
            }.buttonStyle(LinkButtonStyle())
            
            Button(action: {
                NSLog("BorderedButton clicked")
            }){
                Text("BorderedButton")
            }.buttonStyle(BorderedButtonStyle())
            
            Button(action: {
                NSLog("BorderlessButton clicked")
            }){
                Text("BorderlessButton")
            }.buttonStyle(BorderlessButtonStyle())
            
            Button(action: {
                NSLog("PlainButton clicked")
            }){
                Text("PlainButton")
            }.buttonStyle(PlainButtonStyle())
            
        }.frame(width: 400, height: 300)
    }
}

import Cocoa
import SwiftUI

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    var window: NSWindow!


    func applicationDidFinishLaunching(_ aNotification: Notification) {
        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView()

         //  When App runs in backend, PlainButtonStyle Button could be triggered
        window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered, defer: false)
        
        //  When App runs in backend, PlainButtonStyle Button trigger twice
//        window = NSWindow(
//            contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
//            styleMask: [],
//            backing: .buffered, defer: false)
//        window.isMovableByWindowBackground = true
        
        
        window.center()
        window.setFrameAutosaveName("Main Window")
        window.contentView = NSHostingView(rootView: contentView)
        window.makeKeyAndOrderFront(nil)
    }

    func applicationWillTerminate(_ aNotification: Notification) {
        // Insert code here to tear down your application
    }
}

解决办法

我把项目中的所有 PlainButtonStyle 按钮全部改成 BorderlessButtonStyle 了。