簡(jiǎn)單tabView使用
1、點(diǎn)擊第一個(gè)頁面，角標(biāo)數(shù)逐次加1
2、再次點(diǎn)擊第一個(gè)tabItem，tabitem角標(biāo)置零消失
3、點(diǎn)擊其他tabItem，正常換頁面，但是不會(huì)影響第一個(gè)頁面角標(biāo)
??注意：badge是在iOS15.0之后才支持

第一個(gè)頁面

點(diǎn)擊第一個(gè)頁面，角標(biāo)加1

第二個(gè)頁面

第三個(gè)頁面

struct MenuVC: View {
    
    @State private var selectedTab = 0
    @AppStorage("num") var num:Int = 0
    
    var body: some View {
        
        let selection = Binding<Int>(
            get: { self.selectedTab },
            set: { self.selectedTab = $0
                print("Pressed tab: \($0)")
                if self.selectedTab == 0 {
                    num = 0
                }
            })
        
        TabView(selection: selection) {
            one()
                .tabItem {
                    Group{
                        Text("phone")
                        Image(systemName: "phone")
                    }
                }.badge(num)
                .tag(0)
                
            two()
                .tabItem {
                    Text("message")
                    Image(systemName: "message")
                }.onTapGesture {
                    num += 1
                }
                .tag(1)

            three()
                .tabItem {
                    Text("person")
                    Image(systemName: "person")
                }.tag(2)
        }
        
    }
}

struct one : View {
    
    @AppStorage("num") var num:Int = 0
    var body: some View {
        
        ZStack {
            Color.red
            
            Image(systemName: "phone")
                .resizable()
                .scaledToFit()
                .frame(width: 100, height: 100)
                .foregroundColor(.white)
            Text("\(num)").offset(x: 0, y: 100)
                .foregroundColor(.white)
                .font(.largeTitle)
        }.onTapGesture {
            num += 1
        }
    }
}

struct two : View {
    
    var body: some View {
        
        ZStack {
            Color.blue
            
            Image(systemName: "message")
                .resizable()
                .scaledToFit()
                .frame(width: 100, height: 100)
                .foregroundColor(.white)
        }
    }
}

struct three : View {
    
    var body: some View {
        
        ZStack {
            Color.green
            
            Image(systemName: "person")
                .resizable()
                .scaledToFit()
                .frame(width: 100, height: 100)
                .foregroundColor(.white)
        }
    }
}