如何在 Hstack SwiftUI 中将最后一个索引显示为默认值

Posted 2023-02-24

【中文标题】如何在 Hstack SwiftUI 中将最后一个索引显示为默认值

【英文标题】：How to show last index as default in Hstack SwiftUI

【发布时间】：2021-07-07 08:10:41

【问题描述】：

我写了下面的代码，并在scrollview上将数据显示到Hstack中

在我的情况下，我从服务调用中收到 10 个项目，并在 Hstack 中显示了这些项目 当用户第一次进入屏幕时，前 5 天可见，

但我需要先显示最后 5 个日期。

第一次需要看到最后一个索引（进入屏幕时）。

即需要首先显示当前日期

HStack(alignment:.center)
                GeometryReader proxy in
                    ScrollView(.horizontal) 
                        
                        LazyHStack 
                            ForEach(days.indices, id: \.self)  i in
                                CalendarView(
                                    number: days[i].number,
                                    days: days[i].weekday,
                                    color: days[i].isToday ? #colorLiteral(red: 0.9060331583, green: 0.2547450066, blue: 0.3359550834, alpha: 1) : #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1),
                                    textcolor: days[i].isToday ? #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1) : #colorLiteral(red: 0, green: 0, blue: 0, alpha: 1), proxy: proxy
                                )
                                .onTapGesture
                                    print(days[i])
                                    // this is just for replacing the current selection
                                    for j in days.indices  days[j].isToday = false 
                                    days[i].isToday = true
                                
                            
                        
                    
                
            
            .padding([.trailing,.leading],3)

【参考方案1】：

使用 ScrollViewReader

HStack(alignment:.center)
    GeometryReader proxy in
        ScrollView(.horizontal) 
            ScrollViewReader  value in // <== Here
                LazyHStack 
                    ForEach(days.indices, id: \.self)  i in
                        CalendarView(
                            number: days[i].number,
                            days: days[i].weekday,
                            color: days[i].isToday ? #colorLiteral(red: 0.9060331583, green: 0.2547450066, blue: 0.3359550834, alpha: 1) : #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1),
                            textcolor: days[i].isToday ? #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1) : #colorLiteral(red: 0, green: 0, blue: 0, alpha: 1), proxy: proxy
                        )
                        .id(i) // <== Here
                        .onTapGesture
                            print(days[i])
                            // this is just for replacing the current selection
                            for j in days.indices  days[j].isToday = false 
                            days[i].isToday = true
                        
                    
                .onAppear() // <== Here
                    value.scrollTo(days.count - 1) // <== Here
                
            
        
    

.padding([.trailing,.leading],3)