SwiftUI Sheet 与 fullScreenCover 合集

fullScreenCover

参考：How to present a full screen modal view using fullScreenCover()

与 sheet 一致。

Custom Sheet

参考：

• Xcode 14.3 新功能：輕鬆客製化 SwiftUI Bottom Sheet 背景及滾動行為
• How to Display a Bottom Sheet Using SwiftUI

.presentationBackground(.thinMaterial)			// 模糊效果
.presentationBackground(.yellow)				// 设置颜色
.presentationCornerRadius(8)					// 圆角
// When it first appears, the bottom sheet is displayed in medium size. You can expand it to large size by dragging the sheet.
.presentationDetents([.medium, .large])
// supports 4 different sizes including: around 10% of the screen height；a fixed height of 200 points；the standard Medium and Large sizes
.presentationDetents([.fraction(0.1), .height(200), .medium, .large])
.presentationDragIndicator(.hidden) 			// 隐藏指示器
.presentationDragIndicator(.visible)

dismiss()

在 sheet 和 fullScreenCover 中都可以使用

@Environment(\.presentationMode) var presentationMode
// Use: presentationMode.wrappedValue.dismiss()
// 该方法在 iOS 15.0 后被 dismiss() 替代

@Environment(\.dismiss) var dismiss
// Use: dismiss()

.popover

目前看下来 .popover 与 .sheet 没什么区别

struct ContentView: View {
    @State private var showingPopover = false
    var body: some View {
        Button("Show Menu") {
            showingPopover = true
        }
        .popover(isPresented: $showingPopover) {
            Text("Your content here")
                .font(.headline)
                .padding()
        }
    }
}

报错提示 Attempt to present … on … while a presentation is in progress.

参考：

1. How to Fix SwiftUI Sheet Dismissing on First Launch
2. SwiftUI Presentation / Attempt to present View on … which is already presenting

Your .sheet(isPresented: $showingOtherView) { is inside the ForEach. When you set showingOtherView to true, all the sheets in the ForEach will try to present. That’s a looooot of sheets.

传入 sheet 的参数赋值无效

struct ContentView: View {
    
    @State private var item: Item?
    @State private var isPresented: Bool = false
    
    var body: some View {
        Button("Sheet Button") {
            let newItem = Item(text: "Hello World")
            item = newItem
            isPresented.toggle()
        }
        .sheet(isPresented: $isPresented) {
            if item != nil {
                Text(item!.text)
            } else {
                Text("item is nil")
            }
        }
    }
}

struct Item: Identifiable {
    let id: UUID = UUID()
    let text: String
}

上述在弹出 sheet 后，显示的内容为「item is nil」。原因是:

The issue is due to sheet is created before button clicked. The solution for your scenario is to use .sheet(item: approach.

参考：Why does state reset to nil after assignment

解决方案：

struct ContentView: View {
    
    @State private var item: Item?
    
    var body: some View {
        Button("Sheet Button") {
            let newItem = Item(text: "Hello World")
            item = newItem
        }
        .sheet(item: $item) { item in
            Text(item.text)
        }
    }
}

struct Item: Identifiable {
    let id: UUID = UUID()
    let text: String
}

这个用法一般用在 selectedItem 上。