iOS 14 新特性（二）- WidgetKit 桌面小组件-区

假如某组件需要大中小三种类型展示不同的view，可参照此文章进行设置

关键代码

@Environment(\.widgetFamily) var family
    
    @ViewBuilder
    var body: some View {
        switch family {
        case .systemSmall:
            Text("小组件-中杯")
        case .systemMedium:
            Text("小组件-大杯")
        case .systemLarge:
            Text("小组件-特大杯")
        default:
            Text("小组件-默认给个中杯的")
        }
    }

import WidgetKit
import SwiftUI
import Intents

struct OneWordEntry: TimelineEntry {
    let date: Date
    let data: OneWord
}

struct OneWordProvider: IntentTimelineProvider {
    func placeholder(in context: Context) -> OneWordEntry {
        return OneWordEntry(date: Date(), data: OneWord(content: "人类的悲欢并不相通，我只觉得他们吵闹", length: 18))
    }
    
    func getSnapshot(for configuration: ConfigurationIntent, in context: Context, completion: @escaping (OneWordEntry) -> Void) {
        let entry = OneWordEntry(date: Date(), data: OneWord(content: "一言", length: 2))
        completion(entry)
    }
    func getTimeline(for configuration: ConfigurationIntent, in context: Context, completion: @escaping (Timeline<Entry>) -> Void) {
        let currentDate = Date()
        let refreshDate = Calendar.current.date(byAdding: .minute, value: 60, to: currentDate)!
        OneWorldLoader.fetch { result in
            let oneWord: OneWord
            if case .success(let fetchedData) = result {
                oneWord = fetchedData
            } else {
                oneWord = OneWord(content: "很遗憾本次更新失败,等待下一次更新.", length: 18)
            }
            let entry = OneWordEntry(date: currentDate,data: oneWord)
            let timeline = Timeline(entries: [entry], policy: .after(refreshDate))
            completion(timeline)
        }
    }
}

struct widgetEntryView : View {
    var entry: OneWordProvider.Entry
    
    @Environment(\.widgetFamily) var family
    
    @ViewBuilder
    var body: some View {
        switch family {
        case .systemSmall:
            Text("小组件-中杯")
        case .systemMedium:
            Text("小组件-大杯")
        case .systemLarge:
            Text("小组件-特大杯")
        default:
            Text("小组件-默认给个中杯的")
        }
    }
    
}

@main
struct widget: Widget {
    let kind: String = "widget"
    
    var body: some WidgetConfiguration {
        IntentConfiguration(kind: kind, intent: ConfigurationIntent.self, provider: OneWordProvider()) { entry in
            widgetEntryView(entry: entry)
        }
        .configurationDisplayName("My Widget")
        .description("This is an example widget.")
        .supportedFamilies([.systemSmall,.systemMedium,
                            .systemLarge
        ])
    }
}