从HealthKit查询更新SwiftUI

import SwiftUI
import HealthKit

struct ContentView: View {
    @State private var steps: Int = 0
    
    var body: some View {
        VStack {
            Text("Steps Today: \(steps)")
                .font(.largeTitle)
                .padding()
            Button(action: {
                self.fetchSteps()
            }) {
                Text("Fetch Steps")
                    .font(.headline)
                    .padding()
                    .background(Color.blue)
                    .foregroundColor(.white)
                    .cornerRadius(10)
            }
        }
    }
    
    func fetchSteps() {
        guard HKHealthStore.isHealthDataAvailable() else {
            print("Health data is not available on this device.")
            return
        }
        
        let stepsQuantityType = HKQuantityType.quantityType(forIdentifier: .stepCount)!
        let healthStore = HKHealthStore()
        
        healthStore.requestAuthorization(toShare: nil, read: Set([stepsQuantityType])) { (success, error) in
            if !success {
                print("Permission denied for HealthKit data.")
                return
            }
            
            let now = Date()
            let calendar = Calendar.current
            let components = calendar.dateComponents([.year, .month, .day], from: now)
            let startDate = calendar.date(from: components)!
            
            let predicate = HKQuery.predicateForSamples(withStart: startDate, end: now, options: .strictStartDate)
            let query = HKStatisticsQuery(quantityType: stepsQuantityType, quantitySamplePredicate: predicate, options: .cumulativeSum) { (query, result, error) in
                guard let result = result, let sum = result.sumQuantity() else {
                    return
                }
                
                DispatchQueue.main.async {
                    self.steps = Int(sum.doubleValue(for: HKUnit.count()))
                }
            }
            
            healthStore.execute(query)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}