swiftui - SwiftUI - 淡出 ScrollView

Question

我有一个生成的超大图表，我将其放入 ScrollView 以便用户可以向右滚动并查看所有值。我想通过淡出 ScrollView 向用户表明右侧还有“更多内容”。通过应用 CAGradientLayer，Swift 中的某些事情变得很简单。

我的方法是应用从清晰（从 80% 开始）到系统背景颜色（以 100% 结束）的渐变叠加。结果可以在随附的屏幕截图中看到。

问题编号 1：看起来不像它应该看起来的样子。

问题编号 2：尽管应用了 -1 的 zIndex 到叠加层，但一旦应用了叠加层，ScrollView 就不会再滚动了。

知道如何实现这一目标吗？谢谢！

这是我的代码：

struct HealthExportPreview: View {
    @ObservedObject var carbsEntries: CarbsEntries
    
    var body: some View {
        ScrollView(.horizontal) {
            HStack {
                ForEach(0..<self.carbsEntries.carbsRegime.count, id: \.self) { index in
                    ChartBar(carbsEntries: self.carbsEntries, entry: self.carbsEntries.carbsRegime[index], requiresTimeSplitting: index == self.carbsEntries.timeSplittingAfterIndex)
                }
            }
            .padding()
            .animation(.interactiveSpring())
        }
        .overlay(Rectangle()
            .fill(
                LinearGradient(gradient: Gradient(stops: [
                    .init(color: .clear, location: 0.8),
                    .init(color: Color(UIColor.systemBackground), location: 1.0)
                ]), startPoint: .leading, endPoint: .trailing)
            )
            .zIndex(-1)
        )
        .frame(height: CGFloat(carbsEntries.previewHeight + 80))
        .onAppear() {
            self.carbsEntries.fitCarbChartBars()
        }
    }
}

struct ChartBar: View {
    var carbsEntries: CarbsEntries
    var entry: (date: Date, carbs: Double)
    var requiresTimeSplitting: Bool
    
    static var timeStyle: DateFormatter {
        let formatter = DateFormatter()
        formatter.timeStyle = .short
        return formatter
    }
    
    var body: some View {
        VStack {
            Spacer()
            Text(FoodItemViewModel.doubleFormatter(numberOfDigits: entry.carbs >= 100 ? 0 : (entry.carbs >= 10 ? 1 : 2)).string(from: NSNumber(value: entry.carbs))!)
                .font(.footnote)
                .rotationEffect(.degrees(-90))
                .offset(y: self.carbsEntries.appliedMultiplier * entry.carbs <= 40 ? 0 : 40)
                .zIndex(1)
            
            if entry.carbs <= self.carbsEntries.maxCarbsWithoutSplitting {
                Rectangle()
                    .fill(Color.green)
                    .frame(width: 15, height: CGFloat(self.carbsEntries.appliedMultiplier * entry.carbs))
            } else {
                Rectangle()
                    .fill(Color.green)
                    .frame(width: 15, height: CGFloat(self.carbsEntries.getSplitBarHeight(carbs: entry.carbs)))
                    .overlay(Rectangle()
                        .fill(Color(UIColor.systemBackground))
                        .frame(width: 20, height: 5)
                        .padding([.bottom, .top], 1.0)
                        .background(Color.primary)
                        .rotationEffect(.degrees(-10))
                        .offset(y: CGFloat(self.carbsEntries.getSplitBarHeight(carbs: entry.carbs) / 2 - 10))
                )
            }
            
            if self.requiresTimeSplitting {
                Rectangle()
                    .fill(Color(UIColor.systemBackground))
                    .frame(width: 40, height: 0)
                    .padding([.top], 2.0)
                    .background(Color.primary)
                    .overlay(Rectangle()
                        .fill(Color(UIColor.systemBackground))
                        .frame(width: 20, height: 5)
                        .padding([.bottom, .top], 1.0)
                        .background(Color.black)
                        .rotationEffect(.degrees(80))
                        .offset(x: 20)
                        .zIndex(1)
                    )
            } else {
                Rectangle()
                    .fill(Color(UIColor.systemBackground))
                    .frame(width: 40, height: 0)
                    .padding([.top], 2.0)
                    .background(Color.primary)
            }
            
            Text(ChartBar.timeStyle.string(from: entry.date))
                .fixedSize()
                .layoutPriority(1)
                .font(.footnote)
                .rotationEffect(.degrees(-90))
                .offset(y: 10)
                .frame(height: 50)
                .lineLimit(1)
        }.frame(width: 30)
    }
}

标签： swiftuiscrollviewgradient

Answer 1

使用 alpha .mask 怎么样？

您可以使用 alpha 掩码代替您的 .overlay，如下所示：

.mask(
    HStack(spacing: 0) {

        // Left gradient
        LinearGradient(gradient: 
           Gradient(
               colors: [Color.black.opacity(0), Color.black]), 
               startPoint: .leading, endPoint: .trailing
           )
           .frame(width: 50)

        // Middle
        Rectangle().fill(Color.black)

        // Right gradient
        LinearGradient(gradient: 
           Gradient(
               colors: [Color.black, Color.black.opacity(0)]), 
               startPoint: .leading, endPoint: .trailing
           )
           .frame(width: 50)
    }
 )