SwiftUI饼图文本居中与选中扇区透明度调整问题求助

问题1：文本居中修复 #

当前VStack仅包裹文本内容，未占满ZStack的可用空间，导致文本无法精准对齐饼图中央。只需给VStack添加frame(maxWidth: .infinity, maxHeight: .infinity)，让它填充整个ZStack区域，内部文本自然会基于饼图范围居中：

VStack(alignment: .center) {
    Text("Token Allocation")
        .font(.callout)
        .foregroundStyle(.secondary)
    
    Text(String(format: "%.2f", selectedBalance ?? 0.0)) // 可选优化：格式化数字避免多位小数
        .font(.system(size: 20))
        .foregroundColor(.primary)
}
.frame(maxWidth: .infinity, maxHeight: .infinity) // 关键修改

问题2：扇区透明度高亮 #

通过给SectorMark添加opacity修饰符，根据当前扇区的余额是否匹配选中值动态调整透明度，同时处理selectedBalance的可选值与浮点数精度问题：

SectorMark(
    angle: .value("Balance", Int(tokenHolder.balance)!),
    innerRadius: .ratio(0.618),
    angularInset: 1.5
)
.cornerRadius(4)
.foregroundStyle(by: .value("Names", tokenHolder.name))
.opacity(
    guard let selected = selectedBalance else { return 0.3 }
    return abs(tokenHolder.balance - selected) < 0.001 ? 1.0 : 0.3
) // 未选中扇区30%透明度，选中扇区100%高亮

完整修改后的代码 #

struct TokenAllocationChartView: View {
    let tokenHolders: [Token]
    @Binding var selectedBalance: Double?
    
    var body: some View {
        ZStack {
            Chart(tokenHolders) { tokenHolder in
                SectorMark(
                    angle: .value("Balance", Int(tokenHolder.balance)!),
                    innerRadius: .ratio(0.618),
                    angularInset: 1.5
                )
                .cornerRadius(4)
                .foregroundStyle(by: .value("Names", tokenHolder.name))
                .opacity(
                    guard let selected = selectedBalance else { return 0.3 }
                    return abs(tokenHolder.balance - selected) < 0.001 ? 1.0 : 0.3
                )
            }
            .chartAngleSelection(value: $selectedBalance)
            .frame(height: 300)
            
            VStack(alignment: .center) {
                Text("Token Allocation")
                    .font(.callout)
                    .foregroundStyle(.secondary)
                
                Text(String(format: "%.2f", selectedBalance ?? 0.0))
                    .font(.system(size: 20))
                    .foregroundColor(.primary)
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
        }
    }
}

内容的提问来源于stack exchange，提问作者Alexander Paul