2020年开发笔记第一期

SwiftUI中怎么设置选中图片的颜色？

public func accentColor(_ accentColor: Color?) -> some View

Example

import SwiftUI
/// 自定义的Tab
struct CustomTabView<Content:View>: View {
    ///需要展示的内容元祖数组
    /// - Parameter title: 显示标题
    /// - Parameter image: 默认的显示图片
    /// - Parameter selectImage: 选中的图片 图片颜色将由`selectColor`设置
    /// - Parameter content: 对应的内容试图
    let contents:[(title:String, image:UIImage, selectImage:UIImage, content:Content)]
    /// 设置选中图片的前景色
    let selectColor:UIColor
    @State var tabIndex:Int = 0
    var body: some View {
        TabView(selection: $tabIndex) {
            ForEach(0 ..< contents.count) { index in
                contents[index].3
                    .tabItem {
                        TabItemView(title: contents[index].0,
                                    image: contents[index].1,
                                    selectImage: contents[index].2,
                                    index: index,
                                    currentIndex: $tabIndex)
                    }
                    .tag(index)
            }
        }.accentColor(Color(selectColor))
    }
    
}

extension CustomTabView {
    struct TabItemView: View {
        let title:String
        let image:UIImage
        let selectImage:UIImage
        let index:Int
        @Binding var currentIndex:Int
        var body: some View {
            VStack{
                if (currentIndex == index) {
                    Image(uiImage: selectImage)
                } else {
                    Image(uiImage: image.withRenderingMode(.alwaysTemplate))
                }
                Text(title)
            }
        }
    }
}

struct CustomTabView_Previews: PreviewProvider {
    static var previews: some View {
        CustomTabView(contents: [
            ("首页",#imageLiteral(resourceName: "icon_nav_food1"),#imageLiteral(resourceName: "icon_nav_food2"),Text("1")),
            ("首页",#imageLiteral(resourceName: "icon_nav_food1"),#imageLiteral(resourceName: "icon_nav_food2"),Text("2"))
        ], selectColor: .red)
    }
}

Swift使用#if DEBUG

1 第一步在Build Settings->Swift Compiler - Custom Flags->"Other Swift Flags" 在Debug新增"-DDBUG"或者"-D DEBUG"
2 第二部Build Settings->Apple LLVM x.x - Preprocessiong->Preprocessor Macros在Debug新增"DEBUG=1"

Flutter 获取当前Widget所有的子树

对于我们常用的StatefulWidget和StatelessWidget我们可以通过下面方法

createElement().debugGetDiagnosticChain()

SwiftUI cornerRadius方法无法给UIViewRepresentable的UIView生成圆角

需要用UIView的方法设置圆角

view.layer.masksToBounds = true
view.layer.cornerRadius = cornerRadius

UIScroolView实现自定义分页

public func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        /// 实现自定义分页
        if velocity != .zero {
            /// 如果velocity不为空 则代表是用户快速拖动离开的 则滚动到下一个位置
            /// 获取到当前的索引
            guard let currentIndex = currentShopIndex else {
                return
            }
            var index:Int
            if velocity.x > 0 {
                index = currentIndex + 1
            } else {
                index = currentIndex - 1
            }
            index = max(0, index)
            index = min(index, self.currentDisplayModels.count - 1)
            let point = scrollCellPoint(index: index)
            targetContentOffset.pointee = point
        }
    }

SwiftUI 自定义UINavigationBar背景颜色

struct NavigationBarModifier: ViewModifier {
    var backgroundColor: UIColor?
    init( backgroundColor: UIColor?) {
        self.backgroundColor = backgroundColor
        let coloredAppearance = UINavigationBarAppearance()
        coloredAppearance.configureWithTransparentBackground()
        coloredAppearance.backgroundColor = .clear
        coloredAppearance.titleTextAttributes = [.foregroundColor: UIColor.white]
        coloredAppearance.largeTitleTextAttributes = [.foregroundColor: UIColor.white]
        
        UINavigationBar.appearance().standardAppearance = coloredAppearance
        UINavigationBar.appearance().compactAppearance = coloredAppearance
        UINavigationBar.appearance().scrollEdgeAppearance = coloredAppearance
        UINavigationBar.appearance().tintColor = .white

    }
    
    func body(content: Content) -> some View {
        ZStack{
            content
            VStack {
                GeometryReader { geometry in
                    Color(self.backgroundColor ?? .clear)
                        .frame(height: geometry.safeAreaInsets.top)
                        .edgesIgnoringSafeArea(.top)
                    Spacer()
                }
            }
        }
    }
}

extension View {
    public func navigationBarBackgroundColor(_ backgroundColor: UIColor?) -> some View {
        self.modifier(NavigationBarModifier(backgroundColor: backgroundColor))
    }
}

SwiftUI .position 定位不准确

因为position是按照中心点进行偏移定位的