我正在创建自定义textField以使其成为SwiftUI的可重用组件

SwiftUI

struct CustomTextField: View {
    var placeHolder: String
    @Binding var value: String

    var lineColor: Color
    var width: CGFloat

    var body: some View {
        VStack {
            TextField(self.placeHolder, text: $value)
            .padding()
            .font(.title)

            Rectangle().frame(height: self.width)
                .padding(.horizontal, 20).foregroundColor(self.lineColor)
        }
    }
}

用法：

@Binding var userName: String
@Binding var password: String

var body: some View {
    VStack(alignment: .center) {
        CustomTextField(placeHolder: "Username", value: $userName, lineColor: .white, width: 2)
        CustomTextField(placeHolder: "Password", value: $password, lineColor: .white, width: 2)
    }
}

斯威夫特5.0

我在这里使用视觉格式语言（VFL），这将允许在any中添加一行UIControl。

您可以创建一个UIView扩展类，例如UIView+Extention.swift

import UIKit

enum LINE_POSITION {
    case LINE_POSITION_TOP
    case LINE_POSITION_BOTTOM
}

extension UIView {
    func addLine(position : LINE_POSITION, color: UIColor, width: Double) {
        let lineView = UIView()
        lineView.backgroundColor = color
        lineView.translatesAutoresizingMaskIntoConstraints = false // This is important!
        self.addSubview(lineView)

        let metrics = ["width" : NSNumber(value: width)]
        let views = ["lineView" : lineView]
        self.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[lineView]|", options:NSLayoutConstraint.FormatOptions(rawValue: 0), metrics:metrics, views:views))

        switch position {
        case .LINE_POSITION_TOP:
            self.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[lineView(width)]", options:NSLayoutConstraint.FormatOptions(rawValue: 0), metrics:metrics, views:views))
            break
        case .LINE_POSITION_BOTTOM:
            self.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:[lineView(width)]|", options:NSLayoutConstraint.FormatOptions(rawValue: 0), metrics:metrics, views:views))
            break
        }
    }
}

用法：

textField.addLine(position: .LINE_POSITION_BOTTOM, color: .darkGray, width: 0.5)

目标C：

您可以将此帮助程序方法添加到全局帮助程序类（我使用了全局类方法）或同一视图控制器中（使用实例方法）。

typedef enum : NSUInteger {
    LINE_POSITION_TOP,
    LINE_POSITION_BOTTOM
} LINE_POSITION;


- (void) addLine:(UIView *)view atPosition:(LINE_POSITION)position withColor:(UIColor *)color lineWitdh:(CGFloat)width {
    // Add line
    UIView *lineView = [[UIView alloc] init];
    [lineView setBackgroundColor:color];
    [lineView setTranslatesAutoresizingMaskIntoConstraints:NO];
    [view addSubview:lineView];

    NSDictionary *metrics = @{@"width" : [NSNumber numberWithFloat:width]};
    NSDictionary *views = @{@"lineView" : lineView};
    [view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[lineView]|" options: 0 metrics:metrics views:views]];

    switch (position) {
        case LINE_POSITION_TOP:
            [view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[lineView(width)]" options: 0 metrics:metrics views:views]];
            break;

        case LINE_POSITION_BOTTOM:
            [view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[lineView(width)]|" options: 0 metrics:metrics views:views]];
            break;
        default: break;
    }
}

用法：

[self addLine:self.textField atPosition:LINE_POSITION_TOP withColor:[UIColor darkGrayColor] lineWitdh:0.5];

Xamarin代码：

 var border = new CALayer();
 nfloat width = 2;
 border.BorderColor = UIColor.Black.CGColor;
 border.Frame = new CoreGraphics.CGRect(0, textField.Frame.Size.Height - width, textField.Frame.Size.Width, textField.Frame.Size.Height);
 border.BorderWidth = width;
 textField.Layer.AddSublayer(border);
 textField.Layer.MasksToBounds = true;