我们如何在 SwiftUI 中使用 GeometryReader 获取和读取文本的大小? [英] How we can get and read size of a Text with GeometryReader in SwiftUI?

问题描述

我正在尝试根据文本字体的大小读取文本的宽度，正如我们所知，GeometryReader 将所有可能的给定位置交给他，在此代码中，它仅采用给定的帧大小，我通过了它，但是它不需要我的文本大小！我在做什么错?我什么 GeometryReader 开始只读取我的文本大小！不是他自己的帧宽度.

I am trying to read the width of my Text depending on size of Text Font, As we know GeometryReader takes all possible given place to him, in this codes it just take himself the given frame size, that I passed it, but it does not take size of my Text! what I am doing Wrong? I what GeometryReader start reading my Text size only! not himself frame width.

这是我的代码:

struct ContentView: View {
    @State var fontSize: CGFloat = 20.0

    var body: some View {
        Spacer()

        textWidthGeometryReader(fontSize: $fontSize)

        Spacer()

        Text("Font size:" + "\(fontSize)")

        Slider(value: $fontSize, in: 20...40, step: 1)
            .padding()

        Spacer()
    }
}

struct textWidthGeometryReader: View {
    @Binding var fontSize: CGFloat

    var body: some View {
        GeometryReader { inSideGeometry in

            Text("width of Text:" + String(format: "%.0f", inSideGeometry.size.width))
                .font(.system(size: fontSize))
                .background(Color.yellow)
                .position(x: inSideGeometry.size.width / 2, y: inSideGeometry.size.height / 2)
        }
        .frame(width: 400, height: 300, alignment: .center)
        .background(Color.gray)
        .cornerRadius(20)
    }
}

推荐答案

您可以使用视图首选项.

You can use view preferences.

1. 首先为视图大小创建一个自定义的PreferenceKey:

struct ViewSizeKey: PreferenceKey {
    static var defaultValue: CGSize = .zero

    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {
        value = nextValue()
    }
}

1. 创建一个将计算其大小并将其分配给ViewSizeKey的视图:

struct ViewGeometry: View {
    var body: some View {
        GeometryReader { geometry in
            Color.clear
                .preference(key: ViewSizeKey.self, value: geometry.size)
        }
    }
}

1. 在您的视图中使用它们:

struct ContentView: View {
    @State var fontSize: CGFloat = 20.0
    @State var textSize: CGSize = .zero

    var body: some View {
        Spacer()
        Text("width of Text:" + String(format: "%.0f", textSize.width))
            .font(.system(size: fontSize))
            .background(ViewGeometry())
            .onPreferenceChange(ViewSizeKey.self) {
                textSize = $0
            }
        Spacer()
        Text("Font size:" + "\(fontSize)")
        Slider(value: $fontSize, in: 20...40, step: 1)
            .padding()
        Spacer()
    }
}

---

查看首选项是一个相当高级的话题.你可以在这里找到更详细的解释:

---

View Preferences is quite an advanced topic. You can find a more detailed explanation here:

• 视图偏好的魔力SwiftUI
• 检查视图树 - 第 1 部分:PreferenceKey

这篇关于我们如何在 SwiftUI 中使用 GeometryReader 获取和读取文本的大小?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！