值更改时 Swiftui Textfield 不更新

发布于 2025-01-10 05:58:43 字数 904 浏览 1 评论 0原文

我的表单上有一个文本字段，用户可以在其中输入值，但我还想使用按钮更新文本字段的内容。

这是我的代码：

struct test: View {
@State private var amount: Double = 0.0

var body: some View {
    Form {
        VStack {
            HStack {
                Text("Amount EUR")
                Spacer()
                TextField("Type amount", value: $amount, format: .number)
                    .keyboardType(.numberPad)
                    .multilineTextAlignment(.trailing)
            }
            
            Text("Set MAX (999)")
                .frame(maxWidth: .infinity, alignment: .leading)
                .onTapGesture {
                    print("before tap \(amount )")
                    amount = 999
                    print("after tap \(amount)")
                }
            
        }
    }
}

当我刚刚启动应用程序时，第一次点击文本会将文本字段更新为 999，但之后它就不再起作用了。 amount 值已正确更新，但文本字段未反映更改。

你能解释一下吗？

原文

I have a textfield on a form where user can type value, but I would also like to update the content of the textfield with a button.

Here is my code :

struct test: View {
@State private var amount: Double = 0.0

var body: some View {
    Form {
        VStack {
            HStack {
                Text("Amount EUR")
                Spacer()
                TextField("Type amount", value: $amount, format: .number)
                    .keyboardType(.numberPad)
                    .multilineTextAlignment(.trailing)
            }
            
            Text("Set MAX (999)")
                .frame(maxWidth: .infinity, alignment: .leading)
                .onTapGesture {
                    print("before tap \(amount )")
                    amount = 999
                    print("after tap \(amount)")
                }
            
        }
    }
}

When I just launch the app, the first tap on the Text updates the textfield with 999, but after it does not work anymore.
The amount value is correctly updated but the textfield does not reflect the change.

Would you have an explanation ?

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尐籹人 2025-01-17 05:58:43

答案很简单，TextFields 在聚焦时不会更新。要解决此问题，您需要将 @FocusState 合并到视图中，并导致 TextField 在更新变量之前失去焦点。您可以在点击 TextField 之前点击 Text 在自己的视图中进行测试。你会看到它更新得很好。

struct ButtonUpdateTextField: View {
    @State private var amount: Double = 0.0
    @FocusState var isFocused: Bool // <-- add here
    
    var body: some View {
        Form {
            VStack {
                HStack {
                    Text("Amount EUR")
                    Spacer()
                    TextField("Type amount", value: $amount, format: .number)
                        .keyboardType(.numberPad)
                        .multilineTextAlignment(.trailing)
                        .focused($isFocused) // <-- add here
                }
                
                Text("Set MAX (999)")
                    .frame(maxWidth: .infinity, alignment: .leading)
                    .onTapGesture {
                        print("before tap \(amount )")
                        isFocused = false // <-- add here
                        amount = 999
                        print("after tap \(amount)")
                    }
                
            }
        }
    }
}

The answer is simply that TextFields don't update while they are in focus. To solve this problem, you need to incorporate a @FocusState in to the view, and cause the TextField to lose focus right before updating the variable. You can test it in your own view by tapping your Text prior to tapping in to the TextField. You will see it updates just fine.

struct ButtonUpdateTextField: View {
    @State private var amount: Double = 0.0
    @FocusState var isFocused: Bool // <-- add here
    
    var body: some View {
        Form {
            VStack {
                HStack {
                    Text("Amount EUR")
                    Spacer()
                    TextField("Type amount", value: $amount, format: .number)
                        .keyboardType(.numberPad)
                        .multilineTextAlignment(.trailing)
                        .focused($isFocused) // <-- add here
                }
                
                Text("Set MAX (999)")
                    .frame(maxWidth: .infinity, alignment: .leading)
                    .onTapGesture {
                        print("before tap \(amount )")
                        isFocused = false // <-- add here
                        amount = 999
                        print("after tap \(amount)")
                    }
                
            }
        }
    }
}

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