On Focus Lost iOS and Android

Android.kt

@OptIn(ExperimentalMaterial3Api::class)
@Composable
private fun SimpleInput(onFocusLost: ()-> Unit) {
    var textValue by remember { mutableStateOf("") }
    var previousFocus by remember { mutableStateOf(false) }

    TextField(
        value = textValue,
        onValueChange = { textValue = it },
        modifier = Modifier.onFocusChanged { it: FocusState ->
            if (previousFocus && it.isFocused.not()) {
                onFocusLost()
            }
            previousFocus = it.isFocused
        }
    )
}

iOS_15.Swift

private struct SimpleInput: View {
    @State private var text: String = ""
    @FocusState private var isFocused: Bool
    private let onFocusLost: () -> Void
    @State private var previousFocus = false

    init(onFocusLost: @escaping () -> Void) {
        self.onFocusLost = onFocusLost
    }

    var body: some View {
        TextField(
            "INPUT:",
            text: $text
        )
        .focused($isFocused)
        .onChange(of: isFocused) { newFocus in
            if (previousFocus && !newFocus) {
                self.onFocusLost()
            }
            previousFocus = newFocus
        }
    }
}

iOS_17.Swift

private struct SimpleInput: View {
    @State private var text: String = ""
    @FocusState private var isFocused: Bool
    private let onFocusLost: () -> Void

    init(onFocusLost: @escaping () -> Void) {
        self.onFocusLost = onFocusLost
    }

    var body: some View {
        TextField(
            "INPUT:",
            text: $text
        )
        .focused($isFocused)
        .onChange(of: isFocused) { previousFocus, newFocus in
            if (previousFocus && !newFocus) {
                self.onFocusLost()
            }
        }
    }
}