Validate input

compose/snippets/src/main/java/com/example/compose/snippets/text/TextSnippets.kt

@@ -18,6 +18,7 @@
 
 package com.example.compose.snippets.text
 
+import android.graphics.Typeface
 import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.background
 import androidx.compose.foundation.basicMarquee
@@ -43,6 +44,7 @@ import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextField
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -86,6 +88,7 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.em
 import androidx.compose.ui.unit.sp
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewmodel.compose.viewModel
 
 /**
  * This file lets DevRel track changes to snippets present in
@@ -523,7 +526,7 @@ private object TextEffectiveStateManagement1 {
 private object TextEffectiveStateManagement2 {
     class UserRepository
 
-    val viewModel = SignUpViewModel(UserRepository())
+    private val viewModel = SignUpViewModel(UserRepository())
 
     // [START android_compose_text_state_management]
     // SignUpViewModel.kt
@@ -851,7 +854,7 @@ class NanpVisualTransformation() : VisualTransformation {
 }
 // [END android_compose_text_auto_format_phone_number_transformtext]
 
-private val firaSansFamily = FontFamily()
+private val firaSansFamily = FontFamily(typeface = Typeface.DEFAULT)
 
 val LightBlue = Color(0xFF0066FF)
 val Purple = Color(0xFF800080)
@@ -888,3 +891,56 @@ fun PasswordTextField() {
     )
 }
 // [END android_compose_text_showhidepassword]
+
+// [START android_compose_text_auto_format_phone_number_validatetext]
+class EmailViewModel : ViewModel() {
+    var email by mutableStateOf("")
+        private set
+
+    val emailHasErrors by derivedStateOf {
+        if (email.isNotEmpty()) {
+            // Email is considered erroneous until it completely matches EMAIL_ADDRESS.
+            !android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches()
+        } else {
+            false
+        }
+    }
+
+    fun updateEmail(input: String) {
+        email = input
+    }
+}
+
+@Composable
+fun ValidatingInputTextField(
+    email: String,
+    updateState: (String) -> Unit,
+    validatorHasErrors: Boolean
+) {
+    OutlinedTextField(
+        modifier = Modifier
+            .fillMaxWidth()
+            .padding(10.dp),
+        value = email,
+        onValueChange = updateState,
+        label = { Text("Email") },
+        isError = validatorHasErrors,
+        supportingText = {
+            if (validatorHasErrors) {
+                Text("Incorrect email format.")
+            }
+        }
+    )
+}
+
+@Preview
+@Composable
+fun ValidateInput() {
+    val emailViewModel: EmailViewModel = viewModel<EmailViewModel>()
+    ValidatingInputTextField(
+        email = emailViewModel.email,
+        updateState = { input -> emailViewModel.updateEmail(input) },
+        validatorHasErrors = emailViewModel.emailHasErrors
+    )
+}
+// [END android_compose_text_auto_format_phone_number_validatetext]