Code snippet for Compose doc at https://developer.android.com/quick-guides/content/animate-text?hl=en (Animate text character-by-character).

This commit slightly modifies (makes buildable in our repo) the existing code on the current DAC page.

That code, in turn, was BNR's simplified version of Xoogler astamato's Medium article at https://medium.com/androiddevelopers/effective-state-management-for-textfield-in-compose-d6e5b070fbe5

Author: thedmail

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

@@ -38,6 +38,7 @@ 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
@@ -839,3 +840,56 @@ private val firaSansFamily = FontFamily()
 
 val LightBlue = Color(0xFF0066FF)
 val Purple = Color(0xFF800080)
+
+// [START android_compose_text_auto_format_phone_number_validatetext]
+@Composable
+fun ValidateInput () {
+    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
+    ) {
+        val viewModel = EmailViewModel()
+        OutlinedTextField(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(10.dp),
+            value = email,
+            onValueChange = updateState,
+            label = { Text("Email") },
+            isError = validatorHasErrors,
+            supportingText = {
+                if (validatorHasErrors) {
+                    Text("Incorrect email format.")
+                }
+            }
+        )
+
+
+        ValidatingInputTextField(
+            email = viewModel.email,
+            updateState = { input -> viewModel.updateEmail(input) },
+            validatorHasErrors = viewModel.emailHasErrors
+        )
+    }
+}
+// [END android_compose_text_auto_format_phone_number_validatetext]