support using biometrics to auth

app/src/main/java/com/bintianqi/owndroid/Auth.kt

@@ -10,6 +10,7 @@ import android.widget.Toast
 import androidx.biometric.BiometricManager
 import androidx.biometric.BiometricPrompt
 import androidx.biometric.BiometricPrompt.AuthenticationCallback
+import androidx.biometric.BiometricPrompt.PromptInfo
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
@@ -22,12 +23,15 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.ComposeView
+import androidx.compose.ui.platform.LocalContext
 import androidx.core.content.ContextCompat
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentActivity
 import com.bintianqi.owndroid.ui.theme.OwnDroidTheme
+import kotlinx.coroutines.*
 
 class AuthFragment: Fragment() {
+    @OptIn(DelicateCoroutinesApi::class)
     @SuppressLint("UnrememberedMutableState")
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
         val sharedPref = context?.getSharedPreferences("data", Context.MODE_PRIVATE)!!
@@ -40,6 +44,11 @@ class AuthFragment: Fragment() {
                 fragmentTransaction.commit()
             }
         }
+        val promptInfo = PromptInfo.Builder()
+            .setTitle("Auth")
+            .setSubtitle("Auth OwnDroid with password or biometric")
+            .setConfirmationRequired(true)
+        var fallback = false
         val callback = object: AuthenticationCallback() {
             override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
                 super.onAuthenticationSucceeded(result)
@@ -48,16 +57,32 @@ class AuthFragment: Fragment() {
             override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
                 super.onAuthenticationError(errorCode, errString)
                 if(errorCode == BiometricPrompt.ERROR_NO_DEVICE_CREDENTIAL) onAuthSucceed()
+                if(errorCode == BiometricPrompt.ERROR_NEGATIVE_BUTTON) fallback = true
                 if(errorCode == BiometricPrompt.ERROR_CANCELED) return
                 Toast.makeText(context, errString, Toast.LENGTH_SHORT).show()
             }
         }
+        GlobalScope.launch(Dispatchers.Main) {
+            while(true){
+                if(fallback){
+                    val fallbackPromptInfo = PromptInfo.Builder()
+                        .setAllowedAuthenticators(BiometricManager.Authenticators.DEVICE_CREDENTIAL)
+                        .setTitle("Auth")
+                        .setSubtitle("Auth OwnDroid with password")
+                        .setConfirmationRequired(true)
+                        .build()
+                    authWithBiometricPrompt(requireActivity(), fallbackPromptInfo, callback)
+                    break
+                }
+                delay(50)
+            }
+        }
         return ComposeView(requireContext()).apply {
             setContent {
                 val materialYou = mutableStateOf(sharedPref.getBoolean("material_you",true))
                 val blackTheme = mutableStateOf(sharedPref.getBoolean("black_theme", false))
                 OwnDroidTheme(materialYou.value, blackTheme.value) {
-                    Auth(this@AuthFragment.requireActivity(), callback)
+                    Auth(this@AuthFragment.requireActivity(), callback, promptInfo)
                 }
             }
         }
@@ -65,7 +90,8 @@ class AuthFragment: Fragment() {
 }
 
 @Composable
-fun Auth(activity: FragmentActivity, callback: AuthenticationCallback) {
+fun Auth(activity: FragmentActivity, callback: AuthenticationCallback, promptInfo: PromptInfo.Builder) {
+    val context = LocalContext.current
     Column(
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.Center,
@@ -74,7 +100,19 @@ fun Auth(activity: FragmentActivity, callback: AuthenticationCallback) {
         Text(text = "Authenticate", style = MaterialTheme.typography.headlineLarge, color = MaterialTheme.colorScheme.onBackground)
         Button(
             onClick = {
-                authWithBiometricPrompt(activity, callback)
+                val bioManager = BiometricManager.from(context)
+                when(BiometricManager.BIOMETRIC_SUCCESS){
+                    bioManager.canAuthenticate(BiometricManager.Authenticators.BIOMETRIC_STRONG) ->
+                        promptInfo
+                            .setAllowedAuthenticators(BiometricManager.Authenticators.BIOMETRIC_STRONG)
+                            .setNegativeButtonText("Use password")
+                    bioManager.canAuthenticate(BiometricManager.Authenticators.BIOMETRIC_WEAK) ->
+                        promptInfo
+                            .setAllowedAuthenticators(BiometricManager.Authenticators.BIOMETRIC_WEAK)
+                            .setNegativeButtonText("Use password")
+                    else -> promptInfo.setAllowedAuthenticators(BiometricManager.Authenticators.DEVICE_CREDENTIAL)
+                }
+                authWithBiometricPrompt(activity, promptInfo.build(), callback)
             }
         ){
             Text(text = "Start")
@@ -82,14 +120,8 @@ fun Auth(activity: FragmentActivity, callback: AuthenticationCallback) {
     }
 }
 
-private fun authWithBiometricPrompt(activity: FragmentActivity, callback: AuthenticationCallback) {
+private fun authWithBiometricPrompt(activity: FragmentActivity, promptInfo: PromptInfo, callback: AuthenticationCallback) {
     val executor = ContextCompat.getMainExecutor(activity.applicationContext)
     val biometricPrompt = BiometricPrompt(activity, executor, callback)
-    val promptInfo = BiometricPrompt.PromptInfo.Builder()
-        .setAllowedAuthenticators(BiometricManager.Authenticators.DEVICE_CREDENTIAL)
-        .setTitle("Auth")
-        .setConfirmationRequired(true)
-        .setSubtitle("Enter password")
-        .build()
     biometricPrompt.authenticate(promptInfo)
 }