Implement emulation (hopefully!)

app/src/main/java/me/kdcf/aimereader/MainActivity.kt

@@ -50,6 +50,7 @@ import androidx.compose.material3.SnackbarResult
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
@@ -83,7 +84,7 @@ class MainActivity : ComponentActivity() {
     lateinit var adapter: NfcAdapter
 
     var canEmulateCard: Boolean = false
-    var emulationActive: Boolean = false
+    var emulationCardID: String? = null
 
     private val TAG = "AimeReader"
     private val FILENAME = "cards.json"
@@ -158,7 +159,16 @@ class MainActivity : ComponentActivity() {
             val scope = rememberCoroutineScope()
             var snackbarHostState = remember { SnackbarHostState() }
 
-            var selectedCardIndexForEmulation by rememberSaveable { mutableStateOf(-1) }
+            var selectedCardIndexForEmulation by rememberSaveable { mutableIntStateOf(-1) }
+
+            LaunchedEffect(selectedCardIndexForEmulation) {
+                if (selectedCardIndexForEmulation == -1) {
+                    this@MainActivity.emulationCardID = null
+                } else {
+                    this@MainActivity.emulationCardID = cards[selectedCardIndexForEmulation].getHexID()
+                }
+                updateEmulation()
+            }
 
             AimeReaderTheme {
                 Scaffold (
@@ -261,17 +271,28 @@ class MainActivity : ComponentActivity() {
         adapter.disableForegroundDispatch(this)
         val nfcfCardEmulation = NfcFCardEmulation.getInstance(adapter)
         nfcfCardEmulation.disableService(this)
+        Log.i(TAG, "Pausing activity, emulation disabled")
     }
 
     public override fun onResume() {
         super.onResume()
         adapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, techListsArray)
-        val nfcfCardEmulation = NfcFCardEmulation.getInstance(adapter)
+        updateEmulation()
-        nfcfCardEmulation.registerSystemCodeForService(ComponentName(this, AimeHostApduService::class.java), "4000")
-        Log.d(TAG, nfcfCardEmulation.setNfcid2ForService(ComponentName(this, AimeHostApduService::class.java), "02FE000000000000").toString())
-        Log.d(TAG, nfcfCardEmulation.enableService(this, ComponentName(this, AimeHostApduService::class.java)).toString())
-        Log.i(TAG, "activity resumed")
     }
+
+    fun updateEmulation() {
+        val nfcfCardEmulation = NfcFCardEmulation.getInstance(adapter)
+        if (emulationCardID != null) {
+            Log.i(TAG, "Enabling emulation of card $emulationCardID")
+            nfcfCardEmulation.registerSystemCodeForService(ComponentName(this, AimeHostApduService::class.java), "4000")
+            Log.d(TAG, nfcfCardEmulation.setNfcid2ForService(ComponentName(this, AimeHostApduService::class.java), emulationCardID).toString())
+            Log.d(TAG, nfcfCardEmulation.enableService(this, ComponentName(this, AimeHostApduService::class.java)).toString())
+        } else {
+            Log.i(TAG, "Disabling card emulation")
+            nfcfCardEmulation.disableService(this)
+        }
+    }
+
 }
 
 @Composable
@@ -288,7 +309,7 @@ fun CardList(
         Column (
             horizontalAlignment = Alignment.CenterHorizontally,
             verticalArrangement = Arrangement.Center,
-            modifier = Modifier
+            modifier = modifier
                 .fillMaxSize()
                 .padding(innerPadding)
         ) {
@@ -297,7 +318,7 @@ fun CardList(
         }
     } else {
         LazyColumn (
-            modifier = Modifier
+            modifier = modifier
                 .fillMaxWidth()
                 .padding(innerPadding)
         ) {
@@ -327,7 +348,7 @@ fun CardDisplay(
     val coroutineScope = rememberCoroutineScope()
 
     Row (
-        modifier = Modifier
+        modifier = modifier
             .padding(horizontal = 8.dp, vertical = 8.dp)
             .fillMaxWidth()
             .clip(shape = RoundedCornerShape(16.dp))
@@ -383,7 +404,7 @@ fun CardDisplay(
 @Preview
 @Composable
 fun CardDisplayPreview(modifier: Modifier = Modifier) {
-    Column(modifier = Modifier.fillMaxSize()) {
+    Column(modifier = modifier.fillMaxSize()) {
         CardDisplay(SavedCard(byteArrayOf(0x02, 0xFE.toByte(), 0x02, 0x03, 0x04, 0x05, 0x06, 0x07)), true, true, {}, {}, {})
         CardDisplay(SavedCard(byteArrayOf(0x02, 0xFE.toByte(), 0x12, 0x34, 0x56, 0x78, 0x12, 0x34)), true, false, {}, {}, {})
         CardDisplay(SavedCard(byteArrayOf(0x02, 0x00, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07)), true, false, {}, {}, {})

app/src/main/java/me/kdcf/aimereader/SavedCard.kt

@@ -1,6 +1,5 @@
 package me.kdcf.aimereader
 
-import android.os.Parcel
 import android.os.Parcelable
 import kotlinx.parcelize.Parcelize
 import kotlinx.serialization.Serializable
@@ -25,6 +24,11 @@ class SavedCard(private var code: ByteArray, private var friendlyName: String =
         return getPadded().chunked(4).joinToString(" ")
     }
 
+    @OptIn(ExperimentalStdlibApi::class)
+    fun getHexID(): String {
+        return getCode().toHexString()
+    }
+
     fun getDisplay(): String {
         if (friendlyName.isEmpty()) {
             return getSpaced()