Implement reading payload from NfcA tags, replace intent/characteristic value with that

app/src/main/java/systems/kumi/simplerfiddemo/MainActivity.kt

@@ -17,6 +17,8 @@ import android.content.pm.PackageManager
 import android.nfc.NfcAdapter
 import android.nfc.NfcManager
 import android.nfc.Tag
+import android.nfc.TagLostException
+import android.nfc.tech.NfcA
 import android.os.Bundle
 import android.os.ParcelUuid
 import android.util.Log
@@ -35,6 +37,8 @@ import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.core.app.ActivityCompat
 import systems.kumi.simplerfiddemo.ui.theme.SimpleRFIDDemoTheme
+import java.io.IOException
+import java.nio.charset.StandardCharsets
 import java.util.UUID
 
 
@@ -61,6 +65,26 @@ class MainActivity : ComponentActivity() {
         val manager = getSystemService(Context.NFC_SERVICE) as NfcManager;
         nfcAdapter = manager.defaultAdapter;
 
+        // Get required permissions
+
+        if (ActivityCompat.checkSelfPermission(
+                this,
+                Manifest.permission.BLUETOOTH_CONNECT
+            ) != PackageManager.PERMISSION_GRANTED
+        ) {
+            ActivityCompat.requestPermissions(
+                this,
+                arrayOf(
+                    Manifest.permission.BLUETOOTH_CONNECT,
+                    Manifest.permission.BLUETOOTH_ADMIN,
+                    Manifest.permission.BLUETOOTH,
+                    Manifest.permission.BLUETOOTH_SCAN,
+                    Manifest.permission.BLUETOOTH_ADVERTISE,
+                    Manifest.permission.NFC),
+                1
+            )
+        }
+
         if (nfcAdapter != null && nfcAdapter.isEnabled) {
 
             // NFC is available
@@ -80,7 +104,7 @@ class MainActivity : ComponentActivity() {
                     ) {
                         Column(modifier = Modifier.padding(16.dp)) {
                             Status()
-                            Button(onClick = { emitIntent("sample-id") }) {
+                            Button(onClick = { emitIntent("sample-id", "sample-content") }) {
                                 Text(text = "Emit sample Intent")
                             }
                         }
@@ -224,45 +248,72 @@ class MainActivity : ComponentActivity() {
         return String(hexChars)
     }
 
-    fun emitIntent(id: String) {
+    @SuppressLint("MissingPermission")
+    fun emitIntent(id: String, content: String? = null) {
         Log.i("BLE", "Setting characteristic and emitting intent: $id")
 
-        characteristic.value = id.toByteArray(Charsets.UTF_8)
+        if (content != null) {
-        synchronized(connectedDevices) {
+            characteristic.value = content.toByteArray(Charsets.UTF_8)
-            for (device in connectedDevices) {
+            synchronized(connectedDevices) {
-                if (ActivityCompat.checkSelfPermission(
+                for (device in connectedDevices) {
-                        this,
+                    gattServer.notifyCharacteristicChanged(device, characteristic, false)
-                        Manifest.permission.BLUETOOTH_CONNECT
-                    ) != PackageManager.PERMISSION_GRANTED
-                ) {
-                    ActivityCompat.requestPermissions(
-                        this,
-                        arrayOf(
-                            Manifest.permission.BLUETOOTH_CONNECT,
-                            Manifest.permission.BLUETOOTH_ADMIN,
-                            Manifest.permission.BLUETOOTH,
-                            Manifest.permission.BLUETOOTH_SCAN,
-                            Manifest.permission.BLUETOOTH_ADVERTISE
-                        ),
-                        1
-                    )
-                    return
                 }
-                gattServer.notifyCharacteristicChanged(device, characteristic, false)
+            }
+
+            val intent = Intent("systems.kumi.simplerfiddemo.NEW_TAG")
+            intent.putExtra("data", content)
+            sendBroadcast(intent)
+        }
+    }
+
+    fun readFromTag(tag: Tag): String? {
+        NfcA.get(tag)?.use { nfcA ->
+            try {
+                nfcA.connect()
+
+                val bufferSize = 256
+                val result = ByteArray(bufferSize)
+
+                for (block in 4 until 4 + (bufferSize / 4)) {
+                    val command = byteArrayOf(0x30, block.toByte())  // READ command 0x30 for ISO/IEC 14443, and block number
+                    val response = nfcA.transceive(command)
+                    val index = (block - 4) * 4
+
+                    if (index < result.size) {
+                        val length = Math.min(response.size, result.size - index)
+                        System.arraycopy(response, 0, result, index, length)
+                    }
+
+                    if (response.indexOf(0x00) != -1) {
+                        break
+                    }
+                }
+
+                // Assuming the data is encoded in UTF-8 and zero terminated
+                val dataString = result.toString(StandardCharsets.UTF_8).split("\u0000")[0]
+                return dataString
+
+            } catch (e: IOException) {
+                Log.e("NFC", "IOException while reading tag", e)
+            } catch (e: TagLostException) {
+                Log.e("NFC", "TagLostException while reading tag", e)
             }
         }
-
+        return null
-        val intent = Intent("systems.kumi.simplerfiddemo.NEW_TAG")
-        intent.putExtra("data", id)
-        sendBroadcast(intent)
     }
 
+
+
+
     @SuppressLint("MissingPermission")
     fun onNewTag(tag: Tag) {
         val tag_id = toHexString(tag.id)
         Log.d("NFC", "New tag detected: ${tag_id}")
 
-        emitIntent(tag_id)
+        val tag_content = readFromTag(tag)
+        Log.d("NFC", "Tag content: ${tag_content}")
+
+        emitIntent(tag_id, tag_content)
 
         setContent() {
             SimpleRFIDDemoTheme {
@@ -271,9 +322,9 @@ class MainActivity : ComponentActivity() {
                     color = MaterialTheme.colorScheme.background
                 ) {
                     Column(modifier = Modifier.padding(16.dp)) {
-                        Status(tag_id)
+                        Status(tag_id, tag_content)
-                        Button(onClick = { emitIntent("sample-id") }) {
+                        Button(onClick = { emitIntent(tag_id, tag_content) }) {
-                            Text(text = "Emit sample Intent")
+                            Text(text = "Emit Intent")
                         }
                     }
                 }
@@ -283,9 +334,9 @@ class MainActivity : ComponentActivity() {
 }
 
 @Composable
-fun Status(id: String? = null) {
+fun Status(id: String? = null, content: String? = null) {
     Text(
-        text = "Status: ${if (id != null) "Tag detected: $id" else "Waiting for tag..."}",
+        text = "Status: ${if (id != null) "Tag detected.\nID: $id\nContent: $content" else "Waiting for tag..."}",
         modifier = Modifier
     )
 }