feat: subscribe to demo char changes

app/src/main/java/com/example/sensortestingapp/ConnectionManager.kt

@@ -13,14 +13,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
+package com.example.sensortestingapp
-package com.punchthrough.blestarterappandroid.ble
 
 import android.annotation.SuppressLint
 import android.bluetooth.BluetoothDevice
 import android.bluetooth.BluetoothGatt
 import android.bluetooth.BluetoothGattCallback
 import android.bluetooth.BluetoothGattCharacteristic
+import android.bluetooth.BluetoothGattDescriptor
 import android.bluetooth.BluetoothProfile
 import android.content.Context
 import android.util.Log
@@ -28,6 +28,8 @@ import java.util.UUID
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.ConcurrentLinkedQueue
 
+val CCC_DESCRIPTOR_UUID = UUID.fromString("00002902-0000-1000-8000-00805F9B34FB")
+
 private const val GATT_MIN_MTU_SIZE = 23
 
 /** Maximum BLE MTU size as defined in gatt_api.h. */
@@ -59,6 +61,14 @@ data class ReadChar(
     val charId: UUID
 ) : BleOperationType()
 
+
+data class SetNotification(
+    override val device: BluetoothDevice,
+    val serviceId: UUID,
+    val charId: UUID,
+    val enable: Boolean
+) : BleOperationType()
+
 data class DiscoverServicesRequest(
     override val device: BluetoothDevice,
 ) : BleOperationType()
@@ -70,6 +80,12 @@ open class BleListener {
         characteristic: BluetoothGattCharacteristic
     ) {
     }
+
+    open fun onCharChange(
+        gatt: BluetoothGatt,
+        characteristic: BluetoothGattCharacteristic
+    ) {
+    }
 }
 
 
@@ -173,6 +189,15 @@ object ConnectionManager {
         enqueueOperation(ReadChar(device, service, char))
     }
 
+    fun enableNotification(device: BluetoothDevice, service: UUID, char: UUID) {
+        enqueueOperation(SetNotification(device, service, char, true))
+    }
+
+    fun disableNotification(device: BluetoothDevice, service: UUID, char: UUID) {
+        enqueueOperation(SetNotification(device, service, char, false))
+    }
+
+
     // - Beginning of PRIVATE functions
 
     @Synchronized
@@ -235,6 +260,7 @@ object ConnectionManager {
                 return
             }
 
+
         when (operation) {
             is Disconnect -> with(operation) {
                 Log.w("ConnectionManager", "Disconnecting from ${device.address}")
@@ -256,12 +282,67 @@ object ConnectionManager {
                 if (characteristic?.isReadable() == true) {
                     gatt.readCharacteristic(characteristic)
                 } else {
+                    Log.e("ConnectionManager", "Char $charId (${serviceId}) is not readable!")
                     signalEndOfOperation()
                 }
 
             }
 
+            is SetNotification -> with(operation) {
+                val characteristic = gatt.getService(serviceId)?.getCharacteristic(charId);
+                if (characteristic == null) {
+                    Log.e("ConnectionManager", "Char $charId (${serviceId}) not found!")
+                    signalEndOfOperation()
+                    return
+                }
+                val descriptor = characteristic.getDescriptor(CCC_DESCRIPTOR_UUID)
 
+                if (!characteristic.isNotifiable() && !characteristic.isIndicatable()) {
+                    Log.e(
+                        "ConnectionManager", "Char ${characteristic.uuid} (service: $serviceId)" +
+                                " doesn't support notifications/indications"
+                    )
+                    signalEndOfOperation()
+                    return
+                }
+
+                val payload: ByteArray
+
+                if (enable) {
+                    if (!gatt.setCharacteristicNotification(characteristic, true)) {
+                        Log.e(
+                            "ConnectionManager", "setCharacteristicNotification to true " +
+                                    "failed for ${characteristic.uuid} (service: $serviceId)"
+                        )
+                        signalEndOfOperation()
+                        return
+                    }
+                    payload =
+                        if (characteristic.isIndicatable())
+                            BluetoothGattDescriptor.ENABLE_INDICATION_VALUE
+                        else BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE;
+
+                } else {
+                    if (!gatt.setCharacteristicNotification(characteristic, false)) {
+                        Log.e(
+                            "ConnectionManager", "setCharacteristicNotification to false " +
+                                    "failed for ${characteristic.uuid} (service: $serviceId)"
+                        )
+                        signalEndOfOperation()
+                        return
+                    }
+                    payload = BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE
+                }
+
+                gatt.let { gatt ->
+                    descriptor.value = payload
+                    gatt.writeDescriptor(descriptor)
+                }
+            }
+
+
+            // necessary because of IDE type inference bug
+            // https://youtrack.jetbrains.com/issue/KTIJ-20749/Exhaustive-when-check-does-not-take-into-account-the-values-excluded-by-previous-if-conditions
             is Connect -> {
                 Log.e("ConnectionManager", "Shouldn't get here")
             }
@@ -365,11 +446,33 @@ object ConnectionManager {
                 }
             }
 
-            if (pendingOperation is ReadChar) {
+            val op = pendingOperation
+            if (op is ReadChar && op.charId == characteristic.uuid && op.serviceId == characteristic.service.uuid) {
                 signalEndOfOperation()
             }
         }
 
+        override fun onDescriptorWrite(
+            gatt: BluetoothGatt,
+            descriptor: BluetoothGattDescriptor,
+            status: Int
+        ) {
+            val op = pendingOperation
+            if (op is SetNotification &&
+                descriptor.uuid == CCC_DESCRIPTOR_UUID
+                && op.charId == descriptor.characteristic.uuid && op.serviceId == descriptor.characteristic.service.uuid
+            ) {
+                signalEndOfOperation()
+            }
+        }
+
+        override fun onCharacteristicChanged(
+            gatt: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic
+        ) {
+            notifyListeners { listener -> listener.onCharChange(gatt, characteristic) }
+        }
+
 
     }
 

app/src/main/java/com/example/sensortestingapp/MainActivity.kt

@@ -28,8 +28,6 @@ import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import androidx.recyclerview.widget.SimpleItemAnimator
 import com.example.sensortestingapp.databinding.ActivityMainBinding
-import com.punchthrough.blestarterappandroid.ble.BleListener
-import com.punchthrough.blestarterappandroid.ble.ConnectionManager
 import java.nio.ByteBuffer
 import java.nio.ByteOrder
 import java.util.UUID
@@ -138,21 +136,36 @@ class MainActivity : AppCompatActivity() {
             ConnectionManager.connect(scanResult.device, applicationContext)
             ConnectionManager.requestMtu(scanResult.device, Int.MAX_VALUE)
             ConnectionManager.discoverServices(scanResult.device)
-            ConnectionManager.readChar(scanResult.device, DEMO_SERVICE_UUID, DEMO_CHAR_UUID)
+            //ConnectionManager.readChar(scanResult.device, DEMO_SERVICE_UUID, DEMO_CHAR_UUID)
+            ConnectionManager.enableNotification(
+                scanResult.device,
+                DEMO_SERVICE_UUID,
+                DEMO_CHAR_UUID
+            )
         }
     }
 
     private val bleListener = object : BleListener() {
+
+        fun logDemoPayload(characteristic: BluetoothGattCharacteristic) {
+            if (characteristic.service.uuid == DEMO_SERVICE_UUID && characteristic.uuid == DEMO_CHAR_UUID) {
+                val payload = decodeDemoPayload(characteristic.value)
+                Log.i("BleListener", "Demo char received: $payload")
+            }
+        }
+
         override fun onSuccessfulCharRead(
             gatt: BluetoothGatt,
             characteristic: BluetoothGattCharacteristic
         ) {
-
+            logDemoPayload(characteristic)
-            if (characteristic.service.uuid == DEMO_SERVICE_UUID && characteristic.uuid == DEMO_CHAR_UUID) {
-                val payload = decodeDemoPayload(characteristic.value)
-                Log.i("BleListener", "Demo char received: $payload")
-
         }
+
+        override fun onCharChange(
+            gatt: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic
+        ) {
+            logDemoPayload(characteristic)
         }
     }