Some BTLE cleanup:

- the BASE_UUID is shared between all BTLE devices, not miband specific. So are the UUID DESCRIPTORS. Hence these have been moved to AbstractBTLEDeviceSupport
- the gatt-characteristic-property-constants used previously in MiBandNotifyAction are also general, and exposed by the gatt subsystem, hence the specific action has been dropped moving the logic to the NotifyAction class
 - the logic for checking the gatt-characteristic-property-constants has been extended also to the ReadAction and WriteAction class, this way we won't try to read (or write)  a characteristic that isn't readable (or writeable)

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/miband/MiBandNotifyAction.java

@@ -1,64 +0,0 @@
-package nodomain.freeyourgadget.gadgetbridge.devices.miband;
-
-import android.bluetooth.BluetoothGatt;
-import android.bluetooth.BluetoothGattCallback;
-import android.bluetooth.BluetoothGattCharacteristic;
-import android.bluetooth.BluetoothGattDescriptor;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import nodomain.freeyourgadget.gadgetbridge.service.btle.actions.NotifyAction;
-import nodomain.freeyourgadget.gadgetbridge.service.btle.TransactionBuilder;
-
-/**
- * Enables or disables notifications for a given GATT characteristic.
- * The result will be made available asynchronously through the
- * {@link BluetoothGattCallback}.
- * <p/>
- * This class is Mi Band specific.
- */
-public class MiBandNotifyAction extends NotifyAction {
-
-    private static final Logger LOG = LoggerFactory.getLogger(TransactionBuilder.class);
-    private boolean hasWrittenDescriptor = true;
-
-    public MiBandNotifyAction(BluetoothGattCharacteristic characteristic, boolean enable) {
-        super(characteristic, enable);
-    }
-
-    @Override
-    public boolean run(BluetoothGatt gatt) {
-        boolean result = super.run(gatt);
-        if (result) {
-            BluetoothGattDescriptor notifyDescriptor = getCharacteristic().getDescriptor(MiBandService.UUID_DESCRIPTOR_CLIENT_CHARACTERISTIC_CONFIGURATION);
-            if (notifyDescriptor != null) {
-                int properties = getCharacteristic().getProperties();
-                if ((properties & 0x10) > 0) {
-                    LOG.debug("use NOTIFICATION");
-                    notifyDescriptor.setValue(enableFlag ? BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE : BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
-                    result = gatt.writeDescriptor(notifyDescriptor);
-                } else if ((properties & 0x20) > 0) {
-                    LOG.debug("use INDICATION");
-                    notifyDescriptor.setValue(enableFlag ? BluetoothGattDescriptor.ENABLE_INDICATION_VALUE : BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
-                    result = gatt.writeDescriptor(notifyDescriptor);
-                    hasWrittenDescriptor = true;
-                } else {
-                    hasWrittenDescriptor = false;
-                }
-            } else {
-                LOG.warn("sleep descriptor null");
-                hasWrittenDescriptor = false;
-            }
-        } else {
-            hasWrittenDescriptor = false;
-            LOG.error("Unable to enable notification for " + getCharacteristic().getUuid());
-        }
-        return result;
-    }
-
-    @Override
-    public boolean expectsResult() {
-        return hasWrittenDescriptor;
-    }
-}

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/miband/MiBandService.java

@@ -4,13 +4,13 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.UUID;
 
+import static nodomain.freeyourgadget.gadgetbridge.service.btle.AbstractBTLEDeviceSupport.BASE_UUID;
+
 public class MiBandService {
 
 
     public static final String MAC_ADDRESS_FILTER = "88:0F:10";
 
-    public static final String BASE_UUID = "0000%s-0000-1000-8000-00805f9b34fb";
-
     public static final UUID UUID_SERVICE_MIBAND_SERVICE = UUID.fromString(String.format(BASE_UUID, "FEE0"));
 
     public static final UUID UUID_CHARACTERISTIC_DEVICE_INFO = UUID.fromString(String.format(BASE_UUID, "FF01"));
@@ -53,10 +53,6 @@ public class MiBandService {
 
     public static final String UUID_SERVICE_WEIGHT_SERVICE = "00001530-0000-3512-2118-0009af100700";
 
-    public static final UUID UUID_DESCRIPTOR_CHARACTERISTIC_USER_CONFIGURATION = UUID.fromString(String.format(BASE_UUID, "2901"));
-
-    public static final UUID UUID_DESCRIPTOR_CLIENT_CHARACTERISTIC_CONFIGURATION = UUID.fromString(String.format(BASE_UUID, "2902"));
-
     public static final byte ALIAS_LEN = 0xa;
 
     /*NOTIFICATIONS: usually received on the UUID_CHARACTERISTIC_NOTIFICATION characteristic */

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/miband/MiBandTransactionBuilder.java

@@ -17,6 +17,6 @@ public class MiBandTransactionBuilder extends TransactionBuilder {
 
     @Override
     protected NotifyAction createNotifyAction(BluetoothGattCharacteristic characteristic, boolean enable) {
-        return new MiBandNotifyAction(characteristic, enable);
+        return new NotifyAction(characteristic, enable);
     }
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java

@@ -20,7 +20,7 @@ import nodomain.freeyourgadget.gadgetbridge.service.AbstractDeviceSupport;
 /**
  * Abstract base class for all devices connected through Bluetooth Low Energy (LE) aka
  * Bluetooth Smart.
- *
+ * <p/>
  * The connection to the device and all communication is made with a generic {@link BtLEQueue}.
  * Messages to the device are encoded as {@link BtLEAction actions} that are grouped with a
  * {@link Transaction} and sent via {@link BtLEQueue}.
@@ -35,6 +35,11 @@ public abstract class AbstractBTLEDeviceSupport extends AbstractDeviceSupport im
     private HashMap<UUID, BluetoothGattCharacteristic> mAvailableCharacteristics;
     private Set<UUID> mSupportedServices = new HashSet<>(4);
 
+    public static final String BASE_UUID = "0000%s-0000-1000-8000-00805f9b34fb"; //this is common for all BTLE devices. see http://stackoverflow.com/questions/18699251/finding-out-android-bluetooth-le-gatt-profiles
+    public static final UUID UUID_DESCRIPTOR_CHARACTERISTIC_USER_CONFIGURATION = UUID.fromString(String.format(BASE_UUID, "2901"));
+    public static final UUID UUID_DESCRIPTOR_CLIENT_CHARACTERISTIC_CONFIGURATION = UUID.fromString(String.format(BASE_UUID, "2902"));
+
+
     @Override
     public boolean connect() {
         if (mQueue == null) {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/actions/NotifyAction.java

@@ -3,6 +3,7 @@ package nodomain.freeyourgadget.gadgetbridge.service.btle.actions;
 import android.bluetooth.BluetoothGatt;
 import android.bluetooth.BluetoothGattCallback;
 import android.bluetooth.BluetoothGattCharacteristic;
+import android.bluetooth.BluetoothGattDescriptor;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -10,6 +11,8 @@ import org.slf4j.LoggerFactory;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.BtLEAction;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.TransactionBuilder;
 
+import static nodomain.freeyourgadget.gadgetbridge.service.btle.AbstractBTLEDeviceSupport.UUID_DESCRIPTOR_CLIENT_CHARACTERISTIC_CONFIGURATION;
+
 /**
  * Enables or disables notifications for a given GATT characteristic.
  * The result will be made available asynchronously through the
@@ -19,6 +22,7 @@ public class NotifyAction extends BtLEAction {
 
     private static final Logger LOG = LoggerFactory.getLogger(TransactionBuilder.class);
     protected final boolean enableFlag;
+    private boolean hasWrittenDescriptor = true;
 
     public NotifyAction(BluetoothGattCharacteristic characteristic, boolean enable) {
         super(characteristic);
@@ -27,11 +31,36 @@ public class NotifyAction extends BtLEAction {
 
     @Override
     public boolean run(BluetoothGatt gatt) {
-        return gatt.setCharacteristicNotification(getCharacteristic(), enableFlag);
+        boolean result = gatt.setCharacteristicNotification(getCharacteristic(), enableFlag);
+        if (result) {
+            BluetoothGattDescriptor notifyDescriptor = getCharacteristic().getDescriptor(UUID_DESCRIPTOR_CLIENT_CHARACTERISTIC_CONFIGURATION);
+            if (notifyDescriptor != null) {
+                int properties = getCharacteristic().getProperties();
+                if ((properties & BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
+                    LOG.debug("use NOTIFICATION");
+                    notifyDescriptor.setValue(enableFlag ? BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE : BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
+                    result = gatt.writeDescriptor(notifyDescriptor);
+                } else if ((properties & BluetoothGattCharacteristic.PROPERTY_INDICATE) > 0) {
+                    LOG.debug("use INDICATION");
+                    notifyDescriptor.setValue(enableFlag ? BluetoothGattDescriptor.ENABLE_INDICATION_VALUE : BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
+                    result = gatt.writeDescriptor(notifyDescriptor);
+                    hasWrittenDescriptor = true;
+                } else {
+                    hasWrittenDescriptor = false;
+                }
+            } else {
+                LOG.warn("sleep descriptor null");
+                hasWrittenDescriptor = false;
+            }
+        } else {
+            hasWrittenDescriptor = false;
+            LOG.error("Unable to enable notification for " + getCharacteristic().getUuid());
+        }
+        return result;
     }
 
     @Override
     public boolean expectsResult() {
-        return false;
+        return hasWrittenDescriptor;
     }
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/actions/ReadAction.java

@@ -19,8 +19,12 @@ public class ReadAction extends BtLEAction {
 
     @Override
     public boolean run(BluetoothGatt gatt) {
+        int properties = getCharacteristic().getProperties();
+        if ((properties & BluetoothGattCharacteristic.PROPERTY_READ) > 0) {
             return gatt.readCharacteristic(getCharacteristic());
         }
+        return false;
+    }
 
     @Override
     public boolean expectsResult() {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/actions/WriteAction.java

@@ -22,9 +22,12 @@ public class WriteAction extends BtLEAction {
 
     @Override
     public boolean run(BluetoothGatt gatt) {
+        int properties = getCharacteristic().getProperties();
+        if ((properties & BluetoothGattCharacteristic.PROPERTY_WRITE) > 0) {
             if (getCharacteristic().setValue(value)) {
                 return gatt.writeCharacteristic(getCharacteristic());
             }
+        }
         return false;
     }