java - android 4.3 Bluetooth ble don't called onCharacteristicRead()

Question

I've set the notification into android, It is not calling to method onCharacteristicRead()???? It does not enter into the function. Why it is happening so??

Any help is appreciated

Request the solutions.

This is my code:

private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status,
            int newState) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            Log.i(TAG, "Connected to GATT server.");
            // Attempts to discover services after successful connection.
            Log.i(TAG, "Attempting to start service discovery:"
                    + mBluetoothGatt.discoverServices());
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            Log.i(TAG, "Disconnected from GATT server.");
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            gattServices = mBluetoothGatt
                    .getService(SampleGattAttributes.SERVICES_UUID);
            if (gattServices != null) {
                gattCharacteristics = gattServices
                        .getCharacteristic(SampleGattAttributes.CHARACTERISTIC_UUID);
                System.out.println("character-->" + gattCharacteristics);
            }
            if (gattCharacteristics != null) {
                System.out.println("Characteristic not null");
                System.out.println("Characteristic Properties-->"
                        + gattCharacteristics.getProperties());
                mBluetoothGatt.setCharacteristicNotification(gattCharacteristics,
                true);
            }
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }
    }

    @Override
    public void onCharacteristicRead(BluetoothGatt gatt,
            BluetoothGattCharacteristic characteristic, int status) {
        System.out.println("in read");
        if (status == BluetoothGatt.GATT_SUCCESS) {
            byte[] data = characteristic.getValue();
            System.out.println("reading");
            System.out.println(new String(data));
        }
    }

    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt,
            BluetoothGattCharacteristic characteristic) {
        //
        System.out.println("change");
        byte[] data = characteristic.getValue();
        System.out.println(new String(data));
    }
};

Thank you in advance!!

Answer 1

First of all onCharacteristicRead will fire if you have read a characteristic by:

 mBluetoothGatt.readCharacteristic(characteristic);

Reading a characteristic and setting up notifications are two different things. What is the type of your characteristic you want to get data from?

Is it:

• read
• notify
• indicate

If it is read you can read the characteristic using the mBluetoothGatt.readCharacteristic(characteristic); method but if its notify or indicate first you will have to read the characteristic's descriptor by calling:

mBluetoothGatt.readDescriptor(ccc);

Once you read it, it should return data by calling the onDescriptorRead callback.
Here you can set up (subscribe) to the charactersitic through either notification or indication by calling:

mBluetoothGatt.setCharacteristicNotification(characteristic, true)

once it returns true you will need to write to the descriptor again (the value of notification or indication)

BluetoothGattDescriptor clientConfig = characteristic.getDescriptor(CCC);
clientConfig.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
// or
//clientConfig.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
mBluetoothGatt.writeDescriptor(clientConfig);

Once this is done you will get notifications throuhg onCharacteristicChanged callback every time the characteristic changes.

you can read more about Bluetooth connection on Android here
and about Bluetooth Characteristics here