Android SensorTag：writeDescriptor失败

Question

测试设备：android 4.4

Connection工作正常，但我的回调函数的onDescriptorWrite方法永远不会被调用。并且获得了bluetoothGatt和特性。但是当我想设置-CharacteristicNotification和writeDescriptor时，没有收到回调，包括onDescriptorWrite和onCharacteristicChanged。通知代码如下所示：

    private static void enableMagnetometerNotifications(BluetoothGatt     bluetoothGatt) {
    UUID magnetServiceUuid = UUID.fromString("f000aa30-0451-4000-b000-000000000000");
    UUID magnetDataUuid = UUID.fromString("f000aa31-0451-4000-b000-000000000000");
    UUID CCC = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
    boolean ok = false;
    boolean notify = false;

    BluetoothGattService magnetService = bluetoothGatt.getService(magnetServiceUuid);
    BluetoothGattCharacteristic magnetDataCharacteristic = magnetService.getCharacteristic(
            magnetDataUuid);
    notify = bluetoothGatt.setCharacteristicNotification(
            magnetDataCharacteristic, true); //Enabled locally

    if (notify){
        BluetoothGattDescriptor config = magnetDataCharacteristic.getDescriptor(CCC);
        List<BluetoothGattDescriptor> cof = magnetDataCharacteristic.getDescriptors();
        for(BluetoothGattDescriptor a: cof  ){
            Log.i("GattDescriptor ",a.getUuid().toString());
        }
        ok = config.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
        if(ok){
            mBusy = true;
            bluetoothGatt.writeDescriptor(config); //Enabled remotely
            //delay 300 seconds
            waitIdle(300);
        }
    }