在做Android蓝牙BLE4.0开发时，onCharacteristicChanged方法一直不调用，是怎么回事呢？ 30C

这个问题卡了我两天了，一直找不到原因。 我的BLE设备已经连接成功，数据写入也是成功的，设备通知功能也已经打开，可是onCharacteristicChanged这个方法一直无法调用。 各位大神帮我看看啊，有做BLE相关开发的可以加我QQ：879981004，我们一起探讨下。
下面是我的代码：  @Override
        public void onServicesDiscovered(final BluetoothGatt gatt, final int status) {
            super.onServicesDiscovered(gatt, status);
            Log.i("inform", "连接已经成功，正在写入数据");
//        readData();
            btnNotification.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (status == mBluetoothGatt.GATT_SUCCESS) {
                        final List<BluetoothGattService> services = gatt.getServices();
                        new Thread(new Runnable() {
                            @Override
                            public void run() {
                                for (BluetoothGattService bluetoothGattService : services) {
                                    if (bluetoothGattService.getUuid().toString().equals("0000fff0-0000-1000-8000-00805f9b34fb")) {
                                        for (BluetoothGattCharacteristic bluetoothGattCharacteristic : bluetoothGattService.getCharacteristics()) {
                                            if (bluetoothGattCharacteristic.getUuid().toString().equals("0000fff1-0000-1000-8000-00805f9b34fb")) {
                                                try {
                                                    Thread.sleep(500);
                                                    enableNotification(true, bluetoothGattCharacteristic);
                                                    Thread.sleep(500);
                                                    writeWDData();
                                                } catch (InterruptedException e) {
                                                    e.printStackTrace();
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }).start();
                    }
                }
            });
        }我在onServicesDiscovered中设置通知打开，然后进行数据写入。在onCharacteristicWrite中，是可以正常调用的，说明数据写入是成功的啊。这里的enableNotification(true, bluetoothGattCharacteristic); 就是设置打开设备通知功能
/**
     * 通知
     */
    private void enableNotification(boolean enable, BluetoothGattCharacteristic characteristic) {
        if (mBluetoothGatt == null || characteristic == null) {
            return;
        }
        if (!mBluetoothGatt.setCharacteristicNotification(characteristic, enable)) {
            return;
        }
        BluetoothGattDescriptor clientConfig = characteristic.getDescriptor(UUID.fromString("00002902-0000-1000-8000-00805f9b34fb"));
        if (clientConfig == null) {
            return;
        }
        clientConfig.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
        mBluetoothGatt.writeDescriptor(clientConfig);
//        }
    }
下面是我写入数据的代码
 /**
     * 向蓝牙设备写入温湿度数据
     */
    public void writeWDData() {
        BluetoothGattService sendService = mBluetoothGatt.getService(UUID.fromString("0000fff0-0000-1000-8000-00805f9b34fb"));
        if (sendService != null) {
            BluetoothGattCharacteristic sendCharacteristic = sendService.getCharacteristic(UUID.fromString("0000fff1-0000-1000-8000-00805f9b34fb"));
            if (sendCharacteristic != null) {
                byte[] bytes = new byte[5];
                bytes[0] = 0x30;
                bytes[1] = 'b';
                bytes[2] = 'b';
                bytes[3] = 'b';
                bytes[4] = 'b';
                sendCharacteristic.setValue(bytes);
//                sendCharacteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
                mBluetoothGatt.writeCharacteristic(sendCharacteristic);//写命令到设备，
                Log.i("inform", "数据已写入");
            }
        } else {
            Log.i("inform", "UUID错误");
//                String name=  BluetoothDevice.EXTRA_UUID;
//                Log.i("inform",name+">>>>>>>>name");
        }
    }就是这个返回通知的方法，一直不执行：
        /**
         * 蓝牙通知回调
         * @param gatt
         * @param characteristic
         */
        @Override
        public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
            super.onCharacteristicChanged(gatt, characteristic);
            Log.i("inform","已通知成功");        }不是说在数据写入成功后，蓝牙设备会给手机发送通知嘛？可是我已经写入成功了，但是就是在最后这里的用来返回通知的onCharacteristicChanged方法，始终不执行。 麻烦大家帮我看看怎么回事？ 这是公司的项目，已经卡在这里两天了，十万火急啊