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低功耗蓝牙BLE外围模式(peripheral)-使用BLE作为服务端

张云飞Vir

发布于 2020-03-16 08:09:02

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文章被收录于专栏：写代码和思考写代码和思考

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代码可运行

低功耗蓝牙BLE外围模式(peripheral)-使用BLE作为服务端

Android对外模模式(peripheral)的支持

从Android5.0开始才支持

关键术语和概念

以下是关键BLE术语和概念的摘要：

通用属性简档（GATT） - GATT简档是用于通过BLE链路发送和接收称为“属性”的短数据块的一般规范。所有当前的低能量应用配置文件都基于GATT。蓝牙SIG为低能量设备定义了许多配置文件。配置文件是设备在特定应用程序中的工作方式的规范。请注意，设备可以实现多个配置文件。例如，设备可以包含心率监视器和电池水平检测器。
属性协议（ATT） -GATT建立在属性协议（ATT）之上。这也称为GATT / ATT。 ATT经过优化，可在BLE设备上运行。为此，它使用尽可能少的字节。每个属性由通用唯一标识符（UUID）唯一标识，UUID是用于唯一标识信息的字符串ID的标准化128位格式。由ATT传送的属性被格式化为特征和服务。
特性 -A特性包含描述特性值的单个值和0-n个描述符。一个特性可以被认为是一个类型，类似于类。
描述符 - 描述符是描述特征值的定义属性。例如，描述符可以指定人类可读的描述，特征值的可接受范围或特征值的特定的测量单位。
服务 - 服务是一个集合的特点。例如，您可以有一个名为“心率监视器”的服务，其中包括诸如“心率测量”的特征。您可以在bluetooth.org上找到现有基于GATT的个人资料和服务的列表。

角色和职责

以下是Android设备与BLE设备互动时适用的角色和职责：

中央与外围。这适用于BLE连接本身。处于中心角色的设备扫描，寻找广告，并且外围角色中的设备进行广告。

GATT服务器与GATT客户端。这决定了两个设备在建立连接后如何相互通信。

BLE权限

首先，需要在manifest中声明使用蓝牙和操作蓝牙的权限

在应用程序清单文件中声明蓝牙权限。例如： <uses-permission android:name="android.permission.BLUETOOTH"/> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

如果您要声明自己的应用只适用于支持BLE的设备，请在应用清单中包含以下内容：

<uses-feature android：name =“android.hardware.bluetooth_le”android：required =“true”/>

不过，如果您想让应用程式适用于不支援BLE的装置，您仍应在应用的清单中加入这个元素，但required="false"设为required="false" 。然后在运行时，您可以通过使用PackageManager.hasSystemFeature()确定BLE可用性：

 // Use this check to determine whether BLE is supported on the device.  Then
 // you can selectively disable BLE-related features.
 if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
     Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
     finish();
 }

在android 6.0 以后，要想获得蓝牙扫描结果，还需要下面的权限

 <manifest ... >
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     ...
     <!-- Needed only if your app targets Android 5.0 (API level 21) or higher.  -->
     <uses-feature android:name="android.hardware.location.gps" />
     ...
 </manifest>

设置蓝牙

1.Get the BluetoothAdapter

获得蓝牙适配器

 private BluetoothAdapter mBluetoothAdapter;
 ...
 // Initializes Bluetooth adapter.
 final BluetoothManager bluetoothManager =
         (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
 mBluetoothAdapter = bluetoothManager.getAdapter();

2.Enable Bluetooth

打开蓝牙

 // Ensures Bluetooth is available on the device and it is enabled.  If not,
 // displays a dialog requesting user permission to enable Bluetooth.
 if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
     Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
     startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
 }

3.初始化BLE蓝牙广播（广告）

(1)广播的设置 (2)设置广播的数据 (3)设置响应的数据 (4)设置连接回调

    private void initGATTServer() {
        AdvertiseSettings settings = new AdvertiseSettings.Builder()
                .setConnectable(true)
                .build();

        AdvertiseData advertiseData = new AdvertiseData.Builder()
                .setIncludeDeviceName(true)
                .setIncludeTxPowerLevel(true)
                .build();

        AdvertiseData scanResponseData = new AdvertiseData.Builder()
                .addServiceUuid(new ParcelUuid(UUID_SERVER))
                .setIncludeTxPowerLevel(true)
                .build();


        AdvertiseCallback callback = new AdvertiseCallback() {

            @Override
            public void onStartSuccess(AdvertiseSettings settingsInEffect) {
                Log.d(TAG, "BLE advertisement added successfully");
                showText("1. initGATTServer success");
                println("1. initGATTServer success");
                initServices(getContext());
            }

            @Override
            public void onStartFailure(int errorCode) {
                Log.e(TAG, "Failed to add BLE advertisement, reason: " + errorCode);
                showText("1. initGATTServer failure");
            }
        };

        BluetoothLeAdvertiser bluetoothLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();
        bluetoothLeAdvertiser.startAdvertising(settings, advertiseData, scanResponseData, callback);
    }

在被BLE设备连接后，将触发 AdvertiseCallback 的 onStartSuccess，我们在这之后，初始化GATT的服务

4.初始化GATT的服务

(1) 通过 mBluetoothManager.openGattServer() 获得 bluetoothGattServer (2) 添加服务，特征，描述。这些内容要让客户端知道。

    private void initServices(Context context) {
        bluetoothGattServer = mBluetoothManager.openGattServer(context, bluetoothGattServerCallback);
        BluetoothGattService service = new BluetoothGattService(UUID_SERVER, BluetoothGattService.SERVICE_TYPE_PRIMARY);

        //add a read characteristic.
        characteristicRead = new BluetoothGattCharacteristic(UUID_CHARREAD, BluetoothGattCharacteristic.PROPERTY_READ, BluetoothGattCharacteristic.PERMISSION_READ);
        //add a descriptor
        BluetoothGattDescriptor descriptor = new BluetoothGattDescriptor(UUID_DESCRIPTOR, BluetoothGattCharacteristic.PERMISSION_WRITE);
        characteristicRead.addDescriptor(descriptor);
        service.addCharacteristic(characteristicRead);

        //add a write characteristic.
        BluetoothGattCharacteristic characteristicWrite = new BluetoothGattCharacteristic(UUID_CHARWRITE,
                BluetoothGattCharacteristic.PROPERTY_WRITE |
                        BluetoothGattCharacteristic.PROPERTY_READ |
                        BluetoothGattCharacteristic.PROPERTY_NOTIFY,
                BluetoothGattCharacteristic.PERMISSION_WRITE);
        service.addCharacteristic(characteristicWrite);

        bluetoothGattServer.addService(service);
        Log.e(TAG, "2. initServices ok");
        showText("2. initServices ok");
    }

在 openGattServer 方法中，我们需要传入个回调 bluetoothGattServer = mBluetoothManager.openGattServer(context, bluetoothGattServerCallback);

5.配置数据交互回调

回调时间有：连接状态变化，收发消息，通知消息

/**
     * 服务事件的回调
     */
    private BluetoothGattServerCallback bluetoothGattServerCallback = new BluetoothGattServerCallback() {

        /**
         * 1.连接状态发生变化时
         * @param device
         * @param status
         * @param newState
         */
        @Override
        public void onConnectionStateChange(BluetoothDevice device, int status, int newState) {
            Log.e(TAG, String.format("1.onConnectionStateChange：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("1.onConnectionStateChange：status = %s, newState =%s ", status, newState));
            super.onConnectionStateChange(device, status, newState);
        }

        @Override
        public void onServiceAdded(int status, BluetoothGattService service) {
            super.onServiceAdded(status, service);
            Log.e(TAG, String.format("onServiceAdded：status = %s", status));
        }

        @Override
        public void onCharacteristicReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattCharacteristic characteristic) {
            Log.e(TAG, String.format("onCharacteristicReadRequest：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("onCharacteristicReadRequest：requestId = %s, offset = %s", requestId, offset));

            bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, characteristic.getValue());
//            super.onCharacteristicReadRequest(device, requestId, offset, characteristic);
        }

        /**
         * 3. onCharacteristicWriteRequest,接收具体的字节
         * @param device
         * @param requestId
         * @param characteristic
         * @param preparedWrite
         * @param responseNeeded
         * @param offset
         * @param requestBytes
         */
        @Override
        public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] requestBytes) {
            Log.e(TAG, String.format("3.onCharacteristicWriteRequest：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("3.onCharacteristicWriteRequest：requestId = %s, preparedWrite=%s, responseNeeded=%s, offset=%s, value=%s", requestId, preparedWrite, responseNeeded, offset, OutputStringUtil.toHexString(requestBytes)));
            bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, requestBytes);
            //4.处理响应内容
            onResponseToClient(requestBytes, device, requestId, characteristic);
        }

        /**
         * 2.描述被写入时，在这里执行 bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS...  收，触发 onCharacteristicWriteRequest
         * @param device
         * @param requestId
         * @param descriptor
         * @param preparedWrite
         * @param responseNeeded
         * @param offset
         * @param value
         */
        @Override
        public void onDescriptorWriteRequest(BluetoothDevice device, int requestId, BluetoothGattDescriptor descriptor, boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) {
            Log.e(TAG, String.format("2.onDescriptorWriteRequest：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("2.onDescriptorWriteRequest：requestId = %s, preparedWrite = %s, responseNeeded = %s, offset = %s, value = %s,", requestId, preparedWrite, responseNeeded, offset, OutputStringUtil.toHexString(value)));

            // now tell the connected device that this was all successfull
            bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);
        }

        /**
         * 5.特征被读取。当回复响应成功后，客户端会读取然后触发本方法
         * @param device
         * @param requestId
         * @param offset
         * @param descriptor
         */
        @Override
        public void onDescriptorReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattDescriptor descriptor) {
            Log.e(TAG, String.format("onDescriptorReadRequest：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("onDescriptorReadRequest：requestId = %s", requestId));
//            super.onDescriptorReadRequest(device, requestId, offset, descriptor);
            bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, null);
        }

        @Override
        public void onNotificationSent(BluetoothDevice device, int status) {
            super.onNotificationSent(device, status);
            Log.e(TAG, String.format("5.onNotificationSent：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("5.onNotificationSent：status = %s", status));
        }

        @Override
        public void onMtuChanged(BluetoothDevice device, int mtu) {
            super.onMtuChanged(device, mtu);
            Log.e(TAG, String.format("onMtuChanged：mtu = %s", mtu));
        }

        @Override
        public void onExecuteWrite(BluetoothDevice device, int requestId, boolean execute) {
            super.onExecuteWrite(device, requestId, execute);
            Log.e(TAG, String.format("onExecuteWrite：requestId = %s", requestId));
        }
    };

6.处理来自客户端发来的数据和发送回复数据：

调用 bluetoothGattServer.notifyCharacteristicChanged 方法，通知数据改变。

        /**
         * 4.处理响应内容
         *
         * @param reqeustBytes
         * @param device
         * @param requestId
         * @param characteristic
         */
        private void onResponseToClient(byte[] reqeustBytes, BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic) {
            Log.e(TAG, String.format("4.onResponseToClient：device name = %s, address = %s", device.getName(), device.getAddress()));
            Log.e(TAG, String.format("4.onResponseToClient：requestId = %s", requestId));
            String msg = OutputStringUtil.transferForPrint(reqeustBytes);
            println("4.收到:" + msg);
            showText("4.收到:" + msg);

            String str = new String(reqeustBytes) + " hello>";
            characteristicRead.setValue(str.getBytes());
            bluetoothGattServer.notifyCharacteristicChanged(device, characteristicRead, false);

            println("4.响应:" + str);
            showText("4.响应:" + str);
        }

交互流程：

(1) 当客户端开始写入数据时：触发回调方法 onDescriptorWriteRequest (2) 在 onDescriptorWriteRequest 方法中，执行下面的方法表示写入成功 BluetoothGatt.GATT_SUCCESS

       bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);

执行 sendResponse后，会触发回调方法 onCharacteristicWriteRequest

(3) 在 onCharacteristicWriteRequest方法中

        public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] requestBytes) {

这个里可以获得 来自客户端发来的数据 requestBytes

(4) 处理响应内容,我写了这个方法：

    onResponseToClient(requestBytes, device, requestId, characteristic);
在这个方法中，通过 bluetoothGattServer.notifyCharacteristicChanged()方法 回复数据

通过日志，我们看看事件触发的顺序

1.onConnectionStateChange：device name = null, address = 74:32:DE:49:3C:28
1.onConnectionStateChange：status = 0, newState =2
2.onDescriptorWriteRequest：device name = null, address = 74:32:DE:49:3C:28
2.onDescriptorWriteRequest：requestId = 1, preparedWrite = false, responseNeeded = true, offset = 0, value = [01,00,],
3.onCharacteristicWriteRequest：device name = null, address = 74:32:DE:49:3C:28
3.onCharacteristicWriteRequest：requestId = 2, preparedWrite=false, responseNeeded=false, offset=0, value=[41,54,45,30,0D,]
4.onResponseToClient：device name = null, address = 74:32:DE:49:3C:28
4.onResponseToClient：requestId = 2
4.收到:ATE0
4.响应:ATE0 hello>
5.onNotificationSent：device name = null, address = 74:32:DE:49:3C:28
5.onNotificationSent：status = 0