连接到 GATT 服务器

与 BLE 设备交互的第一步是连接该设备。更多 具体来说就是连接到设备上的 GATT 服务器。关联 GATT 服务器，请使用 connectGatt() 方法。此方法采用三个参数： Context 对象，autoConnect（一个布尔值） 指示是否在 BLE 设备完成后立即自动连接到 可用），并且引用了 BluetoothGattCallback：

Kotlin

var bluetoothGatt: BluetoothGatt? = null
...

bluetoothGatt = device.connectGatt(this, false, gattCallback)

Java

bluetoothGatt = device.connectGatt(this, false, gattCallback);

这将连接到由 BLE 设备托管的 GATT 服务器，并返回 BluetoothGatt 实例， 然后，您可以使用它执行 GATT 客户端操作。调用方（Android 应用） 是 GATT 客户端通过 BluetoothGattCallback 用于向客户端传递结果，例如 连接状态，以及任何进一步的 GATT 客户端操作。

设置绑定服务

在以下示例中，BLE 应用提供了一个 activity (DeviceControlActivity) 可连接到蓝牙设备、显示设备数据、 并显示设备支持的 GATT 服务和特征。位于 该活动会与 Service 调用了 BluetoothLeService， 通过 BLE API 与 BLE 设备进行交互。沟通是 使用绑定服务执行，这样， 要连接到 BluetoothLeService 并调用函数的 activity 连接到设备BluetoothLeService需要 Binder 实现，可提供对 服务。

Kotlin

class BluetoothLeService : Service() {

    private val binder = LocalBinder()

    override fun onBind(intent: Intent): IBinder? {
        return binder
    }

    inner class LocalBinder : Binder() {
        fun getService() : BluetoothLeService {
            return this@BluetoothLeService
        }
    }
}

Java

class BluetoothLeService extends Service {

    private Binder binder = new LocalBinder();

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    class LocalBinder extends Binder {
        public BluetoothLeService getService() {
            return BluetoothLeService.this;
        }
    }
}

activity 可以使用以下代码启动服务： bindService()、 传入 Intent 以启动 服务，即ServiceConnection 用于监听连接和断开连接事件的实现，以及一个用于 以指定其他连接选项。

Kotlin

class DeviceControlActivity : AppCompatActivity() {

    private var bluetoothService : BluetoothLeService? = null

    // Code to manage Service lifecycle.
    private val serviceConnection: ServiceConnection = object : ServiceConnection {
        override fun onServiceConnected(
            componentName: ComponentName,
            service: IBinder
        ) {
            bluetoothService = (service as LocalBinder).getService()
            bluetoothService?.let { bluetooth ->
                // call functions on service to check connection and connect to devices
            }
        }

        override fun onServiceDisconnected(componentName: ComponentName) {
            bluetoothService = null
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.gatt_services_characteristics)

        val gattServiceIntent = Intent(this, BluetoothLeService::class.java)
        bindService(gattServiceIntent, serviceConnection, Context.BIND_AUTO_CREATE)
    }
}

Java

class DeviceControlActivity extends AppCompatActivity {

    private BluetoothLeService bluetoothService;

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            bluetoothService = ((LocalBinder) service).getService();
            if (bluetoothService != null) {
                // call functions on service to check connection and connect to devices
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            bluetoothService = null;
        }
    };

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.gatt_services_characteristics);

        Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
        bindService(gattServiceIntent, serviceConnection, Context.BIND_AUTO_CREATE);
    }
}

设置 BluetoothAdapter

服务被绑定后，需要访问 BluetoothAdapter。它应该 检查适配器在设备上是否可用。请参阅设置 蓝牙，详细了解 BluetoothAdapter。以下示例将此设置代码封装在 initialize() 函数，用于返回表示成功的 Boolean 值。

Kotlin

private const val TAG = "BluetoothLeService"

class BluetoothLeService : Service() {

    private var bluetoothAdapter: BluetoothAdapter? = null

    fun initialize(): Boolean {
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
        if (bluetoothAdapter == null) {
            Log.e(TAG, "Unable to obtain a BluetoothAdapter.")
            return false
        }
        return true
    }

    ...
}

Java

class BluetoothLeService extends Service {

    public static final String TAG = "BluetoothLeService";

    private BluetoothAdapter bluetoothAdapter;

    public boolean initialize() {
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (bluetoothAdapter == null) {
            Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
            return false;
        }
        return true;
    }

    ...
}

此 activity 将在其 ServiceConnection 实现中调用此函数。 处理 initialize() 函数的 false 返回值取决于 应用。您可以向用户显示一条错误消息 当前设备不支持蓝牙操作或停用任何功能 需要蓝牙才能工作在以下示例中， 系统会对 activity 调用 finish() 可将用户带回上一屏幕。

Kotlin

class DeviceControlActivity : AppCompatActivity() {

    // Code to manage Service lifecycle.
    private val serviceConnection: ServiceConnection = object : ServiceConnection {
        override fun onServiceConnected(
            componentName: ComponentName,
            service: IBinder
        ) {
            bluetoothService = (service as LocalBinder).getService()
            bluetoothService?.let { bluetooth ->
                if (!bluetooth.initialize()) {
                    Log.e(TAG, "Unable to initialize Bluetooth")
                    finish()
                }
                // perform device connection
            }
        }

        override fun onServiceDisconnected(componentName: ComponentName) {
            bluetoothService = null
        }
    }

    ...
}

Java

class DeviceControlsActivity extends AppCompatActivity {

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            bluetoothService = ((LocalBinder) service).getService();
            if (bluetoothService != null) {
                if (!bluetoothService.initialize()) {
                    Log.e(TAG, "Unable to initialize Bluetooth");
                    finish();
                }
                // perform device connection
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            bluetoothService = null;
        }
    };

    ...
}

连接到设备

初始化 BluetoothLeService 实例后，它可以连接到 BLE 设备。activity 需要将设备地址发送给服务，然后才能 发起连接。该服务将首先调用 getRemoteDevice() 在 BluetoothAdapter 上访问该设备。如果适配器找不到 在具有该地址的设备时，getRemoteDevice() 会抛出一个 IllegalArgumentException。

Kotlin

fun connect(address: String): Boolean {
    bluetoothAdapter?.let { adapter ->
        try {
            val device = adapter.getRemoteDevice(address)
        } catch (exception: IllegalArgumentException) {
            Log.w(TAG, "Device not found with provided address.")
            return false
        }
    // connect to the GATT server on the device
    } ?: run {
        Log.w(TAG, "BluetoothAdapter not initialized")
        return false
    }
}

Java

public boolean connect(final String address) {
    if (bluetoothAdapter == null || address == null) {
        Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
        return false;
    }

    try {
        final BluetoothDevice device = bluetoothAdapter.getRemoteDevice(address);
    } catch (IllegalArgumentException exception) {
        Log.w(TAG, "Device not found with provided address.");
        return false;
    }
    // connect to the GATT server on the device
}

当服务被触发后，DeviceControlActivity 会调用此 connect() 函数。 初始化。activity 需要传入 BLE 设备的地址。在 在以下示例中，设备地址将作为 intent 传递给 activity extra。

Kotlin

// Code to manage Service lifecycle.
private val serviceConnection: ServiceConnection = object : ServiceConnection {
    override fun onServiceConnected(
    componentName: ComponentName,
    service: IBinder
    ) {
        bluetoothService = (service as LocalBinder).getService()
        bluetoothService?.let { bluetooth ->
            if (!bluetooth.initialize()) {
                Log.e(TAG, "Unable to initialize Bluetooth")
                finish()
            }
            // perform device connection
            bluetooth.connect(deviceAddress)
        }
    }

    override fun onServiceDisconnected(componentName: ComponentName) {
        bluetoothService = null
    }
}

Java

private ServiceConnection serviceConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        bluetoothService = ((LocalBinder) service).getService();
        if (bluetoothService != null) {
            if (!bluetoothService.initialize()) {
                Log.e(TAG, "Unable to initialize Bluetooth");
                finish();
            }
            // perform device connection
            bluetoothService.connect(deviceAddress);
        }
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        bluetoothService = null;
    }
};

声明 GATT 回调

一旦该 activity 告知服务要连接到哪个设备和该服务 连接到设备时，服务需要连接到 BLE 设备。此连接需要 BluetoothGattCallback 才能接收 有关连接状态、服务发现、特征 读取和特征通知

本主题重点介绍连接状态通知。请参阅传输 BLE 数据来了解如何 服务发现、特征读取和请求特征 通知。

通过 onConnectionStateChange() 函数。 在以下示例中，回调是在 Service 类中定义的，因此它 可以搭配 BluetoothDevice 发生 服务就会连接到该网络。

Kotlin

private val bluetoothGattCallback = object : BluetoothGattCallback() {
    override fun onConnectionStateChange(gatt: BluetoothGatt?, status: Int, newState: Int) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            // successfully connected to the GATT Server
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            // disconnected from the GATT Server
        }
    }
}

Java

private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            // successfully connected to the GATT Server
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            // disconnected from the GATT Server
        }
    }
};

连接到 GATT 服务

声明 BluetoothGattCallback 后，该服务便可使用 connect() 函数中的 BluetoothDevice 对象，用于连接到 GATT 服务。

通过 connectGatt() 函数。这需要一个 Context 对象，这是一个 autoConnect 布尔值 标志和 BluetoothGattCallback。在此示例中，应用直接 连接到 BLE 设备，因此系统会为 autoConnect 传递 false。

此外，还添加了 BluetoothGatt 属性。这样，该服务就可以关闭 。

Kotlin

class BluetoothLeService : Service() {

...

    private var bluetoothGatt: BluetoothGatt? = null

    ...

    fun connect(address: String): Boolean {
        bluetoothAdapter?.let { adapter ->
            try {
                val device = adapter.getRemoteDevice(address)
                // connect to the GATT server on the device
                bluetoothGatt = device.connectGatt(this, false, bluetoothGattCallback)
                return true
            } catch (exception: IllegalArgumentException) {
                Log.w(TAG, "Device not found with provided address.  Unable to connect.")
                return false
            }
        } ?: run {
            Log.w(TAG, "BluetoothAdapter not initialized")
            return false
        }
    }
}

Java

class BluetoothLeService extends Service {

...

    private BluetoothGatt bluetoothGatt;

    ...

    public boolean connect(final String address) {
        if (bluetoothAdapter == null || address == null) {
            Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
            return false;
        }
        try {
            final BluetoothDevice device = bluetoothAdapter.getRemoteDevice(address);
            // connect to the GATT server on the device
            bluetoothGatt = device.connectGatt(this, false, bluetoothGattCallback);
            return true;
        } catch (IllegalArgumentException exception) {
            Log.w(TAG, "Device not found with provided address.  Unable to connect.");
            return false;
        }
    }
}

广播动态

当服务器与 GATT 服务器连接或断开连接时，需要通知 新状态的 activity。您可以通过多种方式实现这一目标。通过 以下示例使用广播 从服务传递到 activity 的信息。

该服务会声明一个函数来广播新状态。此函数将 操作字符串中，该字符串在广播之前会传递到 Intent 对象 发送到系统。

Kotlin

private fun broadcastUpdate(action: String) {
    val intent = Intent(action)
    sendBroadcast(intent)
}

Java

private void broadcastUpdate(final String action) {
    final Intent intent = new Intent(action);
    sendBroadcast(intent);
}

广播函数设置好后，即可用在 BluetoothGattCallback，用于发送 GATT 服务器。声明常量和服务的当前连接状态 。Intent

Kotlin

class BluetoothLeService : Service() {

    private var connectionState = STATE_DISCONNECTED

    private val bluetoothGattCallback: BluetoothGattCallback = object : BluetoothGattCallback() {
        override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                // successfully connected to the GATT Server
                connectionState = STATE_CONNECTED
                broadcastUpdate(ACTION_GATT_CONNECTED)
            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                // disconnected from the GATT Server
                connectionState = STATE_DISCONNECTED
                broadcastUpdate(ACTION_GATT_DISCONNECTED)
            }
        }
    }

    ...

    companion object {
        const val ACTION_GATT_CONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_CONNECTED"
        const val ACTION_GATT_DISCONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED"

        private const val STATE_DISCONNECTED = 0
        private const val STATE_CONNECTED = 2

    }
}

Java

class BluetoothLeService extends Service {

    public final static String ACTION_GATT_CONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_CONNECTED";
    public final static String ACTION_GATT_DISCONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED";

    private static final int STATE_DISCONNECTED = 0;
    private static final int STATE_CONNECTED = 2;

    private int connectionState;
    ...

    private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                // successfully connected to the GATT Server
                connectionState = STATE_CONNECTED;
                broadcastUpdate(ACTION_GATT_CONNECTED);
            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                // disconnected from the GATT Server
                connectionState = STATE_DISCONNECTED;
                broadcastUpdate(ACTION_GATT_DISCONNECTED);
            }
        }
    };

    …
}

在活动中监听更新

服务广播连接更新后，activity 需要 实现 BroadcastReceiver。 在设置 activity 时注册此接收器，并在 activity 正在离开屏幕。通过监听来自该服务的事件， activity 能够根据当前的 BLE 设备的连接状态。

Kotlin

class DeviceControlActivity : AppCompatActivity() {

...

    private val gattUpdateReceiver: BroadcastReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            when (intent.action) {
                BluetoothLeService.ACTION_GATT_CONNECTED -> {
                    connected = true
                    updateConnectionState(R.string.connected)
                }
                BluetoothLeService.ACTION_GATT_DISCONNECTED -> {
                    connected = false
                    updateConnectionState(R.string.disconnected)
                }
            }
        }
    }

    override fun onResume() {
        super.onResume()
        registerReceiver(gattUpdateReceiver, makeGattUpdateIntentFilter())
        if (bluetoothService != null) {
            val result = bluetoothService!!.connect(deviceAddress)
            Log.d(DeviceControlsActivity.TAG, "Connect request result=$result")
        }
    }

    override fun onPause() {
        super.onPause()
        unregisterReceiver(gattUpdateReceiver)
    }

    private fun makeGattUpdateIntentFilter(): IntentFilter? {
        return IntentFilter().apply {
            addAction(BluetoothLeService.ACTION_GATT_CONNECTED)
            addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED)
        }
    }
}

Java

class DeviceControlsActivity extends AppCompatActivity {

...

    private final BroadcastReceiver gattUpdateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final String action = intent.getAction();
            if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
                connected = true;
                updateConnectionState(R.string.connected);
            } else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
                connected = false;
                updateConnectionState(R.string.disconnected);
            }
        }
    };

    @Override
    protected void onResume() {
        super.onResume();

        registerReceiver(gattUpdateReceiver, makeGattUpdateIntentFilter());
        if (bluetoothService != null) {
            final boolean result = bluetoothService.connect(deviceAddress);
            Log.d(TAG, "Connect request result=" + result);
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(gattUpdateReceiver);
    }

    private static IntentFilter makeGattUpdateIntentFilter() {
        final IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
        return intentFilter;
    }
}

在传输 BLE 数据中，执行以下操作： BroadcastReceiver 也用于以如下形式传达服务发现： 以及来自设备的特征数据。

关闭 GATT 连接

处理蓝牙连接时，一个重要的步骤是关闭 使用它们。为此，请调用 close() 针对 BluetoothGatt 对象调用函数。在以下示例中，服务 存储对 BluetoothGatt 的引用。当 activity 与 服务，连接会关闭，以免消耗设备电池电量。

Kotlin

class BluetoothLeService : Service() {

...

    override fun onUnbind(intent: Intent?): Boolean {
        close()
        return super.onUnbind(intent)
    }

    private fun close() {
        bluetoothGatt?.let { gatt ->
            gatt.close()
            bluetoothGatt = null
        }
    }
}

Java

class BluetoothLeService extends Service {

...

      @Override
      public boolean onUnbind(Intent intent) {
          close();
          return super.onUnbind(intent);
      }

      private void close() {
          if (bluetoothGatt == null) {
              Return;
          }
          bluetoothGatt.close();
          bluetoothGatt = null;
      }
}