與 BLE 裝置互動的第一步是連線至裝置。更多內容
具體來說，就是連線至裝置上的 GATT 伺服器為了連線至 GATT
伺服器連線，請使用
connectGatt()敬上
方法。這個方法使用三個參數：
Context 物件，autoConnect (布林值
表示是否要在 BLE 裝置時自動與其連線
可用)，以及指向
BluetoothGattCallback：
var bluetoothGatt: BluetoothGatt? = null
...
bluetoothGatt = device.connectGatt(this, false, gattCallback)
bluetoothGatt = device.connectGatt(this, false, gattCallback);
這會連線至 BLE 裝置代管的 GATT 伺服器，並傳回
BluetoothGatt 執行個體，
之後就能用於執行 GATT 用戶端作業呼叫端 (Android 應用程式)
是 GATT 用戶端
BluetoothGattCallback 的用途是將結果提供給用戶端，例如
連線狀態，以及任何進一步的 GATT 用戶端作業。
設定繫結服務
在以下範例中，BLE 應用程式提供一項活動
(DeviceControlActivity) 必須連線至藍牙裝置、顯示裝置資料、
並顯示裝置支援的 GATT 服務和特性。根據地
使用者輸入內容時，這個活動就會與
名為 BluetoothLeService 的 Service，
透過 BLE API 與 BLE 裝置互動。溝通過程
是透過「繫結服務」執行，
連結到 BluetoothLeService 並呼叫函式
連線至裝置。BluetoothLeService 需要
Binder實作
為活動提供服務
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
}
}
}
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;
}
}
}
活動可透過
bindService()、
傳入 Intent 即可開始
服務、ServiceConnection
接聽連線和中斷連線事件的實作，以及
指定其他連線選項。
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)
}
}
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);
}
}
設定 BluetoothAdapter
繫結至服務後，服務必須存取
BluetoothAdapter。它應該
檢查裝置是否有可用的轉接頭。請參閱設定
藍牙。
BluetoothAdapter。以下範例會將此設定程式碼納入
initialize() 函式，會傳回表示成功的 Boolean 值。
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
}
...
}
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;
}
...
}
活動會在其 ServiceConnection 實作中呼叫此函式。
如何處理 initialize() 函式中的假傳回值，取決於您的
應用程式。您可能會看到錯誤訊息，指出
目前的裝置不支援藍牙作業或停用任何功能
需要藍牙才能運作在以下範例中
在活動上呼叫 finish()
返回上一個畫面。
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
}
}
...
}
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;
}
};
...
}
連結裝置
BluetoothLeService 例項初始化後，即可連線至 BLE
裝置。該活動必須將裝置位址傳送給服務，
啟動連線。服務會先呼叫
getRemoteDevice()敬上
前往 BluetoothAdapter 存取裝置。如果轉接程式找不到
變更位址的裝置時，getRemoteDevice() 會擲回
IllegalArgumentException。
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
}
}
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
}
DeviceControlActivity 會在服務收到要求後呼叫此 connect() 函式
初始化。活動需要傳入 BLE 裝置的地址。於
以下範例會將裝置位址做為意圖傳遞至活動
外加。
// 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
}
}
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;
}
};
宣告 GATT 回呼
一旦該活動告知服務要連線至哪個裝置與服務
可連線至裝置，服務必須連線至
BLE 裝置。需要「BluetoothGattCallback」才能接收這個連線
連線狀態、服務探索、特性相關通知
讀取與特性通知
本主題著重於連線狀態通知。請參閱轉移 BLE 另闢蹊徑 服務探索、特性讀取和要求特性 通知。
onConnectionStateChange()敬上
函式。
在以下範例中，回呼是在 Service 類別中定義，因此在
可搭配
BluetoothDevice
每個 Pod 的 IP 位址
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
}
}
}
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
}
}
};
連線至 GATT 服務
宣告 BluetoothGattCallback 後，服務即可使用
connect() 函式中的 BluetoothDevice 物件，用來連線至 GATT
必須在裝置上使用額外服務
connectGatt()敬上
函式。這需要 Context 物件，即 autoConnect 布林值
標記和 BluetoothGattCallback。在這個例子中，應用程式
正在連線到 BLE 裝置，因此 false 會傳遞 autoConnect。
系統會一併新增 BluetoothGatt 屬性。這樣一來，服務就能關閉
連線
要求執行虛擬機器
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
}
}
}
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;
}
}
}
廣播更新
伺服器與 GATT 伺服器連線或中斷連線時，必須傳送通知給 新狀態的活動有幾種方法可以完成此操作。 以下範例使用廣播傳送 相關資訊
服務會宣告一個函式，以廣播新狀態。這個函式
，在廣播前傳遞至 Intent 物件的動作字串中
傳送至系統
private fun broadcastUpdate(action: String) {
val intent = Intent(action)
sendBroadcast(intent)
}
private void broadcastUpdate(final String action) {
final Intent intent = new Intent(action);
sendBroadcast(intent);
}
廣播函式設定完成後，
BluetoothGattCallback：將連線狀態的相關資訊
GATT 伺服器系統會宣告常數和服務目前的連線狀態
在代表 Intent 動作的服務中。
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
}
}
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);
}
}
};
…
}
監聽活動的最新消息
服務廣播連線更新後，活動
實作 BroadcastReceiver。
在設定活動時註冊這個接收器，並在
活動離開畫面。透過監聽服務中的事件
活動可以根據目前的
連線狀態。
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)
}
}
}
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「轉移 BLE 資料」中，
BroadcastReceiver 也可用來將服務探索結果傳達為
以及來自裝置的特徵資料
關閉 GATT 連線
使用藍牙連線時，其中一個重要步驟是關閉
。方法是呼叫 close()
函式，BluetoothGatt。在以下範例中
保留 BluetoothGatt 的參照。當活動與
服務，系統就會關閉連線，避免裝置電力耗盡。
class BluetoothLeService : Service() {
...
override fun onUnbind(intent: Intent?): Boolean {
close()
return super.onUnbind(intent)
}
private fun close() {
bluetoothGatt?.let { gatt ->
gatt.close()
bluetoothGatt = null
}
}
}
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;
}
}