一.BLE介紹
BLE是Bluetooth Low Energy的縮寫，又叫藍牙4.0，區別於藍牙3.0和之前的技術。BLE前身是NOKIA開發的Wibree技術，主要用於實現移動智能終端與周邊配件之間的持續連接，是功耗極低的短距離無線通信技術，並且有效傳輸距離被提升到了100米以上，同時只需要一顆鈕釦電池就可以工作數年之久。BLE是在藍牙技術的基礎上發展起來的，既同於藍牙，又區別於傳統藍牙。BLE設備分單模和雙模兩種，雙模簡稱BR，商標爲Bluetooth Smart Ready，單模簡稱BLE或者LE,商標爲Bluetooth Smart。Android是在4.3後才支持BLE，這說明不是所有藍牙手機都支持BLE，而且支持BLE的藍牙手機一般是雙模的。雙模兼容傳統藍牙，可以和傳統藍牙通信，也可以和BLE通信，常用在手機上，android4.3和IOS4.0之後版本都支持BR，也就是雙模設備。單模只能和BR和單模的設備通信，不能和傳統藍牙通信，由於功耗低，待機長，所以常用在手環的智能設備上。
二、基本概念
Generic Access Profile(GAP)
用來控制設備連接和廣播，GAP使你的設備被其他設備可見，並決定了你的設備是否可以或者怎樣與合同設備進行交互。Generic Attribute Profile(GATT)
通過BLE連接，讀寫屬性類數據的Profile通用規範，現在所有的BLE應用Profile都是基於GATT的。Attribute Protocol (ATT)
GATT是基於ATTProtocol的，ATT針對BLE設備做了專門的優化，具體就是在傳輸過程中使用盡量少的數據，每個屬性都有一個唯一的UUID，屬性將以characteristics and services的形式傳輸。Characteristic
Characteristic可以理解爲一個數據類型，它包括一個value和0至多個對次value的描述（Descriptor）。Descriptor
對Characteristic的描述，例如範圍、計量單位等。Service
Characteristic的集合。例如一個service叫做“Heart Rate Monitor”，它可能包含多個Characteristics，其中可能包含一個叫做“heart ratemeasurement”的Characteristic。UUID
唯一標示符，每個Service，Characteristic，Descriptor，都是由一個UUID定義。
三、Android BLE API
BluetoothManager:
通過BluetoothManager來獲取BluetoothAdapter。
BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);BluetoothAdapter:
代表了移動設備的本地的藍牙適配器, 通過該藍牙適配器可以對藍牙進行基本操作，一個Android系統只有一個BluetoothAdapter，通過BluetoothManager獲取。
BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();BluetoothDevice:
掃描後發現可連接的設備，獲取已經連接的設備。
BluetoothDevice bluetoothDevice = bluetoothAdapter.getRemoteDevice(address);BluetoothGatt:
繼承BluetoothProfile，通過BluetoothGatt可以連接設備（connect）,發現服務（discoverServices），並把相應地屬性返回到BluetoothGattCallback，可以看成藍牙設備從連接到斷開的生命週期。BluetoothGattCharacteristic:
相當於一個數據類型，可以看成一個特徵或能力，它包括一個value和0~n個value的描述（BluetoothGattDescriptor）。BluetoothGattDescriptor:
描述符，對Characteristic的描述，包括範圍、計量單位等。BluetoothGattService:
服務，Characteristic的集合。BluetoothProfile:
一個通用的規範，按照這個規範來收發數據。BluetoothGattCallback:
已經連接上設備，對設備的某些操作後返回的結果。- onConnectionStateChange:Callback indicating when GATT client has connected/disconnected to/from a remote GATT server.
- onServicesDiscovered:Callback invoked when the list of remote services, characteristics and descriptors for the remote device have been updated, ie new services have been discovered.
- onCharacteristicChanged:Callback triggered as a result of a remote characteristic notification.
- onCharacteristicRead:Callback reporting the result of a characteristic read operation.
- onCharacteristicWrite:Callback indicating the result of a characteristic write operation.
四、操作流程
google GitHub例子連接BluetoothLe
google Developers Bluetooth SDK reference
首先權限不能忘：
uses-permission android:name=”android.permission.ACCESS_COARSE_LOCATION” />
uses-permission android:name=”android.permission.BLUETOOTH” />
uses-permission android:name=”android.permission.BLUETOOTH_ADMIN” />
除了藍牙權限外，如果需要BLE feature則還需要聲明uses-feature：
uses-featureandroid:name=”android.hardware.bluetooth_le”android:required=”true”/>
按時required爲true時，則應用只能在支持BLE的Android設備上安裝運行；required爲false時，Android設備均可正常安裝運行，需要在代碼運行時判斷設備是否支持BLE feature
1.開啓藍牙
在使用藍牙BLE之前，需要確認Android設備是否支持BLE feature(required爲false時)，另外要需要確認藍牙是否打開。如果發現不支持BLE，則不能使用BLE相關的功能；如果支持BLE，但是藍牙沒打開，則需要打開藍牙。代碼示例如下：
// 檢查當前手機是否支持ble 藍牙,如果不支持退出程序
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
finish();
}
//初始化 Bluetooth adapter, 通過藍牙管理器得到一個參考藍牙適配器(API必須在以上android4.3或以上和版本)
final BluetoothManager bluetoothManager = (BluetoothManager)getSystemService(Context.BLUETOOTH_SERVICE);
// 檢查設備上是否支持藍牙
mBluetoothAdapter = bluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Toast.makeText(this, R.string.error_bluetooth_not_supported, Toast.LENGTH_SHORT).show();
finish();
return;
}
//自Android 6.0開始需要打開位置權限纔可以搜索到Ble設備
//如果 API level 是大於等於 23(Android 6.0) 時判斷是否具有權限，
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
//判斷是否具有權限
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
//請求權限
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},REQUEST_CODE_ACCESS_COARSE_LOCATION);
}
}
Boolean result =isLocationEnable(this);
if (result){
Log.e(TAG, "用戶以打開定位功能===");
}else {
setLocationService();
}
執行完上面的請求權限後，系統會彈出提示框讓用戶選擇是否允許改權限。選擇的結果可以在回到接口中得知：
//執行完上面的請求權限後，系統會彈出提示框讓用戶選擇是否允許改權限。選擇的結果可以在回到接口中得知：
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
if (requestCode == REQUEST_CODE_ACCESS_COARSE_LOCATION) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
//用戶允許改權限，0表示允許，-1表示拒絕 PERMISSION_GRANTED = 0， PERMISSION_DENIED = -1
//permission was granted, yay! Do the contacts-related task you need to do.
//這裏進行授權被允許的處理
Log.e(TAG, "允許定位權限===");
} else {
//permission denied, boo! Disable the functionality that depends on this permission.
//這裏進行權限被拒絕的處理
Log.e(TAG, "不允許定位權限===");
}
} else {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
}判斷定位：
public final boolean isLocationEnable(Context context) {
LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
boolean networkProvider = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
boolean gpsProvider = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (networkProvider || gpsProvider) {
return true;
}
return false;
}
private void setLocationService() {
Intent locationIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivityForResult(locationIntent, REQUEST_CODE_LOCATION_SETTINGS);
}執行完上面的請求權限後回調:
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// 用戶沒有開啓藍牙
if (requestCode == REQUEST_CODE_LOCATION_SETTINGS) {
if (isLocationEnable(this)) {
//定位已打開的處理
Toast.makeText(this, "定位已經打開", Toast.LENGTH_SHORT).show();
}
else {
//定位依然沒有打開的處理
Toast.makeText(this, "定位沒有打開", Toast.LENGTH_SHORT).show();
}
}
else if (requestCode == REQUEST_ENABLE_BT && resultCode == RESULT_CANCELED) {
finish();
return;
}
super.onActivityResult(requestCode, resultCode, data);
}2、設備搜索
BluetoothAdapter.startDiscovery在大多數手機上是可以同時發現經典藍牙和Ble的，但是startDiscovery的回調無法返回Ble的廣播，所以無法通過廣播識別設備，且startDiscovery掃描Ble的效率比StartLeScan低很多。所以在實際應用中，還是StartDiscovery和StartLeScan分開掃，前者掃傳統藍牙，後者掃低功耗藍牙。
由於搜索需要儘量減少功耗，因此在實際使用時需要注意：當找到對應的設備後，立即停止掃描；不要循環搜索設備，爲每次搜索設置適合的時間限制，避免設備不在可用範圍的時候持續不停掃描，消耗電量。
通過調用BluetoothAdapter的 startLeScan() 搜索BLE設備。調用此方法時需要傳入 BluetoothAdapter.LeScanCallback 參數。具體代碼示例如下：
/** * Device scan callback. * BluetoothAdapter.LeScanCallback ：public static interface * onLeScan：Callback reporting an LE device found during a device scan initiated by the startLeScan(BluetoothAdapter.LeScanCallback) function. */ private final BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() { @Override public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) { runOnUiThread(new Runnable() { @Override public void run() { mLeDeviceListAdapter.addDevice(device); mLeDeviceListAdapter.notifyDataSetChanged(); } }); } };
3、設備通信
兩個設備通過BLE通信，首先需要建立GATT連接，這裏我們講的是Android設備作爲client端，連接GATT Server。連接GATT Server需要調用BluetoothDevice的connectGatt()方法，此函數帶三個參數：Context、autoConnect(boolean)和 BluetoothGattCallback 對象。調用後返回BluetoothGatt對象，它是GATT profile的封裝，通過這個對象，我們就能進行GATT Client端的相關操作。如斷開連接bluetoothGatt.disconnect()，發現服務bluetoothGatt.discoverServices()等等。示例代碼如下：
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(TAG, "Device not found. Unable to connect.");
return false;
}
// We want to directly connect to the device, so we are setting the autoConnect
// parameter to false.
//Connect to GATT Server hosted by this device.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
Log.d(TAG, "Trying to create a new connection.");
/**
* BluetoothGattCallback: public abstract class
* onConnectionStateChange:Callback indicating when GATT client has connected/disconnected to/from a remote GATT server.
* onServicesDiscovered:Callback invoked when the list of remote services, characteristics and descriptors for the remote device have been updated, ie new services have been discovered.
* onCharacteristicChanged:Callback triggered as a result of a remote characteristic notification.
* onCharacteristicRead:Callback reporting the result of a characteristic read operation.
* onCharacteristicWrite:Callback indicating the result of a characteristic write operation.
*/
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback(){
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
Log.i(TAG, "onConnectionStateChange.newState = " + newState);
String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
broadcastUpdate(intentAction);
Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
Log.i(TAG, "Disconnected from GATT server.");
broadcastUpdate(intentAction);
}
}
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
Log.i(TAG, "onServicesDiscovered.");
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
@Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
Log.i(TAG, "onCharacteristicChanged.");
//broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
@Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicRead(gatt, characteristic, status);
Log.i(TAG, "onCharacteristicRead.status = " + status);
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
}
@Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicWrite(gatt, characteristic, status);
Log.i(TAG, "onCharacteristicWrite.status = " + status);
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
}
};以下爲獲得Gatt後的相關操作對應的響應方法
//notification to onCharacteristicChanged；
bluetoothGatt.setCharacteristicNotification(characteristic, true);
//readCharacteristic to onCharacteristicRead；
bluetoothGatt.readCharacteristic(characteristic);
//writeCharacteristic to onCharacteristicWrite；
bluetoothGatt.wirteCharacteristic(mCurrentcharacteristic);
//connect and disconnect to onConnectionStateChange；
bluetoothGatt.connect();
bluetoothGatt.disconnect();
//readDescriptor to onDescriptorRead；
bluetoothGatt.readDescriptor(descriptor);
//writeDescriptor to onDescriptorWrite；
bluetoothGatt.writeDescriptor(descriptor);
//readRemoteRssi to onReadRemoteRssi；
bluetoothGatt.readRemoteRssi();
//executeReliableWrite to onReliableWriteCompleted；
bluetoothGatt.executeReliableWrite();
//discoverServices to onServicesDiscovered;
bluetoothGatt.discoverServices();