Android提高之Android手機與BLE終端通信

最近穿戴設備發展得很火，把相關技術也帶旺了，其中一項是BLE（Bluetooth Low Energy）。BLE是藍牙4.0的核心Profile，主打功能是快速搜索，快速連接，超低功耗保持連接和傳輸數據，弱點是數據傳輸速率低，由於BLE的低功耗特點，因此普遍用於穿戴設備。Android 4.3才開始支持BLE API，所以請各位客官把本文代碼運行在藍牙4.0和Android 4.3及其以上的系統，另外本文所用的BLE終端是一個藍牙4.0的串口藍牙模塊。

注：筆者的i9100刷了4.4系統後，竟然也能跟BLE藍牙模塊通信。

BLE分為三部分Service、Characteristic、Descriptor，這三部分都由UUID作為唯一標示符。一個藍牙4.0的終端可以包含多個Service，一個Service可以包含多個Characteristic，一個Characteristic包含一個Value和多個Descriptor，一個Descriptor包含一個Value。一般來說，Characteristic是手機與BLE終端交換數據的關鍵，Characteristic有較多的跟權限相關的字段，例如PERMISSION和PROPERTY，而其中最常用的是PROPERTY，本文所用的BLE藍牙模塊竟然沒有標准的Characteristic的PERMISSION。Characteristic的PROPERTY可以通過位運算符組合來設置讀寫屬性，例如READ|WRITE、READ|WRITE_NO_RESPONSE|NOTIFY，因此讀取PROPERTY後要分解成所用的組合（本文代碼已含此分解方法）。

本文代碼改自Android 4.3 Sample的BluetoothLeGatt，把冗余代碼去掉，獲取的BLE設備信息都通過Log，還有一些必要的讀寫藍牙方法，應該算是簡化到大家一看就可以懂了。本文完整代碼可以點擊此處本站下載。

接下來貼出本文運行的結果，首先是連接BLE設備後，枚舉出設備所有Service、Characteristic、Descriptor，並且手機會往Characteristic uuid=0000ffe1-0000-1000-8000-00805f9b34fb寫入“send data->”字符串，BLE終端收到數據通過串口傳到PC串口助手：
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->service uuid:00001800-0000-1000-8000-00805f9b34fb
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a00-0000-1000-8000-00805f9b34fb
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a01-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a02-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a03-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char uuid:00002a04-0000-1000-8000-00805f9b34fb
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->service uuid:00001801-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:00002a05-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char property:INDICATE
04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc uuid:00002902-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->service uuid:0000ffe0-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:0000ffe1-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char property:READ|WRITE_NO_RESPONSE|NOTIFY|
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc uuid:00002902-0000-1000-8000-00805f9b34fb
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc uuid:00002901-0000-1000-8000-00805f9b34fb
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:26.025: E/DeviceScanActivity(12254): onCharRead BLE DEVICE read 0000ffe1-0000-1000-8000-00805f9b34fb -> 00
這裡紅字是由BluetoothGattCallback的onCharacteristicRead()回調而打出Log

以下Log是PC上的串口工具通過BLE模塊發送過來，由BluetoothGattCallback的 onCharacteristicChanged（）打出Log
04-21 18:30:18.260: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:18.745: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.085: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.350: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.605: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.835: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.055: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.320: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.510: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.735: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:21.000: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone

接下來貼出本文核心代碼：

public class DeviceScanActivity extends ListActivity {
 private final static String TAG = DeviceScanActivity.class.getSimpleName();
 private final static String UUID_KEY_DATA = "0000ffe1-0000-1000-8000-00805f9b34fb";

  private LeDeviceListAdapter mLeDeviceListAdapter;
  /**搜索BLE終端*/
  private BluetoothAdapter mBluetoothAdapter;
  /**讀寫BLE終端*/
  private BluetoothLeClass mBLE;
  private boolean mScanning;
  private Handler mHandler;

  // Stops scanning after 10 seconds.
  private static final long SCAN_PERIOD = 10000;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getActionBar().setTitle(R.string.title_devices);
    mHandler = new Handler();
    // 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();
    }
    // Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
    // BluetoothAdapter through BluetoothManager.
    final BluetoothManager bluetoothManager =
        (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();
    // Checks if Bluetooth is supported on the device.
    if (mBluetoothAdapter == null) {
      Toast.makeText(this, R.string.error_bluetooth_not_supported, Toast.LENGTH_SHORT).show();
      finish();
      return;
    }
    //開啟藍牙
    mBluetoothAdapter.enable();
    mBLE = new BluetoothLeClass(this);
    if (!mBLE.initialize()) {
      Log.e(TAG, "Unable to initialize Bluetooth");
      finish();
    }
    //發現BLE終端的Service時回調
    mBLE.setOnServiceDiscoverListener(mOnServiceDiscover);
    //收到BLE終端數據交互的事件
    mBLE.setOnDataAvailableListener(mOnDataAvailable);
  }
  @Override
  protected void onResume() {
    super.onResume();

    // Initializes list view adapter.
    mLeDeviceListAdapter = new LeDeviceListAdapter(this);
    setListAdapter(mLeDeviceListAdapter);
    scanLeDevice(true);
  }
  @Override
  protected void onPause() {
    super.onPause();
    scanLeDevice(false);
    mLeDeviceListAdapter.clear();
    mBLE.disconnect();
  }
  @Override
  protected void onStop() {
    super.onStop();
    mBLE.close();
  }
  @Override
  protected void onListItemClick(ListView l, View v, int position, long id) {
    final BluetoothDevice device = mLeDeviceListAdapter.getDevice(position);
    if (device == null) return;
    if (mScanning) {
      mBluetoothAdapter.stopLeScan(mLeScanCallback);
      mScanning = false;
    }
    mBLE.connect(device.getAddress());
  }
  private void scanLeDevice(final boolean enable) {
    if (enable) {
      // Stops scanning after a pre-defined scan period.
      mHandler.postDelayed(new Runnable() {
        @Override
        public void run() {
          mScanning = false;
          mBluetoothAdapter.stopLeScan(mLeScanCallback);
          invalidateOptionsMenu();
        }
      }, SCAN_PERIOD);
      mScanning = true;
      mBluetoothAdapter.startLeScan(mLeScanCallback);
    } else {
      mScanning = false;
      mBluetoothAdapter.stopLeScan(mLeScanCallback);
    }
    invalidateOptionsMenu();
  }
  /**
   * 搜索到BLE終端服務的事件
   */
  private BluetoothLeClass.OnServiceDiscoverListener mOnServiceDiscover = new OnServiceDiscoverListener(){

 @Override
 public void onServiceDiscover(BluetoothGatt gatt) {
  displayGattServices(mBLE.getSupportedGattServices());
 }
  };
  /**
   * 收到BLE終端數據交互的事件
   */
  private BluetoothLeClass.OnDataAvailableListener mOnDataAvailable = new OnDataAvailableListener(){
   /**
   * BLE終端數據被讀的事件
   */
 @Override
 public void onCharacteristicRead(BluetoothGatt gatt,
  BluetoothGattCharacteristic characteristic, int status) {
  if (status == BluetoothGatt.GATT_SUCCESS) 
  Log.e(TAG,"onCharRead "+gatt.getDevice().getName()
   +" read "
   +characteristic.getUuid().toString()
   +" -> "
   +Utils.bytesToHexString(characteristic.getValue()));
 }
   /**
   * 收到BLE終端寫入數據回調
   */
 @Override
 public void onCharacteristicWrite(BluetoothGatt gatt,
  BluetoothGattCharacteristic characteristic) {
  Log.e(TAG,"onCharWrite "+gatt.getDevice().getName()
   +" write "
   +characteristic.getUuid().toString()
   +" -> "
   +new String(characteristic.getValue()));
 }
  };
  // Device scan callback.
  private 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();
        }
      });
    }
  };
  private void displayGattServices(List<BluetoothGattService> gattServices) {
    if (gattServices == null) return;
    for (BluetoothGattService gattService : gattServices) {
     //-----Service的字段信息-----//
     int type = gattService.getType();
      Log.e(TAG,"-->service type:"+Utils.getServiceType(type));
      Log.e(TAG,"-->includedServices size:"+gattService.getIncludedServices().size());
      Log.e(TAG,"-->service uuid:"+gattService.getUuid());
      
      //-----Characteristics的字段信息-----//
      List<BluetoothGattCharacteristic> gattCharacteristics =gattService.getCharacteristics();
      for (final BluetoothGattCharacteristic gattCharacteristic: gattCharacteristics) {
        Log.e(TAG,"---->char uuid:"+gattCharacteristic.getUuid());
        int permission = gattCharacteristic.getPermissions();
        Log.e(TAG,"---->char permission:"+Utils.getCharPermission(permission));
        int property = gattCharacteristic.getProperties();
        Log.e(TAG,"---->char property:"+Utils.getCharPropertie(property));
        byte[] data = gattCharacteristic.getValue();
     if (data != null && data.length > 0) {
      Log.e(TAG,"---->char value:"+new String(data));
     }
     //UUID_KEY_DATA是可以跟藍牙模塊串口通信的Characteristic
     if(gattCharacteristic.getUuid().toString().equals(UUID_KEY_DATA)){      
      //測試讀取當前Characteristic數據，會觸發mOnDataAvailable.onCharacteristicRead()
      mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
             mBLE.readCharacteristic(gattCharacteristic);
            }
          }, 500);
      //接受Characteristic被寫的通知,收到藍牙模塊的數據後會觸發mOnDataAvailable.onCharacteristicWrite()
      mBLE.setCharacteristicNotification(gattCharacteristic, true);
      //設置數據內容
      gattCharacteristic.setValue("send data->");
      //往藍牙模塊寫入數據
      mBLE.writeCharacteristic(gattCharacteristic);
     }
     //-----Descriptors的字段信息-----//
  List<BluetoothGattDescriptor> gattDescriptors = gattCharacteristic.getDescriptors();
  for (BluetoothGattDescriptor gattDescriptor : gattDescriptors) {
   Log.e(TAG, "-------->desc uuid:" + gattDescriptor.getUuid());
   int descPermission = gattDescriptor.getPermissions();
   Log.e(TAG,"-------->desc permission:"+ Utils.getDescPermission(descPermission));
   byte[] desData = gattDescriptor.getValue();
   if (desData != null && desData.length > 0) {
   Log.e(TAG, "-------->desc value:"+ new String(desData));
   }
      }
      }
    }//
  }
}

感興趣的讀者可以動手測試一下代碼的運行情況，希望能對大家的Android項目開發有所幫助。