Android BLE藍牙通信

爲了在app中使用藍牙功能，必須聲明藍牙權限BLUETOOTH。利用這個權限去執行藍牙通信，例如請求連接、接受連接、和傳輸數據。如果想讓你的app啓動設備發現或操縱藍牙設置，必須聲明BLUETOOTH_ADMIN權限。
在AndroidManifest.xml文件中添加權限：

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

如果想聲明你的app只爲具有BLE的設備提供，還需要聲明uses-feature：

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

當required爲true時，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：

// 使用此檢查確定BLE是否支持在設備上，然後你可以有選擇性禁用BLE相關的功能
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
    Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
    finish();
}

初始化：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // 初始化藍牙適配器
    final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();
    judgeBluetoothEnable();
}

//判斷藍牙狀態
private void judgeBluetoothEnable() {
    if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
        enableBt = false;
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
    } else {
        enableBt = true;
        mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();
    }
}

private static final ParcelUuid SAMPLE_UUID = new ParcelUuid(UUID.fromString("6e400000-b5a3-f393-e0a9-e50e24dcca9c"));
//private static final String DEVICE_NAME_STRING = "LeShoe01";
//搜索藍牙設備
private void scanLeDevice(final boolean enable) {
    if (enable) {
        mScanning = true;
        List<ScanFilter> bleScanFilters = new ArrayList<>();
        //添加過濾規則
        bleScanFilters.add(new ScanFilter.Builder().setServiceUuid(SAMPLE_UUID).build());
//      bleScanFilters.add(new ScanFilter.Builder().setDeviceName(DEVICE_NAME_STRING).build());
        ScanSettings bleScanSettings = new ScanSettings.Builder().build();
        Log.d(TAG, "Starting scanning with settings:" + bleScanSettings + " and filters:" + bleScanFilters);
        //開始搜索
        mBluetoothLeScanner.startScan(bleScanFilters, bleScanSettings, mScanCallback);
    } else {
        mScanning = false;
        stopScanning();
    }
}
//停止搜索
private void stopScanning() {
    if (mBluetoothLeScanner != null) {
        Log.d(TAG, "Stop scanning.");
        mBluetoothLeScanner.stopScan(mScanCallback);
    }
}
//BLE設備搜索回調
private ScanCallback mScanCallback = new ScanCallback() {
    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        //結果返回
        BluetoothDevice device = result.getDevice();
    }
};

//連接設備
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {// 當藍牙設備已經連接
            Log.i(TAG, "Connected to GATT server.");
            gatt.discoverServices();
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {// 當設備無法連接
            Log.e(TAG, "Disconnected from GATT server !");
        }
    }

    //發現服務
    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            Log.i(TAG, "onServicesDiscovered GATT_SUCCESS");
            BluetoothGattService service = gatt.getService(UUID.fromString("6e400000-b5a3-f393-e0a9-e50e24dcca9c"));
            Txcharacteristic = service.getCharacteristic(UUID.fromString("6e400002-b5a3-f393-e0a9-e50e24dcca9c"));
            Rxcharacteristic = service.getCharacteristic(UUID.fromString("6e400003-b5a3-f393-e0a9-e50e24dcca9c"));
            //接收通知
            gatt.setCharacteristicNotification(Rxcharacteristic, true);
            //發送數據
            Txcharacteristic.setValue(new byte[]{0x3b});
            gatt.writeCharacteristic(Txcharacteristic);
        } else {
            Log.e(TAG, "onServicesDiscovered status: " + status);
        }
    }

    //收到通知
    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
        Log.i(TAG, "---------- onCharacteristicChanged ----------");
        //獲取數據
        byte[] result = characteristic.getValue();
        StringBuilder sb = new StringBuilder();
        String hv = null;
        for (byte b : result) {
            hv = Integer.toHexString(b & 0xFF);
            if (hv.length() < 2) {
                sb.append(0);
            }
            sb.append(hv);
        }
        Log.i(TAG, "onCharacteristicChanged characteristic.getValue(): " + sb.toString());
    }
};