Android 手机蓝牙与BLE设备建立连接 代码

以下是 Android 手机蓝牙与 BLE 设备建立连接的代码示例：

1. 在 AndroidManifest.xml 文件中添加蓝牙权限：

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

2. 在 Activity 中初始化 BluetoothAdapter 对象：

private BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

3. 扫描 BLE 设备并建立连接：

// 扫描时间 10 秒
private static final long SCAN_PERIOD = 10000;

// 扫描回调
private final BluetoothAdapter.LeScanCallback leScanCallback =
        new BluetoothAdapter.LeScanCallback() {
            @Override
            public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
                // 根据设备名称或 MAC 地址过滤
                if (device.getName() != null && device.getName().startsWith("BLE")) {
                    // 停止扫描
                    bluetoothAdapter.stopLeScan(leScanCallback);

                    // 建立连接
                    device.connectGatt(MainActivity.this, false, gattCallback);
                }
            }
        };

// GATT 回调
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        if (newState == BluetoothProfile.STATE_CONNECTED) {
            // 连接成功，开始发现服务
            gatt.discoverServices();
        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            // 连接断开
            Log.i(TAG, "Disconnected from GATT server.");
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            // 服务发现成功，可以进行数据交互
            Log.i(TAG, "Services discovered.");
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }
    }

    @Override
    public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            // 读取特征值成功
            Log.i(TAG, "Characteristic read successfully.");
        } else {
            Log.w(TAG, "Characteristic read failed: " + status);
        }
    }
};

// 开始扫描 BLE 设备
private void scanBLEDevice() {
    if (bluetoothAdapter == null) {
        Log.w(TAG, "Bluetooth not supported.");
        return;
    }

    // 如果正在扫描，则先停止扫描
    bluetoothAdapter.stopLeScan(leScanCallback);

    // 开始扫描
    bluetoothAdapter.startLeScan(leScanCallback);

    // 扫描 SCAN_PERIOD 后停止扫描
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            bluetoothAdapter.stopLeScan(leScanCallback);
        }
    }, SCAN_PERIOD);
}

注意：在建立连接之前需要先扫描 BLE 设备，扫描到符合条件的设备后才能进行连接。在连接建立成功后，需要调用 `discoverServices()` 方法发现设备的服务，然后才能进行数据交互。以上代码仅供参考，实际开发中需要根据具体需求进行调整。