Android 蓝牙开发

低功耗蓝牙就是我们常说是的蓝牙4.0 ,蓝牙之间的通讯每次只能传20个字节。

1.判断蓝牙是否打开

    /**
     * 判断蓝牙是否打开
     */
    private fun isOpenBluetooth(): Boolean {
        val manager = activity.getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager
        if (manager.adapter == null) return false
        val adapter = manager.adapter
        return adapter.isEnabled
    }

没有打开需要去请求打开蓝牙,这里会区分android12系统以上和以下,打开有所区别

    /**
     * 打开蓝牙
     */
    fun openBlueTooth() {  
        //是Android12
        if (isAndroid12()) {
            //检查是否有BLUETOOTH_CONNECT权限
            if (hasPermission(Manifest.permission.BLUETOOTH_CONNECT)) {
                //打开蓝牙
                openPhoneBluetooth()
            } else {
                //请求权限
                requestBluetoothConnect.launch(Manifest.permission.BLUETOOTH_CONNECT)
            }
            return
        }
        //不是Android12 直接打开蓝牙
        openPhoneBluetooth()
    }

    fun openPhoneBluetooth(){
        val intent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
        activity.startActivityForResult(intent, REQUEST_ENABLE_BT)
    }

2.扫描蓝牙

扫描之前需要一些权限,Android也是会区分12以上和以下,不同的手机还有不同要求,比如华为手机12以上也要定位权限。有的手机没有适配,所以建议如下处理(权限多要一点)

    private void requestPermission() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            // Android 版本大于等于 Android12 时
            // 只包括蓝牙这部分的权限,其余的需要什么权限自己添加
            mPermissionList.add(Manifest.permission.BLUETOOTH_SCAN);
            mPermissionList.add(Manifest.permission.BLUETOOTH_ADVERTISE);
            mPermissionList.add(Manifest.permission.BLUETOOTH_CONNECT);
            // 目前知道hw手机需要
            mPermissionList.add(Manifest.permission.ACCESS_COARSE_LOCATION);
            mPermissionList.add(Manifest.permission.ACCESS_FINE_LOCATION);
        } else {
            // Android 版本小于 Android12 及以下版本
            mPermissionList.add(Manifest.permission.ACCESS_COARSE_LOCATION);
            mPermissionList.add(Manifest.permission.ACCESS_FINE_LOCATION);
        }

        if (mPermissionList.size() > 0) {
            ActivityCompat.requestPermissions(this, mPermissionList.toArray(new String[0]), 1001);
        }
    }

开始扫描蓝牙

扫描结果在回调中返回

    //获取系统蓝牙适配器
    var mBluetoothAdapter: BluetoothAdapter? = null
    //扫描者
    private var scanner: BluetoothLeScanner? = null
            
    mBluetoothAdapter = (activity.getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager).adapter
    scanner = mBluetoothAdapter?.bluetoothLeScanner

    //扫描结果回调
    private var scanCallback: ScanCallback? = object : ScanCallback() {
        override fun onScanResult(callbackType: Int, result: ScanResult) {
            addScanResult(result)
        }
    }

    /**
     * 开始蓝牙扫描
     */
    @SuppressLint("MissingPermission")
    fun startScan() {
        if (!isScanning && scanner != null) {
            LogUtil.d(" Thread = " + Thread.currentThread().name, "开始启动蓝牙扫描 ")
            scanner!!.startScan(null, ScanSettings.Builder().setScanMode(SCAN_MODE_LOW_LATENCY).build(), scanCallback)
        }
        isScanning = true
    }

    /**
     * 停止蓝牙扫描
     */
    @SuppressLint("MissingPermission")
    fun stopScan() {
        if (isScanning && scanner!= null) {
            scanner!!.stopScan(scanCallback)
        }
        isScanning = false
    }

3.连接蓝牙

蓝牙连接需要在主线程中进行,三星手机非主线程中连接也可以成功,但是华为手机非主线就会出现连接失败问题.

status 状态:
  • 0 (连接成功),
  • 133(蓝牙不在范围内连接失败,连接超时,及时关掉BluetoothGatt,避免出现257错误,下次连接靠近到蓝牙返回内一般就可以连接成功)
  • 257(这个错误码出现后,一般再就连不上,需要重新开始蓝牙扫描流程)
    @SuppressLint("MissingPermission")
    private fun connectBlueToothGatt(scanResult: ScanResult, device: BluetoothDevice) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
           // 1.连接蓝牙
            bluetoothGatt = device.connectGatt(activity, false, object : BluetoothGattCallback() {
                override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                        if (newState == BluetoothProfile.STATE_CONNECTED) {
                            mainHandler.post{
                                // 2.去发现服务
                                gatt!!.discoverServices()
                            }
                        } else{
                             // 连接失败的处理
                        }
                    }else{
                        if(status == BluetoothGatt.GATT_FAILURE){
                          // 257错误处理
                        }
                        gatt.close()
                    }
                }

                override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
                    super.onServicesDiscovered(gatt, status)
                    // 3.发现服务
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                        //获取DeviceInfoService
                        val mDeviceInfoService = gatt.getService(UUID.fromString(BLUE_TOOTH_GATT_SERVICE_UUID))
                        if (mDeviceInfoService == null) {
                            gatt.connect()
                            return
                        }
                        //获取一个主设备需要去读的特征(Characteristic),获取从设备发送过来的数据0000fff2-0000-1000-8000-00805f9b34fb
                        val readGattCharacteristic = mDeviceInfoService.getCharacteristic(UUID.fromString(READ_GATT_CHARACTERISTIC_UUID))
                        //注册特征(Characteristic)值改变的监听
                        val isEnableNotify = gatt.setCharacteristicNotification(readGattCharacteristic, true)
                        if (isEnableNotify) {
                           val descriptors = readGattCharacteristic.descriptors
                           for (descriptor in descriptors) {
                                descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
                                val isWriteDescriptor = gatt.writeDescriptor(descriptor)
                           }
                        }
                       //获取一个特征(Characteristic),这是从设备定义好的,我通过这个Characteristic去写从设备感兴趣的值0000fff1-0000-1000-8000-00805f9b34fb
                       val writeGattCharacteristic = mDeviceInfoService.getCharacteristic(UUID.fromString(WRITE_GATT_CHARACTERISTIC_UUID))
                    }
                    } else {
                        gatt.connect()
                    }
                }

                override fun onCharacteristicRead(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, status: Int) {
                    super.onCharacteristicRead(gatt, characteristic, status)
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                       // 读成功在这里回调
                    } else {
                        gatt.connect()
                    }
                }

                override fun onCharacteristicWrite(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic, status: Int) {
                    super.onCharacteristicWrite(gatt, characteristic, status)
                    if (status == BluetoothGatt.GATT_SUCCESS) {
                       // 写成功在这里回调
                    } else {
                        gatt.connect()
                    }
                }

                override fun onDescriptorRead(gatt: BluetoothGatt?, descriptor: BluetoothGattDescriptor?, status: Int) {
                    super.onDescriptorRead(gatt, descriptor, status)
                    // 特征值读成功,这里回调

                }

                override fun onDescriptorWrite(gatt: BluetoothGatt?, descriptor: BluetoothGattDescriptor?, status: Int) {
                    super.onDescriptorWrite(gatt, descriptor, status)
                    // 特征值写成功,这里回调
                }

                override fun onCharacteristicChanged(gatt: BluetoothGatt, characteristic: BluetoothGattCharacteristic) {
                    super.onCharacteristicChanged(gatt, characteristic)
                    // 蓝牙发送过来的数据
                    val uuid = characteristic.uuid
                    val receiveData = characteristic.valu
                }
            }, BluetoothDevice.TRANSPORT_LE)
        } else {
            // ....
        }

    }

向蓝牙发送数据

4.开发中碰的问题

  • 30秒内蓝牙连续停止扫描5次,再次扫描就会扫描不到设备,这里系统进行了限制。源码
  • 蓝牙通讯需要设备不忙时进行读写,在上面onCharacteristicWrite,onCharacteristicRead,onDescriptorWrite,onCharacteristicChanged这些回调后设备是不忙的状态。具体看源码,关注mDeviceBusy
  • 华为手机无论是否android12以上系统都需要位置权限
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