Need BLUETOOTH PRIVILEGED permission以及requestMtu导致蓝牙断连问题

在部分Android手机上，当连接上GATTService后直接requestMtu有可能会造成蓝牙连接中断，随后继续重新连接会报错Need BLUETOOTH PRIVILEGED permission

//扫描成功后连接gatt2 BluetoothDevice mRemoteDevice = mBluetoothAdapter.getRemoteDevice(result.getDevice().getAddress());3 BluetoothGatt mBluetoothGatt = mRemoteDevice.connectGatt(getContext(), false, bluetoothGattCallback);

在 BluetoothGattCallback 监听的 onConnectionStateChange(BluetoothGatt gatt, int status, int newState)方法中直接requestMtu(512) 会直接导致蓝牙断开连接

private int setMTUInt = 512; 2  3  4 @Override 5 public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) { 6     super.onConnectionStateChange(gatt, status, newState); 7  8     if (newState == BluetoothProfile.STATE_CONNECTED) { //// 连接成功 9         //虽然这里的boolean会为true但是实际上会失败，并且导致蓝牙断开链接10         boolean requestMtu = gatt.requestMtu(setMTUInt);11         Log.e(TAG,"设置 requestMtu："+requestMtu);12 13     } else if (newState == BluetoothProfile.STATE_DISCONNECTED) { // 连接断开14         //清除缓存,防止Need BLUETOOTH PRIVILEGED permission15         refreshDeviceCache();16         //将MTU的值减少,值可以随意设置17         setMTUInt -= 100;18         // 关闭GATT客户端19         mBluetoothGatt.close();20     }21 }

在监听的onMtuChanged(BluetoothGatt gatt, int mtu, int status)方法中，确认mtu设置成功后，再去请求特征值

@Override2 public void onMtuChanged(BluetoothGatt gatt, int mtu, int status) {3     super.onMtuChanged(gatt, mtu, status);4             5     // 开始查找GATT服务器提供的服务6     gatt.discoverServices(); 7            8 }

随后在监听的onServicesDiscovered(BluetoothGatt gatt, int status)方法中设置特征

@Overridepublic void onServicesDiscovered(BluetoothGatt gatt, int status) {    super.onServicesDiscovered(gatt, status);     if (status == BluetoothGatt.GATT_SUCCESS) {        //设置特征值        requestCharacteristic();    } }

清除缓存的方法，gatt本身有提供清除缓存方法，但是不给外部直接调用，所以使用反射的方式进行调用，建议在每次开启扫描设备时也清除一下缓存，防止链接过其他设备后直接链接新设备报错 java.lang.SecurityException: Need BLUETOOTH PRIVILEGED permission: Neither user 10208 nor current process has android.permission.BLUETOOTH_PRIVILEGED.

public boolean refreshDeviceCache() { 2     if (mBluetoothGatt != null) { 3         Log.e(TAG,"清除缓存 refreshDeviceCache"); 4         try { 5             BluetoothGatt localBluetoothGatt = mBluetoothGatt; 6             Method localMethod = localBluetoothGatt.getClass().getMethod( 7                         "refresh", new Class[0]); 8             if (localMethod != null) { 9                 boolean bool = ((Boolean) localMethod.invoke(10                             localBluetoothGatt, new Object[0])).booleanValue();11                 return bool;12             }13         } catch (Exception localException) {14             Log.i(TAG, "An exception occured while refreshing device");15         }16     }17     return false;18 }