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gatt
BluetoothDevice mRemoteDevice = mBluetoothAdapter.getRemoteDevice(result.getDevice().getAddress());
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;


@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
    super.onConnectionStateChange(gatt, status, newState);

    if (newState == BluetoothProfile.STATE_CONNECTED) { //// 连接成功
        //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
        boolean requestMtu = gatt.requestMtu(setMTUInt);
        Log.e(TAG,"设置 requestMtu："+requestMtu);

    } else if (newState == BluetoothProfile.STATE_DISCONNECTED) { // 连接断开
        //清除缓存,防止Need BLUETOOTH PRIVILEGED permission
        refreshDeviceCache();
        //将MTU的值减少,值可以随意设置
        setMTUInt -= 100;
        // 关闭GATT客户端
        mBluetoothGatt.close();
    }
}

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

@Override
public void onMtuChanged(BluetoothGatt gatt, int mtu, int status) {
    super.onMtuChanged(gatt, mtu, status);
            
    // 开始查找GATT服务器提供的服务
    gatt.discoverServices(); 
           
}

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

@Override
public 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() {
    if (mBluetoothGatt != null) {
        Log.e(TAG,"清除缓存 refreshDeviceCache");
        try {
            BluetoothGatt localBluetoothGatt = mBluetoothGatt;
            Method localMethod = localBluetoothGatt.getClass().getMethod(
                        "refresh", new Class[0]);
            if (localMethod != null) {
                boolean bool = ((Boolean) localMethod.invoke(
                            localBluetoothGatt, new Object[0])).booleanValue();
                return bool;
            }
        } catch (Exception localException) {
            Log.i(TAG, "An exception occured while refreshing device");
        }
    }
    return false;
}