int型转QByteArray（30转成0x1e，0x00）

QByteArray  intToByte(int i)
{
    QByteArray abyte0;
    abyte0.resize(4);
    abyte0[0] = (uchar)  (0x000000ff & i);
    abyte0[1] = (uchar) ((0x0000ff00 & i) >> 8);
    abyte0[2] = (uchar) ((0x00ff0000 & i) >> 16);
    abyte0[3] = (uchar) ((0xff000000 & i) >> 24);
    return abyte0;
}

int bytesToInt(QByteArray bytes) {
    int addr = bytes[0] & 0x000000FF;
    addr |= ((bytes[1] << 8) & 0x0000FF00);
    addr |= ((bytes[2] << 16) & 0x00FF0000);
    addr |= ((bytes[3] << 24) & 0xFF000000);
    return addr;
}