c++ - Embarcadero 无法从 'UnicodeString' 转换为 'unsigned char *'

Question

我正在使用 Embarcadero 的 C++ builder XE

String command1 = "FREQ ";
String command2 = " Mhz\n";
int index = Form1->ListBox1->ItemIndex;

String full = command1.operator +=(IntToStr((index+2)*10)).operator +=(command2);
TcpClient1->SendBuf((BYTE*)full,13,0);Sleep(30);

在最后一行我得到 E2031 Cannot cast from 'UnicodeString' to 'unsigned char*'

我发送的是我的设备（接收器）的命令，格式为（命令，lenght_of_command）。当我以计划文本发送它时

TcpClient1->SendBuf((BYTE*)"FREQ 330.5 MHz\n",15,0);Sleep(30);

一切都好。非常感谢您的帮助。

Answer 1

String映射到UnicodeStringXE。修复代码的最简单方法是AnsiString改用（并停止使用+=运算符，因为您没有正确使用它）：

AnsiString command1 = "FREQ ";
AnsiString command2 = " Mhz\n";
int index = Form1->ListBox1->ItemIndex;

AnsiString full = command1 + IntToStr((index+2)*10) + command2;
TcpClient1->SendBuf((BYTE*)full.c_str(),full.Length(),0);
Sleep(30);

或者：

int index = Form1->ListBox1->ItemIndex;
AnsiString full;
full.sprintf("FREQ %d Mhz\n", (index+2)*10);
TcpClient1->SendBuf((BYTE*)full.c_str(),full.Length(),0);
Sleep(30);

Answer 2

我只会使用 sprintf

char command[999];
sprintf(command, "FREQ %d MHz\n", (index+2)*10);
TcpClient1->SendBuf((BYTE*)command,strlen(command),0);
Sleep(30);