private void button_chgWifi_Click(object sender, EventArgs e)
 {
     if (button_chgWifi.Text == "修改")
     {
         textBox_wifi.Enabled = true;
         button_chgWifi.Text  = "确认";
     }
     else
     {
         textBox_wifi.Enabled = false;
         button_chgWifi.Text  = "修改";
         Global.setWiFi(textBox_wifi.Text);
     }
 }