修复扫码流程异常:

1、在等待数据时不再是"正在扫描"状态，当串口存在数据时才修改为"正在扫描"状态
2、存在测试值时，仍会读取串口，避免串口数据堆积
3、修复读取串口数据时，读取到终止符仍不结束读取过程的异常(漏写!)

app/src/main/java/com/bgycc/smartcanteen/qrcode/BaseQRCodeScan.java

@@ -34,7 +34,7 @@ public abstract class BaseQRCodeScan implements IQRCodeScan {
         }
         byte[] buf = null;
         int len = 0;
-        while (buf == null || end(buf)) {
+        while (buf == null || !end(buf)) {
             byte[] b = new byte[64];
             int l = serialPortIS.read(b);
             if (l == 0) break;

app/src/main/java/com/bgycc/smartcanteen/viewModel/QRCodeViewModel.java

@@ -77,25 +77,20 @@ public class QRCodeViewModel extends ViewModel {
     private Runnable scanRunnable = () -> {
         qrCodeState.postValue(new QRCodeState(QRCodeState.IDLE));
         LogUtils.i(TAG, "开始扫描二维码");
-        // 等待串口数据
-        // noinspection LoopStatementThatDoesntLoop
-        while (!scan.available()) {
-            qrCodeState.postValue(new QRCodeState(QRCodeState.SCANNING));
-            break;
-        }
+        while (!scan.available()) {}
+        qrCodeState.postValue(new QRCodeState(QRCodeState.SCANNING));
         // 读取串口扫描的二维码数据
         String scanData;
-        // 若存在测试数据，则直接读取测试数据
+        try {
+            scanData = scan.scan();
+        } catch (Exception e) {
+            LogUtils.e(TAG, "读取串口数据失败: " + e.getMessage(), e);
+            qrCodeState.postValue(new QRCodeState(QRCodeState.FAILED));
+            return;
+        }
+        // 若存在测试数据，则使用测试数据覆盖
         if (!TextUtils.isEmpty(SmartCanteenUtils.testQRCode)) {
             scanData = SmartCanteenUtils.testQRCode;
-        } else {
-            try {
-                scanData = scan.scan();
-            } catch (Exception e) {
-                LogUtils.e(TAG, "读取串口数据失败: " + e.getMessage(), e);
-                qrCodeState.postValue(new QRCodeState(QRCodeState.FAILED));
-                return;
-            }
         }
         // 需要识别二维码的类型
         String terminalType = PayData.matchTerminalType(scanData);