diff --git a/communication/src/main/java/cn/rrg/com/UsbBulkTransferRaw.java b/communication/src/main/java/cn/rrg/com/UsbBulkTransferRaw.java
index 9aa9128a..3f5a1d08 100644
--- a/communication/src/main/java/cn/rrg/com/UsbBulkTransferRaw.java
+++ b/communication/src/main/java/cn/rrg/com/UsbBulkTransferRaw.java
@@ -74,7 +74,8 @@ public abstract class UsbBulkTransferRaw implements DriverInterface<String, UsbM
                         break;
 
                     case UsbManager.ACTION_USB_DEVICE_DETACHED:
-                        mCallback.onDetach(name);
+                        if (mCallback != null)
+                            mCallback.onDetach(name);
                         break;
                 }
             }
@@ -83,7 +84,8 @@ public abstract class UsbBulkTransferRaw implements DriverInterface<String, UsbM
 
     private void initAndCall(String name) {
         if (init()) {
-            mCallback.onAttach(name);
+            if (mCallback != null)
+                mCallback.onAttach(name);
         }
     }
 
diff --git a/communication/src/main/java/cn/rrg/devices/EmptyDeivce.java b/communication/src/main/java/cn/rrg/devices/EmptyDeivce.java
index 1dbe2862..44e2d6f0 100644
--- a/communication/src/main/java/cn/rrg/devices/EmptyDeivce.java
+++ b/communication/src/main/java/cn/rrg/devices/EmptyDeivce.java
@@ -6,6 +6,7 @@ import cn.dxl.com.Communication;
 import cn.dxl.com.DeviceChecker;
 
 public class EmptyDeivce extends DeviceChecker {
+
     public EmptyDeivce(Communication communication) {
         super(communication);
     }