usbManager返回NullPointerException

Question

UsbManager返回空指针异常 我在这里附上了我的代码。请任何人帮助我。

    05-14 16:07:38.312: E/AndroidRuntime(27314): FATAL EXCEPTION: main
    05-14 16:07:38.312: E/AndroidRuntime(27314): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ims.act/com.ims.act.ConfirmView}: java.lang.NullPointerException
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1970)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.ActivityThread.access$600(ActivityThread.java:128)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.os.Handler.dispatchMessage(Handler.java:99)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.os.Looper.loop(Looper.java:137)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.ActivityThread.main(ActivityThread.java:4517)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at java.lang.reflect.Method.invokeNative(Native Method)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at java.lang.reflect.Method.invoke(Method.java:511)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at dalvik.system.NativeStart.main(Native Method)
    05-14 16:07:38.312: E/AndroidRuntime(27314): Caused by: java.lang.NullPointerException
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.os.Parcel.readException(Parcel.java:1333)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.os.Parcel.readException(Parcel.java:1281)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.hardware.usb.IUsbManager$Stub$Proxy.requestDevicePermission(IUsbManager.java:535)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.hardware.usb.UsbManager.requestPermission(UsbManager.java:361)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at com.ims.act.ConfirmView.UsbPrinter(ConfirmView.java:92)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at com.ims.act.ConfirmView.onCreate(ConfirmView.java:77)
    05-14 16:07:38.312: E/AndroidRuntime(27314):    at android.app.Activity.performCreate(Activity.java:4470)

现在，我发布了一个确认视图。请帮帮我.usbManager.requestPermission（device，mPermissionIntent）返回NullPointerException

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.confirmpage);
        System.out.println("test");
        inData = getIntent().getStringExtra("ShowText");
        Request = getIntent().getStringExtra("Request");
        UID = getIntent().getStringExtra("UID");
        ReqType = getIntent().getIntExtra("ReqType", 0);
        SubType = getIntent().getStringExtra("SubType");
        Receipt = getIntent().getStringExtra("Receipt");
        System.out.println("receipt:" + Receipt);
        Log.d("CONFIRMPAGE", Request);
        StaticTranser.textView = (TextView) findViewById(R.id.status);
        StaticTranser.textView.setText(inData);
        StaticTranser.textView.setTypeface(Typeface.MONOSPACE);
        UsbPrinter();
    }

    private void UsbPrinter() {
        usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
        Iterator<UsbDevice> it = deviceList.values().iterator();
        while (it.hasNext()) {
            device = it.next();
            System.out.println("Devices :" + device.toString());
        }

        PendingIntent mPermissionIntent = PendingIntent.getBroadcast(this,0,
                new Intent(ACTION_USB_PERMISSION), 0);

        usbManager.requestPermission(device, mPermissionIntent);
        registerReceiver(mUsbReceiver, filter);
    }

    @Override
    protected void onResume() {
        registerReceiver(mUsbReceiver, filter);
        super.onResume();
    }

    private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (ACTION_USB_PERMISSION.equals(action)) {
                synchronized (this) {
                    device = (UsbDevice) intent
                            .getParcelableExtra(UsbManager.EXTRA_DEVICE);

                    if (intent.getBooleanExtra(
                            UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        if (device != null) {
                            getConnection();
                        }
                    } else {
                        Log.d("BROADCOST RECEIVER",
                                "permission denied for device " + device);
                    }

                    if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
                        if (device != null) {
                            Log.d("CLOSE USB Connection", "Connection closed");
                            connection.releaseInterface(intf);
                            connection.close();
                        }
                    }
                }
            }
        }

    };

我正在测试三星移动版4.0。我正在使用我的手机连接usb打印机，但它将返回NullPointerException。