Xamarin如何使用终端设备的NFC功能传递卡号等信息给Web页面（Android）

一、前提条件，App必须具有NFC权限。

二、项目中加入监控类NFCCatchActivity.cs

    [Activity(Label = "NFCCatch",Theme = "@android:style/Theme.NoDisplay")]

    [IntentFilter(new[] { "android.nfc.action.TECH_DISCOVERED" })]

    [MetaData("android.nfc.action.TECH_DISCOVERED", Resource = "@xml/nfc_tech_filter")]

    public class NFCCatchActivity : Activity

    {

        NfcAdapter mNfcAdapter;

        PendingIntent mPendingIntent;

        protected override void OnCreate(Bundle savedInstanceState)

        {

            base.OnCreate(savedInstanceState);

            mNfcAdapter = NfcAdapter.GetDefaultAdapter(this);

            if (mNfcAdapter == null)

            {

                //textViewNFC.Text = "NFC is not available on this device.";

            }

            else

            {

                mPendingIntent = PendingIntent.GetActivity(this, , new Intent(this,

                typeof(NFCCatchActivity)), PendingIntentFlags.UpdateCurrent);

                OnNewIntent(Intent);

            }

        }

        protected override void OnResume()

        {

            base.OnResume();

            if (mNfcAdapter != null)

                mNfcAdapter.EnableForegroundDispatch(this, mPendingIntent, null, null);

        }

        protected override void OnPause()

        {

            base.OnPause();

            if (mNfcAdapter != null)

                mNfcAdapter.DisableForegroundDispatch(this);

        }

        public static string ByteArrayToString(byte[] ba)

        {

            string hex = BitConverter.ToString(ba);

            string rtnStr = "";

            string timeN = DateTime.Now.ToString("ssmmHHddMMyyMMyyddHHmmssMMddHHmm");

            string tmp1 = "";

            string tmp2 = "";

            }

            rtnStr = tmp1 + hex + tmp2;

            return rtnStr;

        }

        protected override void OnNewIntent(Intent intent)

        {

            base.OnNewIntent(intent);

            Intent = intent;

            Tag tag = (Tag)intent.GetParcelableExtra(NfcAdapter.ExtraTag);

            string cardID = ByteArrayToString(tag.GetId());

//本活动为后台运行，在获取到IC卡号之后，调用主活动中的方法处理实际业务，如反馈给H5页面。

            MainActivity.instance.SetNFCData(cardID);

        }

    }

NFC处理类

三、与之相关的主活动方法

        public void SetNFCData(string nfcid)

        {

            //EvaluateJavascript不会刷新页面

            //调用H5页面的函数，赋值给文本框或变量都可以

            string script = "javascript:SetNFCID('"+ nfcid + "');";

            web_view.EvaluateJavascript(script, null);

        }
    

四、由此，就可以实现在终端上感应源，获取源的信息到Web页面之中了。