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, 0, 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);
        }
    }

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。