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。

[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。