onNewIntent not called after tapping to another NF

问题:

I'm coding in c# with Xamarin. I tried to share data over NFC from one device to another.

Open browser -> Options -> Share -> App4 to MainActivity

Both of my devices are running the same app and I'm tapping my device to the other device, but nothing happens.

I think it can't reach to onNewIntent().

Did I miss something? I have been confused and keep searching for a week.

Here is my code:

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Nfc;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms;

namespace App4
{
    [Activity(Label = "App4", MainLauncher = false, Icon = "@drawable/icon",LaunchMode = Android.Content.PM.LaunchMode.SingleTop)]
    [IntentFilter(new[] { Intent.ActionSend , NfcAdapter.ActionNdefDiscovered }, Categories = new[] {
    Intent.CategoryDefault,
    Intent.CategoryBrowsable
    }, DataMimeType = "text/plain")]
    public class MainActivity : Activity
    {
        string share;
        PendingIntent mPendingIntent;
        IntentFilter ndefDetected;
        IntentFilter[] intentF;
        TextView testTV;
        protected override void OnCreate(Bundle bundle)
        {

            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);  

            Intent Myintent = new Intent(this, GetType());
            Myintent.SetFlags(ActivityFlags.SingleTop);
            mPendingIntent = PendingIntent.GetActivity(this, 0, Myintent, 0);
            ndefDetected = new IntentFilter(NfcAdapter.ActionNdefDiscovered);
            try
            {
                ndefDetected.AddDataType("text/plain");
                ndefDetected.AddCategory(Intent.CategoryDefault);
            }
            catch { };

            intentF = new IntentFilter[] { ndefDetected };
            NfcAdapter NA = NfcAdapter.GetDefaultAdapter(this);   

            if (NA!=null && NA.IsEnabled)
            {
                Toast.MakeText(this, "Nfc Found", ToastLength.Long).Show();
            }else
            {
                Toast.MakeText(this, "Nfc Not Found", ToastLength.Long).Show();
            }
            testTV = FindViewById<TextView>(Resource.Id.text_view);
            share = Intent.GetStringExtra(Intent.ExtraText);  
            testTV.Text = share;   
    }

        protected override void OnPause()
        {
            base.OnPause();

            NfcManager manager = (NfcManager)GetSystemService(NfcService);
            NfcAdapter adapter = manager.DefaultAdapter;
            adapter.DisableForegroundNdefPush(this);
            adapter.DisableForegroundDispatch(this);
        }

        protected override void OnResume()
        {
            base.OnResume();


            var result2 = new byte[NdefRecord.RtdText.Count];
            NdefRecord.RtdUri.CopyTo(result2, 0);

            NfcManager manager = (NfcManager)GetSystemService(NfcService);
            NdefRecord record = new NdefRecord(NdefRecord.TnfAbsoluteUri,new byte[0], new byte[0], System.Text.Encoding.Default.GetBytes(share));
            manager.DefaultAdapter.EnableForegroundNdefPush(this, new NdefMessage(record));
            manager.DefaultAdapter.EnableForegroundDispatch(this, mPendingIntent, intentF, null);
        }

        protected override void OnNewIntent(Intent intent)
        {

            base.OnNewIntent(intent);
            testTV.Text = "onNewIntent";        
        }
    }
}

and here is my AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="App4.App4" android:versionCode="1" android:versionName="1.0" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="10" />
    <uses-permission android:name="android.permission.NFC"></uses-permission>
    <application android:label="App4"></application>
</manifest>

回答1:

Yes, you are missing something: You registered the foreground dispatch to listen for NDEF messages of the type "text/plain", which means you either expect a Text record or a record with the MIME type text/plain.

ndefDetected = new IntentFilter(NfcAdapter.ActionNdefDiscovered);
ndefDetected.AddDataType("text/plain");
ndefDetected.AddCategory(Intent.CategoryDefault);
intentF = new IntentFilter[] { ndefDetected };
manager.DefaultAdapter.EnableForegroundDispatch(this, mPendingIntent, intentF, null);

However, your app pushes an absolute URI record with an invalid (empty!) type name.

NdefRecord record = new NdefRecord(NdefRecord.TnfAbsoluteUri,new byte[0], new byte[0], System.Text.Encoding.Default.GetBytes(share));
manager.DefaultAdapter.EnableForegroundNdefPush(this, new NdefMessage(record));

In order to match the intent filter, you would need to push a Text record instead:

byte[] text = System.Text.Encoding.UTF8.GetBytes(share);
byte[] language = System.Text.Encoding.ASCII.GetBytes("en");
byte[] payload = new byte[1 + language.Count + text.Count];
payload[0] = (byte)language.Count;
System.Array.Copy(language, 0, payload, 1, language.Count);
System.Array.Copy(text, 0, payload, 1 + language.Count, text.Count);
NdefRecord record = new NdefRecord(NdefRecord.TnfWellKnown, new List<byte>(NdefRecord.RtdText).ToArray(), new byte[0], payload);
manager.DefaultAdapter.EnableForegroundNdefPush(this, new NdefMessage(record));