Android: Scan NFC tag id and just print it when button is clicked

[yacine-karim]

Hello,
thank you for this package,
im trying this sample for an Android application
im just trying to get the stored id from the NFC card and print it on screen
so that i can use later ...
when i scan a card nothing happens, and i don't know how to customize the code too scan the card when the button is clicked.
I followed excactly the instructions :
Thank you

1. i added the NFC capability in the manifest AndroidManifest.xml :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="NFC_NDEF.NFC_NDEF" android:versionCode="1" android:versionName="1.0" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="16" />
    <uses-permission android:name="android.permission.NFC" />
    <uses-sdk android:targetSdkVersion="15" />
    <uses-feature android:name="android.hardware.nfc" android:required="true" />
<application android:label="NFC_NDEF"></application>
</manifest>

2. In MainActivity.cs i added

public NfcAdapter NFCdevice;
public NfcForms x;

3. In the OnCreate method, before LoadApplication(), i added

NfcManager NfcManager = (NfcManager)Android.App.Application.Context.GetSystemService(Context.NfcService);       
NFCdevice = NfcManager.DefaultAdapter;

Xamarin.Forms.DependencyService.Register<INfcForms,NfcForms>();
x = Xamarin.Forms.DependencyService.Get<INfcForms>() as NfcForms;

4. After OnCreate() i added

protected override void OnResume ()
        {
            base.OnResume ();
            if (NFCdevice != null) {
                var intent = new Intent (this, GetType ()).AddFlags (ActivityFlags.SingleTop);
                NFCdevice.EnableForegroundDispatch
                (
                    this,
                    PendingIntent.GetActivity (this, 0, intent, 0),
                    new[] { new IntentFilter (NfcAdapter.ActionTechDiscovered) },
                    new String[][] {new string[] {
                            NFCTechs.Ndef,
                        },
                        new string[] {
                            NFCTechs.MifareClassic,
                        },
                    }
                );
            }
        }

        protected override void OnPause ()
        {
            base.OnPause ();
            NFCdevice.DisableForegroundDispatch (this);
        }

        protected override void OnNewIntent (Intent intent)
        {
            base.OnNewIntent (intent);
            x.OnNewIntent(this, intent);
        }

and i don't want my app to be lauched when a compatible tag is scanned so i didn't add these lines 5 and 6 :

[Activity (Label = "NFCForms.Droid", Icon = "@drawable/icon", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
[IntentFilter (new[]{NfcAdapter.ActionTechDiscovered})]
[MetaData (NfcAdapter.ActionTechDiscovered, Resource="@xml/nfc")]

 <activity>
...
<intent-filter>
    <action android:name="android.nfc.action.TECH_DISCOVERED"/>
</intent-filter>

<meta-data android:name="android.nfc.action.TECH_DISCOVERED"
    android:resource="@xml/nfc_tech_filter" />
...
</activity>

[poz1]

Hello, unfortunately because of NFC works, you can't scan in a precise moment, you've to start the sensor and wait for it to scan.

You can do this subscribing to this event:

INfcForms device = DependencyService.Get<INfcForms>();
device.NewTag += HandleNewTag;

[yacine-karim]

Thank you so much this really helped me, i finished my application