Android: set up NFC app linking

android/app/build.gradle

@@ -211,6 +211,7 @@ dependencies {
     // gif
     implementation 'com.facebook.fresco:fresco:2.6.0'
     implementation 'com.facebook.fresco:animated-gif:2.6.0'
+    implementation "com.hypertrack:hyperlog:0.0.10"
 
     if (enableHermes) {
         def hermesPath = "../../node_modules/hermes-engine/android/";

android/app/src/main/AndroidManifest.xml

@@ -35,8 +35,6 @@
         android:configChanges="keyboard|keyboardHidden|orientation|screenSize"
         android:windowSoftInputMode="adjustResize"
         android:screenOrientation="portrait">
-        <meta-data android:name="android.nfc.action.TECH_DISCOVERED"
-            android:resource="@xml/nfc_tech_filter" />
         <intent-filter>
             <action android:name="android.intent.action.MAIN" />
             <category android:name="android.intent.category.LAUNCHER" />

android/app/src/main/java/com/zeus/MainApplication.java

@@ -37,6 +37,7 @@ public boolean getUseDeveloperSupport() {
         protected List<ReactPackage> getPackages() {
           @SuppressWarnings("UnnecessaryLocalVariable")
           List<ReactPackage> packages = new PackageList(this).getPackages();
+          packages.add(new MobileToolsPackage());
           return packages;
         }
         @Override

android/app/src/main/java/com/zeus/MobileTools.java

@@ -0,0 +1,90 @@
+// based on Blixt LNDMobileTools
+// https://github.com/hsjoberg/blixt-wallet/blob/master/android/app/src/main/java/com/blixtwallet/MainApplication.java
+package app.zeusln.zeus;
+
+import android.nfc.Tag;
+import android.nfc.NfcAdapter;
+import android.nfc.NdefMessage;
+import android.nfc.tech.Ndef;
+import android.nfc.NdefRecord;
+
+import java.util.Arrays;
+import java.io.UnsupportedEncodingException;
+
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.ReactMethod;
+import com.facebook.react.bridge.Promise;
+
+import com.hypertrack.hyperlog.HyperLog;
+
+class MobileTools extends ReactContextBaseJavaModule {
+  final String TAG = "MobileTools";
+
+  public MobileTools(ReactApplicationContext reactContext) {
+    super(reactContext);
+  }
+
+  @Override
+  public String getName() {
+    return "MobileTools";
+  }
+
+  @ReactMethod
+  public void getIntentNfcData(Promise promise) {
+    // https://code.tutsplus.com/tutorials/reading-nfc-tags-with-android--mobile-17278
+    Tag tag = getReactApplicationContext()
+      .getCurrentActivity().getIntent().getParcelableExtra(NfcAdapter.EXTRA_TAG);
+    if (tag == null) {
+      promise.resolve(null);
+      return;
+    }
+
+    Ndef ndef = Ndef.get(tag);
+    if (ndef == null) {
+      HyperLog.d(TAG, "NFC tag is not NDEF");
+      promise.resolve(null);
+    }
+
+    NdefMessage ndefMessage = ndef.getCachedNdefMessage();
+
+    NdefRecord[] records = ndefMessage.getRecords();
+    if (records.length > 0) {
+      // Get first record and ignore the rest
+      NdefRecord record = records[0];
+      if (record.getTnf() == NdefRecord.TNF_WELL_KNOWN && Arrays.equals(record.getType(), NdefRecord.RTD_TEXT)) {
+        /*
+         * See NFC forum specification for "Text Record Type Definition" at 3.2.1
+         *
+         * http://www.nfc-forum.org/specs/
+         *
+         * bit_7 defines encoding
+         * bit_6 reserved for future use, must be 0
+         * bit_5..0 length of IANA language code
+        */
+        byte[] payload = record.getPayload();
+
+        // Get the Text Encoding
+        String textEncoding = ((payload[0] & 128) == 0) ? "UTF-8" : "UTF-16";
+
+        // Get the Language Code
+        int languageCodeLength = payload[0] & 0063;
+
+        // String languageCode = new String(payload, 1, languageCodeLength, "US-ASCII");
+        // e.g. "en"
+
+        try {
+          String s = new String(payload, languageCodeLength + 1, payload.length - languageCodeLength - 1, textEncoding);
+          promise.resolve(s);
+          return;
+        } catch (UnsupportedEncodingException e) {
+          HyperLog.e(TAG, "Error returning ndef data", e);
+        }
+      }
+      else {
+        HyperLog.d(TAG, "Cannot read NFC Tag Record");
+      }
+    }
+    promise.resolve(null);
+  }
+}

android/app/src/main/java/com/zeus/MobileToolsPackage.java

@@ -0,0 +1,22 @@
+package app.zeusln.zeus;
+
+import com.facebook.react.ReactPackage;
+import com.facebook.react.bridge.NativeModule;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.uimanager.ViewManager;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class MobileToolsPackage implements ReactPackage {
+  @Override
+  public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
+    return Collections.emptyList();
+  }
+
+  @Override
+  public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
+    return Arrays.asList(new MobileTools(reactContext));
+  }
+}

stores/InvoicesStore.ts

@@ -221,14 +221,20 @@ export default class InvoicesStore {
     @action
     public clearAddress = () => (this.onChainAddress = null);
 
+    @action
+    public clearPayReq = () => {
+        this.pay_req = null;
+        this.getPayReqError = null;
+    };
+
     @action
     public getPayReq = (
         paymentRequest: string,
         descriptionPreimage?: string
     ) => {
+        this.loading = true;
         this.pay_req = null;
         this.paymentRequest = paymentRequest;
-        this.loading = true;
         this.feeEstimate = null;
 
         return RESTUtils.decodePaymentRequest([paymentRequest])
@@ -249,14 +255,14 @@ export default class InvoicesStore {
                     );
                 }
 
-                this.loading = false;
                 this.getPayReqError = null;
+                this.loading = false;
             })
             .catch((error: any) => {
                 // handle error
-                this.loading = false;
                 this.pay_req = null;
                 this.getPayReqError = error.toString();
+                this.loading = false;
             });
     };
 

utils/LinkingUtils.ts

@@ -1,12 +1,20 @@
-import { Linking } from 'react-native';
+import { Linking, NativeModules } from 'react-native';
 import { localeString } from './LocaleUtils';
 import handleAnything from './handleAnything';
 
 class LinkingUtils {
     handleInitialUrl = (navigation: any) =>
-        Linking.getInitialURL().then(
-            (url) => url && this.handleDeepLink(url, navigation)
-        );
+        Linking.getInitialURL().then(async (url) => {
+            if (url) {
+                this.handleDeepLink(url, navigation);
+                return;
+            }
+            if (Platform.OS === 'android') {
+                const nfcData =
+                    await NativeModules.MobileTools.getIntentNfcData();
+                if (nfcData) this.handleDeepLink(nfcData, navigation);
+            }
+        });
 
     handleDeepLink = (url: string, navigation: any) =>
         handleAnything(url)

views/PaymentRequest.tsx

@@ -93,7 +93,8 @@ export default class PaymentRequest extends React.Component<
             loading,
             loadingFeeEstimate,
             successProbability,
-            feeEstimate
+            feeEstimate,
+            clearPayReq
         } = InvoicesStore;
 
         const requestAmount = pay_req && pay_req.getRequestAmount;
@@ -133,7 +134,10 @@ export default class PaymentRequest extends React.Component<
         const BackButton = () => (
             <Icon
                 name="arrow-back"
-                onPress={() => navigation.navigate('Wallet', { refresh: true })}
+                onPress={() => {
+                    clearPayReq();
+                    navigation.navigate('Wallet', { refresh: true });
+                }}
                 color={themeColor('text')}
                 underlayColor="transparent"
             />
@@ -178,7 +182,7 @@ export default class PaymentRequest extends React.Component<
                         </View>
                     )}
 
-                    {!!pay_req && (
+                    {!loading && !!pay_req && (
                         <View style={styles.content}>
                             <View style={styles.center}>
                                 {isNoAmountInvoice ? (