Introduce logic to distinguish between children of PayButton that use…

… an event stream to report payment status updates back to the widgets and those that operate synchronously Update Google Pay button to use an event stream and avoid lifecycle issues
google-pay · Oct 10, 2024 · 1b0887c · 1b0887c
1 parent 91cc7dd
commit 1b0887c
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Showing 6 changed files with 111 additions and 17 deletions.
diff --git a/pay/lib/pay.dart b/pay/lib/pay.dart
@@ -14,10 +14,12 @@
 
 library pay;
 
+import 'dart:convert';
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:pay_ios/pay_ios.dart';
 import 'package:pay_android/pay_android.dart';
 import 'package:pay_platform_interface/core/payment_configuration.dart';

diff --git a/pay/lib/src/widgets/apple_pay_button.dart b/pay/lib/src/widgets/apple_pay_button.dart
@@ -64,4 +64,7 @@ class ApplePayButton extends PayButton {
 
   @override
   late final Widget _payButton = _applePayButton;
+
+  @override
+  final bool _returnsPaymentDataSynchronously = true;
 }
diff --git a/pay/lib/src/widgets/google_pay_button.dart b/pay/lib/src/widgets/google_pay_button.dart
@@ -66,4 +66,46 @@ class GooglePayButton extends PayButton {
 
   @override
   late final Widget _payButton = _googlePayButton;
+
+  @override
+  final bool _returnsPaymentDataSynchronously = false;
+
+  @override
+  State<PayButton> createState() => _GooglePayButtonState();
+}
+
+class _GooglePayButtonState extends _PayButtonState {
+  static const eventChannel =
+      EventChannel('plugins.flutter.io/pay/payment_result');
+  StreamSubscription<Map<String, dynamic>>? _paymentResultSubscription;
+
+  /// A method to listen to events coming from the event channel on Android
+  ///
+  /// The Android implementation uses an event stream to receive payment results
+  /// in order to circumvent the loss of connection with the Flutter engine when
+  /// the main activity hosting the plugin gets recycled due to resource
+  /// exhaustion.
+  void _startListeningForPaymentResults() {
+    _paymentResultSubscription = eventChannel
+        .receiveBroadcastStream()
+        .map((result) => jsonDecode(result as String) as Map<String, dynamic>)
+        .listen((result) {
+      widget._deliverPaymentResult(result);
+    }, onError: (error) {
+      widget._deliverError(error);
+    });
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    _startListeningForPaymentResults();
+  }
+
+  @override
+  void dispose() {
+    _paymentResultSubscription?.cancel();
+    _paymentResultSubscription = null;
+    super.dispose();
+  }
 }
diff --git a/pay/lib/src/widgets/pay_button.dart b/pay/lib/src/widgets/pay_button.dart
@@ -65,6 +65,13 @@ abstract class PayButton extends StatefulWidget {
     this.loadingIndicator,
   }) : _payClient = Pay({buttonProvider: paymentConfiguration});
 
+
+  /// Defines the strategy to return payment data information to the caller.
+  ///
+  /// This field is defined by implementations of this class to determine if the
+  /// payment result is returned right after calling [Pay.showPaymentSelector]
+  /// or rather received through asynchronous means (e.g.: an event stream).
+  bool get _returnsPaymentDataSynchronously;
   /// Callback function to respond to tap events.
   ///
   /// This is the default function for tap events. Calls the [onPressed]
@@ -77,9 +84,9 @@ abstract class PayButton extends StatefulWidget {
       try {
         final result =
             await _payClient.showPaymentSelector(buttonProvider, paymentItems);
-        onPaymentResult?.call(result);
+        if (_returnsPaymentDataSynchronously) _deliverPaymentResult(result);
       } catch (error) {
-        onError?.call(error);
+        _deliverError(error);
       }
     };
   }
@@ -96,9 +103,15 @@ abstract class PayButton extends StatefulWidget {
   /// Determines whether the current platform is supported by the button.
   bool get _isPlatformSupported =>
       _supportedPlatforms.contains(defaultTargetPlatform);
+  void _deliverPaymentResult(Map<String, dynamic> result) {
+    onPaymentResult?.call(result);
+  }
 
   @override
   State<PayButton> createState() => _PayButtonState();
+  void _deliverError(error) {
+    onError?.call(error);
+  }
 }
 
 /// Button state that adds the widgets to the tree and holds the result of the

diff --git a/pay_android/android/src/main/kotlin/io/flutter/plugins/pay_android/GooglePayHandler.kt b/pay_android/android/src/main/kotlin/io/flutter/plugins/pay_android/GooglePayHandler.kt
@@ -26,6 +26,7 @@ import com.google.android.gms.wallet.PaymentData
 import com.google.android.gms.wallet.PaymentDataRequest
 import com.google.android.gms.wallet.PaymentsClient
 import com.google.android.gms.wallet.Wallet
+import io.flutter.plugin.common.EventChannel.EventSink
 import io.flutter.plugin.common.MethodChannel.Result
 import io.flutter.plugin.common.PluginRegistry
 import io.flutter.plugins.pay_android.util.PaymentsUtil
@@ -47,7 +48,8 @@ private const val LOAD_PAYMENT_DATA_REQUEST_CODE = 991
  */
 class GooglePayHandler(private val activity: Activity) : PluginRegistry.ActivityResultListener {
 
-    private lateinit var loadPaymentDataResult: Result
+    // The stream sink that relays messages back to the Flutter end
+    private var paymentResultEvents: EventSink? = null
 
     companion object {
 
@@ -101,6 +103,12 @@ class GooglePayHandler(private val activity: Activity) : PluginRegistry.Activity
             activity, Wallet.WalletOptions.Builder().setEnvironment(environmentConstant).build()
         )
     }
+
+    /**
+     * Sets or unsets a new value for the stream sink to deliver messages back to Flutter.
+     */
+    fun setPaymentResultEventSink(eventSink: EventSink?) {
+        paymentResultEvents = eventSink
     }
 
     /**
@@ -150,10 +158,6 @@ class GooglePayHandler(private val activity: Activity) : PluginRegistry.Activity
     fun loadPaymentData(
         paymentProfileString: String, paymentItems: List<Map<String, Any?>>
     ) {
-
-        // Update the member to call the result when the operation completes
-        loadPaymentDataResult = result
-
         val paymentProfile = buildPaymentProfile(paymentProfileString, paymentItems)
         val client = paymentClientForProfile(paymentProfile)
         val ldpRequest = PaymentDataRequest.fromJson(paymentProfile.toString())

diff --git a/pay_android/android/src/main/kotlin/io/flutter/plugins/pay_android/PayMethodCallHandler.kt b/pay_android/android/src/main/kotlin/io/flutter/plugins/pay_android/PayMethodCallHandler.kt
@@ -20,12 +20,16 @@ import android.app.Activity
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
 import io.flutter.plugin.common.BinaryMessenger
+import io.flutter.plugin.common.EventChannel
+import io.flutter.plugin.common.EventChannel.EventSink
+import io.flutter.plugin.common.EventChannel.StreamHandler
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
 import io.flutter.plugin.common.MethodChannel.MethodCallHandler
 import io.flutter.plugin.common.MethodChannel.Result
 
 private const val METHOD_CHANNEL_NAME = "plugins.flutter.io/pay"
+private const val PAYMENT_EVENT_CHANNEL_NAME = "plugins.flutter.io/pay/payment_result"
 
 private const val METHOD_USER_CAN_PAY = "userCanPay"
 private const val METHOD_SHOW_PAYMENT_SELECTOR = "showPaymentSelector"
@@ -37,13 +41,18 @@ class PayMethodCallHandler private constructor(
     messenger: BinaryMessenger,
     activity: Activity,
     private val activityBinding: ActivityPluginBinding?,
-) : MethodCallHandler {
+) : MethodCallHandler, StreamHandler {
+
+    private val methodChannel: MethodChannel = MethodChannel(messenger, METHOD_CHANNEL_NAME)
+    private var eventChannelIsActive = false
+    private val paymentResultEventChannel: EventChannel =
+        EventChannel(messenger, PAYMENT_EVENT_CHANNEL_NAME)
 
-    private val channel: MethodChannel = MethodChannel(messenger, METHOD_CHANNEL_NAME)
     private val googlePayHandler: GooglePayHandler = GooglePayHandler(activity)
 
     init {
-        channel.setMethodCallHandler(this)
+        methodChannel.setMethodCallHandler(this)
+        paymentResultEventChannel.setStreamHandler(this)
     }
 
     constructor(
@@ -57,24 +66,45 @@ class PayMethodCallHandler private constructor(
      * Clears the handler in the method channel when not needed anymore.
      */
     fun stopListening() {
-        channel.setMethodCallHandler(null)
+        methodChannel.setMethodCallHandler(null)
+        paymentResultEventChannel.setStreamHandler(null)
         activityBinding?.removeActivityResultListener(googlePayHandler)
     }
 
+    // MethodCallHandler interface
     @Suppress("UNCHECKED_CAST")
     override fun onMethodCall(call: MethodCall, result: Result) {
         when (call.method) {
             METHOD_USER_CAN_PAY -> googlePayHandler.isReadyToPay(result, call.arguments()!!)
             METHOD_SHOW_PAYMENT_SELECTOR -> {
-                val arguments = call.arguments<Map<String, Any>>()!!
-                googlePayHandler.loadPaymentData(
-                    result,
-                    arguments.getValue("payment_profile") as String,
-                    arguments.getValue("payment_items") as List<Map<String, Any?>>
-                )
+                if (eventChannelIsActive) {
+                    val arguments = call.arguments<Map<String, Any>>()!!
+                    googlePayHandler.loadPaymentData(
+                        arguments.getValue("payment_profile") as String,
+                        arguments.getValue("payment_items") as List<Map<String, Any?>>
+                    )
+                    result.success("")
+                } else {
+                    result.error(
+                        "illegalEventChannelState",
+                        "Your event channel stream needs to be initialized and listening before calling the `showPaymentSelector` method. See the integration tutorial to learn more (https://pub.dev/packages/pay#advanced-usage)",
+                        null
+                    )
+                }
             }
 
             else -> result.notImplemented()
         }
     }
+
+    // StreamHandler interface
+    override fun onListen(arguments: Any?, events: EventSink?) {
+        googlePayHandler.setPaymentResultEventSink(events)
+        eventChannelIsActive = true
+    }
+
+    override fun onCancel(arguments: Any?) {
+        googlePayHandler.setPaymentResultEventSink(null)
+        eventChannelIsActive = false
+    }
 }