iOS: Method invocations from native side get lost if sent early, instead of being buffered #95623
Description
Steps to Reproduce
- flutter create bug
- copy first code sample to
bug/lib/main.dart - copy second code sample to
bug/ios/Runner/AppDelegate.swift - open project in XCode and set IOS Deployment Target to 10.0
- flutter run
Expected results:
The native-to-flutter call should be buffered and carried out as soon as the Flutter side is ready. The log should contain "Flutter side received method call: qux".
Actual results:
The method is not called. The inverse flutter-to-native call works as expected and the corresponding log message appears in the log.
The documentation for FlutterMethodChannel.resizeBuffer states:
Adjusts the number of messages that will get buffered when sending messages to channels that aren’t fully set up yet.
For example, the engine isn’t running yet or the channel’s message handler isn’t set up on the Dart side yet.
Code sample
bug/lib/main.dart
import 'dart:developer' as developer;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
@override
State<StatefulWidget> createState() => MyAppState();
}
class MyAppState extends State<MyApp> {
static const _methodChannel = MethodChannel('com.example/foo');
MyAppState() {
_methodChannel.setMethodCallHandler((call) async {
developer.log('Flutter side received method call: ${call.method}');
});
_methodChannel.invokeMethod('bar');
}
@override
Widget build(BuildContext context) {
return const MaterialApp(home: Scaffold());
}
}bug/ios/Runner/AppDelegate.swift
import UIKit
import Flutter
import os
@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
GeneratedPluginRegistrant.register(with: self)
let controller = self.window?.rootViewController as! FlutterViewController
let methodChannel = FlutterMethodChannel(name: "com.example/foo", binaryMessenger: controller.binaryMessenger)
methodChannel.resizeBuffer(256)
methodChannel.setMethodCallHandler() { call, result in
os_log("Native side received method call: %s", call.method)
result(nil)
}
methodChannel.invokeMethod("qux", arguments: nil)
return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}
}Logs
[ +209 ms] com.example.bug: 19613
[ ] Waiting for observatory port to be available...
[ +699 ms] Observatory URL on device: http://127.0.0.1:58364/0q0pgsZkxEY=/
[ +14 ms] Caching compiled dill
[ +110 ms] Connecting to service protocol: http://127.0.0.1:58364/0q0pgsZkxEY=/
[ +201 ms] Native side received method call: bar
[ +63 ms] Launching a Dart Developer Service (DDS) instance at http://127.0.0.1:0, connecting to VM service at http://127.0.0.1:58364/0q0pgsZkxEY=/.
[ +106 ms] DDS is listening at http://127.0.0.1:58367/yFaUD6jPm2k=/.
[ +76 ms] Successfully connected to service protocol: http://127.0.0.1:58364/0q0pgsZkxEY=/
[ +34 ms] DevFS: Creating new filesystem on the device (null)
[ +23 ms] DevFS: Created new filesystem on the device (file:///Users/user/Library/Developer/CoreSimulator/Devices/E5F8DBC3-FA2A-460B-B0C0-D8FC99E8E34B/data/Containers/Data/Application/FC663638-5E91-4239-BC5D-B8E1EF27FF5A/tmp/bugUWqHtw/bug/)
[ +2 ms] Updating assets
[ +88 ms] Syncing files to device iPhone 11...
[ +1 ms] <- reset
[ ] Compiling dart to kernel with 0 updated files
[ +2 ms] <- recompile package:bug/main.dart e22d5742-126e-4e24-b89b-d53bce342ebd
[ ] <- e22d5742-126e-4e24-b89b-d53bce342ebd
[ +88 ms] Updating files.
[ ] DevFS: Sync finished
[ ] Syncing files to device iPhone 11... (completed in 94ms)
[ ] Synced 0.0MB.
[ +2 ms] <- accept
[ +3 ms] Connected to _flutterView/0x7fce31829e20.
[ +3 ms] Flutter run key commands.
[ +1 ms] r Hot reload. 🔥🔥🔥
[ ] R Hot restart.
[ ] h List all available interactive commands.
[ ] d Detach (terminate "flutter run" but leave application running).
[ ] c Clear the screen
[ ] q Quit (terminate the application on the device).
[ ] 💪 Running with sound null safety 💪
[ +1 ms] An Observatory debugger and profiler on iPhone 11 is available at: http://127.0.0.1:58367/yFaUD6jPm2k=/
[ +212 ms] The Flutter DevTools debugger and profiler on iPhone 11 is available at: http://127.0.0.1:9100?uri=http://127.0.0.1:58367/yFaUD6jPm2k=/
Analyzing bug...
No issues found! (ran in 2.3s)
[✓] Flutter (Channel stable, 2.8.0, on macOS 12.0.1 21A559 darwin-x64, locale en-DE)
• Flutter version 2.8.0 at /usr/local/Caskroom/flutter/2.8.0/flutter
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[✓] Connected device (3 available)
• iPhone 11 (mobile) • E5F8DBC3-FA2A-460B-B0C0-D8FC99E8E34B • ios • com.apple.CoreSimulator.SimRuntime.iOS-15-2 (simulator)
• macOS (desktop) • macos • darwin-x64 • macOS 12.0.1 21A559 darwin-x64
• Chrome (web) • chrome • web-javascript • Google Chrome 96.0.4664.110
• No issues found!