Flutter模块集成iOS原生应用后无法完全关闭问题咨询

原因分析 #

复用同一个FlutterEngine时，Flutter的路由栈和应用状态会被持久化保存，因此关闭模块再打开时会回到之前的页面。销毁Engine无效通常是因为实例未被正确释放，或是销毁时机不合理。

解决方案 #

方案1：每次打开时创建全新的FlutterEngine和FlutterViewController #

不再复用全局Engine，每次打开Flutter模块都初始化新实例，确保每次都是全新的Flutter运行环境：

// 打开Flutter模块的代码
FlutterEngine *newFlutterEngine = [[FlutterEngine alloc] initWithName:@"new_flutter_engine"];
[newFlutterEngine run];
FlutterViewController *flutterViewController = [[FlutterViewController alloc] initWithEngine:newFlutterEngine nibName:nil bundle:nil];

// 配置MethodChannel
FlutterMethodChannel *channel = [FlutterMethodChannel methodChannelWithName:@"com.sara.app/myAppChannel" binaryMessenger:flutterViewController.binaryMessenger];
[channel setMethodCallHandler:^(FlutterMethodCall * _Nonnull call, FlutterResult  _Nonnull result) {
    if([call.method isEqualToString:@"exitUpiModule"]) {
        [flutterViewController dismissViewControllerAnimated:YES completion:^{
            // 销毁Engine，释放资源
            newFlutterEngine = nil;
        }];
    }
}];

[self presentViewController:flutterViewController animated:YES completion:nil];

方案2：关闭时重置Flutter路由栈 #

若需要复用Engine，可在关闭模块前通过MethodChannel通知Flutter侧清空路由栈，回到初始页面：

1. Flutter侧代码：

final MethodChannel _channel = MethodChannel('com.sara.app/myAppChannel');

@override
void initState() {
  super.initState();
  _channel.setMethodCallHandler((call) async {
    if (call.method == 'resetRoute') {
      // 回到首页并清空所有路由
      Navigator.of(context).pushAndRemoveUntil(
        MaterialPageRoute(builder: (context) => const HomePage()),
        (route) => false,
      );
    }
  });
}

2. iOS侧修改关闭逻辑：

[channel setMethodCallHandler:^(FlutterMethodCall * _Nonnull call, FlutterResult  _Nonnull result) {
    if([call.method isEqualToString:@"exitUpiModule"]) {
        // 先通知Flutter重置路由
        [channel invokeMethod:@"resetRoute" arguments:nil result:^(id _Nullable result) {
            // 路由重置完成后关闭页面
            [flutterViewController dismissViewControllerAnimated:YES completion:nil];
        }];
    }
}];

方案3：打开Flutter模块前重置路由 #

每次打开FlutterViewController前，通过已复用的Engine对应的MethodChannel通知Flutter重置路由：

FlutterEngine *flutterEngine = ((AppDelegate *)UIApplication.sharedApplication.delegate).flutterEngine;
// 先通知Flutter重置路由
FlutterMethodChannel *channel = [FlutterMethodChannel methodChannelWithName:@"com.sara.app/myAppChannel" binaryMessenger:flutterEngine.binaryMessenger];
[channel invokeMethod:@"resetRoute" arguments:nil result:^(id _Nullable result) {
    // 路由重置后创建并打开FlutterViewController
    FlutterViewController *flutterViewController = [[FlutterViewController alloc] initWithEngine:flutterEngine nibName:nil bundle:nil];
    // 重新设置MethodChannel回调
    [channel setMethodCallHandler:^(FlutterMethodCall * _Nonnull call, FlutterResult  _Nonnull result) {
        if([call.method isEqualToString:@"exitUpiModule"]) {
            [flutterViewController dismissViewControllerAnimated:YES completion:nil];
        }
    }];
    [self presentViewController:flutterViewController animated:YES completion:nil];
}];

内容的提问来源于stack exchange，提问作者Sara Lisa