Flutter Native调用Dart端方法，并获取数据

参考资料：https://blog.csdn.net/julystroy/article/details/87367520

举个例子，我们想从Native端请求Flutter端的一个getFlutterName方法获取一个字符串。在Flutter端你需要给MethodChannel设置一个MethodCallHandler：

platform.setMethodCallHandler(platformCallHandler);

Future<dynamic> platformCallHandler(MethodCall call) async {
    switch (call.method) {
            case "getFlutterName":
            return "Flutter name flutter";
            break;
    }
}

Dart端：核心关键就是直接return 需要返回的数据即可！

Java端：就是用CallBack的形式来接收返回的数据：

mChannel.invokeMethod(RCMethodList.MethodCallBackGetUserInfo, userId, new Result() {
            @Override
            public void success(@Nullable Object arg) {
                if (arg instanceof Map) {
                    Map map = (Map) arg;
                    String userId = (String) map.get("userId");
                    String name = (String) map.get("name");
                    String portraitUri = (String) map.get("portraitUrl");
                    UserInfo userInfo = new UserInfo(userId, name, Uri.parse(portraitUri));
                    flutterCallBack.success(userInfo);
                }
            }

            @Override
            public void error(String s, @Nullable String s1, @Nullable Object o) {
                flutterCallBack.error("获取用户信息失败:" + s, null);
            }

            @Override
            public void notImplemented() {
                flutterCallBack.error("flutter 端没有实现getUserInfoByUserId接口", null);
            }
        });