在颤振中运行隔离；未处理的异常:用户界面操作仅适用于根隔离。

Question

因为我的颤振应用程序运行不流畅，我想问题可能是单线程在颤振。因此，我在运行隔离的第一步，以避免只有一个事件循环。然而，我面临以下问题，这可能是使用隔离的错误：

我正在从类外调用方法addNewChild。我将所有变量转换为map以运行compute方法，并调用addNewChildStatic方法(即static )，如下所示：

    void addNewChild(
    childFacilityId,
    childFacility,
    childGroup,
    groupId,
    childFirstName,
    childLastName,
    userImageFile,
    isHorizontalImage,
  ) {
    Map map = Map();
    map['childFacilityId'] = childFacilityId;
    map['childFacility'] = childFacility;
    map['childGroup'] = childGroup;
    map['groupId'] = groupId;
    map['childFirstName'] = childFirstName;
    map['childLastName'] = childLastName;
    map['userImageFile'] = userImageFile;
    map['isHorizontalImage'] = isHorizontalImage;


    compute(addNewChildStatic, map); //here I run isolate using compute method
  }

addNewChildStatic看起来是这样的：

static Future<void> addNewChildStatic(Map map) async {
    print('COMPUTE addNewChildStatic STARTED');
    WidgetsFlutterBinding.ensureInitialized(); // I have added this because the errors I was getting in the console
    Firebase.initializeApp(); // I have added this because the errors I was getting in the console that there was no Firebase

    final childFacilityId = map['childFacilityId'];
    final childFacility = map['childFacility'];
    final childGroup = map['childGroup'];
    final childGroupId = map['groupId'];
    final childFirstName = map['childFirstName'];
    final childLastName = map['childLastName'];
    final childImageFile = map['userImageFile'];
    final isHorizontalImage = map['isHorizontalImage'];

try{
//methods
} catch(e){
//error handling
}
    }

问题是，我得到了以下错误：

flutter: COMPUTE addNewChildStatic STARTED
[VERBOSE-2:dart_vm_initializer.cc(41)] Unhandled Exception: UI actions are only available on root isolate.
#0      PlatformDispatcher._nativeSetNeedsReportTimings (dart:ui/platform_dispatcher.dart:501:59)
#1      PlatformDispatcher.onReportTimings= (dart:ui/platform_dispatcher.dart:493:29)
#2      SchedulerBinding.addTimingsCallback (package:flutter/src/scheduler/binding.dart:279:26)
#3      SchedulerBinding.initInstances (package:flutter/src/scheduler/binding.dart:211:7)
#4      ServicesBinding.initInstances (package:flutter/src/services/binding.dart:36:11)
#5      PaintingBinding.initInstances (package:flutter/src/painting/binding.dart:20:11)
#6      SemanticsBinding.initInstances (package:flutter/src/semantics/binding.dart:18:11)
#7      RendererBinding.initInstances (package:flutter/src/rendering/binding.dart:28:11)
#8      WidgetsBinding.initInstances (package:flutter/src/widgets/binding.dart:245:11)
#9      new BindingBase (package:flutter/src/foundation/binding.dart:147:5)
#10     new _Widgets<…>

我认为它有一些事情要做，即UI只在主线程中更新，所以我应该在隔离器之间进行一些通信。不幸的是，我不知道该如何处理它。我会感谢任何帮助的人。

非常感谢，提前！

Answer 1

正如您正确地提到的，您只能在主线程上运行UI更新，而不能在通过compute()创建的任何其他隔离点上运行UI更新。

所以你要做的第一件事就是

WidgetsFlutterBinding.ensureInitialized();

然后，对于与隔离器的简单通信，还可以返回值并在FutureBuilder中使用它们(例如)。

static Future<string> addNewChildStatic(Map map) async {
    // Perform some heavy async computation tasks
    // Return a result object in the end (in this case, a string).
    return "Finished calculation"
}

通过

FutureBuilder(
    future: compute(_runningFunction, 10),
    builder: (context, snapshot) {
        if (snapshot.hasData) {
            return Text(snapshot.data);
        } else {
            return CircularProgressIndicator();
        }
  },
),