flutter-plugins [Web] offset != null

Flutter Web: If you put a file on the drag zone, an error occurs as shown below.

Error

_handleMethodChannel: Assertion failed: file:///Users/patr _offset != null is not true dart-sdk/lib/internal/js_dev_runtime/priva dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart packages/desktop_drop/src/channel.dart 96:24 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5 packages/desktop_drop/src/channel.dart 40:36 packages/desktop_drop/src/channel.dart 33:22 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5 packages/desktop_drop/src/channel.dart 31:36 packages/flutter/src/services/platform_channel.dart 404:55 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5 packages/flutter/src/services/platform_channel.dart 401:40 packages/flutter/src/services/platform_channel.dart 397:34 packages/flutter/src/services/binding.dart 380:35 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5 packages/flutter/src/services/binding.dart 377:98 lib/_engine/engine/platform_dispatcher.dart 1121:13 lib/ui/channel_buffers.dart 25:12 lib/ui/channel_buffers.dart 65:7 lib/ui/channel_buffers.dart 130:16 packages/flutter_web_plugins/src/plugin_registry.dart 144:23 packages/flutter/src/services/platform_channel.dart 157:52 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54 dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5 packages/flutter/src/services/platform_channel.dart 155:30 packages/flutter/src/services/platform_channel.dart 340:12 packages/desktop_drop/desktop_drop_web.dart 55:17 dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/ dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/ dart-sdk/lib/html/dart2js/html_dart2js.dart 37285:58 ick386/.pub-cache/hosted/pub.dartlang.org/desktop_drop-0.3.3/lib/src/channel.dart:96:16 te/ddc_runtime/errors.dart 251:49 throw 29:3 assertFailed _handleMethodChannel runBody _async [_handleMethodChannel] runBody _async _handleAsMethodCall runBody _async [_handleAsMethodCall] runBody _async invoke2 invoke push push send _invokeMethod runBody _async [_invokeMethod] invokeMethod operations.dart 334:14 _checkAndCall operations.dart 339:39 dcall

Flutter doctor -v

[✓] Flutter (Channel stable, 3.0.0, on macOS 12.4 21F79 darwin-arm, locale ko-KR) • Flutter version 3.0.0 at /Users/patrick386/flutter • Upstream repository https://github.com/flutter/flutter.git • Framework revision ee4e09cce0 (2 weeks ago), 2022-05-09 16:45:18 -0700 • Engine revision d1b9a6938a • Dart version 2.17.0 • DevTools version 2.12.2

[✓] Android toolchain - develop for Android devices (Android SDK version 32.1.0-rc1) • Android SDK at /Users/patrick386/Library/Android/sdk • Platform android-32, build-tools 32.1.0-rc1 • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7772763) • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 13.3) • Xcode at /Applications/Xcode.app/Contents/Developer • CocoaPods version 1.11.3

[✓] Chrome - develop for the web • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2021.1) • Android Studio at /Applications/Android Studio.app/Contents • Flutter plugin can be installed from: 🔨 https://plugins.jetbrains.com/plugin/9212-flutter • Dart plugin can be installed from: 🔨 https://plugins.jetbrains.com/plugin/6351-dart • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7772763)

[✓] Connected device (2 available) • macOS (desktop) • macos • darwin-arm64 • macOS 12.4 21F79 darwin-arm • Chrome (web) • chrome • web-javascript • Google Chrome 101.0.4951.64

[✓] HTTP Host Availability • All required HTTP hosts are available

• No issues found!

May 24 '22 14:05 Patrick386

Can you give some sample code which could reproduce this issue?

I tested desktop_drop example with flutter 3.0.1 , but it seems work fine.

May 25 '22 13:05 boyan01

I don't know what I did wrong. Here is the sample code.

Sample code

import 'package:desktop_drop/desktop_drop.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {


  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(child: _DropTest()),
     // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

class _DropTest extends StatefulWidget {
  const _DropTest({Key? key}) : super(key: key);

  @override
  State<_DropTest> createState() => _DropTestState();
}

class _DropTestState extends State<_DropTest> {

  @override
  Widget build(BuildContext context) {
    return  DropTarget(
        onDragDone: (DropDoneDetails detail) async {
            print('Detail:${detail.files.first.name}');
        },
        onDragUpdated: (DropEventDetails details) {

        },
        onDragEntered: (DropEventDetails detail) {

        },
        onDragExited: (DropEventDetails detail) {

        },
        child:Container(
          width: 600,
          height: 60,
          color: Colors.amber,
          alignment: Alignment.center,
          child: const Text('Attach files by dragging & dropping, selecting them.'),
        ),
    );
  }
}

Error

Performing hot restart...
Waiting for connection from debug service on Chrome...
Restarted application in 178ms.
_handleMethodChannel: Assertion failed: file:///C:/Dev/flutter/.pub-cache/hosted/pub.dartlang.org/desktop_drop-0.3.3/lib/src/channel.dart:43:16
_offset == null
is not true C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 251:49      throw_
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 29:3        assertFailed
packages/desktop_drop/src/channel.dart 43:24                                                                                   _handleMethodChannel
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/desktop_drop/src/channel.dart 40:36                                                                                   [_handleMethodChannel]
packages/desktop_drop/src/channel.dart 33:22                                                                                   <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/desktop_drop/src/channel.dart 31:36                                                                                   <fn>
packages/flutter/src/services/platform_channel.dart 404:55                                                                     _handleAsMethodCall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/platform_channel.dart 401:40                                                                     [_handleAsMethodCall]
packages/flutter/src/services/platform_channel.dart 397:34                                                                     <fn>
packages/flutter/src/services/binding.dart 380:35                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/binding.dart 377:98                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platform_dispatcher.dart 1121:13               invoke2
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 25:12                                 invoke
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 65:7                                  push
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 130:16                                push
packages/flutter_web_plugins/src/plugin_registry.dart 144:23                                                                   send
packages/flutter/src/services/platform_channel.dart 157:52                                                                     _invokeMethod
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/platform_channel.dart 155:30                                                                     [_invokeMethod]
packages/flutter/src/services/platform_channel.dart 340:12                                                                     invokeMethod
packages/desktop_drop/desktop_drop_web.dart 64:15                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 334:14  _checkAndCall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 339:39  dcall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/html/dart2js/html_dart2js.dart 37285:58                              <fn>

Detail:2021.04.12_Invoice.PDF
_handleMethodChannel: Assertion failed: file:///C:/Dev/flutter/.pub-cache/hosted/pub.dartlang.org/desktop_drop-0.3.3/lib/src/channel.dart:96:16
_offset != null
is not true C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 251:49      throw_
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 29:3        assertFailed
packages/desktop_drop/src/channel.dart 96:24                                                                                   _handleMethodChannel
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/desktop_drop/src/channel.dart 40:36                                                                                   [_handleMethodChannel]
packages/desktop_drop/src/channel.dart 33:22                                                                                   <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/desktop_drop/src/channel.dart 31:36                                                                                   <fn>
packages/flutter/src/services/platform_channel.dart 404:55                                                                     _handleAsMethodCall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/platform_channel.dart 401:40                                                                     [_handleAsMethodCall]
packages/flutter/src/services/platform_channel.dart 397:34                                                                     <fn>
packages/flutter/src/services/binding.dart 380:35                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/binding.dart 377:98                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platform_dispatcher.dart 1121:13               invoke2
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 25:12                                 invoke
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 65:7                                  push
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/ui/channel_buffers.dart 130:16                                push
packages/flutter_web_plugins/src/plugin_registry.dart 144:23                                                                   send
packages/flutter/src/services/platform_channel.dart 157:52                                                                     _invokeMethod
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 123:5                _async
packages/flutter/src/services/platform_channel.dart 155:30                                                                     [_invokeMethod]
packages/flutter/src/services/platform_channel.dart 340:12                                                                     invokeMethod
packages/desktop_drop/desktop_drop_web.dart 55:17                                                                              <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 334:14  _checkAndCall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 339:39  dcall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/html/dart2js/html_dart2js.dart 37285:58                              <fn>

[√] Flutter (Channel stable, 3.0.1, on Microsoft Windows [Version 10.0.19044.1706], locale ko-KR)
    • Flutter version 3.0.1 at C:\Dev\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision fb57da5f94 (2 weeks ago), 2022-05-19 15:50:29 -0700
    • Engine revision caaafc5604
    • Dart version 2.17.1
    • DevTools version 2.12.2

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\Users\SintPatrick\AppData\Local\Android\sdk
    • Platform android-30, build-tools 30.0.3
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.12+7-b1504.28-7817840)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2022 17.1.3)
    • Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
    • Visual Studio Community 2022 version 17.1.32328.378
    • Windows 10 SDK version 10.0.19041.0

[√] Android Studio (version 2021.2)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.12+7-b1504.28-7817840)

[√] VS Code (version 1.52.1)
    • VS Code at C:\Users\SintPatrick\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension can be installed from:
       https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.19044.1706]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 102.0.5005.63
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 101.0.1210.53

[√] HTTP Host Availability
    • All required HTTP hosts are available

• No issues found!

Jun 03 '22 07:06 Patrick386

I have the same issue too, any update about it?

Sep 16 '22 08:09 nicolamazzocato

Submitted this pull request 251c4bb9e4ed6c5e754502e205b6286f7b08077d to resolve the issue...

May 15 '23 12:05 paschalisp

I forgot about this because of other tasks. At that time, I had tested this sufficiently. My guess is that this issue appears to be caused by overlapping drop areas. Testing with a Stack widget can indeed be helpful in identifying the problem.

https://firebasestorage.googleapis.com/v0/b/pronto-386.appspot.com/o/%E1%84%92%E1%85%AA%E1%84%86%E1%85%A7%E1%86%AB%20%E1%84%80%E1%85%B5%E1%84%85%E1%85%A9%E1%86%A8%202022-11-14%20%E1%84%8B%E1%85%A9%E1%84%92%E1%85%AE%208.25.00.mov?alt=media&token=ed8c8037-c6db-4ef7-920c-11de0d8fd00e

May 15 '23 16:05 Patrick386

Test sample: https://github.com/Patrick386/flutter_dropzone_web.git

May 15 '23 16:05 Patrick386

in my case error occurs when I hot reload the web app

May 16 '23 12:05 sajberkurajber90

in my case error occurs when I hot reload the web app

Same here, it throws error only after reloading.

Jul 07 '23 06:07 crizant-mpower

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[Web] offset != null

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