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flutter_swiper_null_safety's Issues

Null check operator used on a null value

======== Exception caught by foundation library ====================================================
The following _CastError was thrown while dispatching notifications for SwiperController:
Null check operator used on a null value

When the exception was thrown, this was the stack:
#0 ScrollPosition.viewportDimension (package:flutter/src/widgets/scroll_position.dart:172:53)
#1 _PagePosition.getPixelsFromPage (package:flutter/src/widgets/page_view.dart:382:19)
#2 PageController.animateToPage (package:flutter/src/widgets/page_view.dart:197:16)
#3 _TransformerPageViewState.onChangeNotifier (package:flutter_swiper_null_safety/src/transformer_page_view/transformer_page_view.dart:590:12)
#4 ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:243:25)
...
The SwiperController sending notification was: Instance of 'SwiperController'

Flutter 2.2.1版本下:

每滑动一页就报一次异常

此问题怎么解决呢？

[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe. 

E/flutter (30989): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
E/flutter (30989): At this point the state of the widget's element tree is no longer stable.
E/flutter (30989): To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
E/flutter (30989): #0      Element._debugCheckStateIsActiveForAncestorLookup.<anonymous closure> (package:flutter/src/widgets/framework.dart:3990:9)
E/flutter (30989): #1      Element._debugCheckStateIsActiveForAncestorLookup (package:flutter/src/widgets/framework.dart:4004:6)
E/flutter (30989): #2      Element.visitAncestorElements (package:flutter/src/widgets/framework.dart:4089:12)
E/flutter (30989): #3      Notification.dispatch (package:flutter/src/widgets/notification_listener.dart:83:13)
E/flutter (30989): #4      ScrollActivity.dispatchScrollEndNotification (package:flutter/src/widgets/scroll_activity.dart:104:63)
E/flutter (30989): #5      ScrollPosition.didEndScroll (package:flutter/src/widgets/scroll_position.dart:907:15)
E/flutter (30989): #6      ScrollPosition.beginActivity (package:flutter/src/widgets/scroll_position.dart:876:9)
E/flutter (30989): #7      ScrollPositionWithSingleContext.beginActivity (package:flutter/src/widgets/scroll_position_with_single_context.dart:114:11)
E/flutter (30989): #8      ScrollPositionWithSingleContext.goIdle (package:flutter/src/widgets/scroll_position_with_single_context.dart:129:5)
E/flutter (30989): #9      ScrollPositionWithSingleContext.jumpTo (package:flutter/src/widgets/scroll_position_with_single_context.dart:195:5)
E/flutter (30989): #10     ScrollPositionWithSingleContext.animateTo (package:flutter/src/widgets/scroll_position_with_single_context.dart:177:7)
E/flutter (30989): #11     PageController.animateToPage (package:flutter/src/widgets/page_view.dart:201:21)
E/flutter (30989): #12     _TransformerPageViewState.onChangeNotifier (package:flutter_swiper_null_safety/src/transformer_page_view/transformer_page_view.dart:590:12)
E/flutter (30989): #13     ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:308:24)
E/flutter (30989): #14     IndexController.next (package:flutter_swiper_null_safety/src/transformer_page_view/index_controller.dart:30:5)
E/flutter (30989): #15     _SwiperTimerMixin._onTimer (package:flutter_swiper_null_safety/src/swiper.dart:369:18)
E/flutter (30989): #16     _rootRunUnary (dart:async/zone.dart:1436:47)
E/flutter (30989): #17     _CustomZone.runUnary (dart:async/zone.dart:1335:19)
E/flutter (30989): #18     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1244:7)
E/flutter (30989): #19     _CustomZone.bindUnaryCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1281:26)
E/flutter (30989): #20     _rootRunUnary (dart:async/zone.dart:1444:13)
E/flutter (30989): #21     _CustomZone.runUnary (dart:async/zone.dart:1335:19)
E/flutter (30989): #22     _CustomZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:1265:26)
E/flutter (30989): #23     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:395:19)
E/flutter (30989): #24     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:426:5)
E/flutter (30989): #25     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)

自动滚动，每滚动一次，报一次错。这个咋回事？

card_swiper EXCEPTION: _CastError was thrown while dispatching notifications for SwiperController

Case:

I am getting this error when my swiper scaffold is in app background.

[*] I am using smooth_page_indicator for showing custom dots pagination

Initially i load the main page (which has the swiper) based on conditions i move to some other page, in the background i am getting these errors/exceptions. Only when swiper is in background of flutter app i get this kind of exception.

Any idea to solve !!!

Error: Null check operator used on a null value

Exception Caught:

======== Exception caught by foundation library ====================================================
The following _CastError was thrown while dispatching notifications for SwiperController:
Null check operator used on a null value

When the exception was thrown, this was the stack:
#0 ScrollPosition.viewportDimension (package:flutter/src/widgets/scroll_position.dart:175:53)
#1 _PagePosition.getPixelsFromPage (package:flutter/src/widgets/page_view.dart:396:19)
#2 PageController.animateToPage (package:flutter/src/widgets/page_view.dart:202:16)
#3 _TransformerPageViewState.onChangeNotifier (package:card_swiper/src/transformer_page_view/transformer_page_view.dart:576:14)
#4 ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:308:24)
#5 IndexController.next (package:card_swiper/src/transformer_page_view/index_controller.dart:110:5)
#6 _SwiperTimerMixin._onTimer (package:card_swiper/src/swiper.dart:388:17)
(elided 10 frames from class _RawReceivePortImpl, class _Timer, and dart:async)
The SwiperController sending notification was: Instance of 'SwiperController'

每次滚动之前的组件都会重新加载

每次滚动之前的组件都会重新加载，轻量化的还好
我3个组件，文字，视频，按钮，滑动几次后卡的很呀，我觉得大概问题是重新加载但是没有销毁之前的组件导致的

每次滚动组件会重新加载，
不销毁之前的组件

这两个问题能不能修复一下

希望就是不要重新加载组件，需要的时候自己调用重绘

type 'Null' is not a subtype of type 'double'

When the exception was thrown, this was the stack:
#0 TransformerPageController.page (package:flutter_swiper_null_safety/src/transformer_page_view/transformer_page_view.dart:171:9)
#1 _PageIndicatorState._createPainer (package:flutter_swiper_null_safety/src/flutter_page_indicator/flutter_page_indicator.dart:235:40)
#2 _PageIndicatorState.build (package:flutter_swiper_null_safety/src/flutter_page_indicator/flutter_page_indicator.dart:250:18)
#3 StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)

just
Index: lib/src/transformer_page_view/transformer_page_view.dart
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8

--- lib/src/transformer_page_view/transformer_page_view.dart (revision 1365b80)
+++ lib/src/transformer_page_view/transformer_page_view.dart (revision 6f7c83ab0aef1ae40f808b5e2a7d6dd123337f49)
@@ -143,8 +143,8 @@
return renderIndex;
}

  • double? get realPage {
  • return super.page;
  • double get realPage {
  • return super.page ?? 0.0;
    }

static _getRenderPageFromRealPage(
@@ -363,7 +363,7 @@

       double position = 0;

  •      double page = _pageController.realPage ?? 0;

  •      double page = _pageController.realPage;

     if (_transformer != null && _transformer!.reverse) {
       position = page - index;

轮播时重绘组件的问题很致命

如果大点的图片会导致轮播的效果割裂，而且如果源是错误的网络图片资源，开了自动开始和循环后会，flutter框架会不停的抛出资源错误，影响调试，pub上面有几个维护至空安全的库都未能解决这个问题

flutter swiper package avoid to swipe to next position, it stay on first

I have a working code before null safety flutter upgrade. But after the migration, the same code doesn't work.

I had a simple horizontal swipe card, but now something force the swipe to stay on the first position. When I remove didChangeDependencies (function I use to load when data change) the swipe is OK. I think when data is load by didChangeDependencies it refresh new Swiper.children( and force to return always to first index position.

But I can't do without didChangeDependencies, how can I do ?

Here is the package https://pub.dev/packages/flutter_swiper_null_safety/example Here is my code:


@override
void didChangeDependencies() async {
SharedPreferences prefs = await SharedPreferences.getInstance();

final MyInheritedWidgetState state = MyInheritedWidget.of(context);
}                                  
                                                      new Swiper.children(

                                                      viewportFraction: 0.8,
                                                      scale: 0.6,
                                                      autoplay: false,
                                                      loop: false,
                                                      control: new SwiperControl(

                                                        size: 25.0,
                                                        color:  Color(0xffff9a7b),

                                                        disableColor: Colors.transparent ,
                                                        padding: const EdgeInsets.all (5.0),
                                                      ),

                                                      children: <Widget>[
                                                      Card1()
                                                      Card2()
                                                      Card3()
                                                      ]

Null check operator used on a null value

flutter: ══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
flutter: The following _CastError was thrown while dispatching notifications for SwiperController:
flutter: Null check operator used on a null value
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 ScrollPosition.viewportDimension (package:flutter/src/widgets/scroll_position.dart:172:53)
flutter: #1 _PagePosition.getPixelsFromPage (package:flutter/src/widgets/page_view.dart:382:19)
flutter: #2 PageController.animateToPage (package:flutter/src/widgets/page_view.dart:197:16)
flutter: #3 _TransformerPageViewState.onChangeNotifier (package:flutter_swiper_null_safety/src/transformer_page_view/transformer_page_view.dart:590:12)
flutter: #4 ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:243:25)
flutter: #5 IndexController.next (package:flutter_swiper_null_safety/src/transformer_page_view/index_controller.dart:30:5)
flutter: #6 _SwiperTimerMixin._onTimer (package:flutter_swiper_null_safety/src/swiper.dart:369:18)
flutter: (elided 10 frames from class _RawReceivePortImpl, class _Timer, and dart:async)
flutter:
flutter: The SwiperController sending notification was:
flutter: Instance of 'SwiperController'

swiper在第一次初始化时会快速滑动一段时间再回复正常

初始化Swpier时，如果images长度为0，当网络请求回来时刷新时，images长度>0，此时就会出现快速滑动现象。

这个问题出现的原因是pageController的初始化initialPage=kMiddleValue一个很大的数，，但此时的itemCount=0。

解决：

在 transformer_page_view.dart 文件下

static int _getRealIndexFromRenderIndex(
      int index, bool loop, int itemCount, bool reverse) {
    int result = reverse ? (itemCount - index - 1) : index;
    if (loop && itemCount > 0) { // 新增itemCount > 0判断
      result += kMiddleValue;
    }
    return result;
  }

首次出现无法切换TAB

首次加载完两个页面，然后切换到第二个页面的时候会出现滑不动，再次滑动就可以，感觉像是丢失焦点了

_onGetSize getting called with dirty context

Error at

flutter_swiper_null_safety/lib/src/transformer_page_view/transformer_page_view.dart

Lines 442 to 451 in 8429674

void _onGetSize(_) {
Size? size;
RenderObject? renderObject = context.findRenderObject();
if (renderObject != null) {
Rect bounds = renderObject.paintBounds;
size = bounds.size;
}
_calcCurrentPixels();
onGetSize(size);
} 

I/flutter (26103): ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (26103): The following assertion was thrown during a scheduler callback:
I/flutter (26103): This widget has been unmounted, so the State no longer has a context (and should be considered
I/flutter (26103): defunct).
I/flutter (26103): Consider canceling any active work during "dispose" or using the "mounted" getter to determine if
I/flutter (26103): the State is still active.
I/flutter (26103):
I/flutter (26103): When the exception was thrown, this was the stack:
I/flutter (26103): #0      State.context.<anonymous closure>
package:flutter/…/widgets/framework.dart:1088
I/flutter (26103): #1      State.context
package:flutter/…/widgets/framework.dart:1094
I/flutter (26103): #2      _TransformerPageViewState._onGetSize
package:flutter_swiper_null_safety/…/transformer_page_view/transformer_page_view.dart:444
I/flutter (26103): #3      SchedulerBinding._invokeFrameCallback
package:flutter/…/scheduler/binding.dart:1144
I/flutter (26103): #4      SchedulerBinding.handleDrawFrame
package:flutter/…/scheduler/binding.dart:1090
I/flutter (26103): #5      SchedulerBinding._handleDrawFrame
package:flutter/…/scheduler/binding.dart:998
I/flutter (26103): #9      _invoke (dart:ui/hooks.dart:161:10)
I/flutter (26103): #10     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:253:5)
I/flutter (26103): #11     _drawFrame (dart:ui/hooks.dart:120:31)
I/flutter (26103): (elided 3 frames from dart:async)
I/flutter (26103): ════════════════════════════════════════════════════════════════════════════════════════════════════

dependencies

dependencies: flutter_swiper_null_safety: ^1.0.3还没发吗？

Exception caught by rendering library 

  body: Column(
    children: [
      Text('test flutter swiper'),
      Container(
        child: Swiper(
          itemBuilder: (BuildContext context, int index) {
            return Image.network(
              "https://via.placeholder.com/350x150",
              fit: BoxFit.fill,
            );
          },
          itemCount: 3,
          pagination: SwiperPagination(),
          control: SwiperControl(),
        ),
      )
    ],
  )

报错Exception caught by rendering library ═════════════════════════════════
RenderBox was not laid out: RenderViewport#8c7d1 NEEDS-PAINT
'package:flutter/src/rendering/box.dart':
package:flutter/…/rendering/box.dart:1
Failed assertion: line 1929 pos 12: 'hasSize'

Slider stopped working for web

After upgrade of flutter to a more recent version the slider stops sliding in web/html when used without "control". I use it as follows:

Swiper(
        itemBuilder: (BuildContext context, int index) {
          switch (index) {
            case 0:
              return InfoPage1();
            case 1:
              return InfoPage2();
            ...
            case 6:
              return InfoPage7();
            default:
              return const Padding(padding: EdgeInsets.all(12));
          }
        },
        itemCount: 7,
        scale: 0.9,
        pagination: const SwiperPagination(
            builder: DotSwiperPaginationBuilder(
                size: 18.0,
                activeSize: 18.0,
                space: 9.0,
                color: Colors.black12)),
      ),

output of flutter doctor is:

/usr/local/Caskroom/flutter/2.5.3/flutter/bin/flutter doctor --verbose
[✓] Flutter (Channel stable, 2.10.0, on macOS 12.2 21D49 darwin-x64, locale de-DE)
    • Flutter version 2.10.0 at /usr/local/Caskroom/flutter/2.5.3/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 5f105a6ca7 (8 days ago), 2022-02-01 14:15:42 -0800
    • Engine revision 776efd2034
    • Dart version 2.16.0
    • DevTools version 2.9.2

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at /Applications/android-sdk
    • Platform android-31, build-tools 30.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 13.2.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • CocoaPods version 1.11.2

[✓] 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-b60-7590822)

[✓] VS Code (version 1.63.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.27.0

[✓] Connected device (1 available)
    • Chrome (web)           • chrome                    • web-javascript • Google Chrome 98.0.4758.80

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

• No issues found!

Any idea on how to fix it? Before a "mouse click and move left/right" initiates a "slide" - now it doesn't notice the mouse click.

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