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excel - 错误：“预期类型为‘列表’的值'，但有一个类型为'Null'的“
最近我在尝试测试是否创建了 Excel 文件时遇到了这个错误。问题是我在最古老的项目之一中使用了相同的代码并且运行良好。我正在尝试使用网络设备，所以当我按下按钮时，将创建 Excel 文件并开始下载。
这是我的代码：
这是我按下按钮时的错误：
══╡例外被手势抓住╞══════════════════════════════════════════ ═════════════════════════ 处理手势时抛出以下 TypeErrorImpl： 需要一个“列表”类型的值，但得到一个“列表”类型的值无效的'
抛出异常时，这是堆栈： 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 抛出
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 84:3 castError
C:/b/ s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 452:10 cast
C:/b/s/w/ir/cache/ builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/classes.dart 635:14 as_C packages/archive/src/zip_encoder.dart 90:34
getFileCrc32packages/archive/src/zip_encoder.dart 135:15
添加文件包/存档/src/zip_encoder.dart 65:7
编码 packages/excel/src/save/save_file.dart 36:25
[_save] packages/excel/src/excel.dart 334:20
save packages/finance_refa/main.dart 46:43
packages/flutter/src/material/ink_well .dart 1005:21
[_handleTap]packages/flutter/src/gestures/recognizer.dart 198:24 invokeCallback packages/flutter/src/gestures/tap.dart 613:48
handleTapUp packages/flutter/src/gestures/tap.dart 298 :5
[_checkUp] 包/flutter/src/gestures/tap.dart 232:7 handlePrimaryPointer 包/flutter/src/gestures/recognizer.dart 563:9
handleEvent 包/flutter/src/gestures/pointer_router.dart 94:12
[ _dispatch] 包/flutter/src/gestures/pointer_router.dart 139:9
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/linked_hash_map.dart 21:13 forEach
packages/flutter/src/gestures/pointer_router。 dart 137:17 [_dispatchEventToRoutes] 包/flutter/src/gestures/pointer_router.dart 123:7
路由包/flutter/src/gestures/binding.dart 445:19
handleEvent packages/flutter/src/gestures/binding.dart 425:14 dispatchEvent packages/flutter/src/rendering/binding.dart 326:11 dispatchEvent packages/flutter/src/gestures/binding.dart 380:7 [_handlePointerEventImmediately] packages/ flutter/src/gestures/binding.dart 344:5 handlePointerEvent packages/flutter/src/gestures/binding.dart 302:7 [_flushPointerEventQueue] packages/flutter/src/gestures/binding.dart 285:32 [_handlePointerDataPacket] C:/ b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platform_dispatcher.dart 1075:13 invoke1 C:/b/s/w/ir/cache/builder/src/ out/host_debug/flutter_web_sdk/lib/_engine/engine/platform_dispatcher.dart 185:5 invokeOnPointerDataPacket C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/pointer_binding。飞镖 130:39 [_onPointerData] C：/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/pointer_binding.dart 543:18
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/pointer_binding.dart 496:21
C:/b/s/w/ir/cache/builder/ src/out/host_debug/flutter_web_sdk/lib/_engine/engine/pointer_binding.dart 210:16 loggedHandler处理程序：“onTap”识别器：TapGestureRecognizer#f5722 ══════════════════════════════════════════════ ══════════════════════════════════════════════════ ══════════