将列表映射到列表的颤振会<int> <String> 引发错误"字符串"不是类型为"int"的子类型

Question

未处理异常:类型'String'不是类型'int'的子类型铸型

else if (value is List<int>) {
prefs.setStringList(
"itemsToLoanCats", [...value.map((e) => e.toString())]);
}

type of 'value' =List<int>

我不明白为什么这不起作用，我使用.toString()

堆栈跟踪

I/flutter (16996): Person This is claiming to be itemsToLoanCats: [0]
I/flutter (16996): saveToPrefs converting GeoPoint...
E/flutter (16996): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: type 'String' is not a subtype of type 'int' in type cast
E/flutter (16996): #0      _CastListBase.[] (dart:_internal/cast.dart:99:46)
E/flutter (16996): #1      ListMixin.elementAt (dart:collection/list.dart:78:33)
E/flutter (16996): #2      ListIterator.moveNext (dart:_internal/iterable.dart:342:26)
E/flutter (16996): #3      StringBuffer.writeAll (dart:core-patch/string_buffer_patch.dart:96:19)
E/flutter (16996): #4      IterableBase.iterableToFullString (dart:collection/iterable.dart:268:14)
E/flutter (16996): #5      ListMixin.toString (dart:collection/list.dart:588:37)
E/flutter (16996): #6      Person.saveToPrefs.<anonymous closure> (package:meloan/model/person.dart:635:72)
E/flutter (16996): #7      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:617:13)
E/flutter (16996): #8      Person.saveToPrefs (package:meloan/model/person.dart:593:20)
E/flutter (16996): #9      _PersonalDetailsScreenState._buildBody.<anonymous closure> (package:meloan/personal/edit_personal_details.dart:1231:30)
E/flutter (16996): #10     _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1072:21)
E/flutter (16996): #11     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:253:24)
E/flutter (16996): #12     TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:627:11)
E/flutter (16996): #13     BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:306:5)
E/flutter (16996): #14     BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:276:7)
E/flutter (16996): #15     GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:163:27)
E/flutter (16996): #16     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:464:20)
E/flutter (16996): #17     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:440:22)
E/flutter (16996): #18     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:337:11)
E/flutter (16996): #19     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:395:7)
E/flutter (16996): #20     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:357:5)
E/flutter (16996): #21     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:314:7)
E/flutter (16996): #22     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:295:7)
E/flutter (16996): #23     _invoke1 (dart:ui/hooks.dart:167:13)
E/flutter (16996): #24     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:341:7)
E/flutter (16996): #25     _dispatchPointerDataPacket (dart:ui/hooks.dart:94:31)

添加:

List<String> encodedList = [];
for(int intValue in (value as List<int>)) {
print(LOG + "intValue: $intValue");
encodedList.add(int.parse(intValue).toString());
}

也不工作，抛出相同的异常。

请求更长的代码片段:

saveToPrefs(SharedPreferences prefs) {
(this.toMap()).forEach((key, value) {
//print("saveToPrefs entered with key: $keynvalue: $value");
if (value != null) {
if (key == "dbProfilePicPath") {
print("PERSON " + "should be saving dbProfilePicPath");
}
if (value is String) {
prefs.setString(key, value);
} else if (key == "position") {
print("saveToPrefs converting GeoPoint...");
double latitude = value['geopoint'].latitude;
double longitude = value['geopoint'].longitude;
prefs.setDouble("latitude", latitude);
prefs.setDouble("longitude", longitude);
} else if (value is List<String>)
prefs.setStringList(key, value);
else if (value is double)
prefs.setDouble(key, value);
else if (value is int)
prefs.setInt(key, value);
else if (value is bool)
prefs.setBool(key, value);
else if (value is Map<String, String>) {
// needs to be stored as a list
List<String>? list = [];
value.forEach((key, value) {
list.add("$key:$value");
});
prefs.setStringList(key, list);
} else if (value is Map<String, bool>) {
// e.g. .Charateristics needs to be stored as a list
List<String>? list = [];
value.forEach((key, value) {
list.add("$key:${value.toString()}");
});
prefs.setStringList(key, list);
} else if (value is Map<String, dynamic>) {
// loanItemFinancials / loanItemDetails?
//prefs.setString('loanItemDetails', json.encode(value));
} else if (value is List<int>) {
// itemsToLoanCats, each loaning category encoded to int
value = value.cast<int>();
print(LOG + 'This is claiming to be itemsToLoanCats: ${value.toString()}');
prefs.setStringList("itemsToLoanCats", value.map((el) => el.toString()).toList());
//prefs.setStringList("itemsToLoanCats", [...value.map((e) => e.toString())]);
}

Answer 1

尝试先将列表编码为json。

encodedList = json.encode(value);
debugPrint(encodedList.toString());
prefs.setString('itemsToLoanCats', encodedList);

Answer 2

OK解决。所以我发现value的类型与我的映射到字符串代码不兼容。

原来value被分配使用.cast<int>()，这不会产生一个适当的列表，它是一个地图?CastList<String, int>.

无论如何，我必须在前面的代码中进行深入研究，并重新配置从prefs中提取该变量时如何分配。

(prefs.getStringList('itemsToLoanCats') ?? []).map(int.parse).toList();

解决它。

哎呀! !感谢大家的关注和鼓励。如果你想发表一个答案，解释为什么.cast<int>产生一个地图，不能像List<int>一样对待，那么我会给答案信用。

非常奇怪，它报告为List<int>，但拒绝这样做🤔