我在for循環外聲明了一個列表，然后在for循環內給這個列表分配了一些值，當在循環內打印時，它的值會更新，但當我在循環后打印它時，它會給我一個空列表。
List<List<String>> chunkSizeCollection(List<String> followedList) {
int counter = 0;
int ongoingCounter = 0;
bool isLessThanTen = false;
List<List<String>> returnAbleChunkedList = [];
List<String> midList = [];
log("in followedlist");
followedList.forEach((element) {
if (counter == 0) {
int difference = followedList.length - ongoingCounter;
if (difference < 10) {
// log("in difference if: $difference");
isLessThanTen = true;
}
}
midList.add(element);
counter++;
ongoingCounter++;
if (counter == 10 || (isLessThanTen && ongoingCounter == followedList.length)) {
returnAbleChunkedList.add(midList);
log("returnAbleChunkedList in counter 10 after adding new val is: $returnAbleChunkedList");
//above log works properly and prints the updated list
midList.clear();
counter = 0;
}
});
//this log on the other hand, returns an empty list
log("returnAbleChunkedList: $returnAbleChunkedList before return");
return returnAbleChunkedList;
}
The output:
[log] returnAbleChunkedList in counter 10 after adding new val is: [[KQTuEPllbmRrlBNvYgZ7oUXwtA63, OZUZOE10IzT8quUFoZbNxZOynU32, fCYIlYemCvbLTc7SpNHw6fCHrcm1, CbcLrtDNOdYZyC23FzEehOrJbKx2, FFvvVHCpPGNKUiXPQD34QdoPqH32, Gk09y59vSVXa1HNhzYvc6Atqnt53, JDO356z8urYQvuktJmc6eNUYqSm2, YesvvNI43gUVYPMfqhG4uRO5t6K2]]
[log] returnAbleChunkedList: [[]] before return
問題在于：
將對象
midlist添加到列表中，然后清除它。因此，您添加的對象將被清空。您必須創建一個副本或添加列表中的元素。