flutter - 如何确定哪个DateTime大于或小于另一个

Question

它应该如何工作:

确保今天今天的在 2020-April-01(timestampValidFrom-firebase时间戳格式)和 2020-April-05(timestampValidTo)之间。

我需要这样的查询。

1)

timestampValidFrom <= today >= timestampValidTo

要么

2)

 .where('timestampValidFrom', isGreaterThanOrEqualTo: Timestamp.now())
 .where('timestampValidTo', isLessThanOrEqualTo: Timestamp.now())

我已经尝试解决此解决方案，但是它不起作用。

DateTime now = DateTime.now();
DateTime yesterday,tomorrow;

yesterday = DateTime(now.year, now.month, now.day); // today 12.00.00
tomorrow = DateTime(now.year, now.month, now.day +1); //tomorrow 12.00.00

if(yesterday.isAfter(snapshot.data[index].timestampValidFrom.toDate())
    || snapshot.data[index].timestampValidFrom.toDate().isBefore(tomorrow) 
    && yesterday.isBefore(snapshot.data[index].timestampValidTo.toDate())
    || snapshot.data[index].timestampValidTo.toDate().isAfter(tomorrow)) {
    // show widget
} else {
    //emplty widget
}

Answer 1

使用difference方法。

final yesterday = DateTime(now.year, now.month, now.day); // today 12.00.00
final tomorrow = DateTime(now.year, now.month, now.day +1); //tomorrow 12.00.00

int diffInDays = tomorrow.difference(yesterday).inDays;
if (diffInDays == 0){
    //custom code
    print( "same day");
} else if( diffInDays > 0 ) {
    // custom code
    print("tomorrow is greater ");
} else{
    // custom code
    print(" yesterday is less" );
}

希望能帮助到你!